Brad Sherrill Chief Scientist Facility for Rare Isotope Beams
10-12 June 2013
Nuclear Structure and Reactions
§ One of HUGS goals is to introduce students to “topics of interest in nuclear physics”. My lectures will attempt to describe what is interesting in the study of nuclei.
§ Lecture 1: Search for the limits of nuclear binding and production of new isotopes
§ Lecture 2: Attempts to model atomic nuclei I § Lecture 3: Attempts to model atomic nuclei II § Lecture 4: Nuclear Reactions § Lecture 5: The origin of atoms – Nuclear Astrophysics I § Lecture 6: The origin of atoms – Nuclear Astrophysics II
Outline of my six lectures
It is important for you to ask questions.
Sherrill HUGS Lecture 1 , Slide 2
Nuclear Landscape
• Chart of the nuclides
• Black squares are the 263 stable isotopes found in nature (> 1 Gy)
• Dark green closed area is the region of isotopes observed so far.
• The limits are not known.
Sherrill HUGS Lecture 1 , Slide 3
§ Let’s define “possible” as lasting long enough to make an atom that could react chemically (10-6 s; probably 10-16 is valid)
§ Neutron drip line
§ Proton drip line
§ Heaviest elements – The claim for up to atomic number 118 has been made at Dubna (Oganessian et al.)
How many isotopes are possible?
22C 20C 13C
p
12C
n
Mass model
Sherrill HUGS Lecture 1 , Slide 4
Open Questions: § How many elements can exist? We are up to element 118 and
counting. § Are there long-lived superheavy elements, with half lives of
greater than 1 year? § Where are the atoms of the various elements formed in
nature? § What makes atomic nuclei stable? We know Strong and
Electroweak forces are involved, but don’t understand how in detail. The inability to answer this question is reflected in our inability to answer the first three questions.
Open Questions in the Search for the Limits
Sherrill HUGS Lecture 1 , Slide 5
History of Element Discovery
Democritus – idea of atoms
India Babylonia Egypt China
Copper Age
1700+ Rise of modern chemistry – Dalton’s Atomic Theory
Source: Mathematica + Wikipedia
Sherrill HUGS Lecture 1 , Slide 6
The history of element discovery 1200-2010
Time of the Alchemists
Chemistry Dalton’s Atomic Theory Cavendish, Priestly, Scheele, …
Mendeleev’s Periodic Table
Particle Accelerators Reactors
Future?
Sherrill HUGS Lecture 1 , Slide 7
Result: Periodic Table of the Elements http://www.sciencegeek.net
Sherrill HUGS Lecture 1
We don’t know the limit. Some estimates are that we have discovered only half of the elements, but we don’t know.
Superheavy: Only stable due to many-body effects
, Slide 8
48Ca-ions
rotating entrancewindow
gas-filledchamber
detectorstation
recoils
position sensitivestrip detectors
TOF-detectors
“veto” detectors
22.50
SH recoil
side detectors
Recently named elements 114, 116; claims for 113,115,117,118 Synthesis of the heaviest elements
Sherrill HUGS Lecture 1
Y Oganessian et al In new element searches fusion happens only 1 in 1018
Z=113
169
, Slide 9
48Ca+237Np
§ Alpha (α)-decay – emission of a Helium nucleus • Why not two protons and two neutrons?
