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B.A.R.C.-978
as
GOVERNMENT OF INDIA
ATOMIC ENERGY COMMISSION
ANNUAL REPORT
OF THE
NUCLEAR PHYSICS DIVISION
Period Ending December 31, 1976
Edited by
C. L. Thaper, N. N. Ajitanand and S. Kailas
BHABHA ATOMIC RESEARCH CENTRE
of, *nrwBOMBAY, INDIA
1978
B. A. R, C. - 9 7 8
oo G O V E R N M E N T O F INDIA& ATOMIC E N E R G Y COMMISSION
i
ANNUAL REPORT
OF THE
NUCLEAR FHYSCS DIVISION
Period Ending December 31, 1976
Edited by
C. L. Thaper, N. N. Ajitanand and S. Kailas
BHABHA ATOMIC RESEARCH CENTREBOMBAY, INDIA
1978
Reports previously Issued In this series are as follows;
BARC-501
BARC-557
BARC-633
BARC-694
BARC-768
BARC-843
BARC-878
Period Ending December 31, 1969
Period Ending December 31, 1970
Period Ending December 31, 1971
Period Ending December 31, 197^
Period Ending December 31, 1973
Period Ending December 31, 1974
Period Ending December 31, 197 5
FOREWORD
This report cowers the research and development activities
of the Nuclear Physics Division during the Calander year 1976.
These have been carried out in the three main research sections of
the Division which are strongly supported by the various service
sections. The Organisation Chart is listed at the end of the report
with a brief indication of the activity of each section.
The feature article describes the interesting relatively new
field of liquid crystals in which the work at the Division has already
made new contributions. A brief introduction at the beginning of the
report from each section outlines the scope of the current research
activity in the framework of the previous work and future programmes.
A strong instrumentation development programme is the backbona
of any high quality experimental research programme. The current
effort in this area has been at the, same level as in previous years,
a major part of which is continuation of the projects undertaken to
meet the long term goals of setting up new facilities. A number of
groups from universities have been utilising the experimental faci-
lities of the Division.
The output of all the research activities of tha Division is
in the form of papers publishad in Journals or reported at national
and international conferences. These add up to more than 80 and
are listed along with the titles of the 8ARC rsports and theses
submitted for Univeraity degrees.
Amongst the other activities, the physics colloquium
haa bean a continuing feature with a large number of talk! given
by viaitors from outside. The teaching and training activities
have continued as before, numbers of the Division have been
taxing very active pert In the organisation of the annual Nuclear
Physics and Solid State Physics Symposium of the D.A.E. as well
as in various academic societies and committees.
fl.K. flehteHead, Nuclear Physics Division
UfJMTENTS
Foreword i
A. FUTURE rtRTICLfc.
1. Liquid Crystals > Phases, Phase Transitions andInstabilities - K. Usha Ooniz 1
B. NUClLrtR PHYSICS
1 . T o t a l ( p , n ) Cross Sect ion fur the Ca(p,n) ScReact ion - Culzar S ingh, S. S a i n i , S. K a i l a s ,A. Cha t te r j ee , 1*1. Balakr ishnan and I*).K. flehta 22
2 . I soba r i c Analog Resonances (IMR) i n the Se(p,n) BrReact ion - 5. K a i l a s , PI. K. Plehta, f.P. l / i yog i , N. Veera-babu, N.K. Ganguly and T.K. Bhat tachar jes 24
403. Alpha Scattering from Ca - rt, Chatterjse, 5. Saini,
S. Kailas, 1*1. Balakrishnan and 1*1.K. Plehta 264. excitation of Shape I sonars in the Uranium Isotopes -
A.C. Athougies, A. Chatterjee, 5. Kailas and M.K. Pehta 26
5. Further Studies on the Resonances in the Reaction32S(c* , Y )36Ar - O.R. Chakraborty, If.A. Esmaran,N.L. Ragoouansi and H.H. Oza ?8
G. Determination of the N&ture of Defoct3 in IrradiatedMetals by Rut her fur d Backscatter ing - Ct.K. Agaruaiand O.K. Sood 32
7. Radiation Disorder in Petals - O.K. Sood and C,. Oearnaley 36
8. A study of Molybdenum Implanted Copper by ScanningLlectren Microscope - O.K. Sood 41
9. Final State Interaction in Pion Absorption on 3He -B.K. Jain 43
10. F in i te Range Distorted Wai/e Calculations for D(d,t)HReaction u/ith a l l the Six Residual in teract ion -A.K. Jain and N. Sarma 45
7311. Intermediate Structure balow the Analogue 5tates In As -
C.V.K. Baba, W.G. Betigeri and V.f". Datar, S.f. Bharathi andA. Roy 50
7112. Isobaric Analogue Resonances in As - C.R. Ramaswamy
N.G. Puttasuamy end T.G. Betigeri SO13. Intermediate Width btructures in °Ti(p,n)50tf Reaction Cxci-
tation Function - S. Kailaa and T.K. fiehta 5114. Nuclear Structure Calculations in V - S. Saini and F.H. Gunys 52
C. FISSION PHYSICS
1 . Wtjdsuremiant of Relative Yield3 and Energy Spectra ofTritons and Alpha Part ic les Emitted in Thermal. NeutronFission of U-2w55 Udincj a Semi-conductor &E-E CounterTelescope - R.K. Choudhury, 0.1*1. Nacjkarni and S.S. Kapoor 56
2i Lany Rdnye Chiiryed Part ic les Emission in Kel/ NeutronFission of 235Lf - B. Krishnarajulu and G.K. Plehta,R.K. Choudhury, 0.F1. Nadkaini and S,S. Kapour - 56
3. Two Parameter Studies of TFbD Response to FissiunFragments for Measurements of Fragment Class andEnergy Dis t r ibut ions - N.N. Aj i tanand, K.N. Iyengarand S.R.S. Flurthy 60
4 . Studies of Frdyment Kinetic Lneryy and Mass Correla-t ions in Thermal Neutron Fission of U-235 EmployingElectronic Coll imation - D.FI. Nadkarni, R.K. Choudharyand j . a . Kapoor 64
5. ti'.imolous Surface Effects on Glass Backed PolywinylToluens Films Radiations - N.N. rtjitanand, K.N. Iyengarand S.R.S. l*1urthy 65
6. Search for Primordial Uuperheavy Clements in Monszitafrom Baach Sands of South India
6.1 Photon Induced X-ray Fluorescence Analysis Studies -S,S. Kapoor, t0?o Ramarnurthy, l*l. Lai and b.K. Kataria 6?
6.2 Alpha and Fi33ion Spoctrum! Studies - 5,S. Kapoor,U.S. Ramamurth'y and S.K. Kdtaria 69
7. Plultiplicity Distribution of Prompt Gamma Rays inSpontaneous Ternary Fission of "*Cf- U«S. Ramamurthy,R.K. Choudhury and 3.C. PlohariUrishna 71
8. * Semi-Empirical Expression for Spacific Luminascencein Plastic Scintillators - N.N. Ajitar.and 74
9. Evaluation of Nuclear Shell Correction Energies forRealistic Level Schemes by Temperature SmearingMethod - M.S. Ramamurthy and S.S. Kapoor 77
10. S&rni-empirical Nuclear Level Oenaity Formula -S.K. Kataria, U.S. Ramamurthy and S.S. Kapour 79
11. Classical Microscopic Description of Particle ClusterCollisions Application to Htiat/y Ion Collisions -W.S. Hamamurthy and S.K. Kataria 81
12. Transmission Throuyh an Inverted Biharmonic OscillatorPotential Barrier - II. Pxakash 84
13. Study of Scission Confiyuration by the Entropy Maxi-misation PlBthod - M. Mrakash, S.K. Kataria andU.S. Ramomurthy 85
D * SOLID STATE PHYSICS
I . Neutron D i f f rac t ion Studiea of Magnetic Materials
1 . Magnetic Form Factor of N i n J u . Q , by PolarisedNeutrons - R. Chakravarthy, 'Z. Plaonav Rao andN.S. Satya Murthy 69
Reoriantation of Ammonium Ions in NH^I, (NH^) 1 6 ^ Q DA^ r
and (NH4)n 1f iKn aA I - P.S. Goyal arid B,A. Dasann§charya 100
at ion of Amrnurium lorSO. - P.S. Goyal and
2. Magnetic Moment Density in Heusler AlloyU.C. Rakhecha, R. Chakravarthy. and N.S. Satya Clurthy 92
3. Magnetic Form Factor in Cobalt-dopad YbFeCL -
S.K. Paranjpe and R.J. Begum 95
II. Neutron Ine last ic .Scattering
1 . Phonon Studiea in KNO (Phase I I ) - K.R. Rao, P.K. Iyengar,fl.H. Uenkatesh and P.R. Vi juyaraghavan 95
2.anA (UU
'0.16 O.i3 . Geometries of Reori entat ion of Amrnurium Ions in (NHA)_ SO.
b.«. uasannacnarya 102
4 . Neutron Inelast ic Scattering from Glycine anddl-ot—Aianino — C.L. Thaper, S.K. Sinha andB.M. Da.3annacharya 104
5. Plult iple Scattering Calculations Using Monta-Carlo
Technique • P.P. Chandra and B.A. Dasannacharya 106
III. Light Scattering and Liquid Crystal Studies
1 . Rotat ional Correlat ion in CgH.„ by Raman Scattering -n.L. Bansal and A.P. Roy 108
2. Raman Scattering Study of ^3j^2 15 Single Crystal -M.L. Bansal, l/.C. Sahni and R.P". Roy 109
3. B r i l l o u i n Scattering in Ethanol and Methanol -K. Usha Deniz, P.S. Parv/athanathan and A . I . («lehta 111
4 . Small Angle Light Scattering from MBBH, Subjectedto fclactric Fields - K. Usha Deniz and A . I . Merita 113
5. X-ray Invest igat ion of the bmectic Phases, P , SH
and SA - K. UshB Deniz, U.R.K. Rao, A . I . Mehta,P.S. Parvathanathan and A.S. Paranjpe 116
6. Phase Transit ions in tha Compounds, p-n-Alkoxyben-zylidene-p-Aminobenzoic Acid - K. Usha Deniz,A.S. Paranjpe, P.S. Parv/athanathan and A . I . Mehta
IV. Plossbauar SpBctroscouy and Compton ProfileStudies
1. Site Preference and Local Environment tffecta inFe, Co Ga - N.K. Oaggi and K.R.P.P1. Rao 1 2 2
•j ™X X
2. Hyperfine Interactions in Ferromagnetic Rh-NnSn =N.K. Jagyi and K.R.P.FI. Rao 1 2 4
3. Spin Glass Behauiour in Cuncentrated Magnetic Systems -N.K. Jaggi and K.fl.P.M. Rao , 125
4. Compton Profile uf Isomeric Cumpuund3 Methyl FormatB* and Acutic Acid - P. UiadUah and l/.C. Sahni 126
5. Charye Tranifur Study in FeAl Uainy Compton Scatter-
iny - P. Chaddah and l/.C. bahni 12Q
V. Theory
1 . Inequal i t ies Between Operator Means - R. Subramanian,and K.I/. Bhagu/at 1 2 9
2 . The t iectro-Magnetic Analogue of Attenuating Rsyleigh -Stoneley Uaves - l.\l.\J. Raghavacharyulu . 130
3 . A Mote on the Parametric Model of Loose. Bonding ofElast ic Half Sphares - I . V . U . Raghawacharyulu 132
E. E-XPERlfteNTAL TLCHNIJUES ANDIWSTRUPlLWTrtTIIJM
1 . Pulsed Opto-feedback S i ( L i ) Oetector X-ray System -Clad an L a i , S.K. Kataria and P.L. Bhatia 134
2 . Single Element Analyser Uaing Balanced F i l t e rTechnique - R.K. Choudhury and 3.C. Hohankrishna 136
3 . Quant i tat ive X-ray Analysis Uding Computer Codes withS i ( L i ) Oetector X-ray Systam - Madan La i , S.K. Katar ia ,B.V.N. Rao and S.S. Kapoor 138
4 . Liquid Helium F a c i l i t y at B.A.R.C. - V. Chopra,T. Srinivasan, A.P. Bagul and N.S. Satya Murthy 141
5* Anci l lary Equipment for Resaarch Work at Liquid HeliumTemparaturet - V. Chopra, T. Srinivasan and A.P. Bagul 142
6 . Helium Gas Production on Laboratory Scale - R.K. Garg,A.n* fteghal, Hanumanth Rao, U. Chopra, T. Srinivasan,A.P. Bagul and N.S. Satya Plurthy 143
7 . A Prototype Hot Neutron Source for CIRUS - S.L. Chaplot,P.R. VijByaraghavan and N.S. Satya rturthy 145
B. Laaer Raman Spectrometer - 1*1.L. Banaal, U.C. Sahniand A.P. Roy
9 . M a t e r i a l Development and Crys ta l Growth -H.R.L.N. riurthy and P.K. Dayanidhi 150
10. Nickel-Coated Glass Pla tes for Neutron GuideTubes - P1.R.L.N. Murthy 151
1 1 . Data A c q u i s i t i o n Uni t fo r Neutron i ipectrometers -A .S . Oeshpande and P.R. Vi jayaraghavan 152
1 2 . A S i m p l i f i e d Incremental Automation for NeutronSpectrometer - S.L. Chaplot and P^R. Vi jayaraghavan 153
1 3 . S taba l i sed Magnet Current Supply fo r SuperconductingMagnet - B.5. Sriniwaaan 155
14 . Van de Graaff Operation and Maintenance - U.A. Ha t tan-g a d i , S.N. M is ra , 0 . 5 . B i s h t , S.G. Shukla, P.R.S. Rao,G.V. B h a t t , 5 . J . Mandke, R.P. K u l k a r n i , N.E. Doctor ,R.U. Patkar and hi. Fernandas 15 '
15 . Tandem Acce le ra to r - M.G. B e t i g e r i , T .P. David,P. Singh and C.V. Rayarappan 159
1 6 . Isotope Separator - U.A. Ha t tangad i , F.R. BhathBna,K.L. Pate l and E. Shallom . 163
17 . Ion Imp lan ta t i on - P.K. Bhat tacharya, I*1.S. Bha t i a ,
b. Gaonkar, Fi.J. Kansara, A.G. Ua9h and N. Sarma 165
1B. Neutron Radioyraphy - N.C, Ja in and Y.D. Dande 167
1 9 . Nuclear Detectors - Y.D. Oancje, N.C. 3 a i n ,G.V. Shenoy , R.S. Udyauar and A.P. Bagool 169
2 0 . Helium - Neon Laser Plasma Tubes - Y.D. Dande,S.R. Chinchanikai? and M.L. Bansal 171
2 1 . Neutron Radiography w i t h 2 5 2 C f - Y.D. Dande 171
2 2 . Se t t i ng up o f a Proton Induced X-ray FluorescenceSystem - P.N. Rama Rao, D.lt. Nadkarni , 5.K. Ka ta r iaand S.S. Kapoor 174
MNO PAPLRS 175
163
OTHtR SLItNTIFIL ACTIVITIES 187
NUCLLAR PHYblCS OIVISIuN STAFF 189
QRG«NIS«TIuN CHART AND SUMMARY OF. ACTIVITIES
LATUR£ ARTICLE
1• Liquid Cryatala t Phasea. Phase Tranaitiona and Instabilities
Introduction
In general, a crystalline solid when heated, malts into an
isotropic liquid(X).Howav9r, some crystalline solids, when heated,
transform into a phase which has an order intermediate between that
of a crystal and an isotropic liquid. A plastic crystal results if
the 3-dimensional positional order of the crystal is preserved but
the orientational order of the molecule is destroyed at the transition,
oolid hydrogen, ammonium sulphate and ammonium halides are examples of
compounds in which such orientational transitions occur. Usually such
compounds are made up of molecules which are almost spherical. If at
the transition, the 3-0 positional order of the crystal is partially
or totally lost, while the orientational order of the molecule is
preserved, a liquid crystal is obtained, Jlany organic compounds com-
posed of long molecules with rigid central portions^exhibit liquid
crystalline phases. Anisotropy of molecular electric polarizability
and the presence of permanent dipole moments in the molecules also
favour liquid crystal formation. The width and the length of the mole-
cule are two important factors which determine the type of liquid cry-
stalline phases in which the compound can exist • It is normally
easy to distinguish between a liquid crystal and a plastic crystal,
although in exceptional cases this is not true.
.During the past decade liquid crystals have assumed great import-
ance not only in many acisntific fields (physics, chemistry and bio-
logy) but also in technology and medicine* It ie even thought that the
key to the mystery surrounding the origin of life an this planet might2)
be found in .the behaviour of lyotropic liquid crystals 'II
To undeutand why liquid crystals are such interesting
-2-
materials, one has to examine tha types of liquid cryatals that
are encountered and alao their properties.
Classification
Liquid crystals can be divided into two broad classes, 1 ) the
thermotropic liquid crystals in which liquid crystalline phases'are
formed when the temperature is changed (e.g. PAA and PIBBA) and 2) tha
lyotropic liquid crystals which are formed in solution and wherein
phase transitions occur when tha concentration of the solution is
varied (e.g. soap and water systems). The lyotropics play an import-
ant rola in biological systems. The thermotropic liquid crystals
can themselves be subdivided into three classes, the nematic, smectic
and the cholesteric liquid crystals (Fig.1). Nematics are those in
CJWSTAl (C) SMECTIC (S) NEH'.TIC W) CHOLESTRIC (CM
ifHi
mi).00.<D>S»
IN-PLANE ARRANGEMENT
fiy.1 Molecular arrangementsin different liquidcrystalline phases. Sis a structured smecticwhereas the Sft phase hasno in-plane positionalorder. <__ ^implies av/er-ags valua.
which only orientational order of the molecules is present, but mole-
cular positional order is absent. In the amectics, in addition to
the presence of orientational order, the centres of mass of the mole-
cules lie on planes which are stacked regularly as in a crystal. Tha
cholesteric can be thouyht of aa nematica wherein the preferred direct-
ion of orientation of the molecule (n) is twisted in a helical fashion
in a direction perpendicular to n, tha pitch of thia helix being
highly temperature sensitive. Because of their structure, cholasterica
can reflect light of a certain wavelength, which ie dependent on the
helical pitch and hanca on the temperature. These ara therefore widely
-3-
used in all applications (medical end technological) requiring
tharmogrephy. '
The smectica can be further subdivided into types which dapend
on the positional order of the molecules present in the smectic
planaa and also on whether the tilt angle (the angle between n and
the smectic planar normal), 8, , which ia a measure of the rotational
order of the molecules with respect to n, ia finite or zero. This* - » •
leads to eight smactic types, S,, S„,.......S . Amongst them, S,,•n a n *
S and S have no in-plane positional order while 5., 3_, S and 3
are atructured smectics with certain amount of in-plane positional
order (Flg.1). 3 ia en unusual smectic having a cubic rather than
a layered structure. Since 6, * 0 for S , 5_ and S phases they areuninxial while i^. S_, S^ and S,, phases are biaxial because 6. i 0
C r G H l '
for these. Although further liquid crystal subciassifications have
been mentioned in literature , they will not be discussed here. In
what follows, only nematic and smectic phases will be considered.
Some Properties of Interest
The macroscopic properties of liquid crystals (LC) are aniso-
tropic because of the anisotroplc nature of the molecules constituting
them. Therefore, one has to deacribe these properties (macroscopic
response functions), using tensors. In the case of uniaxial liquid
crystals (nematics and uniaxial snectics), the tensor, say n, is
o n± o | (1)
0 0
where f1(| and Mj_ a c s t n u tensor components, parallel and perpendi-
cular to n. In these liquid crystals, one can define anisotroplea
such as,
(a) dielectric anisotropy, f\ £ - £..- t, » which can be either
positivs or negative
-4-
{b ) dlamagnBtic susceptibility anisotropy, '/^y.- •%., _ y
which is yenerally positive,
(c) conductivity anisotropy, &.<T- <Tj, - O", » w n i c h i a ganeraliy
positive in nematics, and
(d) diffusiun anisotropy, A. J> - JT>,, — J>ju » which is positive in
nematics, but would be expected to ba negative in uniaxial
smectica.
The presence uf dielectric and susceptibility anisotropies
allows one to align molecules in a LC using electric and magnetic
fields. When an electric field (£) is applied, the molecules aliyn
thamsalt/es parallel or perpendicular to the field, depending on
whether /\e is positius or negative. However, if a magnetic field
£ is applied, the molecules generally align themselves parallel to H.
In the nsmatic phase, the fielda required for alignment are amall
(for example, a magnetic field of 1000 Oersteads is sufficient to
align a sample whose linear dimension is *?/ 0.1mm ), because nema-
tics a n very fluid in nature. Nematic LC films of upto aoout 100/<m
can also be easily aligned by suitably treatiny the surfaces of the
substratea (glass plates) between which the LC film is held. If a
thin film of biO is vacuum-daposited on the aubstratea at an oblique
angle of incidence, the LC molecule* align themselves parallel to the
substrate surfaces (homogeneous alignment ). Usha Oeniz and cowork-8)
ers ' have found that vacuum deposition of thin films of mstals such
as Ag, Sn, Cr ate. on the substrates (the deposition being done
normal to substrate surface) undar appropriate conditions, leads to
the molecules of LCs 3uch as flBBA aligning themselves perpendicular
to tha substrate surfaces (homaotropic alignment). Tha type of
alignment obtained can be easily checked by viewing tha light trans-
mitted through the LC film, whan it it held between polaroide, or by9)
conoscopy. The conoacoplc image obtained by Shattacharya ' with a
film of HBBA, homeotropically oriented by coating the substrates
with Cr ia shown in Tig.2. Nematics are ideally suited for making
displays ' (alphanumeric) because they can ba easily aligned, both
f-'ig. 2 . The conoscopic imageoriented film of MBBA.
horruotropiuaiK
H BABA(N) 2I5°C
Schlieren Texture
H BPA (SH) 28° C
Mosaic Texture
TdBABA (Sc) 155°C
Thread Texture
NBABA (Sc)204°C
Domain TextureFig. 3 Texlurn photographs in different phases.
by small electric fields and by surface treatment of substrates
holding the namatic film. Indeed, nsmatic LCa with positive
are now commercially being used for making liquid crystal displays
(LCDs) for use with wrist watches ate.
Phases
The manner in which the liquid crystalline phases have been
classified according to the molecular packing in aach phaast has
already been described. These phases can be identified by observing
their texture or structure.
a. Textures:
Texture studies are carried out, using a polarizing microscope
with a hot stage for heating the sample to the appropriate tempera-
ture. The texture that the sample exhibits is typical of the liquid
crystalline phase in which the sample exists. ' For instance a
nematic has a typical Jchlieren texture, a b . has a kind of thread
texture and a mosaic texture is associated with structured amectics12)
such aa S . These textures ' are seen in Fig.3. Phase identifi-n
cation using this method is rather ambiguous, sines more than one
phase can have thu same texture. In such cases observation of the
different textures exhibited by the same phase helps. A typical
example is that of some members of the seris^ of compounds, p-n-Alko-
xybenzylidene-p-aminubsnzoic acid in which the high temperature
smectic phaau was identified as the Sc phase ' because of tha finger
print tsxtute (Fig.3) observed in this phase, (for T slightly less
than Tr or T_ .) in addition-to the Schlioren and thread textures.JC*N SC"X
b. Structural
X-ray diffraction measurements can be carried out to study the
structure of liquid crystalline phases. These experiments can be
done using Ni-filtered Cu-K^ radiation and a Laue camera, when
these measurements are done with aligned (monodomain) samples, the
liquid crystalline phase is uniquely determined. However, since it
is not always aasy to obtain monodomain samples one has to make do
with polycrystallins yampj.es. The diffraction patterns obtained
with polycrystalline samples in the different liquid crystalline
phases can ba grouped thusi
(i) Tha diffraction photograph with nametics consist of a diffuse
inner ring (related to 6- , the distance between the electron density
minima at the two enda of the molecule) and a diffuse outer ring
(related to 0, the average intermolecular distance perpendicular to
the long axis of the molecule). One can obtain t and 0 from the
diffraction pattern by using the relation,
j^ 1,2.
X is wavelength of the incident X-raya, B. » 1.229, S * 1.117,
P1 = I , p » 0 and 0, and 6Z correspond to the scattering angles
at which tha maxima or the inner and outer ringa occur. When the
nematic is aligned each ring changes to a pair of crescents, the lines
joining the maxima of corresponding crescents being mutually perpendi-
cular. In the aligned case I cannot be obtained uaing eq. (2), and14 )
one has to usb a relation which depends on the direction of mole-
cular alignment.
(ii) The diffraction pattern for the S , S and a_ phases consists
of a strong and sharp inner ring and a diffuse outer ring. The
smuctic layer thickness, d i« obtained from the inner ring position,
0^, using the Bragg relation
7\-
whereas 0, tha average in-plane intermolecular separation is obtainad
using eq. (2), J - 2. On aligning tha sample, the inner diffraction
ring transforms to two spots whoress tha outar one changes to two
crascents. The Unas joining the two spots and tha maxima of tha
crescents ara mutually perpendicular in tha uniaxial 5. phase. In
th» biaxial 5_ and 3 phases thase lines ara at an angle (90 - 0, ).
(ill) In tha caae of atructured amactics (S , S , i> and S ), the
diffraction pattern consists of a strong and sharp inner ring, ona
or more strong and sharp outer rings and aometimaa several sharp
weaker rings, d can us calculated using eq. (3). D, however, can
only be obtained if one knows or asaumea the symmetry of the lattice
in the emectic plane. Tor example, in the S and S phases where
the molecules are packed in a hexagonal array in the planes,
7\ 41 D &o/z (4)
whe.e Qa ie the position of the etrong outer ring. When these
phaaea are aligned, the *ings transform to spots.
Tha diffraction patterna obtained with a polycryatalline sample
give us the values of d and 0 and from thase one can alao find tha
tilt angle, (9. , in biaxial snectics, the density f (by making
certain assumptions about the molecular packing) ae also & ,T
tha volume expansion coefficient. The tilt angle ia given by
where L ia the length of the molecule, calculated using s suitable
modal and 1 ia the overlap length of molecules in neighbouring
layere. Usha Oeniz et al have done X-ray diffraction experiments
with HxBPA 5^' 1 6 ' in the liquid crystalline phaaea S^, SH and S^.
From their diffraction data, they have not only determined d and 0,
out also Fl<X U = ^oU)2" CbS 3o ) , where v is the volume per} 6 17^l
^ (Fig.4) and 64. (Fig.S)17^ as a function of tempera-
haa been calculated for (1 } 1 « 0 ( ) A
the overlep length measured in the S. phase.
ture. 9± haa been calculated for (1 } 1 « 0 and (2) 1Q » C.44 A,
-10-
i •MRM
- f\<» .f.' • - . • I ' ,
• g
} '
—o-co
1
- (waHnf »
*. i
HI :
260 290 300 320TEMPERATURE(K)
86
60
40 "o
20 a t
0
360
Temperature dependenceof f> and A. in HxBPA j.ntoe S , S and 5. phasas.The lTn«eHare guides tothe eye.
320
TEMPERATURE (K)
fig.5 Temperature depsndence of 8 inHxBPA in the S and S. phases.The solid Una ia calculated fromPIN theory. The dot dashed lineis a guide to the eye.
c. Molecular Dynamical
The positional and oriantational order of a LC phass daterminss
to a grsat extent the natura of molecular dynamics in that phase.
The movements of the molecule it mads up of three parts, (l) ths
tranalational motion of the centra of nass of the molecule, (2J the
rotational motion of tha antira molecule or parts of it, and (3) in-
ternal vibrations of tha molecule* Tha high frequency intarnal vibra-
tions are not as sensitive to phass changes aa are tha othar molecular
motions.
(1) Tranalational Motion!
This motion can ba propagating (phonons) or diffusiva or a
mixtura of both, this last baing tha caaa moat oftan. In tha namstics
and amactica with in-plane disorder (Sft, Sc and Sf) ths diffusivs
modas would ba mora predominant whaxaas in tha structural amectics
tha propagating modas art likely to ba mora predominant.
In tha hydrodynsmic ragime, tha relaxation time for a diffusiva
mod* ia givan by,
-11-
where q la tha aavs-vector of the mode. In nematica and sweeties
with in-plana disorder, thaaa calaxatlon times ara short and Q\\ and"6 2Dj. era fairly larga (^ 10 cm /aac)* In structured smectica tha
diffusion coafficianta ara aavaral ordara of magnitude amallar. Ona
can obtain tha valuea of 0. .5 by high raaolution incoherent Neutron
4uaai-Elaetlc ocattaring (NijEs) and NltR axperimanta. To, can ba obtainad
in a diract fashion from HUIS, tha acatterad spectrum due to tranala-
tional diffusion alone bsing proportional to,
(4,
whara the nautron momentum transfer, Q * q, tha mode wnva-t/ector, and*~ ^ 18)
~^u) la the nautron energy tranefar. For tha £. phases of TBBA ;,~6 2 19)
O|| and Oi have been round by NOES to ba 2.8 x 10 cm /aec. NMR '18)valuea agrae vary wall with this. In the S ' phaee of TBBA ' thadiffusion coefficient ie too email to be detected (Q~ / 6 x•A 5 • average \10 c m V )
Phonon dieperaion raiatlona have also been studied to a email
extent by neutron acattering experiments specially in atructurad2o)
amectica '. There la not enough work done in this field for one tocomment on the propagating modea in different IX phaaee.
(11) Rotational Olffueion Motioni
Thla motion seems to be preeent in ell LCs, whether highly
ordered or otherwise. This motion can toe that of the entire molecule
about ita long axia, or of tha hydrocarbon chains about the chain axle
or of the end methyl groupe. This motion can ba atudied ueing NQES,
N M and NQR. NOES ie the moat direct of the three methode. The Inco-
herent NQCS apectrum ( oC S(U,tt)) for liquid cryetals, In which there
-12-
. - • 1is rotational diffusion with a aingla relaxation time, T D ( • DB
18)where 0R is the rotational diffusion coafficient), is given by
(B)
where $) eigniflea a convolution product, A(q) And B,(Q)e era
coefficients and •CaAc*i) « e Lorentziane whose width* are functions
of 0ft. UsingNQE3, Slnha at al ' have established tha presence of
rotational diffusion in HxBPA. Tha spectral linn shape (Fig.6) in
tha crystalline phase at 300K la that of tha experimental resolution
function wharaaa tha apectru* In tha aupercoolac* S phase at tha seas
teapsrature aaema to consist of an slastic peak •uparposed on a broad
hump, tha latter being due* to rotational diffusion (corraspondlng to
tha first and ftecond term in eq.(8)). Tha eleetic for* factor eaama
Fig.6 Time-of-flight spectra of neutronsscattered from HxBPA in the cry-stalline and S phases at T • 30OKand the scattering angle 9 « 70*.The eemple was,aligned in a mag-netic field H applied parallel to Q.
CHAMMIL
to indicate that thla Movanant la due to tha and hydrocarbon ohaina.
In tha liquid crystalline phasea of HxBPA, 10"t1aec X 'CJJ < 10 aee.
There la no dramatic change in f • •• °ne paaaaa from th» structured
S phase to the S. and nemetlc phaees.
\f
{-13-
(iii) Internal Uibrationai
The study of internal vibrations has been mainly done by infra-22 )
red and Raman suectroscopy . such studies are particularly useful
for atudyinu temperature dependence of different modes near phase
transitions. The chdnyss that occur in the vibrational spectrum at
• phase transition helps us to gat some information on>(l) the
changes of environment that occur for certain parts of the molecule
end J(2) change in conformation of the hydrocarbon chains at the
transition. Tha difference between the Raman spectra for the S R and
S H p h e s e s o f HxBPA 6' showing environmental changes for the hydro-
carbon chains is an example of the former whereas the Raman spectral
evidence indicating the melting of hydrocarbon chains in phosphoii-23 )pid-water system ' is an example of the .Uitter.
Phase Transitions
Liquid crystals are extremely interesting from the point of view
of basic research, because of the rich variety of phase transitions
occuring in them. These transitions can be brought about not only by
• temperature change but also by subjecting the LC to an electric or
Magnetic field, or by applying a pressure to it. We shall only be
considering the temperature induced phase treneitione here.
A phase transition will, In general involve a break-down of some
kind of order (p ) present in the low temperature phase. Thus
p o _ * o .. T -* T t r
where Tfcii is the transition temperature. The phase transition tempera-
tures cen be obtained using Differential Scanning Celorimetry (DSC) or
by texture studies. One can obtain a scheme of traneitions for a
given compound using these two Methods. The heats of transformation,
A H and the transition entropy, A.S(- ^H/Tfcr; can also be obtained
from the OSC Measurements. Tha transition temperatures far the SC~N,
Sc-I and N-I transitions and A S g _N obtained by DSC ' for various
-14-
members of the series,
cn H2 1 ° -<©>"CH " N-<5>'C00H,
are shown as a function of n in Fig.7. It can be observed that
A S C for the hexyl and haptyi. compounds is very small, showingC
that these transitions are of a weakly first order nature. In such
a case, one would expect that correlations between fluctuations of
the relevant order parameters), ^[SPo | y would become quite
strong in the vicinity of the phase transition.
The type of order(s) present in the different LC phases and the
corresponding order parameter(s) p are given in Table I.
