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SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 1 of Lecture 11
Ramesh GuptaSuperconducting Magnet Division Brookhaven National Laboratory
US Particle Accelerator SchoolUniversity of California – Santa Barbara
June 23-27, 2003
High TemperatureSuperconductor (HTS)
Magnet R&D and Designs
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 2 of Lecture 11
The Conventional Low Temperature Superconductors (LTS)and the New High Temperature Superconductors (HTS)
Resistance of Mercury falls suddenly belowmeas. accuracy at very low (4.2) temperature
Low Temperature Superconductor Onnes (1911)
Temperature (K)
Res
ista
nce
(Ohm
s)
New materials (ceramics) loose their resistanceat NOT so low temperature (Liquid Nitrogen)!High Temperature Superconductors (1986)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 3 of Lecture 11
Popular HTS Materials of Today
•BSCCO 2223 (Bi,Pb)2Sr2Ca2Cu3Ox
•BSCCO 2212•YBCCO
•MgB2 is technically a low temperature superconductor (LTS) withcritical temperature ~39 K.
Of these only BSCCO2212 and BSCCO2223 are now available insufficient quantities to make accelerator magnets.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 4 of Lecture 11
Applied Field, T
Univers ity of Wis co ns in-Madis o nApplied S uperco nductivity CenterUnivers ity of Wis co ns in-Madis o nApplied S uperco nductivity Center
De ce mbe r 12th 2002 - Compiled by Pe te r J. Lee - jcprog_02bl.ppt, jcprog_02.xlsDe ce mbe r 12th 2002 - Compiled by Pe te r J. Lee - jcprog_02bl.ppt, jcprog_02.xlsSuperconductor Critical CurrentsSuperconductor Critical CurrentsLegend on next s lide
Crit
ical
Cur
rent
Den
sity
, A/m
m²
10
100
1,000
10,000
100,000
0 5 10 15 20 25 30Applied Field, T
YBCO75 K H||a-b
YBCO75 K H||c
Nb3Al RQHT+Cu
Nb3SnITER
Nb-Ti APC
2223Tape B|_
At 4.2 K UnlessOtherwise Stated
1.8 KNb-Ti-Ta
PbSnMo6S8
1.8 KNb-Ti
Nb3Sn Tapefrom (Nb,Ta) 6Sn5
2212 Round wire
YBCOµbridge H||c
MgB2Film Nb3Sn
1.8 K Bronze
Nb-Ti HT
Nb3Sn Internal Sn
Nb3AlITER
2223Tape B||
2212 Tape
Nb-Ti Multilayer
J c,
A/m
m2
Another Remarkable Property of HTSThe High Field Current Carrying Capacity
R vs. T
HTS
Compare Jc Vs. Bbetween the
conventional LowTemperature
Superconductors(LTS) and HighTemperature
Superconductors(HTS)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 5 of Lecture 11
Advantages of using HTSin Accelerator Magnets
• HTS has a potential to produce very high field magnets• HTS based magnets can work at elevated temperatures
• a rise in temperature from, e.g., decay particles can be tolerated• the operating temperature does not have to be controlled precisely
• HTS based magnets don’t appear to quench in the normal sense•Weak spots don’t limit the magnet performance, instead the localtemperature rises a bit (major difference from LTS magnets).
It becomes a question of heat load rather than a weak spotlimiting the performance of the entire magnet
As compared to LTS, the critical current density (Jc ) falls slowly• as a function of field• as a function of temperature
Translate this to magnet design and accelerator operation:
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 6 of Lecture 11
Challenges with HTS(and the way they are being addressed)
• HTS materials are very brittleWork on magnet designs => make “conductor friendly designs”.
• HTS materials are still very expensiveCost/Amp is coming down continuously, primarily because of theimprovements in performance. Also for some applications, theperformance and not the material cost should be the main consideration.One must consider the overall system and operational cost.