§ Beta (β)-decay – weak decay of proton (neutron) to a positron and electron neutrino
§ Electron capture – atomic electron is captured, anti-electron neutrino emitted
§ Gamma (γ)-decay – nucleus de-excites by emission of a photon § Internal conversion – energy from nuclear transition is carried away by
an atomic electron (very important for transitions in heavier nuclei) § Cluster Decay – for example 14C § Spontaneous fission – for example 252Cf decays by breaking into
roughly equal mass pieces § Proton decay – emission of a hydrogen nucleus, p § Neutron decay – emission of a neutron (observation still controversial)
Radioactive Decay
Sherrill HUGS Lecture 1 , Slide 10
Superheavy Elements
Sherrill HUGS Lecture 1 , Slide 11
115/287
10.59
3 ms2
113/283
10.12
0. s1
111/279
10.37
0.17 s
109/2 57
10.33
9.7 ms
107/2 17
105/2671.2 h
α
α
α
α
α
109/276
9.71
0.72 s
107/272
9.02
9.8 s
113/284
10.00
0.48 s
115/288
10.46
87 ms
105/2681.2 d
111/280
9.75
3 6. s
104/268
α
α
α
α
α 243Am 242Pu, 245Cm
226Ra
Sg/266 0.2 s
Hs/270 10 s
9.06
α 237Np
244Pu, 248Cm 249Cf
34 nuclides
48Ca +
249Bk T1/2= 320d ORNL High Flux Reactor
164
104/270
105/270
107/274
109/278
111/282
113/286
115/290
117/294
103/266 102/266
107/273
109/277
105/269
111/281
113/285
115/289
117/293
104/269
48Ca +249Bk
2009-2012
RiKEN (Japan) 209Bi +70Zn
§ Summary § Figure adapted
from Y. Ogannessian
§ Dubna, RIKEN, GSI, LBL, …
, Slide 11
Collaboration: FLNR (Dubna), ORNL (Oak-Ridge), LLNL (Livermore), IAR (Dmitrovgrad) Vanderbilt University
Today’s Extremes of Z and A Discovery of Element 117
Phys. Rev. Lett. 104, 142502 (2010) Phys. Rev. Lett. 108, 022502 (2012)
Bk from HFIR
Dubna accelerator
Hot cell target prep
249Bk +48Ca 330 days
Sherrill HUGS Lecture 1 , Slide 12
The Challenge of Even Higher Atomic Numbers
780254526
E def
(MeV
)
r (fm)
z (fm
)
bubble
band
normal
`2M. Bender et al., to be published
P. Pyykkö: Phys. Chem. Chem. Phys. 13, 161-168 (2011) “Half of chemistry is undiscovered. Other view– above Z=122 all chemistry is the same due to relativistic effects For stability of Z>120 see also Jachimowicz, Kowal, Skalski, PRC 83 (2011)
Sherrill HUGS Lecture 1 , Slide 13
Half-lives of Superheavy Elements
Log
T (s
ec.)
α
150 160 170 180 190140
5
15
10
20
0
-5
-10 116
118
112
114
110
108
108
Neutron number
α - decay
DeformedShell
SphericalShell
Symbols: exp. values Lines calc. Sobiczewski & Smolanczuk
Sherrill HUGS Lecture 1 , Slide 14
1 year
Element 118 48Ca + 249Cf
Discovery of Isotopes § Fredrick Soddy – Credited with discovery of isotopes
• Extremely talented chemist who began his career at McGill as a lecturer in 1900
• Rutherford came to McGill at the same time. Rutherford needed the help of a Chemist to try to understand radioactivity.
• Rutherford won 1908 Nobel prize "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances” (identified α and β radioactivity)
§ Isotopes • In 1910 Soddy found that the mass of lead from thorium decay
differed from lead from uranium decay • He realized that atoms of a given elements must come in different
forms that he called isotopes (Greek for “at the same place”) JJ Thompson in 1913 showed the first direct evidence – Ne isotopes in cathode ray tube.
• "Put colloquially, their atoms have identical outsides but different insides.” – Soddy Nobel Prize Lecture
• Won Nobel Prize in 1921 for discovery of isotopes
Sherrill HUGS Lecture 1 , Slide 15
McGill
First Synthesis of Radioactive Isotopes
• The first artificial isotopes were produced by F Joliot and I Curie (Nature, 10 Feb 1934 ) by bombarding B, Al, Mg with alpha particles from Po
• “We propose for the new radio-isotopes formed by the transmutation of boron, magnesium and aluminum, the names radionitrogen, radiosilicon, radiophosphorus”
• For this discovery, Curie and Joliot won the Nobel Prize in chemistry in 1935
Sherrill HUGS Lecture 1 , Slide 16
New isotope discoveries per year
Radio- activity
Mass spectroscopy
First accelerators
Projectile fragmentation
WWII
Fusion evaporation Spallation
Reactors
Thoennessen and Sherrill, Nature 473 (2011) 25
Sherrill HUGS Lecture 1 , Slide 17
§ You can find out at the website www.nndc.bnl.gov - National Nuclear Data Center
Where Are We Now?