TABLE I
PhriSB
Nematic
StructuredSweeties•g* s(bi.xf.i)
Order
Urientatiunal order
Nematic order+ 10-positional orderperpendicular to amecticplanes (.It).
Smectic k order4- Rotational order
Smectic C order• in-plane 20-poaitional order.In the uniaxial cases,the rotational orderis absent.
po
n, T
d) is tha angla between n and the long axis of a Molecule. t(B ),
(o(t) .) has been defined by McMillan '. X is a position vector
in tha sweetie plane and K. la a reciprocal lattice vector of tha
in~plane 20-1stties. "
-15-
There is no single theory which can pradict tha temperature
dependence of tha order parameter In all tha liquid crystalline
phasaa. A wean field theory to account for tha H-l transition waa
proposed by Haier-Saupe '. Mcrtiilan(N) and Mayer and ncHillan(fln
using a mean field approximation and certain modal interactions
proposed,(1) a theory for tha S -N tranaitiona ' t*nd>(2) a theory26 i
for tranaitiona between Su, S_, S_ and S. phaseste o L *
Tha tempera-
tura dependence of the order parameter(a), tha apacific heat, C^,
and tha entropy, S, have baan calculated in tha different phases,
using theae theories* It is found that S^-H transition in a homo-
logous series of compound* can changa from aacond to firat order,
aa tha length of the end hydrocarbon chain increaaes. Z\ S_ andA
T- u calculated from ftcflillan's theory for tha relevant compounda
are ahown aa dot dashed linea in Fig.7. Although tha experimental
IAS(Cal/Mol* d*g)
fig.? The transition entropy, & S andthe transition temperatures, T. ,.for transitions S -N and N-l,The solid linea a£e guidea to theeye whereas the dashed linea arecurves calculated from flcrtillan1*theory for the SA-N transition.
t n n
Measurements are for an S-.-N transition, the agreement between theory
and experiment le fairly good, (in theory ' predicts transitions
SM-Sa and S^S. to be of the second order while the other four tran-
sitiona involving these four phases are first order in nature. The
SC-SA transition has indeed been found to be of the sscond order in
T88A.28) The temperature dependence of £>fc calculated from Wl .theory
is shown as e solid line in rig.5. The egreement between theory and
exparimttntal results is poor, as the theory predicts a uaaker first
order transition then that observed by axparimant. This ia also
seen in tha values obtained for &$s _s , with '£±S (Ml theory)
-" 0.5 A s . H A
*•* exp
Tha above mentioned theories do nut take into account fluctua-
tions of the ordsr parametars which are of considerable importance
in the neighbourhood of not only a second order phase transition
but also of a uaakly firat order transition. Correlations bttwaan
fluctuations, ^ISf^l have bean calculated by da Gannas ' near such
transitions, using a Landau-type theory. The correlations than have
an Ornatein-Zernike form,
where < ia the correlation length varying uith tsmpecature as,
V m 1/2 in tha Landau theory. T • T except for transition N-I,c 6)
whera it is aqua! to T» which it sliyhtly smaller than T '•
Depending on the order parameter involved in the transition, one can
use a suitable experimental technique for measuring *£ (T). For
example, if positional order is involved, X-ray or neutron diffraction
measurements can be uaed or if orientations! or rotational order ia
involved light scattering measurements can be uaed to measure ~~% (T).29 )
For the transition N-I, V ia found to be equal to V2 for T S T* \
Instabilities
Various kinds of instabilities can be inducsd in nematic liquid
crystals (NIC) '. We will consider hare only tha e>?ctrohydrodynamic
instabilities which occur in a NLC with A^:<O and &tr^O , whsn •n31 \
•l#ctric fi.id !• appliBd to it. Th«s« «r« tht,(l) Williams Domains
-17-
(eonvective) instability and,(2) turbulanca.
Let u« consider a thin film (thickneae tf <^ 100 /*•) of a
nematic with &€-<p and A<J")o (egi «BBA), held between two glaaa
•ubatrataa with a conducting coating (Fig.8), tha NLC molecules being
•lignad parallal to the substrates in the X-dirsction. The aampla
appears dark when viewed under a microscope between croaaed pdlaroids,
with the polarization of one of the polaroids beiny parallel to the
X-axia. If a voltege, V, ia applied across the NLC film along the
2-axia, for incraaeing valuea of V, one obeervee the following
things: (1) For V smaller than a certain threshold voltage \l^, no
change occurs in the NLC, the dielectric aniaatropy favouring the
already existing alignment along the X-axis, (2) When \l • v , one
obeervea the formation of William* domain* (Fig.9) which are due to
periodic distortion of the nematic align*i«nt. The domain* are
aligned parallel to Y-axia. With a further increase of voltage
above V,« these domaina remain unchanged until a second threehold
ConductingContlng
Glot*Subttralt
NLC ( Mylar[ Light Spactf
bMm
WILLIAMS DOMAINS
v>v,
Sandwich cell with a homogeneouslyaligned sample of a numatic. P andA refer to the polariswr and analyser(they are crossed).
fiy.9 Williams Domain* in asandwich cell.
voltage, V. r ia reeched. At V • V t u r b, tha oomains start becoming
diaordered and mobile and tha-flow becomes turbulent.
The onset of Williams domair.s instability has been explained
by Half rich ' on the basis of cJ.iarga transport end convection
affects. If ons considers the situation when the molecular align-
ment ia perturbed by a small periodic diatortion of thu bending
type considered to O B only a function of x. The increase in the
alastic energy due to the diatortion gives rise to an elastic res-
toring force, since & < r ^ o , there is a current component along
the X-directlon which leads to a charge segregation^ and a field
S C associated with it. The NLC molecules tend to be normal to tha
total field E. + S £ and this electrostatic torque increases the ini-
tial distortion. Tha applied field acting on tha space charges
causes a material flow in alternating directions (Fig«9). This flow
in turn leads to A hydrodynamic torque which tends to increase the
diatortion. At the threshold field t>. the rapturing elastic torque
ia balanced by the diatorting electroatatic and hydcodynamic torques.
Tha threshold voltage V ( - £1t . ) ia given by
where K1 and >\( are tha viscosity coefficients and K 3 3 is tha
elastic modulus far tha bend distortions. It ia interesting to nota
that V ia independent of t. and is dependent only on the ratio,
®\C-t at conductivities and not on their magnitude. Uhan V * V.,33 )
domains are formed and their apacing ia equal to tf. Penz and Ford '
have assumed tha diatortion angle to be a function of both x and z.
They find that higher order instabilities can set in at «n a nVj,
where n • 1,2,3. , and the corresponding domain apacinga wouldOl' (tf/f)« Ptm and Ford auggest that tha intervention of a second
inatability explains tha onaet of turbulences, i.e. W t y r b • u2
Thaaa inatabilities have baan studied by several workers. How-
ever, not Many experiments hava baan dona so far to obaatva tha phaaa
-1:.-
transltional aapacta (if any ara praaent) of auch inetabilitlaa.34 )
Some neutron acattarlng experiments hava bean carried out to
atudy tha bahawiaur of tha ordar parameter (fluid valooity) and
its time-dependent fluctuation* in the vicinity of tha Rayleigh-
Banard instability (an instability, somewhat similar to tha Williamt
Domain* Instability; in tha NLC, PA A. liahta and coworkere35" 6 '
hava triad to study tha William* domain •Transition* (WOT) in tha
NLC* flBBA, by(small anyla light-scattering Maasuremanta (Fig.9).
V, 2 6 Volta for PIBBA. A larga increase in tha scattered lighti ^
intanaity ia observed for V \£ V. for small scattering angles (d<^5 ).
It ia alao observed that near WOT there ara vary larga but slow fluct-
uations of the aeatterad intanaity indicating parhapa that thsae slow
fluctuationa play a dominant part in tha onset of the Williams Domains
Instability in tha NLC.
Several intaraating questions concarnlng tha phase transitional
aapacta of instabilitiaa in NLCs ara, aa yat unanswered. Tha answers,
whan found, will shed light on tha processes responsible for tha onsat
of similar instabilities, not only in neraatic liquid crystals but also
in many other systems.
K. Uaha Oaniz
1} W.H. da Jau and 0. Van dar Veen, Phillipa Res. Repte. 27,, 172(1972).
2) G.T. Stewart in •Ordarad Fluids and Liquid Crystals', Advancesin Chemistry Sariea £3,,P*141, td.R.F. Gould, American ChemicalSociaty, Waahinyton O.C. (1967).
3) G.T. Steward in 'Liquid Crystals' £, Part I, p.75, £d. G.H. Brown,Gordon and Breach, Naw fork, (1969).
4) W. Elaer and R.O. Ennulat, in 'Advancaa in Liquid Cryatala',Vol.2, p.73, Ed. G.H. Brown, Academic Preaa, Inc., Naw York, (1976).
5) A. Oa Uries, J. Phys. (Paris) 36., C1, 1 (1975).6) P.G. da Gannaa «Tha Physics of Liquid Cryatala*, Claradon Praas,
Oxford (1974).7) J.L. banning, Appl. Phya. Latt. 21> 1 7 3 (1972).8) K. Uaha Oaniz, T.K. Bhattacharya and C. rtanohar, Proc. Nucl. Phya.
and aolid itata Phys. (India), l££, 299 (1975).9) T.K. Bhattacharya, Private Communication.
10) L.A. Goodman, RCA Review, 35., 447 (1974).11) H. Sackmann and 0. Oeraus, Plol. CrySt. and Liq. Cryst. 21.
239 (1973).12) A.I. Mehta and K. Us ha Oeniz, Private Communication.13) K. Usha Oeniz, A.S, Paranjpe, P.S. Parvathanathan, £.6. Plirza
and A.I. flehta, To be published in Nuclear Physics and Solidstate Physics (India), 2Q£ (1977).
14) A. Oe Uries, Mol. Cryst. and Liq. Cryat. 1J_, 361 (1970).15) K. Usha Oeniz, U.R.K. Rao, A.I. Plants, A.b. Paranjpe and P.S.
Parvathdnathan, Mol. Cryst. and Lit). Crytst. 42,, 1137 (1977).16) K. Usha Deniz, A.I. Flehta, U.R.K. Rao, P.a. Parvathanathan and
M.S. paranjpe, Phys. Lett. 59A, 203 (1976).17) K. Usha Oeniz, A.I. Mehta, U.K.K. Rao, P.a. Parvathanathan and
A.a. Paranjpe, To be published in Nucl. Phys. and Solid atataPhys. (India), 20£ (1977).
18) A.3. Dianoux and F. Volino, Nyutron Inelastic scattering,Vienna (1977), IAtA-3lt-219/72.
19) G.3. Kruger, H. bpiesucks and R. Van Steenwinkel, 3. Phys.(Paris) 37., C3-123 (197(i).
20) B. Corner, 3. Ooucet, l«l. Lambert, A.II, Levelut and P. Porquat,Neutron Inelastic Scattering, Vienna (1977), IAEA-SI1-219/102.
21) i>.K. Sinha, K. Usha Oeniz, C. Venkataraman, B.A. Dasannacharya,A.a. Paranjpe and P.b. Parvathanathan, Nucl* Phya. and Solidstate Phys. (Indiajj ijjC., 197 (1973).
22) B.J. Bulkin, in 'Advances in Liquid Crystals*, Vol.2, p.199,Id. G.H. Brown, Academic Press, Inc., New York, 1976.
26) 6.J. Bulkin and N. Krishnamachari, 3. Amer. Chem. aoc. 94_,1109 (1972).
24) U.L. I«lcf1illan, Phya. Rev. 4 A, 1238 (1971).25) W.L. ncHillan, Phys. Rev. B A, 1921 (1973).26) R.3. Flayer and IX.L. ncPliUsm, Phys. Kav. 9 A, 899 (1974).27) U. Maier and A. Saupe, I, Naturforach, 13_~A, 564 (1958)| U A,
882 (1959)j IS A, 287 (I960).28) 3.1*1. Schnur, 3.P. Sheridan and fl. Fontana, in 'Liquid Cryatala*,
Pramana Supplement, p.175, Ed. 3. Chandrasekhar,(1974),29) 3.D. Litster in 'Critifcal Phenomena', p.393, Ed. R. C. Plilla,
McGraw-Hill, New York(1965).30) C. Guyon in 'Fluctuations, Instabilitiaa and Phaaa Tranaition',
p.295, Ed. T. Riste, Plenum Preaa, New York (1975).31) R. Williams, 3. Chem. Phys. 39_, 384 (1963).32) W. Helfrlch, 3. Chem. Phya. 51_, 4092 (1969).33) P.A. Penz and G.W. Ford, Phya. Rev. 6, A, 414 (1972).34) T. Riate, K. Qtnes and H. Bjerrum noTler, Neutron Inelaatic
Scattering, Vienna (1977), IAtA-i|<|-219/132.35) A.I. Plehta, Private Communication.36) K. Ueha Oeniz and A.I. Ftohta, Nucl. Phya. and Solid Stats
Phya. (India), 19£, 243 (1976).
-21-
B. HUCLEAR PHYSICS
Hesaarch work at the Van de Greeff Laboratory haa covered
areas of traditional nuclear physics, aa wall aa now well established
field of material research utilising ion beams.
The (p»n) reaction studies on medium weight nuclei at sub
coulomb energies have been extended to two more nuclldes, This
programme has now cowered more than ten nuclldaa and the systematic
analysis of these results have yieldad valuable information on
optical parameters, reaction mechanisms, and spectrcoeopic Infor-
mation of isobaric analog states. Proton scattering studies also
have baen utilised to study the analog states. Resonance spectroscopy
through alpha scattering and (©(,» ) reactions form the other major
programmes of nuclear reaction experiment*.
Plon interaction with nuclei and few body problems Including
clustering phenomene are the major fields of investigation in nuclear
theory. Nuclear structure celculetione for nuclides around mass
number 50 are also underway,
Rutherford Back Scattering (RBS) method has baen utilised to
study defects In natal* Irradiated with ion beams and a detailed
analysis of radiation disorder Induced by such beams in various
metals has baan carried out. Such utilisation of Ion beam technique*
combined with the traditional metallurgical aethoda promises to bs
a very fruitful approach to invsatigatlone in the area of material
science*, and it Is planned to expand this and similar programmes
utilising both the present S.5 f!eV accelerator a* wall a* the 2 flU
tandem whan it becomes operational. '
-22-
1. Total (p.n? cross aectlon for tha Ca(p.ni Sc reaction(Gulzsr Singh*, S* Saini, S. Kailas, A. ChatterJae,n. Balakrithnen end M.K. Mehta)
The total (p,n) croaa eection excitation function for tha
Ca(ptn) Sc reaction haa been measured from £ *" 1.8 MeV to
S PleV in S keV atapa (48CaCo3 target, thicknaaa ~ 1 kaV for
2 MeU protoo) with a 4TT geometry neutron counter. Tha excita-
tion function shown in Figs. 1.1, 1.2 displayed a large number of
structures which could be attributed to fluctuationa of tha
Ericaon type. Tha fluctuation analysia baaed on paak counting
method ' yielded a value of 6+1 keV for the coherence width.
The isobaric Analog Resonances (IAS) ( Ca - Sc pair) at
£ ~ 1.98 and 3.9 Mel/ populated in thia reaction have bean
atudled in detail. The Rob»on-3ohnson ' analytia of che IAR at
3.9 Mel/ resulted in tha axtractlon of tha Spectroecoplc factor
(S ) for the parent atata in Ca. Tha S. value determined waan n
cloaa to unity and thia compared wall with the value extracted
from (d,p) atudiea on the aama target*
* DAE Raaaarch Scholar* Punjab Univacaity1} n.C. Braga Narcazzan and L. Milazzo Colll Prog. Nucl.
Phya. 21 145 (1969)2) K.K. Sekharan and U.K. nehta, Proc. Int. Conf. on r.-opertlea
of Nuclear Statea, (1969) p. 7633) S. Kailaa at al., Nucl. Phya. a Solid State Phya. (lndj,a)
168. 8 (1975)
• • aC* CtuCcn •rf •ct» *-»
: !:xnHe* O0 3
• rRa 39 mm i
TOTAL (p.n) CROSS SECTION (mb)-TOTAL (p,n) CROSS SECTION (mb)-
o
a H-
o «r3 H-O i -< 3
(II C
3 ID• H-»» 3
3 •
• -»
c
o
O
SCo
n
O
c
n
o
3-
CD
CDW
o
TOTAL ( p , n ) CROSS SECTION (mb)- TOTAL (p,n) CROSS SECTI0N(m»-
-24-
2. Itobarlc AnaloQ Resonances (1AR) in the Se(p.n) Brreaction.' (S. Kailaa, fl.K. flehta, Y«.t» •V—jgi*, N. Vsarbahu*,N.K. Ga guly? T.K. Bhattacharjee*)
61 00 80
The Isobaric Analog atatea in Br populated in the Se(p,n) Br
reaction ae compound nuclear resonances have been studied utilising
the 4 Tr neutron counter and thin target technique. The experiment
involved the measurement of total (p,n) cross section excitation
function in 5 kaV steps from threshold upto «* 5.4 l*teV bombarding
energy. The measured excitation function for the Se(p(n) Br
reaction along with the prominent IARs measured in the present work
ie shown in Tig.2 The detailed shape analysis following the procedure
sin&
320
280
240
200
160c.120a
IARS IN 80Se(p,n) 80Br REACTlOWi
{RELATIVE ERROR t s *PROTON OPTICAL PARAMETERSVftu60.l-.6E RR.1.17 a n .0 .75V, ,3E Ft, .1.32 a , • 0.45
~ - THEORETICAL FIT USW»ROBSON JOHNSON PROCEDURE
3.6 3.9 4.0 4.1 4.2 4.3' 4:4 4.5 4.6 4.7 48 49 5.0 5.1 5.2 5.3Ep-PROTON ENERGY (M»V)-LAB
The excitation function for the Se(p,n) Br reaction
measured upto 5.4 MeV bombarding energy. The IARS art
indicated by arrows. The continuous curves over the IARs
are obtained from shaft* f i t t ing procedure.
-25-
of Kailaa et al 1' or tha IARS yielded tha proton partial width
'(• and apactroacopic factor Sn for the ralavant compound and
parent nuclear atataa reapsctively. The results of tha analyaie
are liated in Table.2.Mt ia found that the Sn values obtained
exclusively from (p,n) work compares favourably with that extracted
2)from (p,p) ' and (d,p) works.
• Members of the VEC Project, BARC1) S. Kailas et al., Nucl. Phys. Solid State Phya. (India)
1BB. 8 (1975)2) O.P. Balamuth et al., Phya. Rev. V70.,995 (1968)
Tabla 2.1.
The results of the' shape analysis of Isobaric Analog
Resonances measured in Se(p,n) Br reaction.
o(l"leV)
3.785
4.267
4.813
4.956
5.032
5.198
(keV)
33.+2
6+1
1 1 *
19.+2
2 6 i 2
7.5+2
(keW)
2.3^.1
,80i.13
1.3±.1
8.1£.9
3.8+.3
.9 2.7+1.0
Sp,n
.22
.026
.15
.32
.32
.022
Sd,p
.30
.045
.26
.64
.40
.075
PtP
.09
-
.18
.85
.41
-26-
3. Alpha Scattering from Ca'(A. Chatterjee, S. Saini,S. Kail as, 1*1* Salakrishnan and U.K. ftehte).
In continuation of our earlier measurements ' of the exci-
tation function of the reaction Ca(0C,(X.) Ca, the data has
been extended to the lower enargiea upto 3 Plat/ which completes
the excitation function from 3 l*leV to 5 Met/ in steps of 5 keV at
the following lab. anglesi 64.3°, 120.3°, 136.9° and 165.0°.
Preliminary fits to the data haue been attempted using
single-level and single-channel R-Matrix calculations on the
44basis of some levels in the compound nucleus Ti which have been
confirmed in (cC,Y) work quoted in the literature . Multi-
level, multichannel R-matrix calculations are underway.
1J S. Saini et al., Nuclear Physics end Solid State Physics(India) JJ3B, 16 (1975).
2) Oixon et al. Phye. Rev. £15 fi896 (1977)
4. Excitation of Shape Isomars in the Uranium Isotopes(A.L. Athougies*, A. Chattsrjee, S. Kailas and B.K. flehte)
The delayed fission cross-sections for the 14.S MeV neutron
236 235bombardment of U and U has been measured using plastic track
dstectors in a recoil geometry '. The experimental arrangement
has an annular detector placed in the sane plans as the target
and a catcher foil some distance sway from the target. The annular
detector is effectively shsildsd fron prompt fissions but can
-27-
datact dalayad fiaaion fragments from isomsra dacaying eithar
in flight or aftar reaching the catcher foil. Thara are conai-
darabla arrora because of the large background and low neutron
flux. The raaulta indicate a cross-section of (43+15) * b for
238U(n,n')338l"u and an uppar limit ~< 150 /* b for 235U(n,Y )236"u.
A atatiatical model calculation has baen Made for raactiona
populating the uranium iaomara. The modal takea into account the
double hump potential energy vereua deformation curve with barrier
parameters quoted in the literature. After the formation of the
Initial compound state, dacaya by barrlei: penetration, neutron
emission and gamma amiaaion are takan into account. The sxproaaiona
for the widths for these decay modes involve the level danaitlaa
of the final atataa. In earlier work level denaitiaa given by
Gilbert end Cameron and a eingla particle laval danalty have
been ueed. U» have uaad a recent semi-empirical level denaity
formula given by Ramaaurthy at al. '. Thia formula tikea into
account the affect of ahell correction on the laval denaity and
ita 'washing out1 at high excitation energy* Our reaulte ere In
fair agreement with the available experimental croae-eectiane for
the neutron induced reactlonef but indicate that the data on
deuteron Induced reactiona cannot ba explained on the baala of
the commonly aaaumed reaction mechanisms.
* Research studenttRenaalaer Polytechnic Inatituta1} A. ChatterJee, at a., Nucl. Phya. Solid State Phye. (India) .19B
(1976) and to be published2) V.S. Ramamurthy at. al. Physical Review C (to ba published).
-28-
5. Further studies on the Resonances In the reaction S(0C,V) Ar.(D.R. Chakrabe-ty, M.A. Eswaran, N.L. Ragoouansi and H.H. Ora).
In continuation of the studies reported earlier on the exci-
tation region 10.3 to 11.1 PleV in Ar through the radiative capture
32of alpha particles on S the following detailed inuestigationB of
the resonances were made during the year.
1. Angular distributions of 10.33S and 10.65 MeV gamma raya arising
from the decays, to the ground state, of the resonances, at bombard-
ing energies Eft * 4.15 and 4.51 Mel/, were measured with a Nal(Tl)
spectrometer. These data and the calculated curves for various
assumed spins of the resonances are shown in fig.5.1. These results
establish unambiguously the spins of the E~ « 4.15 l*leV and 4.51 flat/
resonances as 2 + and 1~ respectively.
2. Angular distribution measurements of 8.52 MeV V -ray arising
from the decay of the resonance at Eg * 4.33 ReV (£„ u 10.49 PleV)
•re shown in fig.5.2, along with the A analysis for various assumed
spins of the resonance and for all possible values of the multipole
mixing ratio parameter (tan 5 ) .
At this resonance the decay mode has also been Investigated
by a 30 c.c. Gs(li) detector. It is found that this resonance
decays to the 4.18 MsV (3~) state in addition to the branch to the
1.97 fleV (2+) state.
3. Absolute resonance strengths of all the resonance, studied
in the range E • 4 to 5 Mev have been determined by comparison
ANGULAR DISTRIBUTION OF T-RAYSFROM RESONANCES IN THE REACTION
3 2 S & T ) 3 6 A T .
0.0 0.5 1.0Cos26—-
100.0 -
-90 -65 0 45 90S —•(DEGREES)
Fij.5.2. ANGULAR DISTRIBUTION OFT-RAY FROM RESONANCE IN
-30-
Tabla 5.1
(niv)
4.149
4.33
4.45
4.51
4.66
4.74
4.95
Ex(PI.V)
10.33
10.49
10.60
10.65
10.78
10.85
11.04
(all+10kaV)
2 +
3"
-
1 "
-
-
Transition
O+(G.S.)
2+(1.97)
3"(4.18)
2 + ( i .97)
O+(G.S.)
2 + (L97)
2 + ( i .97)
O+(G.S.)
S m ( 2 3 + 1 '
1.05
1.18
1.06
0.66
0.66
1.33
0.29
1.39
0.23.
(•11 +40*)
T polarity
E2
E1
M1
-
E1 2
P11 (If 2+) 0
Ei(t3~) 3
-
-
: ^
0.3
3.6 x 10~4
.03
-
.45x10~4
.017
,5x10"4
-
•
-
T
.
1
-
(D
(D
-
-
-
-21-
with the lowar energy resonances of known strangfliaV The1' '
resonance strength measurement and the angular distribution data
enable a 7 assignment of 3* for the 10*49 MsV state, further
from the strengths of electric and magnetic dipole traniaitiona
36from the resonances at 10.49 and 10.65 MeV excitation in Ar,
these states can be assigned an iaospin value of T «• 1. These
results are listed in Teble&l.
The 10.49 MeU ( 7 • 3", T « 1) and 10.65 ReV (7*" m 1*( T • 1)
36states identified in this work in Ar are conjectured to correspond
to the 3" and 1~ states with T - 1 expected at 10.31 and 10.64 »eV
2)
excitation according to the calculation of Erne for the negative
parity states on the bssis of shall model calculations with ons
nuclson excited to the f<*/2 t n - 1 1» Some of thsse results ware also
reported in ref. 3*
1) Annual Report, Nuclear Physics Oivision, BARC-B7B (1976)*
2) F,C. Erne, Nucl. Phys. 84 91 (1966)3) N.A. Eswsran, D.R. Chakrabarty, N.L. Ragoowansi, Bull. Am,
Phys. Soc. 2± No. 8 p. 997 (1976) (Presented at the NuclearPhysics meeting of the American Physicel Society at EsstLansing, Michigan, October (1976).
6. Pnterinlaation of the Naturs of Oefacta in Irradiated fgt?:1."by Rutharford-Backacatterinq. (M.K. Agrawal* and D.K. Sood)
Tha radiation damage in metals is largely in the form of
and/or interstitial clusters of point defects, which at high enough
doses saturate to produce complex dislocation networks. It is
important to establish the nature of clusters - i,e, whs-chs;: ti~.;:-y '-•'-'-r
of vacancy or of interstitial type. This has been accomplished fchijr
1)far by rather elaborate contrast analysis techniques ' employing
Transmission Electron Microscopy (TEN). Recently, Rutherford 'i-c--
scattering (RBS) and channeling techniques have been U3ed extensive;
2 3)e.g. ' ' to study some aspects of radiation damage in metala* It har
been generally recognised that the nature of defect clusters cannot
/ ,4)
be determined by RBS techniques. However, Qusre • has suggoatea the:
it may be possible to determine the nature of defect clusters by
observing the dependence of dechannellng cross-section «^ on ths
probing ion energy, E. The calculated, ^ shows widely different1/2
dependences on energy, such as € dependence for dislocation loops
where distortion effects dominate, E° dependence for cavities or oas
bubbles and an E ' dependence for interstitial atoms.
The present work uas undertaken to examine ths capability of
the RBS techniqua to determine the nature of defect clusters in mata.lr.
based on these considerations. In order to ensure mainly one type c';'
defect clusters and. to avoid impurity-defect interaction effects? sess-
ion implantation** (1 x 1Q16Cu+ ions/cm2 at 200 keV) in single
copper uaa chosm for this study. The earlier TEM studies ' have
shown that mainly interstitial clusters are present in self
4)ion irradiated copper at high doaes. One should therefore expect '
_1/2 _,primarily an E ' dependence for G\ Corresponding to interstitial
atoms with some contribution from lattice distortion type dechanneling
RB5 and channeling measurements uare dons with a well collifnated
beam of helium ions. The back-scattered helium particles were
detected at 164° using a surface barrier detector and usual electro-
nics. The Harwell standard target of Bi implanted in Si was used
for energy calibration. The crystal was aligned along a ^110 >
direction using a two axis goniometer, fteasurements of tha aligned
and random spectra were made at three bombarding energies - 2.000,
2.900 and 3.500 CleV for an integrated helium dose of 15 f*"c each.
The results ere shown in fig.(.1 where the measured dachanneled
fraction, X ( = aligned yield/random yield) is plotted vs. ths
6)
channel number. 'Stopping cross-sections of Ziegler and Chu are
used for conversion of channel numbers to depth scale. * Knees' are
observed et all the thxee bombarding energies giving e similar
maximum dieorder depth. The averaged X_ m 4273 A is much laSger
then the LSS projected range of 459 A for 200 keV Cu ions in2)
copper. Following the analysis of Pronko and Oerkle , a tote"
damege per unit length, II £ is determined from the slope of the
line fitting data pointa between the Cu surface and the 'knee1
in Fig.4.1 at eeoh helium energy. The results are shown in Fig.(.2,
which in effect shows the varietion of <H with bombarding helium
energy since N (the number of defect clusters/cm ) is a conetant.
20 200 keV Cu* in COPPERDOSE 7*K>'6 ions/cmJ
s
I
15
10-
1000 2.000 3.000 4.000
HELIUM ENERGY (MeV)
9. 6.2 Variation of <Tj with bombarding energy
no m
6.1 RBS spectra at bombarding helium energy of
a) 2.000 MeV, b) 2.900 CleV and c) 3.5Q0
M n e poseing through the experimonfecl points is the cal-
dependence curve noinialieed at 2.COO P!F>V. The dashed
and clotted lines show similar normalised colouirted curves for £"
1/2and £' energy dependence raep9ct.ivsj.ye The closa agreement of
date points in fig.6,2 with a i£ •"" curve 8!TC:-;;I •;•.;•,>:;; th» rie ' i."r
cluatere are of interstitial typs. It :'.s au.?prising, hoW3ua?5
1/2that ro diotartion Gffecta ceusing eii E' dapsndance ars eean,
In uiaw of ths eariisr TEP1 results' r {-.ha p?osai"i;:. work hsa thaso-*
fore shown that it is possible to determine fc/is rsaturs of defect
cluatsra by observing the energy dopandencB of fcha dochsnnaling
crosa-eection tfj t by R8S fcsohniques.
* Visiting Research Fallow frou the Deportment o? PhyaicerPunjab University, Chandigarh 160 0?4
•• Performed et A.E.R.E. Herwell (UcK,)1) n. Ruhle, PI. Uilken9 and V, Essra'ann,, Phys. Stat. Sol. 11,
819 (1965)2) Pj,P, Pronko and K.L. FlerklG, In Applications, of Ion Beams to
PWtaI» edited by S.T. Picraux, E0P,, EsrWisse and F»L. Vook(Plenum, New York, 1974) p* 481
3) O.K. Sood and G. Daarncleyj; 3. vac0 Sci0 Toohnol. 22.'463 (1975)
4) V. Qua're', Rado Effects 28J 253 (1976)5) G. Dearnaley at al,in Ion Implantation (North Holland, 1973)
p. 168.6) 3.F. Zieglsr and U.K. Chu, Atonic Defca and Nuclear Data
Tables ^3, 463 (1974),
-36-
7. Radiation Disorder In Metals (O.K. Soori and G. riaemaley*) .
Our previoue work on implantation of several ions in single
crystals of Copper ' , Aluminium ' end Nickel ' showed presence
of a discordered zone extending upto many times the ion range.
Similar effect has been reported ' in other metals. The enoma-
1 2;
lously deep disorder waa explained by Sood and Dearnaley ' in
terms of two possible mechaniems based on defect diffusion and
macroscopic plastic flow during implantation. Recently, Borders
and Poata ' have instead proposed that euch a deep disorder is
a result of inadvertent Implanted ion channeling} and that tha
measured dechannsllng is associated with the implanted impurity
itself and not with the host lattice damage. The present work on
a fresh analysis of out1 previous data ' on 27 different ions
implanted in Cu, Al and Ni was undertaken in order to examine the
generel validity of their model.1-3}
All the implantations ' were performed about 7* off axle
to approximately produce the random direction implants. In order
to estimate the effect of a email fraction of implanted ione which
could etill get channeled we follow the procedure of Borders and
Poate ' for deta analysis. For the hoet scattoring, either the
aligned yield or ite ratio with the random yield is plotted as a
function of channel number (depth). FigJ&Jshows such a typical
plot for a random implant of Ru in copper. A well defined 'knee'
ie observed at a depth, X_ • 5230 A. The position of the 'knee',
X^, ia defined as the maximum disorder depth which signifies tha
end of the disorder zone. The impurity (Ru) scattering yield io
plotted in the inset, the abscissa of which is normalised in such
a way that the impurity (Ru) surface scattering ia at the same
anergy (channel number) as the host (Cu) surface scattering*
A log scale is chosen for the ordinate in the In9et. A maximum
range, R is defined as shown in the inset of FigZIat ths inter-FT18X
section of the channeling tail with the estimated background leusl?
The moan range is measured from the peak position of Lhe impurity
profile. Table shows the results for several implantad species
in Cu and Ni. In case of Al, for all the ions implanted, X_ was
found to be v> R . Table shows the effect on increasing tha dose
of 150 keV do ions in copper.