• Large quantities are not availableSituation has significantly improved. We purchased 1.5 km long wire.The tapes are available in similar length. Now we can make coils andmagnets having reasonable length.The technical question is controlling the temperature of reaction furnaceto ~1/2 degree at 880o-890oC over the entire reaction volume.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 7 of Lecture 11
Possible Applications of HTSin Accelerator Magnets
High Field, Low Temperature ApplicationExample: Interaction Region (IR) Magnets for large luminosity upgrade or very highfield main ring dipoles to achieve highest possible energy in existing given tunnel.• At very high fields (>15 T), no superconductor carries as much critical currentdensity as HTS.
Medium Field, Higher Temperature ApplicationExample: Quads for Rare Isotope Accelerator (RIA)• The system design benefits enormously because the HTS offers the possibility ofmagnets to operate at higher than 4K, say at 20-40 K.
Special Benefits of HTS• The HTS can tolerate a large increase in temperature in superconducting coils(caused by the decay particles) with only a small loss in performance.• Moreover, the temperature need not be controlled precisely (Think about an order ofmagnitude relaxation in temperature variations, as compared to the LTS used incurrent accelerator magnets).
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 8 of Lecture 11
Expected Performance ofHTS-based Magnets
Expected performance of all Nb3Snor all HTS magnets at 4.2 K for thesame amount of superconductor:
All Nb3Sn All HTS12 T 5 T15 T 13 T18 T 19 T*
*20 T for Hybrid
Year 2000 Data
All Nb3Sn All HTS12 T 11 T15 T 16 T18 T 22 T
Near Future
Year 2000 data for Jc at 12 T, 4.2 KNb3Sn: 2200 A/mm2
BSCCO-2212: 2000 A/mm2
Near future assumptions for Jc at 12 T, 4.2 KNb3Sn: 3000 A/mm2 (DOE Goal)BSCCO-2212: 4000 A/mm2 (2X today)
Cu(Ag)/SC RatioBSCCO: 3:1 (all cases)Nb3Sn: 1:1 or Jcu=1500 A/mm2
Performance of 0.8 mm dia wire
100
1000
10000
0 2 4 6 8 10 12 14 16 18 20
B(T)
Jc(A
/mm
2)
Nb3Sn (4.2K)
BSCCO2212 (4.2K)
NbTi (1.8K)
NbTi (4.2K)
As of year 2000
(performance in ~100 meter or longer lengths)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 9 of Lecture 11
First Likely Application of HTS:Interaction Region (IR) Magnets
Interaction region magnets for the next generation collidersor luminosity upgrade of existing colliders
(LHC is existing collider for this purpose)can benefit a lot from:
Very high fields Ability to take large energy deposition without much loss in performance Ability to operate at elevated temperatures that need not be uniform
→ For IR magnets, the performance, not the material cost is the issue.→ These magnets can be, and perhaps should be, replaced in a few years.
(for LHC, the first installment may be due ~10 years from now)
All of above makes HTS a natural choice for next generation IR magnet R&D.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 10 of Lecture 11
Construction and Test Results from HTSTechnology Development Program at BNL
10+ kA HTS Rutherford CableBNL/LBL/Industry collaborationHTS Wire HTS Tape
Next Few Slides will Show:
• Results of HTS Tape and Cable Tests
• Construction and Test Results of HTS Coils and R&D Magnets
Please see the tape and cable being distributed
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 11 of Lecture 11
HTS Coil Wound by Hand
Al Bobbin (70 mm radius)(also used, Fe, SS and brass bobbins)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 12 of Lecture 11
0
100
200
300
400
500
0 1 2 3 4 5 6 7 8 9 10 11 12 13Field (T)
Ic(A
)
Measured Performance of HTS Cable andTape As A Function of Field at BNL
Measurements of “BSCCO-2212 cable”(Showa/LBL/BNL) at BNL test facility
Reported Ic in new wires is ~ 3xbetter than measured in the cable.This was a narrow (18 strand) cable.Wider cable with new conductorshould be able to carry 5-10 kAcurrent at high fields!