Sherrill HUGS Lecture 1 , Slide 18
Value of Isotopes
Sherrill HUGS Lecture 1
§ Some examples of the cost of isotopes • May 27 value of Au-197 C$1438/ounce • H-3, tritium, isotope of hydrogen $1.1 M/ounce
§ Normal Calcium (Calcium-40 $.32 per ounce)
§ Expensive Calcium (.2% Calcium-48 $7M per ounce)
§ Among most expensive: Berkelium-249 $644M/ounce
20 protons
28 neutrons
20 protons
20 neutrons
, Slide 19
Goal of Current Isotope Research
Sherrill HUGS Lecture 1 , Slide 20
20 protons
40 neutrons
§ Normal Calcium (Calcium-40 $.32 per ounce – 4 x1023 atoms)
§ Goal at FRIB: Calcium-60 ($10,000 for 1000 atoms)
20 protons
20 neutrons
Isotope Production Scheme • Cartoon of the isotope production process – projectile fragmentation or
fission (Coulomb breakup, transfer, …)
• To produce a key nucleus like 122Zr the production cross section (from
136Xe) is estimated to be 2x10-18 b (2 attobarns, 2x10-46 m2 ) • Nevertheless with a 136Xe beam of 8x1013 ion/s (400 kW at 200 MeV/u) a
few atoms per week can be made and studied (>80% collection efficiency) • For comparison: Element 117 production cross section was 1.3 (+1.5 -0.6)
pb (1.3x10-12 b) (Oganessian, Yu. Ts. et al PRL 104 (2010) 142502) • Few x10-46 m2 is on the order of 100 MeV neutrino-electron elastic
scattering cross sections
projectile target
Sherrill HUGS Lecture 1 , Slide 21
Production and Identification of Isotopes Sometimes looking for 1 event from 1018 beam particles
Example: 40Mg Production 120 pnA 48Ca 140 MeV/u Goal was to produce 40Mg
Sherrill HUGS Lecture 1 , Slide 22
First observation of 40Mg
T. Baumann et al. , Nature 449, 1022 (2007)
€
ρ =m⋅ vB⋅ q
tof =distv
→mq
ΔE (inmaterial)∝ Z 2
v 2
Sherrill HUGS Lecture 1 , Slide 23
LISE++ Simulation Code
The code operates under Windows and provides a highly user-friendly interface. See me at this school for a tutorial session It can be downloaded from the following internet address:
O. Tarasov, D. Bazin et al. http://www.nscl.msu.edu/lise
Sherrill HUGS Lecture 1 , Slide 24
§ The probability of production of a fragment is related to its production cross section:
§ For production cross sections of 1 mb and 9Be target thickness of 1 g/
cm2 the production probability (and fragment rate) is high:
§ Beam of 1014/s beam would yield 7x109 /s § Note: Key is σ – cross section , τ – target thickness, N0 – beam
intensity
Production Probability
dN(τ )dτ
=NaσAt
→ P = N(τ )N0
= 1− e−τ NaσAt
#
$%%
&
'((
τ target thickness (g/cm2) Na Avagodro’s number At target mass number σ production cross section
€
P =N(τ)N0
= 1− e−1⋅6.022×1023 ⋅1×10-27
9⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟ = 7 ×10
−5
Sherrill HUGS Lecture 1 , Slide 25
€
σ = π rt + rb( )2 ≈ 600 mb
Cross Section for Production Beam Target
rt rb 18O 17N 16C 15B
14Be 13Li 12Li 11Li
One nucleon removal Around 50 mb (light nuclei) P ≈ 5% 2n removal 5 mb P = .5% And so on Rule of thumb .1 x for each neutron removed
Actual: 16O +12C interaction cross section: 1000 mb (measured at 970 MeV/u) Note: Above around 300 MeV/u the interaction length is shorter than the electronic stopping range of the 16O so most beam particles can interact
Sherrill HUGS Lecture 1 , Slide 26
§ Fragmentation (FRIB, RIBLL Lanzhou, NSCL, GSI, RIKEN, GANIL) o Projectile fragmentation of high energy (>50 MeV/A) heavy ions o Target fragmentation of a target with high energy protons or light HIs. In
the heavy ion reaction mechanism community this would include intermediate mass fragments.