Now, R indicates the end of implanted layer beyond which
no implanted atoms are present. So, if the model of Borders and
Poate ' is right, one should observe Xn to be ^ R , Although
we observe this quality for all ions implanted in Al8 Tables 7tl,*J»2.
show that X- is significantly much greater than R in several
cases, Majority of the entries in the last columns of tables 74,7-Z
may be seen to differ considerably from the typical experimental
depth resolution values listed in their first columns.. The dose
variation effects summarised in Table provide further contradiction
of their model7'.
17 + 2Fig^jshows the results for a high dose (1 x 10 Flo ions/cm )
implant in Cu. A 'knee' is seen and XQ is once again larger than
l l . .I. i • •
< * •
••••-.... 1 1 F" * • • » • • • • . I I *
;>
c
O
I I -
o
S 5 M
g : i ?
Mil fhi
i i.
! i
a.e£oncsia:
i—-1 *-
cra
eaT3Cra
a:
•arnnommn
Table '?•)
Analyois of Disorder in Implantad Layers,, Ion
dago 1 x 16"" ions/cnTo Random Implants
Host
Copper
<110>
Depth
Resolu-
tion v*
150-200 A
Nickel
<(i10> or
<100>
Depth
Resolution
v*1?5 A
Ion
Ry
Flo
Rb
Eu
Ce
Cs
Ta
Cd
Eu
Sn
£r
Ta
La
Energy(ketf)
300
150
250
300
300
300
200
300
3G0
300
300
200
30Q
L3S
361
276
475
363
363
400
k41
4?7
354
4in
33y
235
374
lisasuradRange(A)
530
681
315
435
435
383
265
R
3575
2458
2609
3106
3789
3S72
156 9
20 i A
\'!ZA
13-;?
376
1627
,555230
3?82
3 72?
3479
3BM
4005
2S07
241V
2122
1626
116£
1673
r -• - •
'iV,s>
<iQ3
'1 Hr
Do8« Dependence for 150 keV No* in Copper,o o
The LSS Range 276 A, Depth Resolution ^200 A
Oose(ions/cB.2)
MeasuredRange (8)
x o -(X)
10
10
10
16
17
Yield too ^2500 2060small
681
325
2998
1951
4360
3154
-620
1362
1203
• -40-
R . An interesting feature is the simultaneous occuranca of
a surface paak (at channel number 396) which climbs to a normalised
yield of 0.84 (opart circle points following this channel ars not
statistically significant being ratioa of vary amall numbers}, when
the tail cf this surface peak ia extrapolated (dotted line in
Fig.), Its intercept coincldas with R . Thus us have o varymax
clear manifestation of two types of dachanneling centres - 1 ) the
strain around the flo implanted atoms/clusters which cause tha
surface peak and 2) tha dieordered lattics atoms which produce
the 'knae'. Therefore the conclusion of Borders and Poets that
deehanneling ia aasociated with tha implanted impurity itself end
tot with the host lattice atoms is not quite Justified
* Atomic Energy Research establishment, Harwell (U.K.)1) D.K. Sood and G. Dsernaley, 3. Vac. St;i. Technoi, .12, 463 (1975)2) D.K. Sood and G. Oearnaley, in Applications of Ion Beams to
Hatsrials, 1975 edited by G. Carter, 3.S. Colligon andW.A. Grant (Ths Inst, of Physics London, 1976) p. 196.
3) D.K. Sood and G, Dearneley, NP and SSP Symposium, Calcutta1976 (to bs published)
4) Pi. Gettings, 0. Mayer and G. Linker, Rad. Effects 2±, 51 (1974)5) I. Nashiyama, p.p. Pronko and K.L. Herkle, Rad. Effects J29,
95 (1976)6) G.W, Bailson, G.U. Farmery and Ft.U. Thompson, Phye, Lett.
46A. 45 (1973)7) a.A. Borders and 3.PI. Poate, Phys. Rev. .I Bf 969 (1976)
8. A Study oT Molybdenum Implanted Copper by Scannlno ElectronMicroscope (D.K. Sood)
In our prBvioua work , anneal behaviour of a surface alloy
of Ho implanted in copper was studied in details by Rutherford
Backscattering and channeling of 3.5 Mel/ helium ions. Range dis-
tributions and substitutional fraction of the implanted Molybdenum
atoms ware studied as a function of isochronal anneal of the speci-
men. It was found (in Fig. 6 of Ref.1) that following an ennoal
at 900°C, the implanted Mo atoms moved suddenly towards the surface
and probably formed precipitatee there. This was accompanied by
an almost complete recovery of radiation disorder. In this paper
we present a study of such surface precipitates and the allied
radiation damage effects using a scanning electron microscope (SEi).
The specimens used in reference "i wars used for the present
work. The details of specimen preparation and o:' Implantation tilth
the Harwell 500-kV Cockcroft Walton accelerator are given therein K
Specimen No. 1 was implanted with 1 x 10 do ions/cm et 150 kaV
with substrate held at -130°C during implantation. It was then
annealed in vacuum ( £ 4 x 10 Tort) isochronally for 60 min at
400, 600, BOO and 900°C. The SEIt studies were then conducted using
the Scanning Electron Microscope at the Metallurgy Division.
Sample No. 2 was also < 1 1 0 ^ copper but it was implanted to
17 + 2a higher doaa « 1 x 10 Mo Ions/cm at room temperature at the
•ama energy. No anneal treatment was given prior to study with SEM.
SCO atudioa were made upto magnifications of 30000 x.
Specimen No. 1 ahows almost perfect cuboids (cube adgs about 0.7?
to 1.02 .m), very much like sugar cubes, Jutting out from the
substrate on the implanted region. These cuboids show very high
contrast implying that they are probably Flo tir:h z8neai. However?
Mo X-ray imaging doss not •bow any appreciable seggreg&tion of Me
in the cuboids. SEM on specimen No. 2 at higher dose doe3 not
show any such cuboids. It is therefore concluded that the cuboids
are not due to Mo precipitates at the surface. Theae could
probably be oxide nuclei formed during oxidation1 at high tempera-
tures in very low oxygen pressure prevalent during vacuum anneal*
Similar observations in other metals havs been reported in
2 3}
literature ' . further work is now in progress to do the Oxygen-
x-ray imaging on specimen Mo. 1 and also on other specimens
implanted at 150, 250 and 350°C, to fix the origin of such cuboids*
No radiation damage effects are seen on specimen No. 1
in agreement with our previous study ', by Rutherford backecatteting.Sample No. 2 however shows substantial surface erosion effects
17+ 2attributed to sputtering at such high doses of 1x10 Fta ions/cm «
1) O.K. Sood and G. Dearnaley, in Applications of Ion Beams toMaterials, 1975 edited by G. Carter, 3.S. Colligon andtil.A. Grant (The Institute of Physics, London, 1976) p. 196.
2) R.E. Clausing, CO. NcHargue and 3.1. Spruiel l , 3. Nucl.Plater S3, 123 (1974)
3) K.R. Lawless, Rep. Prog. Phys. 37, 231 (1974)
-43-
9. Final State Intraction in Plon Absorption on He (B.K. 3ain)
With a motivation to understand the interaction of pions with
the nucleus, study has been made of the absorption of negative pione on
He. The reactions resulting from this capture, which sue have analysed
" 3
ara TT + He-# n+d and n+n+p. These reactions have bsen analysed
earlier , but in them the final state interaction have been neglected
and results are not reported for kinematically different experimental
situations. The Interaction vertex of the pion absorption is described
by the "two nucleon" model, where it is asnumed that the capture
takes place on two nucleone. The Hamilton-Ian for this is taken to
be that described by Eckstein '. The final state interaction in n+d
channel is described by the potential V . which ie given as
where f ara the scattering amplitudes. Sines in the "two nucleon"
model final state interaction between the two nucleone which parti-
cipate in the absorption is already contained in the interaction
Hamiltonian, in the n+n+p branch, interaction of the spectator nuclson
only with the other nucleons need to b« considered. This is described
by an N-N potential which fits the effsctiwt range and the scattering
length '. Tha N-N and n-d wava functions in the final atate ara
-44-
dsacribed in the partial wave analysis.
Tor tha n+d branch the capture probability with and without
the final aLla interaction is 5.1 x 101S aec""1 nnd 5.5 x 10 *'
respectively. They do not differ much as the nd energy is high
( SS 130 WeV). The experimental capture probability is about 6.7 x
101 5
The proton momentum 8pectrum for n+n+p branch is shown in flg.8,1,
for two extreme relative phases of the two terms in the Hamiltonien,
The rSI brings the results in better agreement with the experiments.
DW phase s-
PW1 phase =+1DWJ
V (3He)—Gaussian
200 300
kp (MeV/c)
400
T ig . 9.1 Proton momentum spectrum for n+n+ p branch
1) P.P. Divakaran, Phys. Rav. 221> B 3 8 7 (1965)A. figureau et a l . Nucl. Phys. Bi£ t 249 (1969)
2) S.G. Eckstein, Phys. Rav. .T29, 413 (1963)3) Warner at a l . , Nucl. Phys. A25S. 95 (1975)4) O.A. Zaimidoroga at a l . 3ETP 2±- 1111 (1967)
-45 -
10. Finite Range Distorted Wave Calculations for D(d,t)HReaction with ail the six Residual Interactions (A.K. Osinana N. Sarma)
The differential cross section for D(d,t)H reaction has
been of interest because of the simplicity of t.ho analysis of this
1) 2)four nucleon system '. It uas demonstrated esriia^"' thai; a zartt
range distorted wave calculation for 25.3 PleV reaction doea not
reproduce the observed angular distribution. A finite rerigs
distorted wave Born approximation (DtdBA) calculation has therefore
been performed including all the six residua.!, interactions between
the four nucleons. The exchange terms that arise from entisymma-
trisatlon of the wave functions are alao evaluated.
The differential dross section for the O(dft)H reaction is
written
where Kj , R-t are the wave numbers, A1^ , Pi the reduced
masses end Tj , X the spins ahd TOJ and vv^ the projections
associct.ad wi^h the incident and out going channels respectively.
The matrix element is given by
J »^r% * '
ty and ^f. are the initial and final state wave functions
obtained by solving the Schrodinger equation with the relevant d-d
-46-
10 20 30 40 50 60 70 80 90§ (degrees)
Fig. 10.1 Differential cross section of the O(d,,t)H reaction at 25.3 flel'
The daahtd lint (—) represents a plane wawo calculation and
the solid lins { ) the results of a distorted uava calcu-
lation. The calculated curves are normalised to experiment
at 15°.
and p-t optical potentials and corresponding oouno uaue
y% are the strong short range residual interactions
nucleonst
The spatial integrals that appear in tno mstrJU elements
M,. (jk) have redundant coordlnatas. A separation into Inde-
pendent coordinates is not possible with the uevs functions chosen
for the dsuteron and triton. The evaluation is therafcre simpli-
fied by expanding the various functions as sums of Gsuasiansc
The distorted wave functions for ths initial and finei-
d-d and p-t optical potentials respectively have been expanded in
terms of partial waves. In order to reduce the numb si- of pertisl
waves a prescription is usod that partial waves oF higher angular
momentum, £ *> L era unaffected by the optics'1 potential.- i.e.i fnsx
the distorted wave functions are expressed as
DU( computed) « PW +• a X (DU{^ ) - PW( £ } ).
It has been found that en angular momentum cut off L r.i 5
is sufficient to account for distortions, the higher partial wavsa
are treated in the plane wave limit. Tho angular distributions
computed with distorted 8fid with plane waves ers compared with
experimen^fig. 10.i] The deuteron wave function ia of the Huifchsn
form with parameters that reproduce the free deuteron radiua<>
The plane wave calculation does not reproduce the 37.5° monimum
in the angular distribution} the inclusion of distortions.changes
the shops profoundly and the minimum appears, albeit at e higher
angle.
-48-
6
2 -
10 20 30 40 50 60 70 80 90
*c.m.
Tig. 10.2 Effact of incraaaing dauteron aiza on tha angular distribution
of tha D(d,t)H raaction aa computsd in DUBA. Free dsutron
1.88 "I C d - 4.15 fm), -,-.-| (Rd . 7.95 fm).
-49-
It is possible that in the proximity of another particle,,
tha dsuteron changes its Bizs. Such an effect, an enlargement
of the deutsron from a radius of 1.68 fm to 4.15 and 7.95 ffli ia
observed to sharpen the angular distribution both in Pti/BA and
DWBfl (fig, 10,2! However the minimum is not reproduced in DWBA
unlass the deutoron la expanded to unrealistic values.
The absolute cross section in the forward direction
(14.3°) ia —— s 23,5 mb/ar as againet the exparimsntalAn.
value of 16*4 mb/ar. The PWBA computations give a valud that
is 20 times higher.
The angular distributions have been found to ba relatively
insensitive to the form of nucleon-nucleon interaction as also
to the triton uavefunction. The inclusion of deuteron D-etate
as well as coupled channel wave functiona for tbe scattering
part of uave functions are expected to improve the agreement
further.
1) 3.E. 8roll«y, T.W. Putnam and L. RosenPhys. Rev. 107 (1957) 820
2) U.T. H. Van Oers and K.U. Brockman Or.Nucl. Phys. 48. (1963) 625
-50-
7311. Intermediate Structure trelom ths analogueSta4»a~ln • fta...
(C.V.K. Baoa, P.G. Setigeri, l/.d. Catar, S.tt. Bharethi* andA. Roy*)
72
Earlier studies on the inelastic scattering of protons from Ge
showed several resonances in energy regions in between and even below
the expected Isobaric Analogue states. The average separation of these
levels is about 100 times that expected from the usual level density
formulae. In ordar to establish that the observed structure are genuine
resonances and not fluctuations, a Ge (p,t" ) excitation function in
the energy range of E from 3.0 to 3,4 MeU has baen measured. SeveralP
resonances which are correlated with those observed in the inelastic
scattering have been found. A possible origin for these resonances
in terms of an excited deformed configuration of the nucleus, and the
attempts to experimentally verify this explanation are underway.
* Tata Institute of Fundamental Research, Bombay
12. Isobaric Analogue Resonances in Aa. (C.R. Ramasuamy*,N.G. Puttasuamy* and FI.G. Betigeri).
Excitation functions for the elastically scattered protons off
Ge at 90, 125, 149 and 165° lab angles have been measured in the
incident proton energy ranye of 3.9 - 5.3 Mat/ in stepa of 2 k«V, Th«
resonances in the excitation have been idantifiad as isobaric analogues
' 71
of lou lying bound states in Ge. The excitation functions at different
angles at each of the resonances have been analysed using ANSPEC to
evaluate E I , f" and •» . The proton reduced widths ate
resonance, • ,
-51-
comparsd with the neutron single particle spactrbscoplc factor as
obtained in Ge(d,p) Ge reaction . The couluffl(> energy for As
71Ge ie found to be (10.16) fteV.
* University of Bangalore
1) L.H. Goldman, Phys. Rev. J£5 (1968) 12Q3
13. Intermediate width Structures in Ti(p.n) V reactionexcitation function (S. Kailaa and M.K. Plehta)
The observation of Intermediate Width Structures (IWS) in
measured excitation function for the reaction Ti(p,n) V uas
reported earlier . A systematic analysis has been performed here
to confirm their existence and to predict their energy positions in
excitation function. An autocorrelation analysis of the fine structure
data of this reaction has confirmed the presence of modulating
structures of width t- 100 - r» 150 ketf over and above the fine
structures of width *> 3 kaV (Coherence width). Calculation of the
2)energy positions of IUS based on Izumo'e partial equilibrium model
has been carried out. The theoretically predicted values of their
positions agree fairly wall with that of the experimentally observed
gross structures .
1. 5. Kailas et al, Phye. Rev. Ci^t 17B9 (1975)
2. K. Izrumo, Prog. The Phys. 26, 807 (1961)
3. S. Kailas, Ph.O (Thesis), Bombay University, 1976 (Unpublished)
-52-
14. Nuclear Structure Calculations in 51V (S. Seini andPl.R. G u n y e * ) •
Various attampts hava been maae to axplain the recently accu-
mulated data on the nuclear propertiea of odd Vanadium isotopes in
terms of phenomenologlcal rotatlonrparticla coupling modal. The
results of such calculations depend vary sensitively on the para-
meters employed, indicatiny the necessity of performing microscopic
calculations with raalistic nucleon-nucleon interactions. The calcu-
lations In 51V reported hare are carried out in the framework of
Hartree-Fock projection formalism with tha bana-mlxing between the
lowest four intrinsic states. The affect of variation of the aingle
particle energies in tha pfl-shall configuration apace on the computed
nuclear properties Is also studied. The energy spectrum, static moments
and the electromagnetic transitions in'51V are well accounted by the
same set of single particle energies and the affective nucloon charges
employed in our earlier calculations- in ' V. The calculated
and the experimental spectrum is compared in fig. 14.1. Ths calcu-
lated electromagnetic properties of tha low lying negative parity states
in 51V are listed in Table 1 along with the experimental values.
* Theoretical Reactor Ph> ica Section
1. R.N. Horoshko at. al. Nucl. Phys. A149 (1970) 562
2. B.A. Brown et. al., Phys. Rev. £9 (1974) 1033
-53-
TA8LI 1Tha atatlc raaanta and B(C2) valuaa in B1V eovputad «lth af fa-ctlva chargaa ap • 1.35a and an • 0*31 • at* displayed. Tha B(C2),
CALvaly
3 l
5 / 2
3 /2
3/2
11/2
9/2
9 /2
15/2
13/2
13/2
13/2
I•
and CAL
7/2
3/2
7 /2
7/2
7 /2
5/2
11/2
9/2
11/2
15/2
Ql[7/2)[S/2>17/2)[»/2)
XI ara dona with aat
CAL X
159.90
85.82
79*66
81.03
19.45
27.97
63.711.5510.694.11
-8*42-15.89
4.893,31
CAL XX
151.19
94.47
78.45
78.86
17.3323.6260.241*4410.8014.69-7.38
-14.53S.233.60
'C'and aafc'a'of 8PE reapaeU-
1f9.0106.T70*980.426.819.3
m>
+t
mm
m
-a.4-13.0
5.823.84
£Kpt*4>
154.0 ± 7.6107.0 ± 9,076.0 ± 5.078.0 ± 14.027.5 ± 6.327.5 ± 6.666.0 ± 5.0
-
-
•5.2 ± 1.0
S.1484.20 • 0.70
-54-
80-
6.0
UJ
zo
IUJ
3.0
2.0
1.0
o.o
.(21)-
•09)"(17)
13
15
57
19
1713
15
911
3
7
•17M3
•19
15
•911
191713
15
911
2119
ri3-17
15
11
3
-7-5
Expt. (a) (b) (c) (d) (e)
21
17-19
1513
119
753
Fig. 14.1 A comparison of theoretical and exparimsntal energyspectrum of 51V. The numbers on the right of levelsIndicate 23 values. Theoretical spectrum are computedwith the following sets of single particle snergiesi
< o. o , « C*»/J • * • ' , « < * O • » • « . « <**/»> •4l5>
s o . o ,
All energies are in IteV.
-55-
1 C. FISSION PHYSICS
Tha activities of th» Fission Physics Section during tha year
covsrsd in tha rapart fall into thraa Main categories* experimental
investigations of spontaneous and induced fission reactions, develop-
ment of new instruments and techniques, and theoretical studies.
While tha experimental investigations have baan mostly guided by the
available facilities, thay also demonstrate that there slill exist
many unknown facets of tha fission process which ace to be experimen-
tally studied in detail and which add to the list of unsolved problems
in fission theory. Studios of light charged particle accompanied
fission have received much attention for several years in the section
and the results of the a*, studies have unfolded interesting new features
which ruquire detailed tnu It i parameter studies, some of these multj.para-
meter studies are now baina planned. The section has put in consider-
able work in y^e setting up high resolution Sl(li) X-ray spectrometers
and in their use for routine analytical applications and trace element
analysis. The availability of these systems ha* also enabled us to
Join tha currbnt world wide search for primordial Superheavy elements
in natura through X-ray fluorescence analysis. The theoretical investi-
gations carried out in the suctiun cover not only attempts to correlate
and understand various aspects of the fission process but also studies
in related area* of nuclear phybica such as thermodynamics of excited
nuclei and heavy—ion fusion reactions.
-56-
1. naaauramant 'pt Relative yields and Energy Spectra of Tritons andAlpha Particles Lmittad in Thermal Neutron Fiasljn of U-?35 Using* So/ni-conductor A fc-E. Counter Telescope. (R.K. Choudhnry and
O.i»l. Nadkarni)
An assembly, consisting of an ionization chamber for detecting
fission fragments and a A E-C semi-conductor detector telescope for
identifying and measuring the energy spectra of light charged particles
(LCP) emitted in fission, has been set up at the CIRUi Reactor. The
2 235 2
fissile taryut used is 5 my/cm thick U coated over a 2cm area
which forms the cathode of art argon gas filled ionization chamber. The
A E and £ detectors were 63.6** and 500M thick respectively and were
mounted at a distance of about 3cm from a thin aluminium anode of the
ion chamber which stopped fission fragments and allowed only LCP to
reach the telescope. A triple coincidence between fission, b> E- and L
pulses was taken and the coincident A t and fc were fed to a particle
identifier unit a* uell as to a 2 parameter multichannel analyser.
Over 2x10 LCP were detected and both tno relative yields and energy
spectra of tritons; and alpha particles ware determined. Preliminary
results show that the relative yield of tritons to alpha particles235
emitted in thermal neutron fission of U is S+.ljS and the most proba-
ble energies of tritons and alpha particles aib 7.3+.3 HuU and
15.1+.2 na\l, uhareds their hair width at half the maximum (HwHi*l) are.
3+.3 PieU and S+.2 M*»U respectively.
2352. Long Range Charged Particle Emission in Ketf Neutron Fission of U*.
(B. Krishnarajulu"1" and C.K. nehta+; R.K. Choudhury, O.n. Nadkarniand o.b. Kapoor)
Ue have measured the yields and en»rgy spectra of LCP in the fission
-57-
235of U induced by neutron* of energies 120, 180, 500 and 1020 KeV.
This aneryy range is of particular interest from the point of view of
inveatigatiny tha influence of the transition states on the probability
of emission of LCP."
Tha experimental sat up consisted of an ionisation chamber torange
detect fissions and a semiconductor detector to detect long/charyed
235 2
particles. The U foil was 5 mg/cm thick and 2 cm in diameter
mounted inside tha lonization chamber. Neutrons were produced by
Li(p,n) and T(p,hJ reactions using the 2P1V Wan de Graaf accelerator
at I.I.T., Kanpur. Tha energy spectra of LCP pulses, gated by the
flsslon*LCP coincidence gate ware recorded in a multi-channel analyser.
The fission and UCP count rates were simultaneously monitored. Fast
neutron runs were taken at neutron energies of 120, 180, 500, 800 and
1020 kat/. Thermal runs taken before and after each run were used to
check detector performance and stability and for normalizing the fast
runs. The LRA apectra wars corrected for chance coincidencea and for
energy loss effects.
Tig.2*1 shows tha corrected energy spectra in thermal and fast
neutron runs. Tha spectra ware fitted by Gaussian distributions to
get £4 and £ of the IRA spectra far different incident neutron
energies* and tha results ara shown in fig.2.2. The results on the
LCP yield above 6.S JteV (fig.2.3) shows a marked increase (20*) com-
pared to tha yield at thermal neutron energy in the neutron energy
range of 100 to 500 keW. The observed LRA yield for £.> 12 (1eU is
shown in fig.2.3(b). Thera is a noticeable increase of about 20£ in
the energy range of 200 to 500 katf over the thermal value. From
-58-
f i f l . 2 .1 i t i s seen that there i s a low energy component in the energy
to 15 20 2bALPHA PARTICLE ENERCV. E*(MeV)
30
Fig.2.1 Enargy spectra of light chargad particles in thermal,120 KeU, ISO K«V, 500 KaU and 1020 KaV neutron inducadfission of 2 3 5U.
-59-
spectra in the energy range of 6.5 to i2 l»leV. The yields of the iosj
1 4
0s
17
16
13.
• PRESENT WORK
o DATA OF REF. 1
• PRESENT WORK
o DATA OF REF. 1
j I
0.0 0.2 0.4 0.6 0.6 1.0 1.2 1.4 1.6 1.8 2.0NEUTRON ENERGY En(M«V)
Fig.2.2 Variation of 1*. and *"~ta of th« anoray spsctra ofLCP with nautron anaryy.
energy component was determined by •ubtracting the low energy Gaussian
tail from the data and ware aasiyned to the 'triton1 yield as shown
in fig.2.3(c).
The increase in LCP yield in the neutron energy region of 200 to
500 k«V as compared to thermal neutron fission cannot be due to any
excitation energy dependence of LCP yield. Thus the increase in LCP
yield around Cn»200 kaU may be associated with the increase in the
relative number of fission* proceeding via the wven parity atates
populated by the p-wave interaction* at theae energies. Thb increase
-60-
ln yie ld of part ic les in the energy ranye of 6.5 PleV to 12 rial/ may
..o
-
1.4
U
1.0
M
?.«
2.0
1.6
1.7
I
1
•
I
{
I
I . ^
f
I • I
i
• . i
I
A 1
!
. i .
f|
i
I
(
ii
i
1
(el
(b)
1
«.«
1
(a)•
•
f
M»V <?
i
• I i
Ei >„f f IE >E Mt
OAfA Of
\
ft..
i . i •
<I?M»V
l . I
M»V
WORK
KF.1
I
i f .
ao v u u M ui u u ts w isNEU1RON ENfRGV E n (M*V)
Fiy.2.3 Variation of tha yield of LCP with neutron energy
indicate that the yield of tritone increases by 2-3 times in the
neutron enurgy range of 500 keV. Houuuur, to dray quantitative
conclusions, further studies usiny A E - £ set up for particle identi-
»teation are planned*
• Work in collaboration with the Department of Physics, I.I.T., Kanpur.+ - 0ep*rtnent of Physics, I.I.T., Kanpur.1) O.CI. Nadkarrti, R.K. Lboudhury, P.M. Rama Rao and S.S. Kapoor, Nucl.
Phy». k SSP Bl£, t31 (1975).
3. Two Parameter Studies of TFSO Response,to Flaaion Fr*ati\enta forPleasuramenta of Frau/innt Haas and Lnerov Distributions. (N.N. Hjit-anand, K.N. Iyengar and S.R.S. riurthy)
The development of thin film «cintlllation detectors (TFbO) has
-61-
gained considerable inter&st because they have an advantage over the
more commonly used solid state detectors in their ability to withstand
heavy doses of charged particles without showing any appreciable de-
terioration in performance, With a view to testing the applicability
of the TFSD in fission studies uu have used them in a two-parameter
investigation of the thermal neutron induced fission of U.
The experiment was carried out at one of the osam holes of the
CIRUi reactor which provided a collimated thermal flux of about
7 2 235 2
5x10 nectrons/cm '/sec. A ' U source of thickness 50 JUQii/cm was
slectrosprayed on a VVNa'piratic support. The source was mounted in
between two TFSDs sc that the source ddtectur distance'on either sidee
was 4cm and the aoorcc faced the noutron beam at an any la of 45 to it.
The cua TFuU^ wnra prepared firoin dioSuivHd chips of tt".u scintillator
by a ttichniqua i-e orted earlier . Fig.3.1 shows a typical single
fragment pulse haight aistriu^tian obtJintd by a TF5D.
The liyht output L_ due to a heavy ion with charge I, maH-9 M and
Y L incident on a rlstentor of thickness T is given by the integral
wherw dL/dx is the apecific luminescence of the film and (t-E1) is tha
nnn?gy dmoaited within tha film obtained from a knowledge of th>< opeci-
fiu enaryy Io.i9 (C/dx. Tha integration waa carried out numerically by
u«ine a sfimi-ompriLal axprasaion for dL/dx. Tha results were fittud
-C2-
with polynomial expie>sions for L in terms of E/l"l and
J 10.000
, - - - .3i io n "» •»•
CHANNEL NO. —»
Fig.3.1 aingia fraymant TFi»O pulse height distribution.
By associating the tvo puak positions in the dynode pulses
height distribution with fragments of specified L/n and 2 the
corresponding L distribution uas ubtainad for each TFDO. Next an
iteration procedure uas used to obtain the masses (M , I*12) and
energies (E1, £2) of the pair fragments from L1 and L.2 using the
following necessary and sufficient conditionsi
U » (92/236}Mi , i-1, 2
(11+1*12 * 236 (mass conservation)
fl1E1 a FI2t2 (momentum conservation) (2)
Li » Li (T'-e'/ (P/n)i ) i=1, 2 from polynomial expression.
Fig.3.2 shows the total kinetic energy and mass distributions end tha
average total kinetic energy versus mass correlation obtained by the
above analysis of the TFSO data. They are compared with the corres-
ponding results obtained by convuntiunal solid state detector measure-
2)ments ' and it is seen that thu TFSO technique is able to reproduce
-63-
th# general features reasonably wall.
20
5 ie
5 16
<° 12
10e
•
•
•
. (c )
V"•* •
a
•H
70 80 90 100 110 120 130 140 150 160 170FRAGMENT MASS (AMU)
Tig.3.2 Rssulta of data analyuiai a) Class distribution b) Average tingleand total kinetic energy Vs. maas c) width of total kineticenergy Vs. mass. Continuous linee - semiconductor results.Dots - TFSO results with calculated response function. Crosses -TFbO results with a slightly inflected response function.
1 . N.N. Ajitanand and K.N. lyangar, Nucl. Inst. & Math. 133(1976)71.2. H.W. Schmitt, 3.H. Nailer and f . 3 . Walter, Physc. Raw. 141(1966)1146.
4. Studied of Fragment Kinetic fcneroy and Mass CorraJ.ati.on8 inThermal Neutron Fiasion of U-235 t-mploying Electronic Colllma-tiun. (O.M. Nadkarni, R.K. ChoudhuTy and 5.S. Kepoor }
In the measurements of fragment ma33 and energy correlations
from a measurement of energies of pair fragments, it is desirable
to haws a minimum deterioration of the mass resolution from the
finite source thickness affects, etc. The source thickness effects
can be reduced by collimating the fragments in near perpendicular
direction to the source plane. This can be achieved in a straight
forward manner, if a pair of semiconductor detectors are employed.
Ule have studied a method of collimdtion in tha case of yriddsd ion
chamber employing 2 TO geometry, and investigated mass and energy
235
correlations in thermal neutron fission of U for coliimdted frag-
ments. Electronic collimdtion was achieved in the back~to-back yridded
ionization chamber bjy recording coincident grid and collector pulse
heights on both sides of the chamber on a magnetic tape by means of
a four parameter data aquisition system, to give the fragment energies
and angles event by event. The angles 8 which the fragment makes with
respect to the electric field direction is calculated from the BXpre-11 a#
asion for the grid pulse height V » - (1 - - cos8), where a is the
total chargs released, C tha capacitance of the grid, d the cathode-
grid distance and R* is a quantity which depends on tha fragment
range. This enables us to calculate « event by event from a know-
ledge of V and fragment energy and thus tha electronic collimation
was achieved by selecting only those evants in which fragments «morg«
•t near 90 angles to the target foil. In fig.4.1 the fragment mass
distribution obtained with and without the electronic collimation
(anyl«» limited to within 32 ) ars shown by continuous and dottad
-65-
linea, respectively. It ia seen that thu electronic coliimation
Fig.4.1 Fis3ion fragment massdistribution with andwithout electroniccollimation.
Fission Fragment Mass.amu
reaults in significant improvement in the fragment mass distribution
due to rejection of events with appreciable energy losses* in the foil.
The variation of the average E and the width ° t^ of total kinetic
energy distribution as a function fragment masa havs also bean'deter-
mined, and furthur work on analysis of data is being continued.
5. ftnamoloua Jurfaco Effects on Glass Backed Polvvlnvl Toluepy fl^ma dua toRadiations. (N.N. Ajitanand, K.N. lyangar and S.R.S. Plurthy)
We report soma unusual radiation induced effect• produced in
thin polymer films prepared by a apscial technique. Although radia-
tion ia known to produce a variety of affect* in plastica the nature
and intensity of the phenomena described hara ara not amenable to an
aaay explanation. The films were prepared on glaas alida by a technique
reported earlier ' and had the following compositiont
Polyvinyl Toluena - Baaa polymer
Para terphenyl - 3%
diphyloxaiolyl-benzene (P0P0f')-u.05;£
Tha sat up for direct irradiation of the film ia shown in fifl.5.1.
-66-
The slide is fixed on the face of a photomultiplier which is mounted
EVACUATEDCf SOURCE
Fig.5.1 Set-up for observa-tion of physicalafreets of radiationon the film as wellat ita scintillationresponse.
•EAUNO
in a chamber evacuated to rotary vacuum. The effect of a 17 hour
235irradiation with a weak U source ( SO d.p.s.) kept 3cm from the
film la to cover the film surface with numerous, easily visible,
spherulitic surface crack patterns. Under a crossed Nicola it is
aeen that there ia a high degree of alignment along the cracks.
Similar effects ere observed under fiasion fragment irradiation. The
patterns are atar shaped as well as helical.
Euan when the alpha source is covered with an aluminium
2
foil 6mg/cm thick which completely ato^s the alpha particles, the
film still develope similar patterns in large numbers. A atainlese
steel absorber 380mg/cm thick, however, protects the film successfully
from such effects showing that penetrating radiation from the eource
- 8T -
cause these affects.