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
0 1 2 3 4 5 6 7
H, T
Ic(1
.0uV
), A
//-Low//-HighPerp H
Measurements of “BSCCO 2223tape” wound at 57 mm diameterwith applied field parallel (1µV/cmcriterion)(field perpendicular value is ~60%)
(self field correction is applied)
BSCCO 2212 Cable Test
BSCCO 2223 Tape Test
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 13 of Lecture 11
020406080
100120140160180200
5 10 15 20 25 30 35 40 45 50 55 60 65
T(K)
Ic(@
1 µV/
cm)
Half Coil #1
Half Coil #2
Half Coil #3
Half Coil #4
Critical Current as a Function ofTemperature & Field
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
0 1 2 3 4 5 6 7
H, T
Ic(1
.0uV
), A
//-Low//-HighPerp H
For very high field magnet applications, we are interested in low temperatureand high field characteristics of high temperature superconductors.
However, these conductors still have significant critical current at higher temperature.Testing at Liquid Nitrogen (LN2) temperature is much more easier than testing at LiquidHelium (LHe) temperatures.
BNL has developed and extensively used LN2 testing in HTS cable, coiland magnet R&D.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 14 of Lecture 11
HTS Cable and Coil Testat Liquid Nitrogen
•LN2 testing is mucheasier than LHetesting•Yet LN2 testing givesa good indication ofthe cable behavior inLHe
FreezingPoint
BoilingPoint
Testing of HTS cables (or tapes) at LN2 is a powerful method even if thecables are to be used in magnets that would operate at LHe temperatures
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 15 of Lecture 11
BSCCO-2212 Cable “Pancake Coils”
HTS cable is carefully wound in large radius pancakecoil for testing at liquid nitrogen temperatures
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 16 of Lecture 11
Ic Tracking Between 4.2 K and 55 K
Ic of various 3 m sections at 4.2 K and 55 K
1
10
100
1000
0 1 2 3 4 5 6 7 8 9 10 11Section No.
Ic fo
r 1 µ
V/c
m
Ic1@55KIc1@4.2K
Mix strand cable test, BNL 12/00
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 17 of Lecture 11
Correlation between Tc and Ic
Tc and Ic Correlation @ 4.2 K and 55 K
62636465666768697071727374
0 20 40 60 80 100 120 140 160 180 200 220 240 260Ic (A)
Tc (K
)
4.2 K55 K
Mix strand cable test, BNL 12/00
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 18 of Lecture 11
Ic as a function ofTemperature
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 19 of Lecture 11
Correlation between Tc and Ic
Better cables (withhigher Ic) also havebetter Tc
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 20 of Lecture 11
BNL Measurements of Various Cables from Showa(Note: Continuous progress in cable performance)
Ic as a function of T in various Bi2212 cable from Showa
0
50
100
150
200
250
300
350
400
55 60 65 70 75 80T (K)
Ic, A
mp
(for 1µV
/cm
)
Cable 5 (1 mm)Cable 4 (1 mm)Cable 3 scaled to 1mmCable 3 (0.8 mm)Cable 1 scaled to 1mmCable 1(0.8 mm)
(without self field correction)
Extrapolated 4 K performance of 20 strand cable (#5) (wire dia = 1 mm) :~5 kA at high fields and ~9 kA at zero field
Test Dates:Cable 1: 06/00Cable 3: 01/01Cable 4: 07/01Cable 5: 11/02
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 21 of Lecture 11
Improvement in Tc of BSCCO-2212Cable from Showa
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
56 58 60 62 64 66 68 70 72 74 76 78 80Temperature (K)
Volta
ge ( µ
V/cm
)
10
9
8
7
6
5
4
3
2
1
sections 4&5 are the best
sections 8&9 are the worst
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
80 84 88 92 96 100 104 108 112T, K
V, µ
V/c
m
Turn-1
Turn-2
Turn-3
Turn-4
Turn-5
Turn-6
Turn-12
Turn-13
Turn-14
Note the improvements both, in the absolute value and in the spread.