§ Spallation (ISOLDE, TRIUMF-ISAC, EURISOL, SPES, …) o Name comes from spalling or cracking-off of target pieces. o One of the major ISOLDE mechanisms, e.g. 11Li made from spallation of
Uranium. § Fission (HRIBF, ARIEL, ISAC, JYFL, BRIF,…)
o There is a variety of ways to induce fission (photons, protons, neutrons (thermal, low, high energy)
o The fissioning nuclei can be the target (HRIBF, ISAC) or the beam (GSI, NSCL, RIKEN, FAIR, FRIB).
§ Coulomb Breakup (GSI) o At beam velocities of 1 GeV/n the equivalent photon flux as an ion passes
a target is so high the GDR excitation cross section is many barns.
Production Mechanisms – High Energy (more in lecture 4)
Sherrill HUGS Lecture 1 , Slide 27
Spallation From Wikimedia Commons: http://en.wikipedia.org/wiki/File:Spallation.gif
Sherrill HUGS Lecture 1 , Slide 28
Method of discovery of the isotopes
Sherrill HUGS Lecture 1 , Slide 29
§ Funded by DOE Office of Science – 2020 completion
§ Key Feature is 400kW beam power (5 x1013 238U/s)
§ Separation of isotopes in-flight • Fast development
time for any isotope • Suited for all
elements and short half-lives
Major US Project – Facility for Rare Isotope Beams, FRIB
Sherrill HUGS Lecture 1 , Slide 30
Isotope Separation On-Line ISOL
§ Highest power ISOL facility - >50 kW § Programs in nuclei, astrophysics, symmetry tests,
condensed matter, medical isotopes
Major Canadian Facility – TRIUMF ISAC and ARIEL
Sherrill HUGS Lecture 1 , Slide 31
100 µA, 500 MeV, p
projectile
target 5 mA, 25 MeV, electrons
Rare Isotope Production Methods
Sherrill HUGS Lecture 1 , Slide 32
Worldwide Growth of Rare Isotope Beam Facilities
Sherrill HUGS Lecture 1 , Slide 33
How many isotopes might exist?
§ Estimated Possible: Erler, Birge, Kortelainen, Nazarewicz, Olsen, Stoitsov, Nature 486, 509–512 (28 June 2012) , based on a study of EDF models
§ “Known” defined as isotopes with at least one excited state known (1900 isotopes from NNDC database)
§ Represents what is possible now
Sherrill HUGS Lecture 1 , Slide 34
The Number of Isotopes Available for Study at FRIB (next generation facilities)
§ Estimated Possible: Erler, Birge, Kortelainen, Nazarewicz, Olsen, Stoitsov, Nature 486, 509–512 (28 June 2012) , based on a study of EDF models
§ “Known” defined as isotopes with at least one excited state known (1900 isotopes from NNDC database)
§ For Z<90 FRIB is predicted to make > 80% of all possible isotopes
Sherrill HUGS Lecture 1 , Slide 35
Uncertainty in Estimates Estimated Possible: Erler, et al. to be published
Sherrill HUGS Lecture 1 , Slide 36
Open Questions: § How many elements can exist? We are up to element 118 and
counting. § Are there long-lived superheavy elements, with half lives of
greater than 1 year? § Where are the atoms of the various elements formed in
nature? § What makes atomic nuclei stable? We know Strong and
Electroweak forces are involved, but don’t understand how in detail. The inability to answer this question is reflected in our inability to answer the first three questions.
Open Questions in the Search for the Limits
Sherrill HUGS Lecture 1 , Slide 37
§ History of nuclear physics - E. Segre, From X-Rays to Quarks, W.A. Freeman & Co, San Francisco, 1980
§ Heavy element searches - Heaviest nuclei from Ca-48-induced reactions, Yu. Oganessian, J. Phys. G 34(2007) R165-R242.
§ Isotope searches - http://www.nscl.msu.edu/~thoennes/isotopes/ § Rare isotope science – Geesaman, Gelbke, Janssens, Sherrill, Annu.
Rev. Nucl. Part. Sci. 2006. 56:53–92 § Rare isotope production – Geissel, Munzenberg, Riisager, Ann Rev.
Nuclear and Part. Science Vol. 45 (1995) 163-203.
References
Sherrill HUGS Lecture 1 , Slide 38