As a result of the complex interactions of radiations with the
film and glass backing it is possible that stresses may develop within
the film giviny rise to the phenomenon of crazing. It is known that
the crazed material ia highly oriented and in a polymer with crystall-
2)ine regions, the craze follows a systematic pattern .
It must be stressed that the explanation offered here ia tentative
and more work needs to be done before the phenomena can be properly
understood.1. N.N. Ajitanand and K.N. lyengaf, Nuci. Inst. £ :;=ith. 133 (1976)71.2. A. Peterlin and H.C. Olf, Polymer, 0. Sci. Symposium No.50(1975 )243.
6. Search for Primordial Suuarheavv Elements in Honazite from BeachSands of South India.
6.1» Photon Induced X-rav Fluorescence Analysis Studies, (b.o. Kapoor,V.S. Ramamurthy, M. Lai and S.K. Kataria)
As a part of out programme to investigate the possible existence
of primordial auperheavy elements in Plonazite from beach sands of South
India, studiea of photon induced X-ray fluorescence spectra from thin
samples of the mineral were carried out. A 5mm diameter collimated
2<*1beam of electromagnetic radiations- from a 100 mCi Am source filtered'
through a lmm copper disc was used for X-ray excitation of the sample.
Honazite obtained from tha Chavara (CH) and Manavalakurichi (flK) beach
sands of South India, were studied. The sampled were mounted at 45* to
the incident photon beam direction, and the fluorescent X-rays were
energy analysed with a coolad 30mm x3mm Si(Li) X-ray spactro'meter of
about 230 eV enargy resolution. Fig.6.1 shows a. typical spectrum
- 68 -
obaarvad for a aa.pla. Tha charactariatlc L-X-r«y p.uxa of Thorium
-69-
and Uranium and the K-X-ray peaks of rare earth elements dominate
the epeotrum* Fig.6*2 ahowa portiona of the spectrum for CM and NK
•onazlte samples covering the window region of low background where
the cheracteristlc l-X-rey lines of auperheevy elements, if preaant,
ior
• 1 0 * -
: *.'• 3 i
• , .*
• / • ' • •
«1
1
t
1 1.
Ji1A
1*•.«
••• ^
* CN -8 1 /*»*Hf».
*r .MH . :j ^ 73 Mf %
;V
r 1 1 ft.
18 22 24Ex(Kev)
26 26
Tig.6.2 Portions of X-ray spectrum for CH monazita, dK monaziteand for a synthetic sample.
are axpactad* It waa found that tha accumulated data of a nuaber of
runs each of aeveral daya duration do not ahow any convincing peaks
above the background at the expected locatione for euparheavy ela-
•ente which era above the present sensitivity of detection or about
10 ppa by weight for oleaent 126.
6*2* alpha and Fission Spectruw Studlee .(S.S. Kapoor, V.S. Raw•urthy and S.K. Kataria)
Special methode have been developed for the preparation of
very thin aaaplee of the aonazite Mineral for alpha and fleelon
-70-
spectrua etudlee without any chemical treatment. Finely ground
powd«r of tha Mineral waa Made airborne by islng an aerosol
ganarator and waa dapoaitad on a aillipore filter by eucking.
Fig. $.3 shows a typical alpha »pact rum obtained Trow, a eource. Tha
500
ou
1000
Fiy.6.3 Typical alpha- spectrum rrom a thin monazite source.
quality or tha eource ie ae good as that obtained froa a electro
plated aourca. In another variation of the Method* the airborne
particle* ware charge aeparatad in a atrong electro etatic-field
•nd dapoaitad on thin aluainluaj roils. The quality of tha alpha
apactra obtained froM such a source ware the same ee the earlier
one. The investigations are in progress.
Atteapta ware alao Made to record tha L-X-ray apactra in
coincidence with the alphe particles. Because of poor atatiatica
-71-
obtained BO far, ths results are
+ Work done in collaboration with Or.P. Kotrappa, Health Phv«ic«Division.
7. Multiplicity Distribution of Prompt Gamma Ravs in SPQrttffngflU*Ternary fission of 2 5 % f f (V.i. Rafltamurthy, R.K. Chaudhury and3.C. Hohankrishna")
In continuation of our earlier work on the mean and the width
of the gamma ray multiplicity distribution in spontaneous binary
fission of Cf, wa have now carried out the neaaurements of the
first and second moments of the prompt gamma ray multiplicity di»-
252tribution in spontaneous ternary fission of Cf ts « function of
the energy of LCP, by means of the multiple coincidence technique.
Fig,7.1 shows the experimental set up, whsrt two Nal(Tl)
detectors were used to detect fission gamma rays a..d • semi-con-
ductor detector was us«d for detection of t-CP. Double and triple
LCP OsiectorAtlSOftJM
OET 1
Nnl(Tl)
DET Z
NoI(TO
252Cl Sourct
Tig.7.1 Schematic diagram of the experimental aet up.
-72-
coincldanca gataa LCP- 7^, IXP- V^ and LCP-Y^- \respectively
wera ganeratsd and the LCP spactrun was recorded in coincidenca
with these gates. Data ware recorded on a 1024 channel analyser,
in which the first quadrant contained the ungated spectrum, the
second and third quadrants double coincidence spectra and the
fourth quadrant the triple coincidence spectrum. If (^(i), C2(i),
C (i) and C (i) are the counts par channel in the four quadrants,
then the following relations hold:
ceo %] WO
where C(i) » ^ ( i ) + C2(i) + C3(i) + C4(i), -H^^Jl-t " a the
detection efficiencies of the gamma ray detectors including solid
angle factors and Pn(i) is the probability of emission of n gamma
rays par ternary fission for channel number i. For the present
geometry the detection efficienciea JL^ and -*l.aare or the order
of 3 %. It is, therefore, reasonable to assume that the probability
of more than one gamma ray entering the sane detector in the saws
event is negligibly small. On* than obtains the following simple
relations for the coincidence counting rates.
>
The bars over the quantltiee rapreasnt the average taken over the
-73-
antlre aultiplicity distribution lx(i).
Fro* tha abova relations ona can obtain tha valuaa of' ' • \
nti T ? C # aftar eliainating tha solid angle factors and
aaauolng that ths average nuabar of gaaae ray* par binary fission
is 1.16 tlaea that in ternary fission. Aaauaing a Gaussion shapa
for tha multiplicity distribution1^ tha width of tha distribution
is obtainad froa tha ralation « ~ { O * >?tO->T7O • Fig.7.2
shows ths variation of -fHO *n<ifCO with LCP snsrgy, along with tha
aaaaurad LCP anargy apsctrua.
Fig.7.2
a) Energy spectrum of LCP.
b) Variation of n with LCP energy.
c) Variation of O"""with LCP energy.
It ia aean that tha aaan nuaber of gaaaa rays per ternary
fission, >\" is nearly indepandant of tha anargy of LCP within tha
axparlaantal arrora. Tha width of tha aultiplicity distribution
is also nearly independent of ICP anacgy but ins abaoluta Magnitude
of C averaged ovar anargy of tha LCP i« aigniflcantly largar than
tha corresponding valua of 4.2 t 0*4 in tha ease of binary fission .
This can imply ' that the spin distribution or tha fragments in
ternary fission has a smaller average valua than in binary fission*
This is reflected by the fact that the distance between the two
fragments is larger in ternary fission than in binary fission• Tha
near independence of tf~ on LCP energy implies absence of correlation
between position of LCP emission and interfragment distance, which
2 )waa noticed earlier in trajectory calculations of Chaddhury .1. U.S. Ramamurthy, ft.K. Choudhury ancfj.C. flohenkrishna, Pramana
8,, 322U977)*2. R.K. Choudhury, P1.Sc ITheaif), Bombay university (1976;.• Training Division, BARC.
8. A Semi-Empirical Depression for Specific Luminescence inPlastic Sclntiilators. (M.N. Ajitanandj
Here we present a naw model which allows a simple expression to
be davalopad for the specific luminescence. This exprasaion with s
single set of parametere gives a remarkably good fit to tha low
energy data, a reasonably good fit to the high energy data for heavy
lone and also reproduces the qualitative features of the light
charged particle data.
The basic assumption of this model is that the luminescence
produced due to sn elemental path length dx of a charged particle
in the plastic scintillator is proportional to tha effective volume
of acintiilatot apses spanned by the electrons scattered out by the
-75-
chargad particla.
Tha axpraasion for apacific luminaacanca on tha baaia of thia
•odal can Da writtan in a ampla cioaad fora aa
whara r m ttN
N .
and
x
Tna fiva constants a, b, c, d, g, wara round by doing a fit
to tha low and high anargy axpariaantax data. Tha baat yaluaa of
tha conatanta ara
a m 2.1209,
b « 0.065373,
c » 0.76649,
d m 1.4134,
g • 0.68453.
In figa. 8.1 and 8.2 wa show dl/dx curwaa actually obtainad
with thaea conatanta for varioua haavy iona in tha low and high
anargy ragion togathar with tha axpariajantal data. It la aaan
that tha fit to tha low anargy data ia vary good indaad whila for
-76-
tha high energy data the agreement in quita satisfactory, tvan
Fig.8.1 Calculated and experimental low energy data for specificluminescence.
Fig.8.2 Calculated and experi-mental high energy datafor specific lumine-scence.
2 J •ENERGY/HUCIEON ( M A )
for light charged particles (protons and alphas) there is good
agreement betwaan tha calculated and experimental curvee (Fig.8.3).
| oV
MPfMMNIU• U.PHH.%• MIOTONI
1 • fCNCMY (MM)
Fig.$.3 Calculated and ex- -perimental specificluminaacence forlight, ions.
In all theae calculationa tha sane aat of parameter valuea hawa
EHEMT LOSS OF FISSION FRMMENTS (MM)
Fig.8.4 Calculated ana Bxpsri-mental TFSp roaponsefor f ission fragments.
bean used.
-77-
It was also possible to calculate the light output L as a
function of energy.loss in the plastic i.e.,
where £. and Ex are the initial and final energies of the heavy
ion traversing a film of givun thic*-ne3S<. The calculations for
252the most porbable heavy and light fragments of Cf spontaneous
fission are shown in Fig.8.4 together with the experimental data
4 }reported in an earlier paper. The trend of the data points is
well reproduced by thd calculations.
1 ) n.L. Muga, G.L. Griffith, H.W. Schmitt and H.E. Taylor, Nucl.Instr. and Oath. 11 (1.973) 581.
2) n.L. Pluga, Nucl. Instr. and Moth. 124 (1975) 541.3) PlrL. Pluga and G. Griffith, Nucl. Instr. and Meth. 109 (1973) 269.4) N.N. Ajitanand aifcd K.N. Iyengar, Nucl. Instr. and fieth. 133
(1976) 71.
9. Evaluation of Muclear Shell Correction Energies for RealisticLevel Schemes Oy Temperature Smearing Method (U.S. Ramamurthyand S.S. Kapoor)
The temperature smearing method of evaluating nuclear shell
correction energies, developed by us earlier ' and demonstrated for
the single particle energy level scheme generated for a modified
harmonic oscillator potential, has been extended for realistic
single particle level schemes generated for finite depth potentials.
The method is based on the following well known expressions for the
•ntropy 5 and the excitation energy E for a system with a smooth
-78-
•ingle particle level density
S «. 2 a,T'
= 2 iTi*i—1.3,5....
wh> the coefficients a are related to the sinyla particle
level density and its derivatives at the chemical potential,
and the simple relation L sE - 4 , where L is ths excitationx x s ' x
energy at temperature T and A is the ground state shell corr-3
ection energy. It is not known apriori as to how many terms will
be required in the polynomial expressions for the entropy and the
excitation energy and utut temperature range is appropriate for
the calculation of At using the above relations . It is therefore
necessary that the evaluated values of & are insensitive to the
temperature range and the number of terms chosen. We have examined
2)
thsca points for the single particle level scheme of Bolsterili et »1
generated for a folded Yukawa potential. Fig.9.1 shows the sensitivity
of the calculated values of ^ for a typical case with respect to3
i , when a tempuratura range of 4.0 to 4.1 fleU is used and withffluX
respect to the temperature range used with i »4. The observedmax
asymptotic constancy of (E -E ) show the validity of ths method. A
slightly different procedure for routine calculations has also bean
invBstigatud by us where the calculation of A *a carried out on
the basis of the function (ST/2-E ).
Tho zero temperature intercept of (ST/2-E ) Is the shall correction
- 7 9 -
anergy. As before asymptotic constancy with respect to i and
I •ft
Ul
• t.u?
***Pu (SPHERICAL SHAPE)— PROTONS
--NEUTRONS x " ~
JL
Pu (SPHERKALSHAPe)• PROTONS. _ • - — •• NEUTRONS,,-*
T(M«V)
Fig.9.1 Calculated (E -C ) versus tha temperature for a givenorder (i^ »x4)xand uarsus L_^ for a temperatureranga 4.1 to 4.1 PleV. max
tha tamparatura ranga uaad ia requirad for a raliabla aatimata o f ^
No breakdown of tha method waa encountered while applying tha method
to calculations of shall correction energie* of actinide nuclei for
various shapes or interest in fieaion including thoaa shape* where
3)the usual Strutlnsky procedure fails to Qive a unique value \T ) U.S. Ramamurthy and a.S. Kapoor. Phvs. Latta're 42 B (1972) 399.2) «. Bolatarli at al, Phya. Rev. C5 (1972) 1050.3) V.S. Ramamurthy, n. Prakash and S.S. Kapoor, Phya. Letters
62 B (1976) 124.
Semi-empirical Nuclear Level Density Formula. (S.K. Kataria,V.S. Ramamurthy and S.S. Kapoor)
An analytical sami-empirical nuclear level density formula with
shell sffacts bsssd on tha numerical calculations of laval dansitlss
-80-
from • sat of single particle energy levels has bean proposed
earlier . The following simple expressions wera obtained for
the excitation energy Ex and entropy S of a nucleus as a function
_ _ ,;
<"«•>> TT-T .. "TUT
S- l a y * As / T^wr COJKof temperature T. S - * » T > - ^ _ _ _ _ _ _
where a is the liquid drop mudel value of the level density para-
meter, w is related to the major shell spacing in the single
particle levels, and ^ s is the shell correction energies. With
conventional corrections for the pre-exponential factor, angular
momentum dependence and nuclear pairing effects, these aquations
are uaed to calculate the nuclear level densitias. An analysis of
the neutron resonance spacings of about 100 spherical nuclei has
shown that the generally assumed linear dependence a -A/K is in-
adequate and there is evidence in the experimental data for the
dependence of a on surface to volume ratio of the nuclei. Taking
guidance from the distribution of s.p. levels in a potential well
of volume of \i and surface area S, tha following functional form
for a is proposed £• - t A (l- £ ." « 0
where B is surface area in units of the surface'area of a sphere
of the same volume. Fig.10.1 shoua the plot of the experimental
value of a / A versus A '3, where a is obtained by fitting tha data
nucleus by ,nucleus. The data are consistent with the above funct-
ional for and the best values of V and £ were found to be 0.176 Clev"1
and 1.0 respectively. A plot of calculated ratio [XVO is shownt h ex p
in Fig,10.2. It ia seen that even for deformed nuclei the formula
- 81 -
rua^>on-idly d u j d f i t s w i t h no evidence fo r dn unhancem«nt
030 -
501ot» -
01
a/AX
P
- ^
- V (1 -p AV3>• .176.1.0
" * - ^
i
SPHERICAL NUCLEI
•
01 03
Fiy.10.1 Plot of the "experimental" a_ /A versus A
'0
01
: i
> •
' -V3
.•
i
•
i
1
* • / * ' * • * *
- .
i
-
Fig.10.2 Plot of thecalculatedratio 0../D
th expversus A. K
100MASS NUMBER A
200
of the level densities due to completely decoupled extra rota-
tional degrees of freedom contrary to general belief. An in-
teresting, consequence of the form for a, is the prediction of
reduction in the value of a for deformed shapes of nuclei as
in the case of fission transition state.
I) U.a. Ramumurthy, J.K. Kataria and o.u. Kapoor. IfltA-190Vol.II, 117 (1976).
11. Classical Microscopic Description of Particle ClusterCollisions:Application to Heavy Ion Collisions. (U.S. Rana-murthy and a.K. Kataria)
In studying ths dynamics of heavy ion collisions, both
microscopic no'els and macroscopic model3 have m*t u.ith only
partial 3UCC83S till now and require several modifications before
thay can fully describe the various processes that take place, as
for instance the large scale transfer of energy from relative [notion
to the internal excitation energy of the colliding iona. We have
investigated the collision between two bound particle clusters, by
solving numerically the classical equations of motion simultanaously
for all the particles in ths clusters. Taking guidance from the
molecular dynamics description of calssical liquids, me have chosen
a two body force of the Lennard-Jonea form, whore the potential bet-
ween two particles is given by the expression
with £ = 2.2 New and<T=* 1.8 fm, the particles freeze into clusters
that resemble nuclei as regards such macroscopic properties as the
average binding energy per particle and aize in thair ground state.
In a typical collision calculation, the two clusters in their ground
stats are allowed to collide into each other with a given impact
parameter and velocity. The trajectories of all tho particles are
computed and the resulting particle coordinates as a function of
time ara used to calculate various collective* quantities. We yiva
bslow some typical results obtained for ina collision of two clustero
each with 16 particles. Fig.11.1 shows typical particie trajectories
for the two cases, hiad-on collision leading to complete fusion and
peripheral collision leading to deep inelastic scattering. Fig.11.2
shows ths calculated Centre of mass trajectories of one of tho
clustors in collisions with different impact parameters. All eel-
:• *
* "" fig.11,2 Calculated centre of maaatrajectories for differentimpact parameters.
Fig.11.1 Typical particletrajectories for ahuad-on and a peri-pheral collision.
dilations nave been carried out for laboratory bombarding snorgy
of 133 Cleu. It can ba seen from tha figures that the model can
bring out most of the «sa»ntlal features of heavy ion collisions
such as complete fusion, deap inelastic scattering and particla
exchange. The present modal calculations, while baing classical,
do not involve some of the inadequacies of the conventional liquid
drop model such as, shape parametrisatiori,viscosity etc* We be-
lieve that these calculations can,not only provide important guide-
lines for a macroscopic description as in a selection of relevant
dagreas of fraadom^but can also serve is a ycoei 3l'-*itig point for
• semiclassical microscopic description.
12. Tranamjaslon Threuah an Inverted biharmonic Oscillator Poten-tial Barrier. (M. Prakash)
The penetrability through an inverted harmonic oscillator
potential has been investiyated by Hill and Whaeler in the context
of the potential barriar which a nuclaus cr.countera on ite way to
2 )
fiaaian. In the present work it haa been shown that the Schrod-
lnger equation for an inverted biharmonic oscillator potential is
also exactly solvable and in the limit of harmoniclty, tha Hill-
Wheelar formula ensues. Shown in fig. 12.1 is the exact psitocrebi"
lity as a function of tha ratio of tha oscillator fiequvncioa when
0-52-
Fig.12.1 Exact penetrability for the inverted biharmonic oscillatorbarrier as a function of the ratio (w /w ).
the height of the barrier ia equal to the energy of the incident
particle. The maximum value of the penetrability Is 0.5 at *.•**„,
end falls off on either aids of (w./i*- «1 ). For purposes of com-
parison the validity of JWK8 methods in obtaining the penetrabilities
through an inverted biharmonic oscillator has been assumed (the
potentit!. is not smooth «t x»0 and therefore the JWKB method faila),
•nd the exact penotrability is compared with those obtained from JWKB
methods in fig. 12.2 for some typical values of the oscillator
Fig,12.2 Exact (full curves) and 3WKB (chain curves) penetrabilitiesas a function off a L/\l . (a) V =1.0, 4 a. =1.0, <wo«2.D;(b) \M-1.0, fcu.,-1.0, tS 2=
5' 0-
frequencies and the height of the barrier. It is evident that the
penetrability obtained from JWKB methods agree with the exact rosulte
only at low values of the incident energies.
1) 0. Hill and J.A. Wheeler, Phyo. Rev. 09., 1102 (1953).2) CI. Prakash, J.Phys.AjHath.Gen. 9,, 1847 (1976).
13• Study of Scission Configuration by tha Entropy flaximisationWathod (1*1. Prakash, S.K. Kataria and V.s>. Ramanurthy)
Studies of static scission configurations of fissioning nuclei
based on potential energy minimisation have been made in the past
to explain qualitatively, many features of low energy fiseion of
actinide nuclei. Of recent origin is the renewed interest in the
existence of a scission barrier as it has important implications in
•any aspects of heavy-ion induced reactions also. In the present
work , we have initiated a study to determine the scission point
characteristics by raaxiraisincj the entropy of the fragment systoia
instaad of minimising tho potential energy, as a fchoroodynraraic
systura at o i'inito temperature rainiraiaas its free energy and not
the potential antsiyy. The nuclaus at tho scission point is des-
cribed by two overlapping sphsroids with diffuses srattw distrilju-
2 )tions"' whosa equivalent sharp aurfacas ara aapart-teri by a £},&"
tsnes 'd'. The potential energy of tho system is assumed to ccn~
sist of the liquid drop anorgias and pairing and stieii corroctione
pli,s tho coulomb and nuclear interaction onsrgi.es of tha sphsroids
with diffuse surfacos, Tha probability of formation of eny fi3sian
fragment pair is th»n governod by the ontropy of tho sysinm<> The
most probable fragmont dsformations ore obtained by raoxiisising vho
ontropy. Tha distance botwecn the fragmont tips is provided by tho
9addl« point condition, <i prescription which makas the treatment of
tha scission point modal frsa of paramatnc fitting. Typical results
for nuclei in the mass rsgion **=*180-220 are givsn bolow.
The following table shows the results on itsan kinetic unargy
of fragments as obtainad by tho dynamical model of Nix •» and tho
scission point model of present work. Tha experimental Jata sro
those of Plasil et al '
Compoundnucleus
A t 2 1 3
85 A t
20181 l i
8 2 P f a 1 9 8
Q
1.42
1 .2
2.07
2 . 0
Expt .
148+4
'38+4
14 7+4
128+4
ETCalc(Nix)
150
142
142
130
Calc(Preaent)(PlBV 1
153
142
146
132
-87-
In fig. 13.1 wa ahow the raaulta on maaa distributions. As
obsarvad experimentally, the width of maea distributions increasea
Fig. 13.1 Calculated mass distri-butions as a function ofthe nuclear temperature '€'
tO M 100 120 KO 160MASS(omul
jtith incraasing excitation energy. For all tha nuclidas wa have
atudiad so far, tha widths ara found to ba in agraamant with tho90
obsarvad experimentally.
Further calculations ara baing dona by including highar order
daformations for tha fragments and by taking into account tha shall
and pairing corrections in tha potential energy, to obtain results
on tha experimentally obaarvad features of fission for nuclei In
tha actinida region.
•1 ) l*l. Prakash, S.K. Kataria and U.S. Rasiamurthy, Nucl.Phys. *Solid State Phys. (India) 19£, 127 (1976).
2) K.T.R. Oavias and 3.R. Nix, Phys. Raw. C14., 1977 (1976).3) 3.R. Nix, LftL Report 17958 (1968).4) F. Plasil, O.S. Burnett, H.C. Britt and S.G. Thompson, Phye.
Rev. 142., 696 (1966).
-88-
0. S>OL1Q STATE PHYSICS
The Solid State research activities have as in the past mainly
centred around neutron scatteriny usiny the CIRUS reactor but it will
bo seen from tha current raport that sevwral other interests are grow-
iny and thorn are results to show in liyht scattering and compton
profile studios, Liimilarly, the Cryogenic facilities which are being
set up will start yielding useful work in a year or two.
The neutron scattering work has reached a great degree of
sophistication da seen, for example, from the spin density studies
on magnatite and the work on the reorientation of the ammonium ion
in its sulphates. But a good deal of time is being spent in thinkino
about the techniques to be employed and the instruments to be built for
uas with the R5 reactor. Momentum in this work will build up in the
coming
The feature article on liquid crystals will indicate tne amount
of work that has been performed here with a relatively small effort.
It is symbolic of the types of expert knowledge that has been acquired
and also generated in thu section on difftrent types of materials
although initial interest in taking them up for study was purely
academic.
I. Neutron Diffraction Studies of Haematic flat a rial 3
1 • ftaunatic rorm Factor atudv of Ni q7Run n-j bv Polagiacd
Nautron3 (R. Chakravarthy, I. Plafinav R4o and (M.S. Satys Hurthy)
The Ni rich Ni-Ru alloy is a systam in which tha variation of
saturation magnetisation with Ru concentration does not follow the
Slater-Pauling curve. From the magnetisation data ' the initial
decrease in the total moment per added Ru atom is 3.0f^^ and it is
2)about 4.4/^g according to diffuse neutron scattering measuraments «
In order to find the variation in the magnitude and distribution of
.local moment on Ni, we have taken up a systematic study on
Ni, Ru (x • 0.03, P.06 and 0.09) alloys.
Polarisation ratio for 13 independent reflections in <^110>
zone were measured. Two samples of differenf thickness (0.6 mm,
0.3 mm ) were employed and were 30 cut that different equivalents
of tha same reflection had widely different neutron path lengths.
This enables one to check approximately the presence of secondary
extinction. Also tha polarisation ratios for the stronger (inner)
reflection which are most likely to be affected by extinction, were
measured at different points on the rocking curve and were found to
vary indicating tha presence of secondary extinction. To etart with,
a graphical analysis to correct for tha secondary extinction waa
applied to data of tha (111) reflection. Tha slops (g) of tha ex-
perimental y vs UT curve (y-extinction parameter, Q - reflectivity,
T - absorption weighted path lengths) aa QJ-? 0 is 1600. Experi-
mental extinction curve fitted with tha one calculated using g • 1600
-go-
In iachariasen'a formula. Later, in the detailed liaat squares
analysis of the entire data including polarisation ratios of all
tha equivalantB and those measured off the Bragg peak ware made
usiny the two parameter (spread and size of mosaics) Bscker-Cappercs
formalism for extinction. The best fit was obtained for typs 1 S3~
condary extinction yielding g - 1360 + 71. Ths extinction corrected
magnetic structure factora are shown in Tig. 1.1.
0.U
0.3
o
"0.2
cz
0.1
0.0
T TT
N'O97
100]
)31)
T 1
RUQ-03
.22)
)33)
TT
T
(00<
T
o OBSERVED VALUES
• CALCULATED VALUES
9 a
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.6 0.9 1.0Sin 0/A in A"'
Fig .1 .1 Magnetic structure factors in Ni... n ,Run , , , .U.9( U«UJ
Experimental magnetic structure factors were interpreted in
the framework of Linear auparposition modal in which
c is the concentration of Ru and At... » Ma aro tnB localisariNl Ku
momenta for Ni dnd Ru in tha alloy, f*? and ff p art the sphsricsi
part, of tha magnetic form factor for tha respective elements. The
second term in the square brackets reflects ths aspbericity of tha
form factor duo to the crystalline environment. Similar term for
Ru was neglectad due to tha smallnas of c. In "ctr; lsaat squares
analysis, tha experimental spherical form factor for Pd was used
for fD since no spherical form factor for Ru is available. Best
4 ) spfit was obtained using floon'a experimental ' form factor for f^^
2+and ^.J*^ correaponding to free ion in Ni state. Tha results of
the fit «rs
A N i » 0.582 + 0.0CJ5 /*•£>
/~{Hu M -3.08 + 0.33 Mb
Y N 1 - 0.165 + 0.014
In the alloy, tha nickel local moment is found to be less than
that in pure Ni, signifying a reduction of about 3/4g, per impurity
atom. The smaller value of the tg population given by y^. in ths
alloy compared to that in Ni (Y~m 0.19) indicates that unpaired ele-
ctron density distribution in alloy is more aepherical compared to
that in Ni.
The sign and magnitude of moment on Ru atom can be qualitati-
vely explained on the basis of Friadel'a ' model of virtual bound
at-<>-' (v.b.a.). In the caso of a strong perturbation, the moment
on tha a to ii is given by
whoro A. Z is tha difference in the number of valance electrons in
tha impurity and host and p is the number of empty states in virtual
bound l*vel. Using the experimental value of ,M in aquation (2),
we get p = 5/2, implying that the impurity v.b.s. is situated vary
near the Fermi leval of the host with half the number of states
being empty. This feature is consistent with the conclusion obtainsd
6)from the resistivity and thermoelectric power measurements .
1 ) 3. Crangle and 0. Parsons, Proc. Ft. Soc. A 255. 509 (i960).2) 3.8. Comly, T.N. Holden and G.G. Low 3. Phy3. C 1, 458 (1966).3) 3.W. Cabla and C O . iilallan, Phys. Rev. Letters 3£f 278 (1975).4) R.FI. Hoon, Intern. 3. Fldgnetism 1_, 219 (1971).5) 3. Friedel, Nuovo cimento 2_,"~287 (1958).6) 3. Ourand and F. Gautier, 3, Ph"ya. Chem. Solids 21» 2 7 7 3
2. ndQnetic Ploment Denistv in the Heualar Alloy qu?l*lnftl (l/.C. R»-khachJ, R. Chakravarthy and N.b. Satya Wurthy) ~
A preliminary report of tha measurements on tha ferromaynetlc
Haualar alloy Cu^flnAl was given in tha previous annual report .
The actual composition of the alloy is now known to ba
Cu_P1nn o,, Al with the saturation maynetisation par formula
unit at 300 K as 2.89 H&
Polarised neutron measurements (forX* 0.92 A, P • 0-93,
f a 0.99) were made for a total of 47 indapandant reflection*
-93-
ln /ilo\, / 001 / and < 112 *on«s. Intagratad Bragg intensity
meensurementa with unpolarisad neutrons (X= 1*24 A) uiara also mado
for 11 high angla reflections in ^ 1 1 0 ^ zone, to determine the
Mean nuclaar scattering amplitudes for the different sites.
The experimental polarisation ratios were analysed to obtain
the magnetic structure amplitudes. The ratios of magnetic-to-nuclear
structure amplitudes, n/Ht for the three groups of reflections
(h,k,l all odd) h,k,l all even with (h+k+l)/2 even or odd) were
plotted against sin QA . They were found to closely scale to the
2+flh free ion form factor, showing thereby that the moment density
2+resides primarily on the Pin sites and has an Mn like form factor.
Since the odd reflections are much weaker in intensity compared to
the even ones, the near proportionality of the three Fl/N curves also
shows the extinction to be negligible.
The IVN values were refined for magnetic moments at different
sties, assuming the Pin free ion form factor for the Fin sites (and
for the nominal Al sites when fin atoms were presumed to occupy thssa
wrong sites due to disorder) and tha Cu + form factor for the
Cu-sites. The asphsricity of tha /Vt moment was considered in a purs
(octahedral) crystal field modal. The analysis showed about 2>% ax-
cess of 3d electrons in the Eg orbitals i.e. the estimated popula-
tions are
Eg • 4 3 * T2g
The moment par Hn ion waa found ta ba \ 3.2/4^ at room temperature,
e value close to thet raported by Takats '. The moment on Cu is
found to be extremely small (* 0.03 + .O.OiSMg, ) but its sign is
3 4)positiva as anticipated * . This Cu-moment miyht actually be a
little higher ('>0.1/i,j) as some (In ions may be occupying (anti-
forromagnatically) the nominal Cu-sitns. Thi3 is indeed suggested
from the refinad negative moment value for the Al sites (2-0.1/10,
The obaarvnd and fitted M values, for the odd rofloctiona
only, are compared in Fig. 2.1o Tha agreement is good throughout.
1.0
0.0
O OHSFRVF.D• C*Lnil*TtD
(f)DtJ REFIlFr.flOM'j 0HI»l
i li el II i 5 3 I'ffgS'g" Ui i i i t i i i i i i
Sin 9/* — 'i ' •
».O O.t 0.? O.J O.t Ofi OJS 0.7 o.fl P.f 1.0
Fig.2.1 magnetic structure amplitudes in Cu flnQ
The differences in the It values of pairs of reflections were eel-
culated for tha observed and the calculated (fitted) values. The
two were found to agree in eign for .JII the pairs, thus unequi-
vocally establishing the asphericity of the moment density about
the rtn sites. This is in contrast to tht completo sphericity re-
portad for the moment density about the Pin sites in another Heusior
4 )alloy PdjFlnan '.
The analysis of polarised neutron data showed that the axttn-
ction was negligibla. It was, however, not possible to determine
the precise value of extinction parameter r> from the refinement of
unpolarised neutron intensities. The effect of including small
extinction in the analysis was examined and was seef to raise the
deduced moment value for Pin and also alter th* sign and magnitude
of possible small conduction electron polarisation. Tha latter use
therefore not possible to establish from these measurements. Tha
other conclusions drawn above remain unchanged.
1) V.C. Rakhecha, ft. Chakravarthy and N.S. Satya Iturthy, Annualleport of the Nuclaar Physics Division (1976) 8ARC - 878, p.65.
2) H. Takata, J.Phys.Joc.3apen 20, 1743 (1965).3) T. Kasuya, Sol. btata.Commun. 15,, 1119 (1974).4) Y. Ishikawa, K. Tajiwia and P. Radhekrishnan, J.Phya.aoc.
Japan 4£t 1597 (1976).