Cable obtained~2 years ago
Cable obtainednow (Feb. 03)
1 µV/cm1 µV/cm
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 22 of Lecture 11
HTS Magnet R&D andTest Program at BNL
HTS Tape Coil Program:• Started ~ 4 years ago• Six 1-meter long coils built and tested
10-turn HTS Cable R&D Program with rapid turn around• Cost effective with rapid turn around
�encourages systematic and innovative magnet R&D�allows many ideas to be tried in parallel
•Started ~2 year ago20 coils with brittle materials (5 HTS, 15 Nb3Sn) built and tested
12T high background field R&D Program• Will address issues related to high field, high stressperformance of HTS
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 23 of Lecture 11
Common Coil Magnets With HTS Tape(Field quality in 74 mm aperture to be measured soon)
A coil being wound withHTS tape and insulation.
Two HTS tape coils incommon coil configuration
0.0
0.5
1.0
1.5
2.0
210 230 250 270 290 310
Current, A
Volta
ge G
radi
ent, µV
/cm
Magnet Voltage Gradient
Inner Section of Coil #1
Outer Section of Coil #1
ASC Common-Coil Magnet4.2 K
1µV/cm
-70
-60
-50
-40
-30
-20
-10
0
10
0 100 200 300 400 500 600 Max. Energizing Current Density, A/mm2
Res
idua
l Dip
ole
Fiel
d, G
auss
IGC
ASC
Nb3Sn
Size, mm Turns StatusNb3Sn 0.2 x 3.2 168 TestedIGC 0.25 x 3.3 147 TestedASC 0.18 x 3.1 221 TestedNST 0.20 x 3.2 220 Under constructionVAC 0.23 x 3.4 170 Under construction
Status of HTS tape coils at BNL
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 24 of Lecture 11
HTS Cable Magnet Program
BSCCO 2212 cable appears to be the most promising hightemperature superconductor option for accelerator magnets
• Higher current for operating accelerator magnets•Plus all standard reasons for using cable
HTS Cable
A good and productive collaboration has been establishedbetween labs (BNL, LBL) and industries (IGC, Showa).
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 25 of Lecture 11
BSCCO Wire (Year 2000)Ic-B characteristics of new wire
0
100
200
300
400
500
600
700
0 2 4 6 8 10
new dataconventional wire
Ic (A
)
Magnetic field ( T )
at 4.2K
29/05/00
Ic (4.2K 0T) : 640A Jc (4.2K 0T) : 490kA/cm2
Size : 0.81mmd
Number of filament : 427 Material of outer sheath : Ag alloy Material of inner sheath : Ag Ag/SC ratio : 3.0 Tensile strength (R.T.) : 120MPa
Showa Electric
T. Hasegawa, “HTS Conductor for Magnets”, MT-17, Geneva.
Jc(12T,4.2K)~2000 A/mm2
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 26 of Lecture 11
Vacuum Impregnation Setup
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 27 of Lecture 11
HTS Coils in Support Structure
Coils are heavily instrumented. Thereis a voltage tap after each turn. Datawere recorded from all 26 voltage taps.
Coils are assembled for the mostflexible and extensive testing. Fourleads are taken out of the cryostat.During the test the coils were poweredseparately and together in “commoncoil” and “split-pair solenoid mode”.