3. Waqnatic Form Factor in Cobalt-doped YbraO, (S.K. Paranjpe andR.J. Segum)
1 Z)Purs YbFeO, exhibits two first order magnetic transitions '
corresponding to the indapandent ordering of the Fe and Yb
Below 627 K the Fe moments are coupled antiferromagnetically with
a slight canting with respect to each other which givaa rise to a
small spontaneous moment perpendicular to the antiferromagnetic
axis. Below B K the direction of the spontaneous magnetisation
is along a-axia, which changes to c-axis when the temperature ie
increased and the ordering of rare earth moments also disappears.
The present study is on a single crystal of Vbfe , Co 0 •
Such doping may change the atomic coordinates as well as magnetic
properties. Our results show that the unit cell dimensions and the
atomic coordinates remain practically the same after doping but a
drastic change takes place in thB magnetic properties. The Cd
doping has resulted in a reorientation of the spontaneous moment
from c to a-axis.
The magnetic and chemical unit cell dimensions being the same,
many reflections have mixed nuclear and magnetic intensities but
the (Okl) reflections, with both k and 1 odd, have no nuclear con-
tributions. Hence all such reflections measured in <^100 zone
can be analysed to yield the moment direction. If the ordering
1 2 ) 2were of G type, as for purs YbfeO, ' , the q - values would have
been same for all reflections in <^100 "> zone and tha intensities
of (011) end (013) would be the same after correcting for form
facotr. However observed intensity of (013) was very much weaker.
apsides, the intensities uf (011) and (101) reflection* were found
to be nearly equal which is not possible in G type of ordering. An
analysis of reflections in <^1OO~> zone showed that the ordering
-97-
is of G type.
Fe iona occupy octahedral sites only in rare earth ortho-
ferritea and henca the experimental form factor as shown in
Fig.3.1 is that of Fe + in octahedral crystal field. For com-
10K.N
FORM FACTOR OF Fe3*
tS
0.6-
0.4-
02 -
0.00.2 a*
3+
0.6
Fig.3.1 For* factor of Fa3+ in Yb C O0 , 0 9
0 3 '
3+3+parlson, other experimental and thaoratical Fe form factors
havs also bean included in the figure.
It haa been known that the spin reorientation phenomenon in
orthofarrites is controlled by the magnetic anisotropy. The weak
magnetic interaction between iron and rare earth iona can causa
a polarisation of the latter. At high temperatures the polari-
sation ia negligible and so is the associated anisotropy. When
tha tsmparatutG ie lowered the paleriaation end the anisotropv
both incraasa affecting a spin reoriuntation. oo it is not un-
axpactad that the substitution of FB by a small amount of cobslt;
which ia hiyhly eniuotropic, can afTfeot e spin rBorisntation,
1) 0. Trevoa, J. Appl. PhyB. 3j6, 1033 (196S),2} a. flaraachal, J . olwardiere, J . Phya. 3_0, 967 (1969).
-99-
II. Neutron Inelastic Scattering
1. Phonon Studies in KNQ (Phase II) (K.R. R«o, P.K. Iyengar,A.H. l/enkatesh* and P.R. Uijayaraghavan)
Potassium nitrate (KNQ,) crystallises at room temperature
in the aragonite structure, this being orthorhombic with space
group 0 _., unit cell containing four molecules. This phase is
generally referred to as phase II or oi-phase. We have measured •
the phonon dispersion curves along AC Q 1§ 03 a n d A C 0 0 0 directions
(a a 6.4255 8, b * 5.4175 8 and c - 9.1709 A) using neutron in-
elastic scattering techniques at CIHU-J reactor. Since a very large
number of brances are associated with the dispersion relation,
selected regions of reciprocal space are chosen for measuring
phonon intensities on the basis of group theoretical considerations
of selection rules for neutron scattering, fig.1.1 shows the nature
Fig. 1.1 Phonon dispersion curve* in KN0_ at room temperature.Oaahsd line* - froa tlaatic constant data, full Unasguid* to the
-1 ""'C-
of thu dispersion relation obtained so far. Thess preliminary
results indicate that the acoustic branches are in fairly good
agreement with those deriv/abie on the basis of elastic constant
data. Further analysis of the phonon shapes and their frequencies
would be carried out taking into account resolution effects. Theo-
retical formulation of the lattice dynamics would be takun uu ir
the nseir future.
+ on loan from RRC, Kalpakkam
2. Reorluntdtion of Ammonium Ions In NH^I, ( W H - ) Q K 34-JLLand (NH, )» ,c K,n Q/ I (P.a. Goyal and B.A. tiaSannacnSrya \
The reorientational dynamics of amnonium ions in NaCi phase
of NH4I, (NH 4) Q > 1 6 K0#64land i^)Q^6 K()>84 6r ha, been studied
by means of neutron quasi-elastic scattering. *11 the salts have
Nad-type structure at room temperature. NH. I undergoes a NaCl
to CsLl phase translation at 2b6 K but the mixed salts retain the
NaCl structure down to low temperaturea.
Noutton quasi-elastic scattering experiments hawe been carried
out in the momentum transfer ranye of 1.54 to 2.18 A using the
rotating cryjtai dp^ctrometer at CIRUb reactor. The incident neu-
trons had an energy of 4.78 meU and the energy resolution used in
the present measurements was about 7% at the incident energy. The
experiments on NH I and (NH ) K 1 were performed at room
-1 0"! -
temperature. For (NH.)„ , , K_ _. Br the measurements were made4 U» 1 O 0.84
at 115, 220 and 300 K. The reorientational broadening was observed
in all the spectra.
In the NaCl phase, NH. ion resides in an octahedral surround-
ing with six halides as neatest neighbours. A tetrahedral NH ion
does not find octahedral environment suitable for ordering. =>tru-
2) 3)cture work on the NaCl phase of NH.I ' and NH Br ' shows that
hydrogen-density distribution is in fact nearly spherical around
every nitrogen with broad peaks along (JQO]| direction. To analyse
the data of neutron quasi-elastic scatttuing experiments, we chosa
4 )rotational diffusion model \ which gives an entirely spherical
cloud.
The characteristic times Taa defined within the framework of
4 )rotational diffusion model ' were found to be 3.1 + 1 and 2.4 + 1
psec for NHA1 and (NH.)n . K I respectivoly, at room temperature.
The T v/alues for (NH. )„ „,*„_. Br at room temperature, 220 and
115 K are 14.8 + 6, 15.2 + 2 and 19.5 + 5 paec respectively. That
is, in our measurements, we do not find any systematic increase
in Z in going from 300 to 115 K. If one assumes that T is given
bY X " ToBxpt ^/k^T ) o u r results suggest that in the Nad phase
of mixed ammonium bromide, the barrier hindering the rotational
motion of NH* ions is very email.
Flora experiments are underway on the triple-axia ipectrometer.
-1(2?-
1 ) H.O. Kim, P.3. Goyal, G. Venkataraman, B.A. Dasannacharya andC.I. Thaper, jolid Stats Com-n. 8,, 889 (1970).
2) R.S. Saymour and A.U. Pryor, Ac7a, Cry at. 26B, 1487 (1970).3) U. Pr«s3, Acts, Cryst. 29£, 257 (1973).4) \l. bears, Can. J. Phys. 45., 237 (1967).
3. Geomatrlaa of Haorientation of Ammonium Iona In (flH.)2SO, and
IT^Vo.16*0.84 J 2 S°4 <P'S« Goyal and B.A. OasannlcRarya)
Rotational dynamics of NH+ ions in (NH) aO. and
l(NH>i)r. <£Kn Q,»1 o5*^ n a 9 beet1 studied uaing neutron quasi-olastic
•oattariny tachniqua. The unit cell of ( N HA) 7S 0A h a s t w 0 tyP88 of
NH* ions which are denoted by NH*(I) and NH*(II)1'. The mixed salt
H4^O.16KO.84^ 2S04 O o n t a l n* QnlV NH*(ll) ion« 2\ In th»
method of analysis ', ^NH4'^250A d a t a 9 i w e s a n "ffsctiva form factor
* ff(Q) - n d a n affective relaxation time ? ff for the two amaoniu*
ions* In the present Investigation a modified method of analyaia
has been suggested for obtaining the information about the two iona
separately. It is tthOMn that the effective form factor depends on
relative values of Tj and tf with respect to the instrumental
resolution. If both tha ammonium ions have X. values in tho energy
window of the spectrometer, then A #f(Q) i 8 a n arithmatic mean of
tha form factors A (Q) and AI1((J) of the two NH* lonsf otherwise
differant combinations of A (Q) and A (Q) are measured. From prr»
sant method of analysis, it has bean found that in (*>H. }.S0 ,
between 227 and 420 K, and that both Xx and ?£ ara in
the energy window of our spectrometer (3 psec to 75 psec). The
value of A n ( Q ) and Tn tot NH*(II) ware obtained from tha Mixed
aalt data. A.(Q) and Tr were obtained by combining Che data
from pure (NH ) iiO and those from the mixed salt. The values
of' rT and TVL at room temperature have been found to ba
10.4 + 3.0 and 15.8 + 1.1 psec respectively. This is thB first
determination of T t and "CJQ separately. in the paraelei.tric phase.
Tha dsrived form factors A (Q.) and AJJCQ) o f t h e t w 0 NH^ i o n s
have been compared with the calculated form factors based on three
models for thB geometry of NH. ions reorientations. We find that
none of tha models explains the measured form factors. They can
however be described by the following equation:
[4- O S
Hera Q is the wave vector transfer and R is the inter proton dis-
tance in NH ion. The value of n in the above Lqn. is 2.5 for
A (Q) and it is 3.0 for A (Q). From this we conclude that rotation
of NH.(II) ion abouL various N-H bonds is not equally probable, and
that there is a distribution of relaxation times. The rotation of
NH.(i) on the other hand seems to be equally probable about all tha
four N-H bonds. These conclusions are consistent with nautron
diffraction results1K
1) C O . Schle.nper and U.C. Hamilton, a. Chem. Phys. 44,, 4498 (1966).2) P.P. Chandra, B.A. Oaaannacharya, P.S. Goyal, P.K. Iyengar,
K.H. Rao, C.L. Thaper and A.H. Venkatesh, Phys. Lett. 57A.463 (1976).
3)' H.J. Kim, P.S« Goyal, G. l/ankataraman, B.A. Oasanacharya andC.L. Thaper, jolid atate Comm. 8., 889 (1970).
-104-
4. Neutron Inelastic Scattering from Glyclne and dl-°<.-ftlanina(C.L. Thaper,J.K. jinha and 8.A. Dasannacharya)
Amino acids are the building blocks of protein*. For a com-
plete understanding of molecular conformation and the nature of
hydrogen bonding in these systems, structural as well as dynamical
studies are called for. While several amino acids have been in-
vestigated from the structural point of view, studios on the
dynamics are only a few. Us report here neutron inelastic experi-
ments on two amino acids, namely glycine and dl^tf-alanine with a
view to identifying torsional motions of NH, in the former and
NH_ and methyl groups in the latter. Glycine and dl-oC-Alanine
crystallise in monoclinic and orthorhombic unit cell respectively,
with four molecules per cell. Hydrogen bonds are formed between
hydrogen of NH^ and oxygen from the three neighbouring molecules.
The experiments have been performed on polycrystalline sample
both at room temperature and 100 K using the Trombay filter-detector
spectrometer . The 9pectra at 100 K, corrected for room background,
are shown in fig.4.1. These reveal a great daal more detail than by
earlier neutron experiments performed with poorer resolution and at
2 3)room temperature ' . The resolution of the present experiment*, in
which a Cu(111) was used as monochromator for glycine and fll(111)
for dl-o<-alanine, is shown by the horizontal bars in the figure.
For identifying the NH, and methyl group motions, ws have com-
pared our results with infrared and earlier nautron experiments and
- 1 0 5 -
calculation* based on normal coordinates analysis ' '. On the
basis of this the intense peaks at 523 cm" and 513 cm in
glycine and dl-oi-alanine respectively are attributed to the
torsional motion of NH*. The peak at 284 cm" in alanine, which
>-
-CD
aSin
8
RON
saW
5
j
22
6
B
«
3
2
1
i • i " fc • i • i
^ A\ / \\ A./ \\ /> / \
-H N ~\KhJ * I
-~ A/J/'—\
• * •/ 1- • • e*» *•
i . / • i • i , iIdOO 800 700 600 500
1 i
\ V
«
A
x |
(00
1 I
GLYCINEH H
H-^-^-C
H H
T.100H«t>»90#
!
300
i
*°\ .o
f •
f
dl-^-ALANINE __H H
H CH3 °
1200
j
1
I
^ 1|
--
1ENERGY TRANSFER (in Cm"1)
fig.4,1 Neutron inelastic scattering from glycine anddi-oc-alaninu at 100K.
is absent in glycine is assigned to CH, torsion. Infrared experi>-
ments on N and C - deuteratsd glycine suggest the coupling of
- C modea to NH? or CH_ motions. Our measurementsCOO and N -
seem to confirm this coupling, as otherwise these modes would have
been barely aeen. Several observed peaks are found to be broader
-106-
than tha experimental resolution. The widths of the peaks could
either bB due to the presence of more than ona peak, anharmonicity
or due to the dispersion of tha concerned modes.
1) C.I. Thaper, B.A. Oasannacharya and P.K. Iyengar, Nucl. Inst.and methods VT3i 15 (1973).
2) V.O. Gupta and K.O. aingh, Chem. Phys. Letters. 5_, 218 (1970).3) V.O. Gupta and N.U. Krishnan, J. Phys. J33_, 572 (1970).4) A.m. Owiwedi and V.D. Gupta, Ind. J. of Biochem. and Biophys.
±0, 77 (1973).5) R.B. Srivastava and V.Q. Gupta, Ind. J. of Pur a and Appl.
Phy3. ,!£, 596 (1972).
S. Hultiple Scattering Calculations Usinq Monte-Car J.o Technique(P.P. Chandra and B.A. Oasannacharya). ,
Multiple scattering'correction in neutron scattering experi-
ments may be calculated in one of the two ways: by direct integra-
tion of the neutron transport equation or a Itonte-Carlo simulation
method. Recently we have adopted a computer programme capable of
calculating first and second order spectra for a neutron inelastic
scattering experiment. The input information to the programme is
a matrix of values for the function S((J,oJ) defined as
Mir *•
An appropriate 'model* is required to get this matrix. Only
values of S(Q,oJ) for positive u are supplied. Values or S(Qfco)
for negative OJ are calculated by the condition of detailad
balance. The programme performs calculations and prints results '
at equal intervals of time-of-flight of neutrons and thus thasa
-107-
rssults can be compared with experimental data directly. A typical
example of the results obtained by this programme for liquid Silaneo
at 137 K are shown in F ig .5 .1 . The scattering angle ia 45.3 • The
10
to1
> • TOTAL NEUTRON FLUX
. . SWGLY SCATTERED NEUTRON FLUX
• • DOUBLY SCATTERED NEUTRON FLUI
«
511. ANE<J,r 45.3*T.137*K
4» MS IN 10M O3« 1*M
TIME OF fUGHT (|1 Sec./meter)
Fig.5.1 Calculated spectra from liquid silane at 137K
model used to supply S(Q, U>) mesh and other various parameters are
described elsewhura '. The time taken for this calculation on
BCSM-6 computer is about 0.54 seconds per tine-of-flight bin
per 1000 neutron histories.
1) fl.U. Johnson, A.E.R.E. - R 7682, Harwell Report (1974).2) C.L. Thaper and B.A. Oatannacharya, Pramana 6^, 383 (1976).
-1 ce-
n t . Uoht Scattering, and Liquid Cryitil Studiaa
1. Rotational Correlation In C H . by Raman Scattering (fl.L. San-aal and A.P. Roy) b 1Z
Raman spectroscopy provide* a powerful tool for investigating
molacular motion in pure liquid*. The polariaad (Xi.) and depola-
rised (I.) Una profile* have bean recorded for various bands in
C*H«n uaing a Ha-Ne laaar (power^25 «w) operating at 6328*. A6 12
polarisation scrambler waa introduced in the beam to eliminate the
dependanca of grating efficiency on the atate of polarisation of
tha beam.
Fig,1.1 showa tha dapolarised apactrum for the V5- vibratlonal
band (802 cm" ). Tha reoordad NWNA for I,1 and I, are 2 cm" and
5 cm" reepactively (Instrumental HWHPI t 1*2 cm* ). Preliminary
400
^ mo-Jo (80? ciri1)
Ramnn Sr>«Slrutn IA
AUI (cm1)
Fig.1.1 Tha dapolarizad 1^5 vlbrational band in C H .6 12
-109-
analysis shows that the line profile can not be fitted using «
Lorentzian over the complete range. This would imply that the
relaxation time obtained by earlier workers ' assuming a simple
diffusion model is inadequate for a complete description of corre-
lation function in C.H .o 1 2
1) F.J. Bartoli and T.A. Litouitz, J. Chem. Phya. 56,, 404,413 (1972).
2. Raman Scattering Study of Synthetic As S Single Crystal(Pl.t.. Bansal, U.C. aahni and A.P. Roy)
Previous study in synthetic As 5 has prompted the specu-
lation that laser irradiation produces a polymeric product. We .
report here Raman scattering study in As S . Our objectives
are twofold. Ons is to unambiguously separate the two phonon modes
from the one phonon modes through temperature dependent study and
secondly to delineate the effects of laser irradiation on the
Raman spectrum of the sample.
The spectra were recorded using synthetic single crystals
(size : 2mm x 1mm x 0.1mm) whose composition and crystallinity
were established through chemical analysis and X-ray diffraction
respectively. Raman spectra were excited using a He-Ne laser
(6328 A).. To avoid laser heating of the sample, power of the in-
cident radiation on the sample watt adjusted to 2 mw. Because of
near matching of the energy gap with the frequency of laser light,
scattering cross-section was considerably enhanced. In order to
-11 C-
distinguish tha onB phonon Raman Unas fro« cornoinat Ion raodaa the
spectra ware recorded at 2JO K'and 3U0 K and were found to be com-
pletely depolarized, presumably owing to high optical activity of
the sample at the exciting wavelength.
The major modes identified are at 60, 142, 216, 342, 352 and
362 cm . Thesu compare well with the apectra observed for
As S 1', The lines at 117, 156, 136 and 234 are attributed to
two phonon processes. After irradiation of the sample by laser
radiation, the significant changes that occur in tha spectrum (Sea
Fig.2.1} are t i) appearance of'a strong line at 233 cm and a
Tig.2.1 Raman spectra of As-ii 1s.«troom temperature before andafter laser irradiation.
2')0 2I7O 150 100 5 0 "Raman Shift (Cm'1)
band at 354 cm ii) simultaneous decrease in intensity of tha
-1 —1lines at 186 cm and 362 cm .
1 ) L.J. Porter and G.C1. aheldrick, 3. Chem. Soc. 0. Trans. 1347(1972).2) G.P. Kothiyal and B. Ghosh, J. Crystal Growth 32., 29(1976).
Pr x.1-inuln 5cg t t : ••lr>'j In. . " Jt i'*>".K «•"••-» ••.hon J ^ r K , i . l u h ' - . a ' ' '.
i.n th« ueocity of aco';.«tic MVE«, propagating
S.n niolisciil-jr .liquid1! occurs i'? c o f f i n r?P^u^r!cy rsngps which i re
er: to internal ihnr.nai ralaxatior o£ structuraJL »elaxatior
•-. o '.he for. nation of rSine.m, triirtsra a*;c. ) or hoth . In
3ssori.at.9d .'ir.inirfs .-s-ich sis alsoHol.-, di'-.^-juyh b'">*".h !'••: laxation
proc«.'-.••-yj? ax.L'it, E i m c t u t a i re laxat ion i ^ t'i« do^i^^nt process
beca'jsk- thu I'itTKt.i'.'nai speci f ic he=!t« •».?« not. i a r ye . We have
p s r f m R d B r i i l o u i n scattf ic i r.q ia»si>r'.wnt8 «*jLt'» two "iich ar.iociated
Liqu ids, Lthanui. and I"i8t"-.«nul .in t.rci^r to styd^ 8fcriji..iur->l re laxat ion
occur jng in therr. Ths -Jt r i ic t j ra l ruJ.axatio^ t ime, 'v~ ,-.j. , i n thess
1:.quids it- ~o largs at rocinn teir,ierntur R (:" ?.?. C) tha i the i/slocj ty
of thn hypr-*fir-i"ic .-•'odBS, "1/ -^ "\- _-N thf. ve loc i ty a!. infj.f< -.fl •:?coij.r;(.ic
f raqijEnr.j', "'•"*",. _ riser e-auHP rap id ly ivi.t.i t"PDPC nt.T s sr> that at s u f f i -
c i e n t l y hi-jh t8.T;paiatu??p=, I/'"-, " i / " *.hB wfi.,ocity wf scnustiv; wawga cf
\ ezy lev. r r cjuanny, /ii, .vSs h^ ' f rnlr.-* i n t ! l^ : ' is
»»'in.?e, u..i .-. "XTT"..;^, '.*-,, ^<?.i « %-.hn Bril.:-?uii> shift ani "^s'-*-" °" r 4-
wit" f<_ i'f.lr^ « purara^ter whir.:' i s i fu^cjfiun of tho SD«r.i.'*ic heafca
O ? t'n* r. J fi'; p•- ,
exps- i
-112.-
• nd GR grade ftothanal, filtered through Whatman filter paper (542)
wars used. Plethanol man studied in tha range, 23*C <_T<; 5Q*C, whereas
Ethanol was only studied at 23*C. The Brillouin scattering aeasure-
2)ments ware made with a Fabry-Perot Spectrametar ' using a He-Na
light source ( A* 6328A). Free spectral ranges of 1B.6GHz. and
were used to observe the Srillouin shifts.
The observed Brillouin shifts, \}a at 23 C, are plotted as a
function of Q (-ATr/X si" «/2, 6 bbing the scattering angle) for
the two alcohols in Fig.3.1. The.straight lines represent,
B CH3OH-O- C2H5OH—*
10 1 2
WAVE VECTOR, Q (105 Cm"1)F ig .3 .1 Variat ion of "V with Q, for Itethanol (CH-OH) and
t ( ) 3t thanol (CoHc0H).
w h e r 9 w a 8 • S S u m e d t 0 b s to tha value of
ultrasonic velocity ( ~\fQ , fiethanol = ' 116-Z-in/sec and \f ,
Ethanol -z. 1153.2- m/sec "j? '. Our values of 1 / " («2 IT X/ft/^i )
4 )agree quite well with thoae of Sunanda Bai ' . binea no velocity- I
dispersion has been observed, we can deduce that T _ ^ OL) /'V T^
The temperature dependence of ~\f in Methanol is shown in Fig.3.2
for Q m 1.8x10 cm" . \/~~ decreases fa i r ly fast with increasing
temperature for 23*C (j <_43°C but for T ^,3°C, I d v7dT \ decreases.
I f we assunta that VT»50»C
than the half way point given
in £q.(1) 1* reached for T - 30»C where V n » 3.1 GH . Using Eq.(2),D Z
-11V
we obtain a valua of 3.Qx10~ gee fcr Tj^. . Since T (ar»d nance
20 30 40
Temperature (°C)
Fig.3.2 Temperature dependence of y for Methanol.
has a distribution, this value is roughly indicative of the centre
of this distribution for
+ Research student from Bombay University.1) K.F. Harzfeld and T.A. Litovitz, 'Absorption and Oispets^on of
Ultrasonic ulauoa' (Academic Press, Mew York, 1959).2) K. Usha Deniz, P.a. Parvathanathan and A.S. Paranjpe, Ind. J.
Phys. 5^, 2B3 (1S7S ).3) A. Uaisaler, 3.Am. Cham. Soc. TO, 1634 (1948).4) K. oun«nda Bui, Proc. Ind. Acad. Sci. 15,, 349 (1942).
4. Snail Angle Light Scattering from WBBA. Subjected to Electricriaida" (K. Usha Oeniz and A.I. nehta*}
Aligned films of nymatic liquid crystals (NLC) with negative
dielectric anisotropy (£it<0) contained in sandwich cells, when
subjected to electric fields, applied perpendicular to the film
-11 4-
surfacB, ahou the fallowing effects! Far voltayes,y up to a
threshold voltage, \/( of a feu volts, ths alignment of the mole-
cules dues not change. For V=V| instability sets in and Williams
Domaina ' make their appearance in the liquid crystals. If the
voltage is further increased, at a second threshold voltage, V^
(which is expected to be equal to 2-V( ) another instability
(turbulence) sets in and one obtains dynamic scattering of light.
uJe have studied the onaet of these two instabilities in the NLC,
1*18S<t, using microscopy and small angle light scattering.
NBBA is an NLC in the temperature range, 295 K to 320 K.
aanduiich calls containing M6BA films of thickness, ranging from
40 /* it to 100 /Mm mere used in our experiments. A polarizing micro-
scope uas used to observe the onset of instabilities. The light
source in the small-angle light scattering experiments was a He-Ne
laser ( /\ = 623BA) and a photo-diode was usad as a detector. The
light scattered at angles, Q , in the ranges 0 <^9 <^ 20* and
30' <^8 <f 2s, was observed with angular resolutions of ?' and. 24*
respectively. The sample temperatures in all observations was
about 296 K.
The microscopic observations have shown the presence of
Williams Domains in PIBBA for \jy/\lf^2.S volts. The domain size
and arrangement were irregular, showing that tha NLC was not aligned
well (see Fig.4.1a). At V * &«5 volts the domains changed in
appearance (Fig.4.1b), Above this voltage ths domains were aaan
to move slowly and at 7 volts these movements became vigorous,
114 a
(a) 4.4 VOLTS (b) 6.5 VOLTSPolaroids X; magnification 80
Fig. 4.1 Microphotographs of MBBA.
- 115 -
indicating the presence of turbulence. Thus V^Cti? volts) ia
•bout 2V|«
The light scattering experiments carried out Tor Q <^ 20'
showed that at all the scattering angles studied, there is a Maximum
in the scattered light intensity for Vt? 3.2 volts. A typical vol-
tage distribution is shown in Fig.4.2. The values, Vm» f o r diff-
erent 0 , ranged from 2.a to 3.5 volts. The increased intensity
near V?y\ is thought to be due to critical scattering caused by the
onset of the instability, which causes domain formation. V| has
been determined to be 3.15+0.35 volts. In the experiments done in
the range 3Q'(Q S2*, a new peak appears (Fig.4.2) at V=V(T|"7 wolts.
The general shape of this peak is similar to that observed for V-Vj»
This peak is thought to be due to setting in of turbulence. In this
-116-
oaaa Vyy, tangsd from 6.4 volts to 7.2 volta and V watt found to be
9
0 5 10 15 20
APPLIED VOLTAGE. V ( Votts )
Tig.4.2 Scattered Ugh intensity versus applied voltage, V, TorPI6BA.
•qual to 6.8+0.4 volts. Thasa values of V| and V^ art in good
agreement with those obtained by microscopy. I t is found that the
anhancad intensity, I od log( VM~ V) ' o t both sata of measurements.
* Research student from Bombay University.1} W. Helfrich, flol. Cty«t. and U q . Cryst. 21., 187 (ig73).
S. X-Ray Investigation of the Smactlc Phases. P . S and S(K. Usha Oeniz, U.R.K. Rao+, A.I. Mehta*, P.S. PSrvathanathanand A.S, Paranjpe)
The scheme of transitions involving the crystalline and liquid
crystalline phases of HxBPA, has betn described elsewhere '. We
have carried out X-ray diffraction measurements vxth HxBPA, to deter-
mine the temperature dependence of (1) amectic layer thlcknesst
-117-
6, (2) in-piane intermolecular distance, 0, and (3) the molecular
tilt anyle, 6., in the phases P and S .t Z n
2 )Two seta of measurements were made t (•) heating the sample
from room temperature (RT£25*C) to 350 K, and (b) cooling the
sample from room temperature to 250 K and heating it back to RT. d
was obtained from tha X-ray data, using the Bragg relation,
}\ «2dSin« (where 29 is the scattering angle). 0 was calculated
from the results, using the relation , }K » ~J~3DSin«, in the SH and
P2 phases, and the equation , 1.117A«2DSin«, in the S^ phase.
B was calculated, using the relation, d/L * Cose , where L is the
length of the molecule (24.44A2').
The temperature dependence of d, 0 and 9 , Tor the two sets
of measurements, are shown in Tigs.5.1 and 5.2. For T S290 K, tha
following features are observed (Fig.5.1). The temperature varia-
tion of both d and 0 can be fitted to straight lines for
290 K / T <^334 K in the 5H phase. Above 334 K, d increases
rapidly with increasing temperature, a feature related to the pre-
sence of the phase transition S —'S , at 337 K. buch a rapid' changeM n
is not observed in 0. The tilt angle decreases slightly between
290 and 334 K, but rapidly for temperatures beyond 334 K. Its
behaviour indicates that tha transition SL,—*SA i s o f tha first
1 ) 4 1
order, a feature found by OSC ' and also predicted theoretically '.
From our measurements of d (^24.0 A) in tha S. phasa, we find that
there is an overlap of tha molecu.es in tha adjoining emectic layara,
to tha extent of 0.44 A. A modified value of «t(»Coa~1d/(l-0.44))
-118-
i . found, by assuming t h . sams overlap in the SH phaas aiso, and
this is shown in F ig .5 .1 .
24
23
21
20
19
18
,30°
ff
*-*_.
« 0
I I1*1
•l
• Cos"1 d/(L-Q.U)
5.2
S.t
s.o
4.9
O(A)
300 320 340
TEMPERATURE (K)
Fig.5.1 Variation of d, 0 and « withtemperature in HxBPA forT > 290K. The straight linesrepresent f i t s to the experi-mental values of d and 0.
o, b 6 (pooling, heating)» , • O(cooling,h*a(ing)
X
2 0 260 270 260 290
TEMPERATURE (K)
Fig.5.2 Variation of d, D and 9. withtemperature for T <^300K. Thestraight lin«9 represent fitsto the experimental values ofd and 0, obtained while cooling.
For T^3Q0 K, (Fig.S.2), the following observations are of
intaresti (1) Valuta of d,obtained both while heating and cooling
can ba rittad by a single straight Una, showing that the P ^ &H
tranaition doas not affact df (2) * aingla atraight Una can fit
tha two sets (cooling and heating) of values of 0 only for T ) 270 K.
Tha values of 0 obtained while heating fro* 250 K seam to follow the
"113-
d o t - d a s h e d curve fo r 250 K < T < ( 2 7 0 K, Sines 0 ( 4 . 8 5 A f o r
T ( ? . ,„ , taking the analogy of lipids ', we believe that the2 H
hydrocarbon (he) chains in the HxSP* molecules are arranged parallel
to bach -th»r in the P phase, but this ordered arrangement is lost
at the P_—>S., transition) (3) 9. has a smooth variation throughout* n C
thia temperature range.
+ From Chemistry Division, BARC.* Research student from Bombay University.1 ) K. Usha Oeniz and U.ft.K. Rao, Piya. Lett. 9A, 208 (1976).2) K. U3ha Oaniz, U.R.K. Rao, A.I. Plehta, A.b. Paranjpe and P.S.
Purvathanathan, Hoi. Crytt. and Liq. Cryst. 42^ 1137 (1977}
3) A. Oe Uriea, Plol. Cryst. and Uq. Cryst. 213, 119 (1973).4) R.3. May si and W.l. dcdillan, Phya. Rev. Ag_ 899 (1974).5) A. Tardiau, V. tuzzatli and F.C. Reman, 3. dol. Biol. 75, 711 (1973).
6. Phaaa Tranaitlons in the Compounds, p-n- Alkoxybanzylidana-p-Awinobanzoic Acid* (K. Usha Oeniz, A.S. Paranjpe, P.S. Parva-thanathan and A.I. riehta++)
of the homologous series of compounds, p-n-alkoxybenzy-
lidene-p-aminobenzoic acid,
C H tovrO <Q>-c«^ N-<g>-cooH
are known to exhibit liquid crystalline phases batwean 100*C and
300 C. The phase transitions involving both crystalline and liquid
crystalline phases in the methyl, hexyl, heptyl, nonyl and tetradecyl
(n « 1, 6, 7, 9 and 14) members of this series have bean investigated
visually and by ObC measurement* made with a Oupont 900 Thermal
Analyzer at Jardar Patal University, (l/aiiabh Vidyanayar)* Some
texture studies* have baan carried out to ascertain the nature of the
-120-
liquid cryata.Ui.na phasaa in that a compounds.
Tha tranaition temparaturea obtained by ua, using the visual
and DSC tachniquaa (whlla haating tha compounds) «e also thoaa values
quoted by othsra ', are given in Tabla 6.1. Thsre ia good agreement
between tha valuea of tha transition temperature obtained in tha
different nteaauremente. Preliminary texture atudiaa aeem to indicate
that the high temperature amectic phase, S., ia amectic C.
TABLL 6»1
1
196*
1 (.) 205+* -
209 + b
160*+a
(.) 168
172+b
286*
i,+b
172» 260*
.) 176+" (.) 265+"
269+b
162*
{.} 146"* (.) i67+i
172+b
205* 251*
(.) 208+* (.) 254+* (.)
212+b 259*15
CO 99H137*
149+b
226* 244*-+a
(.) 226^ (.) 249" ( O• +b
230" 253
14 (O 104+b12611
(.) 125H
2271
(.) 234+b
All tamperaturea are given in *C.K,, K2 Cryatallinai S,, S2 Saacticj N Nenatici I leotropic liquldj* Reference 1| • praaent maaauramantai a vlaual| b DSC(heating at
/ (' - abaent.
The iiyJts oT transformation, £\H, obtained from our OJC m»-sum-
mon ts, for the different transitions are given in Table 6.2. In these
results, we find the following interesting features} (1) In the hexyl
and haptyl compounds & K 'or the transition S.—>N is quite small, in-
dicating that the transition is weakly first order in character in
these compounds, (2) in the nonyl and tstradecyl members, the phase
52(sm«ctic) might be a crystalline phase, tale hava,however, labelled
it as amectic liquid crystalline because of the large value of
H _ (indicative of major structural changes) and because thisV*S2
phase supercools considerably, (3) the hexyl compound haa a glassy
transition (not shown in the tables) whereas the heptyl compound
doe* not.
TABLE 6.2»*
n
1
6
7
9
14
(
(
(
(
(
K2
. )
0.).)0
5.
3 .
0.
3.
4 .
35
65
22
71
15
K1
-
-
( . ) 2.27
-
-
S2
-
-
-
( • ) 2
( • ) 3
.55
.43
S1
-
( . ) 0.26
( . ) 0.27
( . ) 0.B8
( . ) 3.58
N
( . ) 1.17
( . ) 1.26
( . ) 1.38
( . ) 1.93
-
I
( • )
( • )
( • )
( • )
( . )
AH ia given in k cal/mole( . ) present, - absent
+ Compound prepared by Bio-Organic Division, BARC.++ Research student from Bombay University.* Work don* in collaboration with Ore Dressing section, BARC.1) 3.S. Oave and P.R. Patel. rial. Cryat. 2_, 115 (1966)
-122-
IV. Ho'asbauar Spectroscopy and Compton Profile
1 . aite Preference and Local Environment Effects in Fe, ^Co^Ca(N.K. Oaggi and K.R.P.f). Rao) .-,
In an earlier study of Fe.Si with Small amounts of other
tranaition metal atom T (leading to Fa. T Si) it was concluded«J—X X
that T atoms to tha left of Fa in tha periodic table prefer the
8 site of the Hsusler lattice, while T atoms to tha right of and
below Fe preferably occupy (A,C) sites. Us hsva studisd the
site-preferenca and dependence of magnetic moment on tha local
environment for Co and Fe in Fe Co Ga for x * 0,1,2. Tha main
result* are summarized in Tables 1.1 and 1.2.
Aa is evident from Table 1.1 the site-preferance in Fe, Co Ge
is similar to that observed in Fe_ai, aven for much larger amounts
of substitution of Fa by Co (upto x « 2).
Table 1.1
Material (A,C} B ' 0
Fe3Ga (Fa/a)
(CQCO)
It was also found (eee Table 1*2) that the magnetic moment on both
2 iCo and Fe atoms la strongly dependant upon tha number of a -p atoms,
hare Ga, raaidlng in their NN shell. The dominant part of tha mea-
aurad hyperfine fields (HF) at the'nuclei of T atoms cornea from tha
core polarisation term, which is proportional to the magnetic moment
Fe
Fa
Fa
Ga
Ga
Ga
57or tha ion (ss«i F i y . 1 . 1 } . Ths I&omsr s h i f t of the Fa nucle i
Table 1 .2
MaterialNucleusand s i t a
No. of atom9 in NN s h a l l HF <<, magne-t i c moment
T at urns Ga KOa
C*2FaGa
Fa CoGa
Co FeGa
Fa2CoGa
CoGa
Fe(B)
Fa(A,C)
F«(A,C)
Fa(B)
Co'vA,C)
to(A,C)
:O(M,C)
Co{A,C)
F«(A,C)
a Co
4 Fa
4 Fe
4 Fe , 4 Co
3 Fa
4 Fe
S Fd
4 Fe
0
04
«
0
5
4
3
4
8
310
2iO
235
310
153
184
219
193
0
00
Gd atorni (INN)
R8l.tiv«! hyparfin. fiald <HF) «t T nuelal In Co,function of Ga atoma In INN ahall. 2 •• m
-1K4-
eontinuously increases as the numbsr of Ga atoms in i ts NN shell
increases. These two sets of observations indicate that the re-
duction of the magnetic moment (hence the HF) is dua to the transfer2 1
of electrons from the electronegative s p element Ga into the
d states of transition metal atoms. This increase in the number of
3d electrons enhances the shieldiny of the 3s electrons from the
nucleus, decreasing the s electron density at the nucleus. This is
seen as an increase in the Isomer shift.2 )
The N W results ' show that the transferred HF at Ca nuclei is
pouitii/e and about 50 Kua in magnitude. The conduction electron
polarization contribution to HF at any site in ferromagnetic hosts
3 ) 4 )has been estimated to be negative , The models due to 3ena Ge'ldart '
and Blandin - Campbell ' also give HF at s p elements as impurities
in Fa and Co to tie negative. The positive value experimentally
observed is therefore not easy to understand.
1} T.J. Burch, T, Lireuta and 3.K. Budnick, Phya. Rev. Lett.33.,421 (1974).
2) N.K. Jaagi, K.R.P.ft. Rao, A.K. Graver, L.C. Gupta, R. Vijaya-raghavan and Le Oang Khoi, Proc. Int. Conf. on Hyp. Int.,fiodison, USA (1977).
3) n.B. Stearns, Phya. Rev. B4_ 4069 (1971)} ibid BS.,4383 (1973).4) P. Jena end O.3.W. Geldart, Solid Stats Commn. li.,139 (1974).5) A. Blandin and I.A. Campbell, Phya. Rev. Lett. 3J_,51 (1973).
2* Hyperfine Interactions in Ferromaonatic Rh-HnSn (N.K. 3aggiand K.R.P.n. Rao)
The hyperfine interactions of nuclei of non-magnetic Sn atoma
in th« ferromagnetic Haualer alloy Rh-HnSn (T • 420 K) have be«n
-125-
studiad from BB K to 45U K. Ths variation of tha transferred hyper-
fins field mas found to follow a smooth Brillouin function. Earlier
studies on some other Rh-based Heusler alloys exhibited interesting
structural transitions. However, the present study revealed no such
phase transition in P
3. Spin Glass Bi.hayj.our in ConcanUated liaynatic Systems (N.K. Jaggiand K.R.P.CI. Rao)
The spin-glass transition in RKKY-coupled magnetic systems like
Ajj-fa, Jjj-Pln etc. has attracted much attention in recent years. A
question of some importance ir this context is* 19 it possible to have
spin glass behaviour without invoking RKKY interaction, say in concen-
trated maynetic mixtures?
Ue have, to this end, investigated an laing ttamiltonian H, for
a quenched binary mHijnwtic alloy A 8. , (where pure A is a fwrro-
magnat and pure 6 it an antiferrowaynet), by tha Honte Carlo method*
H is given by,
H - - I- IT
where J's are quenched random sita-variablss which have values +2,-
if the site ia occupied by an A atom, and -3. x: it ia occupied by
a B atom (0 , 3 N 0). Fur 3 * 1.1, J • 1.0 and x • 0.5 the system
exhibits the following fingerprints of a paramagnetic to spin glass
transition around a temperature Tg.
1. There is no long range order at any temperature.
2. A rounded peak in the magnetic specific heat at Tg.
-126-
3. A rounded peak in tha magnetic auscaptibility around T£.
4. Fisld-cooliny effects .
5. Long timu relaxation of the magnetisation below T,Q.
6. A highly deywnarate magnetic ground state with the Isingvariables (X\ distributed randomly up and down over tlr-lattice sites.
for a higher concentration of A (x • 0*6), the system becomes
ferromagnetic as is expected. The study suggests that systems like
Co(S Se ) and Co On. , which are ferromaynatic for x «• 1 andX 1 **X * XI **X
antiferromagnwtic for x « 0, nay show a spin-glass phase for intar-
madiata walues of x. Thla la bsing investigated.
A. Compton Profiles of I3omerlc Compounda Mathyl Formate andAcetic Acid" (P. Chaddah and V.C. Sahni)
For a complex molecule it le helpful to view It in terms of
certain components and then explain its properties In terms of those
of its components. Such an approach would be vary fruitful if the
Idea of "transferability" of properties of the components ia found
to be a good approximation, and Compton profile (CP) experiments
provide one testing ground for this idea. Since the pioneering work
of Ouncanson and Coulson , who proposed that the CP of certain mole-
cules could be analysed in terms of the contributions from bond ele-
ctrons, several studies have been made on various hydrocarbons. Re-
-•ently, Epstein et al ' studied three isowers (of C. H D0 o), dioxana,4 o 2
n-butyric acid and iso-butyric acid, so «a to see the difference
between CP's of -dioxana and the acid, that is given by
J-U + 3__ - 3_Q - JQH, where various 0's refer to correeponding
-127-
bonds. Since the total number of electrons in these molecules is
large, uie explored if some smaller (isomaric) molecules also provided
similar profile differences that would be easier to detect experiman-
3)tally. So we choae ' the isomers methyl formate (C1F) and acetic acid(AM) with the formula C H 0,.
The measurements were done at the room temperature, using
59.54 Kev Y-rays from a Am source of atrength 100 mCi. The
scattered photons were detected and energy analysed using a Si(Li)
detector and a 512-channal analyser, whose slope was fixed at
68.5 eV/channel. Over 1QU00 counts were collected per channel in
the peak region. And, after applying background corrections the
observed profiles are displayed in Fig.4.1 alongwith the calculated
results. The localised molecular orbitals etc. needed for the profile
5.01
4.0
I 3.0ma.4
2.0
1.0
0.0
METHVL FORMATE
ACETIC ACIO
66.0 67.0 48.0 49.0
ENEBQV IN KtV —
SO.O SI.O
Fig.4.1 Comparison of measure (dots) and theoretical (anoothcurve) Compton profile*. Error bara a m indicated at•one points.
-128-
4 ).:alculation were taken from Cpstain ', and fur comparing theory
with experiment we have convoluted tha calculated profile with the
instrumental resolution function, and also modified it for energy-
dependent corrections. As can be seen the agreement between theory
and experiment is good (although the measured CP is slightly broader),
and we, therefore, feel that this scheme should be tried for other
systems.
1 ) W.£. Ouncanson and C.rt. Couleon, Proc. Cambridge Phil.32,406 (1941).
2) I.R. Epstain, B.G. ulilliams and W.J. Cooper, J. Chain. Phys.58.,4Q98 (1973).
3) P. Chaddah and V.C. bahni, Chem. Phys. Lett. 46,, 311 (1977).4) I.R. Cpstain, J. Chem. Phya. 53,,4425 (1970).
5. Charge Transfer Study in FaAi Uaino Compton Scattering(P. Chaddah and I/.C. Sahni)
Electronic structure studies of transition metal aluminidas
using NOR and soft X-ray studies tyavo lead to the conclusion that
there is a transfer of electrons from aluminium to the transition
metal d-band. The extant of charge transfer indicated by the two
experiments ia, however, vary different. No Fermi surface measure-
dents hav/a been raportad in theaa compounds, presumably because of
their intrinsic disorder. Since Compton Profile (CP) experiments
do not suffer from such, restrictions on tha sample, a CP study of
the charge transfer in FeAl was undartakan. The sample was prepared
by arc; melting, annealed and X-ray analys-ed to confirm a CsCl stru-
cture'. Chemical analysis gave its composition as Fe 7*ic Q v*
T n"
observed profile was analysed by a simple modal in which tha transi-
fc.ion mstal d-band was traated via th? Ranotmalisad Free Atom model,
and tha remaining conduction electrons were treated as free. The
breakdown of the Impulse Approximation for the 1s electrons of both
iron and aluminium was accounted for. Our results are in good agree-
ment with the charge transfer given by soft X-ray studies, and show
that the NPIR results overestimate the d-band occupancy.
V. Theory
1 . Inequalities Between Operator fleans (R. Subramanian andK.V. Shagwatj
There is a great 0eai of interest in recent years on operator
inequalities and their application to establishing bounds on quantum
niBChanicdl overlap integrals and expectation values. In this conne-
ction we have studied some inequalities between various means of
positive operators. (A positive operator is one that gives a non»
negative expectation value in every state, fleana are deflned-except
for the geometric mean - in the usual way). Whereas it is doubtful
if mean of an arbitrary order r £• (- co,oO J of i set of (nun-commu-
ting) operators will find an application in physics or elsewhere,
tha arithmetic and harmonic means of positive-definite matrices
(corresponding to r * + 1 and r • - 1 respectively) does find a
realisation in practice in terms of the characteristic impedance
matrix of a series (or parallel) combination of n-port networks,
(it is well known that tha impedance matrix of an n-port network
-130-
ia a positive definite matrix.)
Ue found some vary interesting differences between tha inequali-
ties between means of operators and the corresponding ones far positive
real number a. Denoting the mean of order r by PI , we haue for real
numbers fl ^,11 whenever oo y r ~y 8^>_cO . But for operators ua find
that this is valid only if r and s lie outside the interval (-1 , 1 ),
Ua havw also ahown, by means of suitable counter-sxamplys, that the
inequalities are violated when r and s lie in the interval (-1, 1 ).
The above results have also been extended to weighted means of
operators.
2. The Electru-flaqn*»tic Analogue of Attenuating Raylelqh-Stoneleylilayws (l.V.w. Raghavacharyulu)
The propagation of elastic wavss along a free surface of a
semi-infinite elastic body was studied by .Raylaigh. This study
generalised in the case of interfacial waves propagating along the
interface of two elastic half spaces by Stoneley ' . The electro-
magnetic analogue of the Stoneluy waves is implied in the work of
3)
Sommerfeld . In this rap cut we shall be interested in the attenua-
tion properties or these interfacial waves when the dielectric half
apacea are separated by a conducting sheet of finite thickness in
general, and in the limiting case of vanishing thickness of the sheet
under some suitable limiting conditions in particular, further, we
establish in tha limiting caaa a new form of tha boundary conditions
at tha interface which givaa tha dispersion CwLation directly.
Specifically 1st ua consider two physically different dielectric
-13-;-
half spaces separated by a sheet of conductor of thickness 2d and
electrical conductivity Q- . We wish to consider the attenuation
propagation of electromagnetic waves along the conductor. For that
us shall first solve the tjleetromagnetic equations in the three regions
and apply the usual boundary conditions at the two interfaces to obtain
the dispersion relation. Now we wish to consider the propagation of
eluctromagnatic waves along the conductor in the limit when the thick-
ness of thri conducting sheet becomes vanishinyly small (d -> 0) and the
electrical conductivity becomes infinitely large ( tr-too ) such that
th«* product (r d » ^ remanis finite. The limiting condition for the
propagation of attenuated electromagnetic waves along the sheet are
obtained from the general case of finite thickness. Now, we show that
thu limiting solution can «lso bu obtained directly by an appropriate
modification of thu usual boundary conditions at the interface of the
two dielectric half spaces. This is achieved by the requirement that
the jump of the magnetic field across tha interface is proportional to
the electric field at the interface, the constant of proportionality
being the limit of thw product cr d (=<}). Finally the new equation
for the phase velocity in these limits ia given by
in the usual notation.
1) Stonaley, R., Proc. R. Soc. London, iler. A, lQ6i 416 (1924).2) Banghar A.R., riurty S. Gurajada, Raghavacharyulu I.V.V.,
J. Acoust. Soc. Am. 6£« 1071 (1976).3) Sommerfeld, A. Lectures on Theoretical Phyaica, Electrodynamics
Uol.III,- Acad. Press (INC). New York (1952).
.„ 1 7.'.
3. A Note on tha Parametric Plbdal of Loo»a Bonding of ElasticHalf apacea (I.V.V. Raghauacharyulu)
1 )In «n earlier paper a unified approach of tha possible bondings
between tuo elastic half-apaces in contact with each other along a
plans interface was studied using the modal of a v«ni3hingly thin
liquid layer between the two elastic half spaces whan their plane
faces are parallel with vaniahingly small shear viscosity coefficients
Assuming that the two elastic half space* are separated by a Newtonian
viscoua liquid layer of thickness H, and of shear viscosity coeffi-
cient y\^ , tha condition for tha existence of interfacial waves propa-
gating along tha layer is derived* This analysis naturally falls into
threa distinct cases for the possible limits of "M./H as H —» 0 namely
(1) \ is finite or tends to zero such that *[ /H —> bo , (2) 'H.
tends to zero such that "*X/H —*0, and ( ) "^ tends to zero such that
""l/H ^f- 0, finite. The analysis is carried out in each ore af these
separate cases and it is established that the case.(3) subsumes cases
(1) and (2), consistent with the requirement on the model that it should
be the generalization of the two particular casws oubuuming them.
From tha theoretical point of view it is obviously necessary to
establish directly, that cases (1) and (2) are indeed recoverable from
caau (3) in the limits when the bonding parameter \/H is infinity or
zero respectively without taking recourse to the secular equation as
done in the paper. However, in the papwr it was established by direct
verification that the conditions an the model ware satisfied. As can
be easily Sean indeed the limits i{ . H-)+ oG in case (2) invalidate
the expansion sxp( i^ * h\ ) • 1 +1^^H+—and retaining terms upto
first order only which ia valid in caaa (3). (Sea the analysis in the
initial stage of tha study of case (3) . Note however, the analysis
of similar terms in case (1) does not give rise to the same difficulty.
This shows that the possibility of recovering the cases (1) and (2)
from case (J) has to do with the general physical modal under considara-
tion. In fact a direct establishment of this possibility without going
to the secular determinants should eliminate tha apparent contradiction
of the limits conaistant with the basic aim of the paper, namely to
establish a generalised bonding between the two elastic half spaces.
Now, vik write Y\ m X H + and establish that the parametric range of
£ is indeed given by — I fc <1 consistent with the physical model
under consideration. In this range of £ it follows that V^ H —? 0
for i m 1,2,3,4. All the three physical cases are covered by this
range of fc. and the analysis enables ua to write uxp (^^Hj- 1 + V}^.H
retaining the first order term only. The general analysis of secular
determinant is now carried out in the usual way which holds for the
three cases simultaneously.
Now from the form of >\ it easily follows that thu limiting
cases (1) and (2) correspond for £ in the ranges — 1 ^ €. <^o and
0 < £_ <\ i respectively and the case (3) corresponds to £_ m 0. The
analysis of the limiting cases as H —9 0 are hence aiso recovered by
taking formally tL eith.r to infinity ur zero respectively. Thus
ws> have established that the aim of tha model is indeed magnifiei-
wntly satisfied.
1 ) A.R. Banghar, Gurajada S. rturty and I.V.U. R-ghavuuharyuiu,3. Acoust. Soc. Am. 6£, 1071 (1976).
I . CXPfca.tPtt.NTAt A NO INaTRUI'ifc.NTAT ION
1 . P u l n d Qa^qfaadback S j ( L i ) Detector X-ray Syatan (ftadan L « l ,S.K. Ka tar ia and P,L. flhatia*}
W« have sat up a pulaed optofeadback X-ray system, wi th an
energy r e a o l u t i o n of 275 eV a t fln K^ of 5 .9 Kav . Tha aamo
d s t t c t o t ayaten uaad wi th draioTeadback p r e a m p l i f i e r giwaa an anaryy
t a s o i u t i o n of 320 at/, f o r S.9 Kav FlnK^ - U n a , demonatraUng the
s u p a r i o r i t y of pulaed optoTaadback p r e a m p l i f i a r . F i g . 1 . 1 ahoua the
125•pactrum of I takan w i th a pulaed optofeadback prsampl i f io r endlOOOOr
I flWa FEEDBACK HtEAMPUTCT
MO 150CHANNEL NUMBER
200
fig.1.1 t apactru* taken with drairtfeedback and optofeadback*
with drainfaadback prsampiifier at a countrate of 1000 opa. Tha
auparlor performanceof the pulaed optofeedback ayaten ia aeen in
the fora of good aeparation of Km , end Kp of Ta K-Xraye wbich ie
not eeen for the other ayatea even at 1000 opa. It way be Mentioned
-135-
that thio comparison has bean mads with a drainfaedback aystem giving
an energy raaolution of 220 a<J at 5.9 Kew at low countrata.
fig«1.2 shows the anargy resolution of the two system aa a
Fiy.1,2 Energy resolutionversus count rate*
no low woooCpunlrtlt ( c p i i
function of the counting rate for Fa source. It ia seen that th«
enargy resolution of tha optofesdback system remains constant till
20,000 cps.
In order to be able to utiliae tha good performance of the system
at auch high countrate, it ia necessary to use good pile-up rejector
system. Fig.1.3 shows one typical spectrum of Ag and Ta K , - -Xrays
at 20,000 cpa with and without the pile-up rajector. All the counts
above 33 Kev peak are pile-up counts and it ia aeen that tha pile-up
rejector reducee these pile-up counts by a factor of about 200.
Tha pulsed optofaedback X-ray system haa distinct advantages
over the drainfaedback X-ray system in its resolution performance at
high count rates and in tha presence of high anargy background encoun-
tered in experiments. This system is planned to be uaad in proton
induced X-ray flunca»cenc« studies, and in tha K-Xr*y studios of
252Cf fission fragments. '
IOOOO.
1000
wo
10
" *
H I KcVt.
,OPK> FEEM1CK PWgAMUFKN
I -WITH MLEUP MU^tTOR
3i,o n -wmcur rutr mxatm
3SJ
wFig.1.3 Spectra with
and withoutpila-up rejector.
BO wo noCHANNEL NUMKR
1 ) O.A. Landis, F.S. Gouidiny, R.H. P«hl and 3.1, Walton, ICttTransactions in Nucl. ^ci. Vol. NS-18, 1, Fab. 1971.
2. Jingle Elomnnt Analyaar using balanced Filter Technique (H.K.Choudhury and O.C. OohanRrishna)
A single element analyser system using Nal(Tl) detector end
balanced filters has been developed to detect presence of gold in
any sample. Fly.2.1 shows the schematic set-up of the assembly.
23SX-rays front the sample excited by Pu source pass through either
of the filter* and are detected by the Nal(Tl) detector. The trans-
mission of X-rays in tha energy region of 5 keV to 15 keV have been
-137-
watchad for the two filters except in tha ragian of band pass formed
farf
— SAMPLE— COLLIMATOR— RADIO ISOTOPE SOURCE
— FILTER— Nol (TO CRYSTAL
—PHOTO MULTIPLIER TU&E
fig.2.1 Source-sample-detactor assembly.
by the absorption adgua of the two elements forming tha filters.
238Gold L X raya are excited by Pu source and are counted after
interposing the two filters one after the another. The difference
in count* is then proportional to tha amount of gold present in the
•ample. The filters were made of Gallium and Copper compounds and
ware prepared by mixing weighed amounts of fins Oxide powders of these
element* with apoxy and moulding them in a teflon mould. The filter
thickneasss ware finally adjusted by matching them in the region of
5 keV by counting ssattered X rays from a dummy sample. Preliminary
calibration results obtained for standard samples of gold ara shown in
Fig.2.2, which shows a good linearity of counta with concentration of
gold in tha aaaple. Tha counting system was fabricated in the electro-
nic a section of nuclear physics division.
Fig.2.2 Counts versus goldconcentration insample.
•«• MIM
-138-
3. quantitative X-ray Analysis Using Computer Codaa with Si(Li)Detector X-ray System (Hadeh Lai. a.K. Kataria, B.U.N. Rao*and U.S. Kapoor)
Lnergy dispersive X-ray fluorescence system employing Si(tl)
detector X-ray apectrometer of an energy resolution of 220 at/, set
up in the section, haa been in uae for applications to analytical
241 125 238problems using Am , I and Pu as exciting redioisotopea.
Recently much effort haa baen devoted to develop methods and computer
codes for quantitative analysis using thin aampla technique with e
single element standard.
In this computer coda the observed experimental spectrum of
X-ray peaks of various alemente are fitted to a number of Gaussians
representing varloua K or L X-ray lines. Gaussian peak profiles of
X-ray linea for varioua elements are computed from energy calibration
and energy resolution of the X-ray system ea function of energy of
the X-rays, and also using intensity ratios of X-ray lines of each
element. Correction due to differential absorption in tha specimen,
beryllium window for X-ray linea of a single element is applied so
that the complete profile may be fitted to the experimental spectrum
without affecting the Intensity ratios* The background is fitted as
a linear combination of three terms - constant, parabolic and linear*
The computed intensities I of X-ray linee of any element of a sample
and that of standard element are employed in the following relation
to compute concentrations m. of elements of the aampla.
h " JQ G KJ
-J CJJ •» J J J
where I ie the intensity of exciting radioiaotope, G, the geometrical
-139-
factor batwaan aourca and aaapla and datactor, K. 1* tha ralative
ability to axcita and datect the X-ray line* or diff-xant slamanta
and it ia given by tha relation
where f l a tha photoalactrlc croaa aaction for tha a«citing tadia-
tiona, * . ia tha fXuoraacant yiald, 3 tha Jump ratio, T tha
tranaaiaaion of rXuoraacant radiation in ita path, C tha datactor
africiancy and f Is tha fractional intanalty of tha X-ray lint
aaployad for coaputation. C. ia tha ••If absorption corractionJ
factor for absorption or incidant and axcitad radiations in tha aample.
Tha abova procadura mna coaputar coda waa taatad by analysing a
set of synthstic apacimans praparad aa thin aamplaa. A typical obsarvad
X-ray epactru* of a aaapla along with laaat squara fittad apactrun is
shown in Fig.3.1« Tha computed valbaa of I G * . for a numbar of-•»-
too
tte
•«• Exp. SpectraFitted Spectra
II »•CNAHNCl
Fig.3.1 Typical epectru* of a sample.
-HO
•lcwants ara plottad In fig.3.2 agalnat «(, tha atandard valuaa
Fig.3.2 Computad Io6»j »«•«• "j*
Tha laaat aquara rittad atraight Una to thaaa pointa ahoua that tha
agraamant la battar than 5%. Tha praaant mathod or quantltativa
analysla la ganarally appllcabla for all typaa of aaaplaa and la being
uaad for ganatal analytical problawa*
CSIR Pool Officar.
*• liquid HBIIUW Facility at B.A.R.C. («. Chopra, T.A.P. Bagul.aid «i.a. ia*.ya flurthy)
A helium liquifier machint PLHs 212 ha* baon inataJled aa a
centnl facility for providing liquid haliu» raasarch work at low
and ultra low tenpataturea.
The unique feature of the machine i-. tha*. Vw rojrl
for fooling; the warn y«a down to about 20K 's produced in two cryo-
head* A and 8, (Fig.A.1) which are independent of tha cold box where
ths liquid le produced. This maana negligible need of approaching
tha lnaids of the cold box for maintenanca purposae and hanca aaauraa
long life of tha machine.
COM*. C»tn » C»-»o a
95 OK- FREE LIQUFIEU
COMPRESSiiS1 CRYO GENFIMTOR A) CRYO GENERATOR Bi coin BOX
(V
•
\
• SPANEl
Block diagram of haJ.tu-n liquififf iiaa>in« PLHB 212.
Tha cr/ohaada produce cftld by atirlina, cycling of pure hallu«
and the cold produced by them ie brought into tha cold box bv a
rolling iHanhrar«m-*.ypB{ o.ll-fres coin.nr?«RQr C (r.l2.4«1}» Because
of the special design of the cbiKprBaeor no further purification of
the compressed gas ia required before cooling it. Tho gaa to be
liquifiad is cooled by this cold ga» wia heat exchanger*. Final
liquification is carriud out by adiabatic expansion in the ejector
and Joule-Thompson exapnaion. Tho liquid produced ia collected in
the liquid helium dewars.
The machine ia rated at about 12 litre/hour and due to high
temperature of the cooling water it haa been producing liquid at
•bout 8 litres/hour. The proposal for modifying the cooling water
•yetem ie beinj made. The machine haa baan operative for about four
month* by now. It haa run about 200 hours and total liquid produced
and disbursed to users is about 600 litsaa.
S> Ancillary tqulpwan^ for Raoearch Work at Liauld Helium Tempera-tures (V. Chopra, T. Sriniwasan and A.P. Bagul)
A glaaa cryoatat (Fig.5*1) haa been completed along with ite
mounts and haa been teated. It ie capable or holding about 1.25 litre*
of liquid helium for about 15 houra• The cryoatat h*s been uaed for
testing of • 3.C. coil upto ebout 3OK Causs. The critical temperature
ftf superconductors has been measured in this cryoatat. The cry ••tat
ie capable of providing tomperature from 1.5K to 300K.
A aupetconducting switch for use in conjuction with the s.c.
-14: -
nagnet has been designed and fabricated.
MAONCT LfAOS
110. HELIUM
r
Pufnf
THERMOMETER LEAO«
HI5M WkCUUM
SAMPLE LEA05
LID. HITMOEN
-tUPERCONOUCIIN*MAONET
Fig.5*1 A schematic sketch of the glass cryostst for tastingsuperconducting coils.
6. Halluii Gas Production on Laboratory Scala (R.K. Barg , A.fl.rieghal"*, Hanumanth Rao*, V. Chopra, T. Srlnivasan, *.P. Baguland N.3. Satya flurthy)
On a laboratory scale about SO cubic ft. of 98.5Jt purs haliu*
gat hat been produced indigenously. The imoure heliu« gas consisting
of mainly air and sons hydrogsn impurities la obtained •• • by-product
-1.14-
fram the ftonazita sands processing plant at I.R.E. Always, K era Is-.
The hydrogan impurity of about 1^ was removed in a laboratory scale
hydrogen ramovar, designed and fabricated at the Chemical Engineering
Division (Fig.6.1 ) and consisting of a bad of CuO maintained at about
300 + 20"C. Hare the hydrogen impurity gets converted to water. The
hydrogan free helium mixture is coolad in water-cooler and driad in a
silica gal/«olecular sieve column and is collected in low pressure
gas bag.
lEMPERATURECONTROLLEDHEATER
Fig.6.1 Helium gas production on laboratory seals.
-145-
Tha gas is than compressed to a high pressure of 2QD psi and
can be purifiad to 99.9?£ pure helium gas by passing through tno
halium purifier unit. Tha purifiar consista of a) oil fiitar and
separator; b) cold drisr to gat rid of moisture in tha gaa| and c)
an eight bed activated charcoal column immersed in liquid nitrogen.
The purified gas is collected in high pressure cylinders. It is
recommendBd that the total quantity of impure helium gas processed
per batch should be about 80 NN for efficient and economical produ-
ction of helium gas. A high preusure compressor rated at about
2000 psi would be required for the purpose. There is a proposal to
recover all the He from I fit. monazite processing operation. It is
learnt that this would amount to about 3000-4000 NW of He per year.
The method of collection of helium gas from the monazite sands also
need to be modified so that thB raw gag itself will contain less air
impurity.
The hydrogen remover needs to be scaled up and modified by us*
of more efficient catalyst like Oeoxo catalyst or nickle catalyst to
remove the hydrogen completely and from larger volumes of the gas.
Th« Chemical Engineering Division is looking into these modification*,
+ From homical Engineering Division.
7. A Prototype Hot Neutron Source for CIRUS (S.L. Chaplot, P.R.Vijayeraghavan and N.S. Satya flurthyj
A prototype hot neutron source for one of the 12" beam holes in
-146-
C1RUS has baen takan up for design, fabrication and aubaaquent insta-
llation, with a view to gaining axperlanca in tha design features and
estimation of neutron gain factor*.
Fig.7.1 ahowa the schematic diagram of the proposed assembly.
Tha hot source chamber made of Alflg, alloy containa a block of
graphite heated by nuclear radiation and insulated by carbon felts
and molybdenum fails.
estimation of the performance of the proposed hot aourca is made
using a heavy monoatomic gas modal. The incident spectrum was assumed
to be consisting of a (laxwellain at reactor moderator temperature and
an O A ) epithermal spectrum. For calculating the hot source tempera-
ture we have uaad the known nuclear heating data ', assuming this to
arise from Y^-raya alona. Tha insulation due to the carbon felt haa
bean calculated from its average thermal conductivity. The increase
in hot source temperature dua to the reflecting molybdenum foils has
bean estimated from the available experimental data '. The maan tero-
3)perature of a graphite hot source sphere placed in the qraphlts
reflector ie given by
where T • wean neutron temperature! T. • hot source temperature)n n
T » aurrounding reflector temperature, R • radius of equivalent
hot aource .phare, (R * . (3/2) R 2 L ) 1 / 3 end $ - f j — ^ ), i ^
tranaport Mean free path of thermal neutrona in graphite, n • retio
V BE*M HOLE.
(CIRUS)
(MOt 10 SCALE)
VACUUM PUMPANDTHERMOCOUPLECONNECTORS
F i g . 7 . 1 schematic diagram of the hot source assembly.
0.1 0.2 a3
ENERGY (»V)-»
Fig.7.2 Hot source and neutron temperaturesi/s source length.
Fig.7.3 Neutron ^ain ws neutron energy,
-148-
of mass of • graphite atom to that of a neutron, H * radius of
Cylindrical hot source, 21 m length of cylindrical hot-aource.