Two Hall probes (between the twocoils and at the center of two coils)also recorded the central field.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 28 of Lecture 11
Performance of Coil #1 and Coil #2 in CommonCoil Test Configuration in Magnet (DCC002)
Voltage difference between each consecutive turn and on each coil
Measurements in HTS Magnet DCC004 at 4.2 K
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 29 of Lecture 11
Magnet DCC006: 2nd HTS Dipole(Magnet No. 6 in the common coil cable magnet series)
74 m
m a
pertu
re to
mea
sure
fiel
d qu
ality
HTS
Cab
le L
eads
to m
ake
high
tem
p m
easu
rem
ents
A v
ersa
tile
stru
ctur
e to
test
sin
gle
ordo
uble
coi
ls in
var
ious
con
figur
atio
ns
4 thermometers on the coils
Voltage taps on each turn
Heaters on the magnet to makecontrolled change in magnet temp
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 30 of Lecture 11
Critical Current in Mixed Strand Cable
Ic in ten 3 m long sections at 4.2 K(non-destructive test)
0
50
100
150
200
250
300
0 1 2 3 4 5 6 7 8 9 10 11
Section No.
I c fo
r 1 µV
/cm
and
0.1
µV/
cm
(1uV/cm)(0.1uV/cm)
Mixed strand cable tested at BNL prior to winding coil
Mixed strand cable(2 BSCCO 2212, 16 Ag)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 31 of Lecture 11
Measured Ic of Various Turns
Coil #2 of Mixed Strand Cable
0.00.51.01.52.02.53.03.5
0 50 100 150 200 250
I(A)
Volta
ge A
cros
s Tu
rns
( µV/
cm)
Turn #1 Turn #2
Turn #3 Turn #4
Turn #5 Turn #6
Turn #7 Turn #8
Turn #9 Turn #10
Turn No. 1-7
Turns No. 1-7 show an Ic close to the best measured in cable prior to winding.This suggest a low level of degradation.
Mixed strand cable(2 BSCCO 2212, 16 Ag)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 32 of Lecture 11
020406080
100120140160180200
5 10 15 20 25 30 35 40 45 50 55 60 65T(K)
Ic(@
1 µV/
cm)
Half Coil #1
Half Coil #2
Half Coil #3
Half Coil #4
Measured Critical Current as aFunction of Temperature
0
510
15
2025
30
3540
45
45 50 55 60 65
Mixed strand cable(2 BSCCO 2212, 16 Ag)
4 coil halves (2 each of two coils)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 33 of Lecture 11
Performance of HTS Coil in theBackground Field of Nb3SN Coils
Short sampledefinition for HTS
Measured electrical Resistance of HTS coilin the background field provided by variousNb3Sn coils in the magnet DCC008R
Field in various coilsNb3Sn HTS Nb3Sn
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 34 of Lecture 11
Performance of HTS Coil in theBackground Field of Nb3SN Coils
Performance of HTS cable in coil (before and after winding)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 0.5 1 1.5 2 2.5 3 3.5 4H(T)
I(kA
)
Ic,kA Iss(kA)I(Nb3Sn)=9kA I(Nb3Sn)=6kAI(Nb3Sn)=0kA I(Nb3Sn)=3kA
INb3Sn=0kA INb3Sn=0kA INb3Sn=0kA INb3Sn=0kA
DCC008R
Ic Before Winding
Ic After Winding
HTS coil was subjected to various background field by changing current in“React & Wind” Nb3Sn coils (HTS coil in the middle and Nb3Sn on either side)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 35 of Lecture 11
Low Field Magnet Applicationsof HTS in Accelerators
Medium Field, Higher Temperature ApplicationExample: Quads for Rare Isotope Accelerator (RIA)• These applications don’t require very high fields.• The system design benefits enormously because the HTSoffers the possibility of magnets to operate at higher than 4K, sayat 20-40 K.• The HTS can tolerate a large increase in temperature insuperconducting coils (caused by the decay particles) with only asmall loss in performance.• Moreover, the temperature need not be controlled precisely(Think about an order of magnitude relaxation in temperaturevariations, as compared to the LTS based accelerator magnets).