Fig.7.2 shows the hot source and neutron temperatures respecti-
vely as a function of the length (»2L) of the source for a radiue ')f
9 cms and insulation thickness of S cms. The gain from the hot
source, of neutrons of energy E is given as
where (p and (y are respectively opithermal (1/t) and thermal
Maxwellain flux . Here f is the overall flux reduction from the
ruactor core to the new effective neutron source due to flux gradients
in the reflector and is equated to exp ( - 2L + 0 + 2) — — (3)
1where L * diffusion length of thermal neutron in graphite. Thia is
shown in Fig.7.3. The maximum sain is 14 at £ 0.3 eV. from the
calculation we find that the gain of neutrons of energy (0.3 ev) doe*
not fall below 90jt of its maximum value for the renge (both R.,L • 8 to
11 cm). Hence these parameters may be chosen in thia range depending
on convenience. As the model is a simplified one its results are only
to be used as a qualitative guide. A more detailed calculation based
on the Monte-Carlo method ir !?einu planned. These details and the
details of the present calculation will be published in a separate
report.
1) P.J. Dyne and U. Thuraton, AECl-432 (1957).
-149-
2) 0. Abeln, W. Orexel, U. Glaaer, F. Gompf, U. Reichardt andH. Ripfel, Inelastic scattering of neutrona, IACA (Vienna)Vol. II, 331 (1968).
3) F.3. Webb, Raact. Sci. and Tech. (A/6) V7,, 187 (1963).
6. Laser Raman Spectrometer (P1.L. Bansal, V.C. Sahni and A.P. Roy)
The performance of the spectrometer has bean improved by incor-
porating certain modifications. The new collection lena ayatarn, com-
prising of six len«es corrected for aberrations, haa enhanced the
aiynal at the entrance slit by a factor of flue. Further, the provi-
sion for step scanning haa been introduced to enable digital recording
of data, A refrigerant cooling system ia now employed for the photo-
multiplier housing. Fig.8.1 dhows the 459 cm" bend in CC1 recorded
both in the analogue and digital mode. The ieotope structure ie seen
clearly indicating improvement in the resolution of spectrometer ',
To excite the Raman spectra, 4 He-Ne laser haa been set up. The
0wavelength of the radiation is 6328 A with a power output of 25 mw.
The length of the plasma tube is about 1.5 metres and internal dia-
meter ia 3mm. The resonator cavity ia formed by a littow prism and a
concave mirror (transmission: 2.5£ ; radius of curvature 1 6 metres).
-150-
SAMPLE : CCI4(50% in Cycirhexane )
EXCITING SOURCE': !5mW \-e-tie laser
x
~ 5CAN SPEED :
TIME CONSTANT:
I
-
" 1
ANALOG MODE
H "*"*~2-9 cnT'/mln. II
tO (*c*. { I
I I\
\»4
\)
>L1 A/
1 1 1
RESO'..U
11
|
SCAN STEP : 0
COUNTING TIME:
1 ^r i
D I G I T A L
-, l•*» cm /rnln.. j40 »*c«. j '
|
1f(?/
f
1
MO0E
-
\\1
• ,
\ -
*v ..' • *
1 1
-i 3000
- 200C
2
OO
- )000
490 480 470 460 4S0 440
RAMAN S H I F T ( e m ' 1 )
490 480 470 460 450 4',0
R AM AN S H I F T ( c m " 1 )
f i g .0 .1 The 459 cm band in CC1. showing isotope structure*
1 } fl.L. Banaai, T.R. Rao, V.C. Sahni and A.P. Roy, BARO878, AnnualReport of tha MuclsdC Physics Division, p.133 ( )
9. Wat aria 1 OBveloument and Crystal Growth (n.R.t .Nt Plurthy andP.K. Dayanidhi)
Alloyai Tha following alloys wars praparad, analyaad and mads nwail-
able to tha axparimanters in tha Division.
-151-
Co Gax 1-x
(for x * 0.50 to 0.54 in spinylass phase)
Co * 1 t fa «1C u .5 u.5 0 . 5 0 .5and Hi m
0.5 0.5
Cu _0.
e , Co Fe Ga0.0J 2
Prspared for
flossbauar btud
Compton Profile! SUs-Ks^
Perturl>ycJ
Mo'ssbauar uforS<
»tt.T.\
and Te. Co Ga
Single Crystalat A Bridgman apparatus capable of ops3i: t.iiio -st "i'<0i]ni;
for the growth of single crystals in cylindrical form ii,?? hser. ser up
* Single crystal of bismuth A cms lon^ and 1.5 ct« in diameter has baen
made u^ing this apparatus. Growth of germanium single csyatai:- in th<».
form of slabs by zone refining technique is in progress,.
10. Nickel-Coated Glads Plates for Neutron Guido TubesClurthy )
float glass plates of dimensions 100 x 20 x 1 en have
been tust^d for flatne£a uaing oblique incidence intsrft-rora^'.er snci
found to have cyiindricity with a 'bow' of 140^( over one mtst^r
l#nyth which corresponds to a macroscopic flatness of abou> ,' x ii,-"'
o
radians. These plates have bean coated with n icke l of ^ 1200$! th ip
nets , which has buan m«asurdd by i>si.ny X-ray back scst t t i r ; n<! i,,->:v-,^
11. Data Acquisition Unit for Neutron Spectrometers (A.S.and P.M. )
A standard data acquisition unit for a neutron spectrometer
consist;, at a signal channel linked to a printer and a monitor channel
coupled with a control channel for automatic normalisation of neutron
data with respect to chdnyns in neutron flux falling on the monitor
counter. Usiny inteyrated circuits which perform many of the opere-
tiur.j required far the aboue purpose, a single compact unit has been
oaiiynnj, fabricated and put into operation. A short description of
thu unit i» yiven below:
The unit consists of
(a) Signal jcaier (b) Monitor ScalBr (c) Tinier (d) Pre^ettablo
monitor and (e) A line printer interface.
(a) and (b) are simple aix digit decade sealers which use 7490, i.e.,
chips for counting and 7441 and decoder driver, i.e., chips far display
by Nixia tubes. Monitor Sealer haa an option to count either internal
clock pulses to work aa a simple timer or neutron beam monitor pulses.
Praaettable Monitor
This system haa nina 7490 integrated circuit decade sealer chips
in cascade,, out of which the last two of the most significant decades*
are decoded and brouyht to thumbwheel switches. These thumbwheel
switches used in conjunction with a coincidence circuit enables the
selection of any present number in tha range 1 to 99, to produce an
output uihan the yslactad number matches with that in the last two digits
of the prassttable monitor. The acala factor is chosen by another
-153-
awitch and thus this system provides fo selection of any number of
the typo A x 108 where A lisa between 1 and 99 and B between 0 to ?.
Line Printer Interface
A self-explanatory block diaijram of thia interface ia given
below, for a single diyit (Fig.11.1)
POISE » «E!FI rustHO fll »H ».|) I) |
n n n n nO i l • <
BLOCK DIAGRAM OF THE LINE PRINTER INTERFACE
Fiy.11.1 Line printer interface.
12. A Simplified Incremental Automation for a Neutron Spectrometer(5.L. Chaplot and P.R. Vi jayarayhauan)
An integrated circuit control unit for incrBtnental automation of
a neutron spectrometer has been designed, fabricated and installed.
The system uaaa a five channel punched paper tape reader (manufactured
by H/». Hindustan Teleprinters Umitad) which givaa a sequential output
-154-
of ths data punched in the tape. Instead of decoding the punched
data in ths normal fashion, the five bits of information are independ-
ently uand to controi five functions on an "off/an* basis. The infor-
mation contained in the five channels in tapa is stored in JK flip-
flops, thu selection of the. flop being done usinj a timing cycle obtained
from an appropriate reference point in the 'start' pulse from the tape
rodder. The stored information is used to control tha data collection
and the operation of the spactromyter. The fioui chart is giuen fcBiow;
Readnext cods
Flow Chart
Punched paper tape(codad instructions)
Paper tape reader(reads ths cooed instructions)
Main control unit
1. Decode and store2. Timing different instructions
3. Instructdata collection
Howe •psctrometrir armsby ons step («• required)
4. Rsceiva back signals
5. Instruct tapa raadar to raad next coda
"NsutronMonitor Itsignal sealers
2«, <p , Y «ndbackground motors ofthe spactromater
13. Stabiliaed flaqnat Currant Supply for Superconducting Magnet(B.b. Sriniv/asan)
A stabilised maynat current supply capable of ^iviny a stable
and adjustable direct currant supply for use in neutron diffraction
studies in cgnjunction with uuper conductiny maynst has been built.-
The low voltayu dirsct currant supply is* obtained from a sbconclur
winding of a slap down transformer by rectification u-s_,ig thd bridge
Circuit employing hiyh current silicon rectifiers (01 to 04) as shoum
in Fiy.13.1. Tha A.C. component in the output voltage is smoothenec*
STANOARORESI5TENCE
0. 50 Amp
SUPERCONDUCTING
COIL
'BRIDGE RECTIFIER
Fig.13.1 Stabalised majnet current supply.
by a bank of condensers and the direct current flows through a
transister bank and a precision standard Wanyanin rssister connected
in series with the magnet coils. To obtain current regulation feed
back from the load current is given to the transister bank in such e
-156-
chat when the load resistance or supply voltage varies, ths
voltage drop across the tranaistar bank changes to hold thw current
constant to within Its rating of 5 volts.
The surrent stability is better than 0.4i for 5# change in th«
mains voltage. The ripple factor was 5j£ at full current in a load
of «05 ohms. This haa been improved upon to obtain 1£ current ripple*
This unit has beun developed for ^rogrumming the rate of supply
of current to super-conducting magnet coils. Tha ramp generator
provides complete stability in the hold position and a smooth linear
sweep of current over a period between 1 minute and 10U minutes. Th^
generator can be stopped or reversed or the speed of the sweep changed
at any time.
-157-
14. Uan-de-uradff Operation and Fldintenance (V.A. Hattangadi, S,I\UFlisra, O.S. Bioht, 5.U. Shukla, P.R.5. rtao, G.V. Bhatt, 5.3.Handku, R.P. Kulkarni, Wi£. Doctor, H.U. Patkar and N. Fernanda)
The 5.5 n&\J Uan-da-Uradff accelerator, which completed its 15th
year of almost continuous operation, was run for 7300 hours durinj the
curront year, bomu 41 Ou hours, of thase, have besn utilised for actual
research work by various yroup-j from B.A.rt.C, T.I.F.R. and other insti-
tutions, while. 3200 hours account for the time lost due to machine
breakdowns. About 1428 hours ware naBded for the periodic r^placement
of ion sources, vacuum pump and other regular maintenance work.
The problem of low proton yield from the ion source, which account;
for most of the breakdown time, has been finally 9olved satisfactorily,
The gas manifold in th« tarmin<3l which feeds the gas to tha ion source
was found to ta trib ma->.n source of contamination by axtrantjou5 impuri-
ties and it was hence replaced by a stainless steal manifold which was
carofully cleaned dnd jjruved ieaKiight on a helium m<*ss spectrometer c
This, coupled with U M of ultra hiyh purity hydrogen and standardised
reconditioning proceduruj, has resulted in improving the proton yield
to a value comparable with that of the imported source. As the pra-
ctice of replacing the ion source once every ten days, for each new
run, has been introduced from the last two cycles of experiments,
several ion sources have been reconditioned in the laboratory with,
generally, good reproducible results.
Tha other main recurring operational problem - the erratic
behaviour of the main diffusion pump with its sudden loss of pumping
speed, resulting in a rise in the system pressure - has been
-158-
by thin tdinpoiaiy in.ssu;;: of portodir cleaning and
wermi~; op of the main vapour traps on the diffusion pumps. HDUUVC:,
•s a more permanent solutiun, it is proposed to replace the present
outdated mercury diffusion pump by a modern oil diffusion pump with
a much higher speed and use uf the very low vapour pressure silicons
oils, such aa OC 705 supplied by OUPONT, which ats now svaiiablt
ThB development of tha Thermo mechanical leak is in continuous
proyress. Both the r aproducibility and Hnearltv of operation »-PV6
been improved by introducing ths procedure of pre-conditioning the
leak through several thermal cycles prior to uaa and replacing the
Invar rod by Nickel-Iron alloy with a low coefficient of thermal
expansion developed by the Metallurgy Division. Several Thermo mecha-
nical leaks have been fabricatad and used in continuous operation in
the Terminal. Some operational problems, which still remain^ are
being looked into.
Two high power oacillator circuits using tha 8£L 250CX tubes
have boen uired and tested for prolonged periods o-f operation. The
naui oscillator giving about 100 Watte R.F, Power output will os used
eventually to replace the present oscillator in the Terminal, which
gives an output of only about 35 watts. An old oscillator circuit
using 6072 pantodsa has also b»sn rewired and tested at 120 uat.ta
output power.
It is proposed to rewira the Terminal completely with en
improved layout as with th« present layout servicing of the Terminal
supplies is found to bs vary tedious and tlma consuming. The new
••59-
iffycut. hon been drawn out and scrae af tha units havs
wirsd and tested.
15. Tandem Accelerator (fl.G. Setigeri, T.P. Oai/id, P. Singh andCcU. Rayarappan)
1 . VoltagB Generator* Tha fabrication of the pressure vassal is aj«ii
undar way at the Central Workshops, B.A.R.C. and is expactsd to bs
ready in two to three months.
A support structure using I-beam3 and 9teel plates was made to
mount the column sections. Both tha column Bections uero than
supported horizontally canti-leverad from tha ba3e plates at either
end. No sag was noticed at the terminal ends of either of the sections
H feu ceramic insulators ware earlier tested at the Central Workshops
to determine the shear strength (yield point) at the collar of these
insulators. The minimum value measured was 1600 Kg.
The charging mechanism which includes the inverted motor, pulley,
belt, charging screen, collector screen and the down charge measurament
screen was then mounted (fig.15.1). Also the resistor chain boxes menu
installed in both tha eectiuhs. The belt was run continuously for a
nimber of hours to check motor performance belt tension, terminal
vibration etc. The vibration at the terminal has been negligibly small.
Dynamic balancing of both the motor and the terminal pulley ha9 been
carried out before installation. Voltage fis* on the terminal due to
self (friction) charge was about 100 kl/ during the initial run which
came down to -- 30 k\l during tha later test runs.
160
Fig, 15.1. Charging Svsicin
Fig. 1S.2. Column sections with dome
Tha two sections were connected by a cylindrical terminal caver
made of aluminium (this will be replaced by a stainless steel couar
later) and belt charge was slowly raised (Fig.15.2). The terminal
voltage (measured by monitoring the column current in aeries with the
chain of resistors) could be raised to «/ 450 kV about which sparking
was observed across tht? apark yaps. The charging current uas about
12 uA. Increase in charging current increases tha frequency of spark-
ing as could be expbcted. Further raising of voltage can be dons after
installing the accelerator in the pressure vessel.
2. Accelerating tubei Tho S.S. electrodes were etchod each for 10 rnts.
in a dil. solution of oxalic acid and sulphuric acid at 85*C and cleaned.
The electrode glass sections were ground to shape and degreased witft
trichloroethelene. These ware araldited, five sections at a time, uaing
a specially designed jig to maintain the electrode alignment (50-50
homogenous mixture of araldita AW-106 and hardner HI/ 953U uias used as
the cold sstting adhesive). The ultimate shear strength of the glass
to electrode Joint was tasted at the Central Workshop tasting facility
and was found to be 2.4 tons. It may be mentioned hers that the weight
of eithBr section of the accelerating tube is approx. 25 Kg. The five
section aub assemblies were teatad in a chamber with high vacuum inside
and a pressure of 16 atmospheres outside. After thaaa vacuum and
pressure teats two complete tubes (each having 51 electrode sections)
were made joining with the same araldita mixture using another jig to
ensure the electrode alignment. Both thaaa tubaa hava baan tastad
with high vacuum systems and round satisfactory.
3. Beam transport! Tha 20* ion aourca magnet and ita stabilised
7-162-
pouier supply has boen desiynsd, built and tested. All the beam
transport tubes a m under fabrication. A set of electro magnetic
beam deflectors (4 element) havs bean designed and these are under
fabrication at thn Nuclaar Phyaica Division Workshop. Design and
drawiny of the +20° beam analysing magnet has been completed. This
maynut is noui under fabrication at the Central Workshop, B.A.R.C.
A prototypu 6mm 10, 38Umm long gae btripper assembly was fabri-
cated. This was tested with a simulated accelerating tuba to study
the feasible prosauro yradisnts with ths 9" diffusion pumps to be used
with tandum machine. A preasura of 2x10 tarr could bs reached in ths
tube part niaintaininy a pressure of /v> 10 microns ur more in the
stripper canal w..th continuous gas feed.
4. Vacuum systems* All ths required vacuum systems have been procured
and tested. An on-line cold trap chamber with high trapping efficiency
has been designed. Four of these have besn already fabricated and tested.
5. Measurement and controls The carona control feed back system for
voltage stabilization and the control slits are yet to be fabricated.
Voltage measurement will be dons by a generating voltmeter as also by
monitoring the column current. The system for gas feed and strippar
chambur control along with its associated gears has been designed.
The -shed for installation of ths machine ia being renovated.
Dusign of the sliding support structure for the accelerator column
with the pressure vessel and flange has been taken up.
-163-
16. Isotope Separator (U.A. Hattangadi, F.R. Bhathana, K.L. Pateland C. Shellom)
The main analysing magnet for the OUPIAS mass separator has been
delivered by the Central Workshop and installed in its position an
the cement concrete platform in the Van-de-graaff Laboratory. The
assembly of the massive, 24 tonna electromagnet presented some diffi-
culties in its installation arising mainly from lack of sufficient
space for free movement of the large blocks and absence of overhead
crane for handling tha heavy material; the entire assembly of the
magnet, comprising of some 22 yoke members, has therefore been done
employing only a small, mobile "fork-lift", pneumatic jacks and skilled
labour from the workshops. The matching cif the yoke members, the
alignment and levelling of the pole-pieces has been checked at each
atuge of assembly using a sensitive spirit level. However, the magnet
assembly work was prolonged over quite a feu months as the energising
coils for the magnet uere not delivered by the manufacturer in time
ouiny, both, to a last-minute price revision and some technical problems
involved in the manafacture of the coils.
The magnet coils consist uf some ten, double mound pancakes, each
having to layers of 20 turns of a hollow, water-cooled, 1/2 in. square,
aluminium conductor. Tha coil is somewhat oval in shape, conforming
to the shape of the magnet pole piece, with a width of about 0.75 metre
and 2 mtrs. length. Par the turn-to-turn electrical insulation, a
fibreglass tape apoxy system has been used. Each pancake has some 8-10
welded joints on the aluminium conductor, which were proved leak tight
at hydraulic pressures upto 300 psi prior to winding the tapes. It ui3 3
-164-
oriji.naj.iy planned to employ a fibrsglasa tape, that was pra-impre-
gndteid in &poxy <*nd semi-cured by the manufacturer, the final curing
bbimj carried out after the completion of the taps winding. However,
as tho pre-impregnated t«pu, with ail the stringent processing condi-
tions to bu mat with w»s found to ba too inflexible and brittle to
give d good, tiyht, adherent winding the scheme was abandoned and
reverted to the normal, "wet lay-up" of the tape, with th» epoxy being
applied is the taping proceeds. Another manufacturing difficulty which
came up was that th« brittle fibrsglass would ba damaged invariably
during the shaping of the conductor to the required coil form| it was
solved, however, by the simple expedient of farming the coil first from
the bare alumlniu* conductor without application of *ny tape and subse-
quently, pulling out the turns, in the manner of a helical spring, to
add the insulation. Prior to the final cansolidation of the coils, each
pancake has bean tested for dlmentional accuracy, electrical insulation
and water leakage under pressure.
The aain deflection chamber has been constructed by fitting on the
magnet polepieces flat, metal flanges sealed by specially formed neo-
prene gasket* The gasket, in ths form of a three dimensional, octagonal
frame, was made tjy joining together pieces of long, neoprsne cords. A
number of commercial cements were tried but no suitable adhesive could
ba found to give a well-nude, durable gasket-joint. Finally, a silico.iy
adhesive compound was found to give the best results. It has been
possible to pump down the deflection chamber to an ultimata pressure
of 5x1O*6 Torr.
Four 1Q H orifice vacuum Gate Ueilves have been manufactured to our
*
-165-
dasign in the Central Horkshop and those have been individually
tasted for micro-leaks under high vacuum.
A novel mechanical control system for the extraction alectrodn
capable of giving at laast four independent movements of the electrode
has buen designed and a small model of this mechanism (which consists
of mainly pulleys and strings) has baen constructed and tried out in
the laboratory although not yet incorporated in our machine.
An an JUB multiplexer system has been developed using locally
available I.C's for use with the proposed telemetering and tele-control
system for the Van-de-Graaff accelerator and it has been tested for
performance on the Test Bench.
17. Ion Implantation (P.K. Bhattacharya, M.S. Bhatia, 3. Gaonkar,PI.J. Kansara, A.G. Wagh and N. Sarma)
1 . 100 Kaw Ion Implantation Facility
A 100 KeV ion implantation facility has been set up in
Van-de-Graaff laboratory to mother the necessities of Ion Implantation
in solid stats devic* fabrication, surfaca treatment of materials with
metallic ions and studies of optical integrated circuits. The ion
implanter consista of a high voltage (step-variable) supply, ion-source,,
ex tractor-cum-focusing lens, mass analyser, accelerating tuba, raster
and target assembly along with its vacuum system ( Ref.1 ). The high
voltage supply can be made variable uithin suitable limits ovar and
above steps of 20 KV upto its maximum CHT rated at 100 KV at 10 mA.
Thu ion source is hollow cathode electron bombardment type and any
solid or gas introduced in the hollow potential well gets ionized by
-166-
electron bombardment • A ring anoda at 200 V suppresses and
for in y thu plasma as concave meniscus on the exit, aperture of the ion
source. Thu extractor-cum-focuainy lens requires maximum extractor
voltage of 4.5 KV and focus voltage of 16 KV to form a fine focusseii
beam of upto mass antimony. The pre-analysis of the ions by a 14"
magnetic mass analyser defines the required mess before putting them
through the final acceleration potential. A typical mass spectrum is
shown In Ref»1, Ion beam negotiates further a drop of 100 Ktf by
about 10 KV/inch through the constant gradient acceleration column end
peases via a mass defining slit into an X-Y raster.
The X and Y scanners of the raster makes the baam to cover a
2
rectangular cross-section of 3x3.5 cm (max). The calculated homoge-
neity of about 99/4 can be achieved for all implants in general, except
when maximum raster scan is required. At present a single target
chamber is used Mostly but a multi wafer targst chamber is also ready.
Liqgid nitrogen cooling is provided for each target chamber and implants
free from carbon deposits have bssn ensured.
Implantation of B, Ar, P ate* were tried on Mi-Silver alloys for
Indian Telephone Industrie*, Bangalore for corrosion studies on relay
contacts, for Physics Department Itarathwada University on Iron foils
for Mossbaunr Studies and for IIT Oelhi on p i n type silicon wafers
for solar call application SiQ- was also bombarded with Ar ions
to study..damegs and annealing behaviour of Si0_ passivation layers
for Solid Stats Physics* Laboratory, Oelhi.
2. Solar Ceils 4 o-n Junctions
Low resistivity (1 to 9 -O.-c«) 500 micron thick (carrier life
• *? -167-
•,*"*••
'•?,
time 25 microaec) n type ^ 1 1 1 / silicon wafers were polished,
cleaned and bombardud with singly charged gallium, ions over a 2.5 cm
at eneryies between 75 and 300 KeV. Solar cells usi; _ a four finger
j.'.. !J.5 mm width geometry aluminium contact yore studied. An anti refle-
ction coatiny of silicon monoxide 900 A thick on the front face of thu
surface increased the efficiency to about 7%.
Junction characteristics of p on n implants were studied for
various dosage implants and I-V characteristics measured. C-V chara-
3/2cteristics shuued V dependence confirming that multienergy implant J
using 75, 15U, 225 and 3QU KeU Ga ions can give abrupt junctions.
1) P.,K. Bhattacharya et al, Nucl. Phys. and Solid itate Phys. (India),19B, 249 (1976).
18. Neutron Radiography (N.C, Jain and Y.D. Oande)
1. Fuasibility .axperiments with Flexible Linear shaped Cord of Uikram
Sarabhai Space Centre u/uru continued. Discontinuities in the explosive
powder were simulated by removing the powder ovar lengths of 1,2,3 and
5 mm. M silicon rubber backing was also added to the cord to make it
'*-.'•.:' muro representative of the cord in actual use. The radiographs clearly•V
imaged all th& discontinuities through the Pb sheath and the silicon
'•; rubber bdckiny. A 300 mm dia. mock-up of the separation system is now
'-; auaited from USSC for future tests.
. . 2. Cellulose Nitrate, as a Solid jtate Track Detector is now emerging
••••;V as a v/iable alternatiws to foil/film detector system in Neutron Radio-
'';•.'.}:• graphy. M screen of Li and/or B converts neutrons into OC particles
which leave permanent damage tracks in the adjoining plastic material.
The tracks can be made visible by chemical etching, to give a radio-
.'-. graph. The advantages of this technique over foil/firm technique are
168
Fig. 18,1. Track etch neutron radiograph of a Visual QualityIndicator (VISQO-
1) Complete fli*.T,s insansitivity
ii) Infinite time integration capability
iii) Comparable resolution capability
iv) Cheaper and easier processing.
Some radiographs have been mads at the Apsara facility using
Kodak Pathe' CA8015-8 plastic film, which is coated on both aides •
layer of lithium Tetraborate. The typical neutron exposure was
1D 210 n/cm and tha CN film was etched for 240 mln in 2.5 N NaOH soln.
at room temperature. Some examples are shown in Fig.18.1.
19. Nuclear Detectors
1. SF Proportional Counters (Y.O. Oande, R.S. Udyawar and A.P. Bagool)
30 5tandartid counters were made and supplied to users in BARC.
The davelopmsnt of BF counters for Oil well logging application
was completed. ONUC at prseent uses 8 Russian made counters, connected
parailer in a ting formation. The main requirements are low natural
background (3 cpm), stability over a range of -10°-120* C and a plateau
length and slops of minimum 100 U and 10% per 100 V respectively.
The development want through 4 stages, namely
a) A 18 mm di« BF- tube working in tha range of 27°-120* C
b) A 1B mm dia He tube working in same temperature rangs
c) A a anode annular BF_ counter to replace the 8 Separata counters
in the ring, and finally
d) A 50 mm dia x 225 mm long single anode BF- counter having following
specifications
-170-
Filgas t 60 cm Hg 6F,, 90% 8 enrichment.
Plateau Length" I 300 Volts at 27'C
200 Uolto at 120°C
Plateau Slope j 2.4$ per 100 V at 27»C
A% par 100 V at 120°C.
Background : 20 cpro.
This final prototype has undergone field testa at Ankalashuar
oil fields and haa bean reported to be satisfactory.
2. Position Sensitive Detectors (Y.O. Dandu, N.C. Jain and G.U. Shenoy)
Development of a linear position aaneitiv* detector for X-rays
has continued. A BO mm dia x SO cm long detector has a largo number
or 3 mm dia Al windows along the datactor length. A collimated source
or Co is moved from ona window to another to change th« position of
the events. The output from an Analog Charge Divider, indicatad tn»
position. The above detector gave a central linear region of 30 cm,
with a position resolution of 10.5 mm FWHPI. The aane detector tested
by electronics Oivieion usiny Rise-Time Discrimination method gave •
linearity range of 50 cm and resolution of 2.7 mm fWHfl, A sscond
detector, 25 mm dia x 225 mm long haa shown improved resolution (1.7 mm
FWHM) with tha rise-time discrimination method.
3. Soft X-ray Detectors (Y.D. Dande, G.V. Shenoy end A.P. Bagool)
A total of 25 detectors for flosabauer Spectrometery were made/re-
proceased for BARC ae well ea other users*
-171-
20. Helium-Neon Laser Plasma ,Tub»» (V.O. Oande,. S.H. Chlnchanikarand n.L. Bansai )
A beginning haa baan made to fabricate medium power laser plasma
tubas for light scattering experiments. A 3.5 mm dia x 1700 mm long
tuba has been assembled. The tube employs a central Al cathode and
two tungsten pin* as anodes. After careful alignment with a portable
He-Ne laser, the tuba was filled to 1.5 torr with Ha-Ne (6 : 1 ) mixturs.
The available stead/ power from this laser was approximately 25 mw at
6328 A.
*'• Neutron Radiography with Cf(Y.D. Cande)
The high specific sctivity of Cf spontaneous fission source
( 2.3 x 10 n / sec / gat ) makes it an ideal source
for transportable Neutron radiography facility for industrial applica-
tions* investigation in thiB direction are under way at the Birmingham
University, U.K. Relative Flux plotting in 'three different moderators
viz. Mater, transformer oil and polythene-water showed a 50% higher
252flux in the last moderator compared to water. A 10 fig Cf source
was used fot these investigations.
A small neutron radiography facility was designed and build
using 10 cm dia polythene core surrounded by 14 cm of water as moderator
(Fig.21.X) A 6* conical hole in the central polythene, lined with Cd
over the bottom 10 en length served as a divergent collimator. A 10 mm
thick Pb plug WMS used to filter the gamma radiation from the source.
At a L/0 ratio of 3D, the estimated neutron flux was 100 n/cm -sec. A
161 hr exposure on .025 mm Gd/Industrex 0 film, gave fairly sharp radio-
graphs. Fig.2.1,2 ehowa an air-craft turbine-blade, with traces of resi-
dual core material in ita cooling channels.
POLYTHENE
Fi|.Z1.1.C f-252 NEUTRON RADIOGRAPHYASSEMBLY
173
Fig. 21.2 Neutron radiograph of an aircraft blade made with Cf 252 net Iron radiography.
-174-
22. Setting up of a Proton Induced X-ray fluorescence Syatam(P.N. Rama Rao, O.fl. Nadkarni, S.K. Kataria and S.S. Kapoor)
A chambar for the work of proton Induced X-ray fluoraacenca
analysis has bean designed, fabricated and assembled. This consists
of a Si(Li) X-ray spectrometer, a sample holder and changer, a beam
collimator, an integrated shield to cover the X-ray spectrometer to
minimise the extraneous background and a covering chamber connected
to the beam port of the 5.S flaU Van da Graaff accelerator.
The X-ray spectrometer consist* of a cooled Si(Li) X-ray
detector with cooled FET as the first stags of the pre-amplifier
and operated in the opto-alactronic fsad back node giving a resolution
of the order of 270 eV for the 5.9 Kev K-X-ray Una.
The sample holder and changer consist of 15 aluminium discs
with periferal holes to hold the samples sandwiched between the discs
and a shaft in the centre of this disc which can be rotated from
outside the chambar without breaking the vacuum. At a time ten samples
can ba loaded with the remaining two positions uasd for viewing tha
bean with a quartz window. The sample changer la mounted at 45° with
respect to both the baan direction and tha detector assembly. Tha
X-ray spectrometer can ba alidad inaida the chamber to facilitate
operation of tha apectronatar at its optimum count rate.
Preliminary work haa baan dona to ensure that the entire assembly
is leak (froof and haa attained vacuum of tha order of 3x10* TORR. The
PIXE system has bean mounted on tha baan port to carry out initial cali-
bration runs. Further planning of the work on PIXE analysis is in pro-
gress.
JOURNAL ARTICLES
A.R. Banijhar, U.S. Piurthy and I.V.W. Raghavacharyulu, "On tha Para" U r i cModal of Loose Bonding of Elast ic Half Spaces", 3. Acoust. So<- Aii.6£, 1C71 (1976) .
M.L. Bansal, T.R. Rao, U.C. Sahni and A.P. Roy, "Laser Raman Spo«;ro -metar", Indn. 3. Phya. 5£, 199 (1976) .
fl.L. Bansai, U.C. Sahni and A.P. Roy, "Oynaraics of L K i _ x ( N H 4 ) x ) oCuCl .2H 0 by Laser Raman Scatter ing", Indn. J . Phy«. SiO, 151 (H<'<':
P. Chaddah and V.C. Sahni, "QPUl Calculations of tho Compton Prof i lu oi", Phys. Le t ts . 5 .^ , 323 (1976) .
P.P. Chandra, B.A. Dasennacrtefrya, P.5. Goyal, P.K. lynngar, K.R. Rao,C.L. Thapor and rt.H. Vnnkatesh, "Neutron Ine las t ic Scattering fromFlixdd iiaita T(NH ) K 1 5 o
4"» Pny9« L» t ts . 57A, 463 (1976) .
3.A. Ofl.iannacharya, A.. Kollman, T. Springyr , "Nautron Raylaigh andBr i i lou in Scattering in Normal 4 Ha" , .^hys . Le t ts . 55A, 337 ( I 9 7 t ) .
K. Ushd u'iri.7. and U.H.K. '^au, "CISC and X-ray D i f f rac t ion Studies ofhxBPA", Phys. Le t te . 5,5*, 20a (1976) .
rt.j. Lb^dbutter, R.fl. Richardson, H.A. Oasannacharya and U.S. Howells ,"Inconcrt-nt Neutrcn wtiasi-Liaatic scatter ing Studies on theAnisotropic se l f Oiffusion in N'am<atic and Sweetie A Phase* ofLH&XL", Lhem. Phys. Ls t ts . 3£, 501 (1976) .
T.R. Rao, r..L. BP-nse.'., U.C. isahni and A.P. Roy, "5tudy of Internal,*iodea j f 50~~ in LiKSO ", phys. st<»t. a o l . ( b ) 75., K-11 (1976) .
C.F. Sampson, F.A. Uadywood and N.5. Satya Murthy , "Structural Trans i -t ions in U_P. and U_A#.", 3ournal of Physics (C) 9., *035 (1976) .
C.L. Thaper and 9.A. Oasannacharya, "Dynamics of Liquid Si1ana",Pramana £ , 383 (1976) .
P.K. Bhatt-»charya, N. Sarma and A.R. Wagh0 "Effect of Ion Implantatxoi01 the Refractiwa Index of Glass", Ptamana 6_, 102 <1S75}.
11.A. tswaran, O.R. .Chakrabarty and N.L. Ragoouansi, "Unbound £>tin "*b«r through Radiative Capture of ©( -Par t iB laa in 3 2 3 " ,Hu l l . Am. Phya. So«. 21., 997 (1976) ,
-176-
S.K. Gupta, "Background Phase Shift in R-matrix Theory", Phys. Reu.C13. 1326 (1976).
S.K. Gupta, M.S. ehatia and S.S. Kerekatte, "naaa^rement of theApparent Non-linearity gf Analysing Magnets", Nucl. Instrm.Methods. 1_31_, 403 (1976).
8.K. Jain, "Piun Single Charge-exchange Reaction an Nuclei Near the(3,3) Resonance", Pramana 6_, 226 (1976).
S.K. 3ain, "Depondonce of Pion-Nucleua Total Cross Section on theNuclear Density and Pion-Nucleon Off-shall Amplitude", Pramana7,, 287 (1976).
S. Kailas and Fl.K. fluhta, "Thermo-Nuclear Reaction Rate* from (p,n)Reactions"> Pramana J_» 6 (1976).
S.N. Misra, S.K. Gupta and O.K. Hehta, "Installation of Pre-injectionIon Source - l/n Analyser Syatem on the 5.5 Ml/ Wan de GraaffAccelerator at Trombay", Nucl. In3trm. (lethods. 135, 447 (1976).
L.V. Namjushi, S.K. Gupta, ft.K. Plehta and S.S. Kurekatte, "ResonanceSpectroscopy of ^^S; Nucleus in the Excitation Energy Range 14.27to 15.U2 MeV", Phys. Rew. £13, 915 (1976).
Pl.A. Rahman, fl.A. Auai, i*l. Rahman, H.P1. Sengupta and S.K. Gupta, -•"A NotB on the Possibla 4"1" Analogue - Antianalogue Stata in Si",Lett. Nuowo Cimento 12., 290 (1976).
N. Sarma, "(licrominiaturiaing the Optical Bench", 3. Phys. Education4_, 11 (1976).
N.N. AJitenand and K.N. Iyengar, N0n tha Technique of Preparation ofHigh Duality Thin Film Scintillators", Nucl. Inst. & Plathoda133. 71 <1976).
R.K. Choudhary, S.S. Kapoor, U.n. Nadkarni, P.N. Rama Rao andS.R.S. Clurthy, "Studios of Mass and Energy Corralations inThermal Neutron fission of U-235 Accompanied by Long RangeAlpha Particles", Pramana 6,, 64 (1976).
S.K. Kataria, "Scission Configuration in Uuarternary Fisaion",Pramana !_, 126 (1976).
5.K. Kataria and V. S. Ramamurthy, "Nuclear Level Densities in SelfConsistent Field Approximation", Pramana 7_, 407 (1976).
• 1 7 7 -
n. Prai-.eeh, "Transmiasien Through an Invertad Biharmonic Osci l latorPo ten t i a l " , J . Phys. (A) £ , 1847 (1976) .
U.S. Ramainurthy, PI. Prakaah arid S.b. Kapoor, "On the Uncertainties inths Shell Correction by Strutinsky Smearing Procedure for CertainShapes Relevant in Fission", Phya. Let ta . 62B. 124 (1976) .
1 . Work dona at KPrt, Ju l ich , Ut. Germany,2 . Uork done at Harwel l , tnyland.
PriPlRa PRLiENTt.0 AT CUNFERt.NCC-5 AND MEETINGS
Nuclear Physics & bolid i t a t e Physics Symposium (CME), AhmedabadOecember 1976
R.J, Begum, Pl.F. Col l ins , L.M. Corlisa and O.M. Hastings, "A SingleCrystal Neutron D i f f rac t ion Study of fo As".
P. Chaddah and l/.C. Sahni, "Compton Pro f i l e Study of FeAl".
R. Chakravarthy, L. fiddhaw Rao and N..S. Satya Murthy, "Form FactorStudy of Ni Ru. ._ by Polarised Neutrons".
U • 97 u • u*3P.S. Goyal, P.P. Chandra, C.L. Thaper, K.R. Rao and 0.A. Dasannacharya,
"Temptdtature Dependence of the Reoriantat ional Motion of AmmoniumIons in (NH4)2SU4 and [ ( N ^ ) 0 J 6 « 0 . 8 4 3 2 S0 4" .
K. Usho Oaniz, A . I . Nehta, U.R.K. Rao, P.S. Parvathanathan and A.S.Paranjpe, "Temperature Dependence of the iimectic Layer Thicknessand Inplane Intsrmolecular Distance in the Smectic Phases of HxBPA".
K. Usha Deniz and A . I , Plehta, "Influence of E lec t r ic Fields on SmallAngle Light Scattering from I*I3BA".
N.K, Oaygi, K.R.P.m. Rao and P.K. Iyengar, "Possib i l i ty of Spin GlassBehaviour in Systems with only Short-Range In teract ions! A TwoOimensional Computer Study".
L. riadhav Rao and G. Paret te , "Smell Angle Neutron Scattering Studyof I/O in the Temperature Range 400 to 600K".
L. Madhav Rao, "Study of Impuri t ies in Ferromagnetic Alloys byNeutron Scattering and Hossbauer Spectroscopy".
P.S. Parvathanathan and K. Uaha Oeniz, "Br i l lou in Scattering fromClethyl and t t h y l Alcohols".
1 . Uork dona at BNL, U.S.A.
V.C. fUkhecha, K.R. Rao and N.S. Satya flurthy, "Spin Waves in
K.R. Rao, P.K. lyengar, A.H. Venkatesh, P.R. Vijayaraghavan anrS.F. Trevino, "Coherent Neutron Scattering Studies in K.\jr.(".
R.G. P i l l a y , P.N. Tondon, H.G. Osvara, N.K. Jaggi and K.R.P.". o,"Hyperfina Interact ion Studies in Ferromagnetic Rh-MnSn".
A.H. t/enkatesh and K.H. Rao, "A Simple White Seam Neutron Oii • : t.-onTechnique".
J.V. Yakhml, b.K. Paranjpe and C. Planohar, "Possib i l i ty of 0| (. J I /Induced flott Transit ion in Fe_0." .
3 4
M.K. Agraual and O.K. Sood, "Determination of the Nature of Oef.ct.uin I r rad ia ted Platals bv Rutherford-backscattering".
C.V.K. 8aba, n.G. B a t i g y r i , U.fi. Qatar, b.n. Bharethi and A. Rv. ,"Intermediate Structuru Below the Analogue States in As".
P.K. Bhattacharyu, A.G. Wagh, S. Gaonkar, M.S. Bhatia, I t . J . Kan3araand N. jar ma, "Study of the ICT Implantar **.
O.R. Chakrabarty, PI.A. Csuiaran, N.L. Rdgoowansi and H.H. Oza,"Unbound Status in 3 6Kr Through Radiative Capture of -Pa r t i c l esin 3 2 S « .
A. Chattor jes, A.L. Athougieis, a. Kailas and II .K. ftehta, "CrossSections for Excitat ion of Shape Itomsrs in Uranium Isotopes".
V, Gopal, M. Gopal Rao, N. Sarma, P.K. Bhattacharya and A.G. Wayh,"Ion Implantation and tha Anneal Behaviour of Thermally GrownSiO2 Films".
Gulzar Singh, S. S a i n i , S. Ka i l as , A. ChatterJee, PI. Salakrishnanand M.K. Mehta, "Total ( p , n ) Croat Section for the Ca(p,n ;<iSScReaction".
A.K. 3e in , "Observation of Clusters i n Light Nuclei Through Knoct - i j :Reaction".
A.K. Jain end N. Sarma, "F in i te Range Oistorted Wave Calculation?for O(d,t)H Reaction at 25.3 CleV".
B.K. Ja in , "Pion Absorption on He".
S. Kailcis arid 1*1.K. Mehta( "Isobaric Analogue Resonance att «* 2.339 MaU in the 5 1V(p,n) Cr Reaction".
S. Kdilas and Pl.K. Plehta, "Intermediatp Width Structures in50Ti(p,njE>DV Reaction Exci tat ion Function".
Kiran Ku. ar and rt.K. -lain, " Invest igat ion of Oeuteron - AlphaUsinj n-Alpha In te rac t ion" .
C.R, Ramaowamy, N.G. Puttdsuiamy and M.G. Be t i ye r i , "Isobaricrtesonancd in '^Aa".
5, i jaini and M.R. Uunye, "Muclear Structure Calculations in V".
O.K. Sood, "A btudy of Mo Imfjlanted Copper by Scanning Llectranfticroscope ".
O.K. iood and G. Duarnaley, "Radiation Disorder in Pletals".
U.P. \ / iyogi , S. Kai laa, S. oa in i , iv,.K. flehta, N.K. Ganguly, N. Ueera-bahu and T.K. Bhattacharjee, "Isobaric Analogue Resonances inthe Bube(p,n)8(JBr Rejc t ion" .
N.N. Hjitanand, K.N. Iyengar and o.R.S. Murthy, "Anamolous Surface Order-ing due to Interaction of Radiation with Polywinyl Toluene Films".
N.N, Ajitanand, K.N. Iyengar and S.R.S. Hurthy, "Two ParameterStudies of TFD Response to Fission Fragments for Measurements of
Mass and Eneryy Distributions".
N.N. Ajitanand and S.R.S. fiurthy, "Time of Flight Studios of FissionNeutrons Pas^iny Through Lithium HydriJe".
S.K. Kataria, U.S. Ramamurthy and S.S, Kapoor, "On a New Semit.mpirical Nuclear Level Density Formula with Shell Lffects".
S.S. Kapoor, R.K. Choudhary, "Interpretation of fission FragmentAnisotropies at Intermediate Excitation Energies".
B. Kr ishnaraju lu, G.K. Mehita, R.K. Choudhary, D.f). Nadkarni andS.S. Kapoor, "Long Range Par t ic le Emission in KoV Neutron Fissionof 2 3 5U".
Lai, S.K. Kataria and P.L. Bhatia, "Pulsed Optofeed Back $i(Li)Detector X-ray System".
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O.fl. Nadkarni, R.K. Choudhury and S.S. Kapoor, "Studies of FragmentKinetic tnuryy and Mass Correlations in Thermal Fission of 238UUsing liridded Ion Chamber".
M. Praksah, S.K. Kataria and I/.S. Ramamurthy, "Study of ScissionConfiguration by the tntropy Maximization rtathod".
U.S. Ramamurthy, "Thermodynamics of Excited Nuclei and Nuclear LevelOenaitias".
Conference on Neutron Scattering, Gatlinburg, Tennessee, Dune 1976
P.P. Chandra, B.rt. Oasannacharya, P.S. Goyal, P.K. Iyengar, K.R. Rao,C.L. Thaper and rt.H. Venkatesh, "Ammonium Ion Dynamics in(NH4)2S04 and [ > H 4 ) x V j 2 SO/'.
S.K. Paranjpe and R.O. Begum, "A Neutron Diffraction Study ofCobalt-Ooped
U.C. Rafcchecha, K.R. Rao and N.S. Satya Plurthy, "Clagnons in
International Conference on Play net ism, Armsterdam, 1976
S.K. Paranjpe and R.3. Begum, "Spin Density and Form Factor of FeIons in Cobalt-Oopod YbFeO ".
U.C. Rakhecha, K.R. Rao and N.S. Satya Murthy, "Acoustic Spin WaveDispersion in LI ,,,Fe 0 ".
Lowell Conference on the Interaction of Neutrons with Nuclei, 3une 1976
B.A. Oasannacharye, P.S. Goyal, P.K. Iyengar, C.L. Thaper and G. Ven-katacaman, "Re-orientation Dynamics of Ammonium Ions in NH.I".
D.fi. Nadkarni, R.K. Choudhary, P.N. Rama Rao end S.S. Kapoor,"Energy Spectra and Yields of Alpha Particles, in Fast NeutronFission of 23S
I/.S. Ramemurthy, S.K. Kataria and S.S. Kapoor, "Semi EmpiricalWye1ear Level Density Formula with Shell Effects".
S, KaUas, P.K. PiRhte, Y.P. Viyoqi -rid N.K. Ganguly, "NeutronCpticnl potential from sub Coulomb (p,n) reaction data onmedium weight nuclei", Int. Conf. on the interaction ofneutri-nr, uith nuclei, Lowell, U.S.*. ,(1976).
Pt.K. Plekta, ft.L. flthougies, S. Kallaa and A. Chatterjee, "Cxcitationof shape isomers in Uranium isotopes by 14 PieV neutron bombard-••"ent", Int. Conf. on the Interaction of neutrons uith nuclei,Louall, U.S.A., (1976)
I n t isrn.jt i c n d l Conference on F u r r i t e s , BellGvue, France, September 1975
\I.C. Rjkhoc.'-iu, R. Ch<Jkrauarthy dnd N.S. ddtya Hurthy, "Apparant LouA-bitb iioment in fu 0 '',
N.b. L<dtya Murtny, "PolarisecJ Neutron Diffraction in Ferrites".
- .tA nayionai otudy Group Meeting on HeaHarch Reactor Utilization,Banduny, auyust 1976
Y.J. Jrindt! and P.K. Iyunyoir, "Status Report on Neutron Radiographyat rr
P.K. IyunL,jr, "Ruvieu of Ndutron bcatteriny in Trombay".
P.K. Iybnybr, "Nbutron opectrometry and Computing Facilities".
D.K. 3ain, "(TT.NN) Reactions for touclyar structure Studiss", Inter-national Conferencu on Few Body Uynamics, Delhi 1976.
G. Parisot, \.lt. batya Murthy, 1*1.T. Hutchings and U.B. Buyers,"Jauidov Lxcitations in KCoF_", Progress Reports of the Institute,Laup-Langevin 1976.
U.S. Ramamurthy, b.K. Kataria and S.S. Kapoor, "On a New Approach tothe Calculation of Shell Correction energies of Nuclei from BoundSinyle Particle Levels", International Conference on SeloctedTopics in Nuclear Structure, Oubna 1976.
K.R. Rao, "Neutron Studies of Molecular Solids", IAEA Advisory GroupMeeting on Neutron Scattesing in Applied Research hold atLjubljana; Yugoslavia, Dec.1-4 (1976).
-1R?-
RLPuftTS ISSUED
V.5. Ramamurthy, M. Prakash and S.S. Kapoor, "On the Uncertainties inthe Shell Correction by itrutinsky Smearing Procedure for CertainShapea Relevant in Fiasion", BARC-B68 (1976).
K. Usha Deniz, P.S. Parvathanethan and A.S. Paranjpe, "Fabry-PerotSpectrometer for High Resolution Light Scattering Investigations",
(1976).
BUOK ARTICLES
O.K. Sood and G. Dearnaley, "Ion Implanted surface Alloys in Copperand Aluminium1*, Application of Ion Beams to Materials, Eds.C. Carter, J.S. Colligon and U.A. Grant, Institute of Physics,London, 1976.
THESES
The following theses were submitted during tha year for awards ofvarious degraeat
S. Kailas, "(p,n) Reaction Studies Below tha Coulomb Barrier onMedium Weight Nuclei" for Ph.O degree of Bombay University.
M. Athougiws, "Shapa lvonerism in Uranium Nuclei**, for Ph.O degreeto Renslar Polytechnic Institute, Troy, New York, U.S.A. Thiswork waa carried out at the Division under tha supervision of• Divisional Scientist.
R.K. Choudhury, "Studies of Long Range Alpha Particles Emitted inNuclear Fission", for P1.Sc degree of Bombay University.
Sheala Flukhopadhyay, "Optical Modal Potential for Composite Particlee"for Ph.O. degree of Bombay University.
•I.-?-3-
PHYSICS CuLlUa,UU AT BARl
The following colloquia inert* held during the period covered bythis report:
"Nuclear Physics with GeV Accelerator", George Igo, University ofCalifornia, U.S.M., Jan. 5, 1976.
"Neutron Physics Programme with the Texas A4F! Cyclotron", L. Northo-Jiffe, A£F] University Texas, U.S.A., Jan. 6, 1976.
"What can ba learnud from Knockout Reactions at VEC Energies",L.f. Radish, Odpartment of Physics & Astronomy, University of
• Maryland, Maryland, U.S.A., Jan. 8, 1976.
"Status of studies of Two-system Int. in Nucl. Physic*11, SamshBr Ali,Oiructor, Atomic; Energy Cantra, Dacca, Banyia Odsh, Jan. 20, 1976.
"Status of "Lampf" ", flahauir 3«in, Loa Alamos Scientific Laboratory,U.S.A., Oen. 31, 1976.
"Polarisation Method of Determination of Body Uawes from Remote SeismicSources,", O.K. Kadrov Jnd I.P. Hashilow, Instituts of Physics oftarth, Academy of iiciuricas, noscow, UiiBR, Feb. 2, 1976.
"A Hiyh Resolution Saismoloyical Probe into the tsrth'a Interior",n.K. Sen Gupta, Visiting Scientist, Seismology Section, Feb. 3, 1976.
"Alpha induced fission of U", B.W.N. Rao, Feb. 4, Z976.
"Lattice Dynamics of Stimi-conduct ora", Kailash Rustaqi,' Laser Section,QARC, Fab. 10, 1976.
"Spectroacopy of exotic atoms", G. Backenatosa, University of Basel,Switzerland, March 2, 1976.
"Evolution of Neutron Scattering Experiments on Liquid Crystals",6.A. Oasannacharya, flatoh 9, 1976T
"Transfer Reactions and Nuclear Structure", R.K. Bansal, PhyiiceOupartment, Panjab Univoraity, Chandigarh, March 26, 1976.
"Hudiuiti Energy Neutron Phyaica Rssuarch at Crocker Nuclsar Lab",T.S. Subramaniam, Nuclsar Laboratory, Oavia Campus, Univsraityof California, April 13, 1976.
-184-
"Oecoupling of Hyperfine Interaction in Ion* Recoiling into Vacuum",H.C. Jain, T.I.T.R., April 20, 1976.
•Effective Interaction* in NucleiM, R.K. Tripathi, T.I.F.R., April27, 1976.
"High Powar Ha-Ne Laser", A. rtallik, Institute of Ar»a««r.t Techno-logy, Puna, June 22, 1976.
"Neutron (Diffraction of Bionoleculea", A. Saqueira, June 29, 1976.
"Hany-Body Interactiona and Lattice Dynamic* of Binary CrystalsH,R.K. Sinyh, NREC College, Khurja, nearut Univeraity, July 1, 1976.
"Applications of Low tnergy Accelerators", 1*1.G. Betigeri, July 16, 1976.
"Oense Matter; Observation, Speculation and Theory", V.H. Pandharipande,University of Illinois, Urbana, U.S.A., August 12, 1976.
*(p,V) resonance studies with the Oynamitron Accelerator", 3.B. Garg,Department of Physics, State University of New York at Albany,U.S.x., August 25, 1976.
"Some Interesting Inequalities for Matrices", R. Subramanian, September7, 197b!
"Phonon Induced Metal-Insulator Transitions in by3terns such as NiS",O.K. Ray, Laborutoire da flay net isms, CNRS, Grenoble, September7, 1976.
"Marteneitic Phase Transition in Metallic Solid*", O.K. Ray, Labora-toira da Wagnetiame, CNRS, Grenoble, September B, 1976.
"The evolution of Solar System as aeen through Nuclear Processes ofthe Past", U.S. Venkatavaradan.T.I.F.R., September 28, 1976.
"Alpha Transfer in the a-d Shell", N. Anantaraman, The University ofRochester, Rochester, New York, October 7, 1976.
"Recent Advances in Polarised Neutron Spectrometry", N.S. Satya Murthy,October 12, 1976.
"Theories of the Stopping Power of Heavy Ions in matter", A.P. Pathak,University of Roorkee, Roorkee, November 23, 1976.
"Nuclear Spectroacopic Studiea at Heidelberg and SIN, Zurich",C.A. Wlednar, Max-Planck Inatitute for Kernphyaik, Heidelberg,December 3, 1976.
"Some Hecant Developments in Cryogenic", B.S. Blaissa, TechnicalUniversity of Delft, Holland, Oecember 6, 1976.
-185-
"Recent Cryogenic Uork at the Institute of Physical Problems",V. Pushkow, Institute of Physical Problems, Academy of Sciences,USSR, Dec umber 14, 1976.
"Applied Superconductivity work in Switzerland", 3.L. Olaan, SolidState Physics Laboratory, Zurich, Switzerland, December 16, 1976.
"Properties of Layered and Planar Magnets", W.L. Pokrovsky, LandauInstitute of Theoretical Physics, Moscow, Oecember 23, 1976.
"Two Phonon Bound Stats in Crystals", S.I/. Lordansky, Landau Instituteof Thtortsticd 1 Phydics, Moscow, Oecsnioer 24 t 1976.
•Members of the Physics Group, B.A.R.C
LLCTURtS ANO
Lectures and Seminars presented by (Division members outside BARCduriny th& year included the following *
Y.Q. Oande, "Modern Trends in Isotropic Neutron Radiography", NationalSymposium on Industrial Isotope Radiography, Tiruchirappalli,Tamil Nadu, 1976.
Y.O. Odnde, IM.C. Jain and R.S>. Udyawar, "Neutron Radiography, ofordnance storus, Pyrotachnigue Oet/icea and Co.uposita Materials",National symposium on Industrial Isotope Radiography, Tiruchira-ppalli, Tamil Nadu, 1976.
B.rt. Oanannacharya, "Density Fiuctuatian in Simple Liquids", Seminaron Current Trends in Physics, Institute of Physics, Bhubaneshwar1976.
K. Uiha Deniz, "Phase Transitions In Liquid Crystals", Laser Section,BARC.
K. Usha Deni?, "X-ray Oiffraction and Neutron Scattering Studies ofthB Liquid Crystalling Phasps in HxBPA", Institute of Science,Bangalore.
K. Usha Deniz, "Liquid Crystals", Tata Institute of FundamentalResearch, Bo'"bdy.
C.S.P. Iyar, H.M. Bajpai, G.R. Plody, Ma dan Lai, "I.notopic X-rayFluorescence in Metallurgy", Seminar on flattal.lurgy AnalysisRavi Shankcir University, Jaipur, Feb. 1976.
-186-
N.C. Oein, "Thermal Neutron Radiography", Advanced Course in IndustrialRadiography, BrtRC.
S.K. Kataria, "Recent Progress in Nuclear Fission Studies", INSAAwardae Lecture Ser iea- I I .
D.K. Mehta, "Small Accelerator, their Promises and Prospects",Symposium on Radiation Physics..
A.S. Paranjpe, "Liquid Crystals end Their Applications to DisplayDevices", Holkar science College, Indore.
U.S. Ramamurthy, "Some Rare Hodaa of Fission - What do wb lsarn fromthem?", Seminar on Current Trends in Physics, Institute ofPhysics, Bhubaneshwar 1976.
D.K. Sood, "Ion Implantation", Seminar on Low Energy Cyclotron,Punjab University, Chandigarh.
D.K. Sood, "Back-Scattering Techniques", UGC Group fleeting on IonImplantation, .Bombay University.
P.S.P. Nathan, "Relaxation Processes Aasaclatad with the Absorptionof Acoaustic Waves in Liquids", August 10, 1976.*
A.P. Roy, "Photon Bunching", August 20, 1976.*
K.R.P.n. Res, "The Spin-Glasses", August 27, 1976.*
K.R. Rao, "Tht Queai-One-Dimensional Conductor KCP - The NeutronicView", September 17, 1976.*
N.S. Satya Hurthy, "Repert en some papers from 'International Con-ference en negnetism* 1976". September 24, 4976.+
P. Chaddah, "Electron Mem enturn Densities in Simple Pelyatomic mole-cules", Octeber 4, 1976.*
A . I . Mehta, "Rayleigh.end Brilleuin Scattering frem Gases".Octeber 8, 1976.
•Selld State Phyelc* Sectional Sealner
01hrir j c l g n t i f it:_ Ac t i •*!t 1Ba
Th« members of t.ha :)ivi3inn h*wa benn act ively involved in
iny and Tiiiininy Programmes, oryonisation of Symposia and hava
d on various com.n i t t r e» of tha Oepartriont of Atomic tnaryy,
u und tha Indian Physics Association. A brief account
a c t i u i t i s s i i a
Like1 the pruuious yo t f j , warioua cou^uoa in Nuc l««r
ia it£»tu f'hysicij «".-..•; >Ju<iitLin .'•'dchjnj.ca warp delivered to tha
t;-di,-io»3 of the 3.*,H.C. Trwinin-j' Schuol and oost graduate students
of fiu Jjniviirivitv of Honb^yt A courts nf lncturaa on "aosonanca
•-.cjctijri.-." wat. aluo ij.i>/«n to the post graduate atudfinta of Sardar
f'oitl univcroity 'frtllabh Uidyanaaar. Pprnbors of the Division have
pi«iybd a iunjinu rol:> ic framina tti* S> iiabi far the P.^.R.C. Training
Uhooi and tht) Uniuorsity c-f f'
Trair-ing far ' 'l.itionai Jcifnca Talor«t jH^rch Sc^ol^ra flnd
refresher course far Pirst GTdduafce Un.ivf»raity Tsjachgro werp
at ranged. Thcsn pr-jj-Tair-nas t>ra «< roguAcir f«-»tur(» dur.ing the summer
and ar* constantly r sv i s ,d n accordance with tha feedback from the
r ec ip ien t s .
for saw'-'ral yi<<ra, m-jnOctrs of the i)'.«ifli.oo hava b*«n organiaing
-188-
tha Nuclear Physics and the Solid State Physic* Symposium of the
Department of Atomic Energy. This is a National Symposium, held every
year towards the end of Oecembsr, in which the members of the Physics
Community from all over the country get together and discuss their
work. This year's Symposium uias held at Gujarat University, Ahmadabad
during December 27-31 . The Convener and Secretaries of the Symposium
are from this Division. The proceedings of the Symposium are published
under their guidance.
SCIENTIFIC rtNQ RESEARCH BODIES
Members of the Oivision have been actively involved in the
promotion of scientific and research activities in the Country and
have been starving on several national committees. During the year of
this report they have been connected with!
Research grants and Scholarships to Universities from the Board
of Research in Nuclear Science of the Department of Atomic Energy)
Utilization of the kfariabla Energy Cyclotron at Calcutta;
University Grants Commission's ad hoc Committees for special
assistance programmes to Universities;
Board of Studies for Physics and Selection Committees for the
tnaching Staff in several Universities;
Indian Physics Association, both in its National Committee
and Bombay Chapter
-189-
NUCLt-AR PHYSICS DIVISION aTAFF
A. UHN-OL-GHAAFF.
1 . Nuclear Reactions
2 .
3 .
M.KS.Kn.s.ss.
. Ptehta
. Gupta1
Balakrishnan. KerekatteKailas
rt, ChatterjeuHohd. IsmailS.S,r w
. bainirurnanHoo
w a v • ) • ! na i iugo
Gulzar Singh^
B.C
CI.G
a.p
II.AN.LO.HH.H
. Sinha
. Bttiyeri
. rtnand
. k.suiaran*'
. Rayoouansi
. Chakraborty
. Oza
Nuclear Reaction Thuory
N.B.KA.K
Sanna. Jain. Jain
Nuclear Spectroscopy
C. V\i.mP.OU.SM.Y1*1.G
.K. Baba
. Oatar
. Bhalerao
. Ambekar
. Maze
. Patwatdhan
5 .
6 .
7.
N.O.KP.K.1.5A.GPI.3S.G
5ar<na. Sood. Bhattacharya. Bhatia. Wagh. Kansara. Gaonkar*
t/an-de-Graaff Plaintanance
W.AS.NS.G
o.sP.RG.I/R.PS.Jn.ER.U
& ODerationa
. Hattangadi
. Plishra
. Shukla
. Biaht
. Sundar Rao
. Bhatt
. Kulkarni
. fiandke
. Doctor
. Patkar
Isotope Separator
V.AF.RK.LE.
. Hattangadi
. Bhathena
. PatelShallom
Tandem Accelerator Pro.iact
n.Kn.c3.NT.P
. fight a
. Rotlgari
. Soni
. DavidPitambar SinghC.U . Rayarappan
1 On leave to CEN de Bruyacaa-la Chatel, Francs.2 Research Student, Punjab Univeraity, Chandigarh.3 On leave to Rochester Univtraity, USA.4 Research Student, Bombay Unii/ar«lty.
-190-
6 . FISJOION PHYSICS StCTIONi
R. RamannoS.S.
o.n.U.S.N.N.S.K.R.K.
Kapoor. NadkarniRamamurthyMjitanandKatariaChowdhury
PI. Prakash
P.N. Rama RaoMa da n La 1b.R.B.R.K.M.S.L.B.U.
S. Piucthy
Bal la llyen ,arRaots
N. Rao5
C. SOLID iTMTt PHY6ICS
1• Neutron ScatturinoP.KB.A
K.ftC . u
P . iS.KP.Prt.H
N.SL.H.3U.CS.KR.S.R
. Iytinyar
. Oasannacharya
. Hau
. Thapur
. CoyaX
. Sinha
. Chandra
. Uenkatesh
. batya Ourthy("iadhau Rao2
. Beyum
. Hakhuoha
. ParanjpaChakrawarthy. Tendulkar^
P.R. UijayaraghavanB.S. Sriniva3anM.R.L.N. murthyP.K. OayanidhiA.S. DeshpandeS.L. Chaplot
2. Light Scattering &Liquid Crystals
K. Usha DenizP.S. ParvathanathanA.S. ParanjpeA . I . flehta3
A.P. RoyU.C. SahniPl.L. BansalT.R. Rao3
3. ftossbauer Studies
P.K. IyengarK.R.P.fi. RaoS.C. Bhargaua^N.K. Jaggi
4 . Compton bcattarlng
V.C. SahniP. Chaddah
5. Loui Temperature Physics
N.S. oatya ClurthyU.K. ChopraG. OharmaduraiT. i r in ivaaanA.P. Bagool
6. Theoretical Group
R. SubramanianI.V.U. RaghevacharyuluK.U. GhagvatS. Jyot iS.L. Narasimhan
1 Partly on Foreign Service to IAEA at Bandung, Indonesia.2 Partly on lea we to CEN da Saclay, France.3 Research Scholar, Bombay University*A On leave to Technical University cr Denmark.,5 Pool Officer, CSlfl.
- 1 9 1 -
SUPPORTING F A C I L I T I L S I
1 . Neutron Detect T «
Y.O. Danda5
N.C. JainR.S. UdyauarG.V. ShanoyS.R. ChinchaniKaa?
2 . Electronics Oeaiqn * Qavalopman't
U. SinghV.H.R.S.U.G.3.N.N.O.
5hahKotharoGaonkar •
3oshiKalikar
Workshop
J.N.K.R.V.B.S.R.O.S.C.S.V.O.
SoniOhailDikshitSawantChawlaPatilSansare
Administrative4.
T. Ramanujam?Vijaya RauindranathA.3. KulkarniR.S. PillaiPrema KrishnanB.R. GauharK.K. Kanitkar
1 Partly on IAEA fal'lbwahip to Harwell, UK,2 mainly with the Physica Group Offica.
Organization Chart andSumnary of Ac t iv i t iuS 1976
VAN Q£ CRMAFF LAB.
Headfi.K. ICHTA
Nuclsar RaactionaNuclsar Spactroacopy A
StruoturaNuclaar Thaory.ten I«pl*ntatioo Studlaa
W«nd«-graaff MaintenanceA Operation
leotope SeparatorTandea Accelerator Project
Neutron and X-ray DetectorsNeutron Radiography
(Y.O. Oande)
PHYSICS GROUP
DIRECTORP.K. IYLNGHR
NUCLLAR PHYSICS DIVISION
H£*Ofl.K. itHTrt
±FISSION PHYoICS
Head6.S. KAPOOR
Cxpariaental Fi»;aion StudiesFission TheoryNuclear TheoryX-ray Fluorsacsncs AnalysisProton-induead X-ray Studies
SUPPORTING FACILITIES
electronics gand Development.
(W. Singh)
SOLJO STATC PHYSICSHead
U.S. SATYA rtURTHY
Neutron Scattering-.5sgn*t ic StructuresSpin Density Distr ibut ionsPhonon • nsgnon Neasurewsnt*nplaoular A Liquid Dynamics6*e*-Technique Oevelopwant
Light acat ier lngLiquid Crystsl StudiesConpton Sostteringflossbauer SpactroecopyLow Tmnperatura StudiesPvsparation of Alloys A CrystalsTheory
Workshop
(O.N. 5oni)
Administration
(T. Ramanujam)
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