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 36 of Lecture 11
High Temperature Superconductor (HTS)Quads in Fragment Separator Region of RIA
RIA fromNSCL Web Site
BNL/NSCL Collaboration:We propose HTS quadrupoles forthe first three magnet elements inthe RIA Fragment Separator.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 37 of Lecture 11
Basic Requirements of Quadrupolesfor Fragment Separator in RIA
They are the first magnetic elements in the fragment separator for RIA• Required Gradient: 32 T/m in the first quadrupole of the triplet.• This gradient points to superconducting magnet technology.
� Quads are exposed to high radiation level of fast neutrons (E > 1 MeV)� Beam looses 10-20% of its energy in production target, producingseveral kW of neutrons.� A large fraction of above hit the superconducting quadrupole triplet.
• This raises several short tem and long term time scale issues.
Basically, we need “radiation resistant” superconducting quads, working in a“hostile environment”, where no known magnet has ever lived so long before!
Room temperature, water cooled copper magnets produce lower gradientand/or lower aperture quads. That will lower acceptance and make inefficientuse of beam intensity. Also moving quad back and adding more shielding,requires higher gradient and larger aperture quadrupoles.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 38 of Lecture 11
Short Time Scale Issues
Superconducting magnets will quench if large amount of energy is dumpedon superconducting coils (over several mJ/g).
In addition, there is a large constant heat load on the cryogenic system :~ 1 W/kg to the cold mass.
• The temperature increase must be controlled within the acceptabletolerances of the superconductor used.
• The large amount of heat deposited must be removed economically.
• HTS appear to have a potential of offering a good technical and a goodeconomical solution with the critical current densities that are availabletoday (of course, we can always do better with higher Jc).• However, we need to develop magnet technology and prove that theabove potential can be utilized in a real magnet system.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 39 of Lecture 11
Long Time Scale Issues
• One must look at the impact on the material properties ofsuch a radiation dose over the life time (estimated 1019
neutrons/cm2 in the region of 0 to 30 degrees in ~12 years ).
• Iron and copper are expected to be able to withstand about~100 times the above dose.
Note: The normal water cooled electromagnet can notgenerate the required field gradient.
The development of the radiation resistant superconductingmagnet designs & technologies is highly desirable for RIA.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 40 of Lecture 11
Significant Reduction in NeutronFluence at Larger Angle
0.1
1
10
100
1000
0 10 20 30 40 50 60 70 80 90
Solid Angle (degree)
Dos
e (n
eutr
ons/
sr/p
artic
le)
n/sr/p
T. Kurosawa, et al., Phys Rev C, Vol 62, 044615
Note:A large (almost exponential)reduction in Neutron Fluenceat higher angle.
NOTE: The radiation dose onsuperconducting coils can besignificantly reduced by movingthem outward (larger solid angle).
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 41 of Lecture 11
Proposed Alternate Design for the 1st RIAQuad in the Triplet of Fragment Separator
A Super-ferric design with yoke making significant contribution to field.Racetrack Coil is at x = 22 cm and yoke starts at Ryoke = 5.5 cm
RIA T1
0
5
10
15
20
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A Warm Iron Design withRacetrack HTS Coils
• Coils are movedfurther out to reduceradiation dose.• Field lines arefunneled at the poleto create largergradient.• Warm iron(cryostat around thecoil), to reduce heatload on the system.
BNL/NSCL Collaboration
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 42 of Lecture 11
Insulation in HTS Coils Built at BNL
Two double pancake NMR coils,one with kapton insulation and theother with stainless steel. HTS Test Coil for an Accelerator Magnet
BNL has successfully tested several HTS R&D magnets and test coils made with BSCCO2212 and BSCCO 2223 tape. A unique and very pertinent feature of these coils is thesuccessful use of stainless steel as the insulation material between turns. This technique wasdeveloped to provide a strong mechanical coil package capable of withstanding the largeLorentz forces in a 25T environment, but will also provide a highly radiation resistant coil.
S.S. insulationworks well with
superconductors
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 43 of Lecture 11
Summary and Status of the Alternate Designof the 1st QUAD in RIA Fragment Separator
• HTS Quads can operate at much a higher temperature (20-40 K insteadof 4K).
•The iron yoke is warm (or at least at ~80 K, which can be cooled by liquidnitrogen). This brings a major reduction in amount of heat to be removed atlower temperature.
• The coils are moved significantly outward to reduce radiation dose by alarge amount.
• HTS can tolerate an order of magnitude higher temperature variationsduring operation.
• The possibility of stainless steel insulation is highly attractive.
• It is shown that the field quality requirements can be met.
Apart from providing a good technical solution, this designshould bring a large reduction in the operating costs.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 44 of Lecture 11
Near Term R&D Program at BNL
Present the results to accelerator community so it can makean informed decision about the viability of HTS inaccelerators to take advantage of exciting benefits it offers.
• Build a series of 10 turn coils with better HTS cable
• Build ~40 turn coils after the technology is reasonably developed
• In parallel build ~12 T magnet with Nb3Sn to provide background field
• Assemble hybrid magnet to study issues related to the performance ofHTS coils in high field environment
•Study field quality issues related to HTS magnets
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 45 of Lecture 11
Cut-away View of the 12 T Magnet
Cut-away view of the 12T Magnet
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 46 of Lecture 11
12 T Magnet: The Important NextStep in HTS R&D Program
• At present, HTS alone can not generate thefields we are interested in.
• Nb3Sn coils provides high background fields.The HTS coils will be subjected to high fieldand high stresses that would be present in anall HTS magnet. Therefore, several technicalissues will be addressed.
• Since 12 T Nb3Sn magnet uses similartechnology (building high field magnet withbrittle material), it also provides a valuablelearning experience in building an all HTShigh field magnet.
HTS COILS
LTS COILS • Important design consideration: Allow asimple mechanism for testing HTS insert coils.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 47 of Lecture 11
High Field Magnet Designs with HTS
Applications Under Considerations• Common Coil 2-in-1 Dipole Design for Hadron Colliders• Neutrino Factory Storage Ring/Muon Collider Dipole (and Quads) Design• Interaction Region Magnets (Dipole and Quadrupoles) for High
Luminosity Colliders (e.g. for LHC Luminosity Upgrade)
NOTE: High TemperatureSuperconductors (HTS) areuniquely suitable for generatingvery high fields since, unlike inconventional Low TemperatureSuperconductors (LTS), thereduction in critical currentdensity as a function of field ismuch smaller at very high fields.
Performance of 0.8 mm dia wire
100
1000
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0 2 4 6 8 10 12 14 16 18 20B(T)
Jc(A
/mm
2)
Nb3Sn (4.2K)
BSCCO2212 (4.2K)
NbTi (1.8K)NbTi (4.2K)
As of year 2000
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 48 of Lecture 11
Operation of HTS BasedAccelerator Magnets
• HTS based magnets don’t appear to quench in a normal way.
• One (or even a few) weak spot (s) won’t limit the ultimateperformance of the magnet. That would only cause the localtemperature to rise a bit but the magnet will continue to operate.
• This becomes more a question of the heat load rather thanthe weak spot limiting the performance of the whole magnet.
• This is a major difference from the LTS based magnets wherea single weak spot limits the performance of the entire magnet.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 49 of Lecture 11
SUMMARY
HTS has potential to make a significant impact on thedesign and operation of future accelerators
•HTS can generate high fields•HTS can work at elevated temperature
HTS cable and coil testing at Liquid Nitrogen (LN2)temperatures has been found reliable and productive
•Good correlation between higher temperature (LN2) andlower temperature testing•LN2 tests are much easier, faster and cost effective
New “conductor friendly designs” allow HTS “React &Wind” technology to be incorporated in accelerator magnets
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