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Journée thématique DAPNIA «Almants supraconducteurs»
High Temperature Superconductivity (HTS)
Opportunities & Challenges;R&D Activities in the US
Yukikazu IWASA Francis Bitter Magnet Laboratory
Massachusetts Institute of Technology Cambridge, MA 02139-4208
Orme des Merisiers, Bât. 774, Amphi Bloch, Saclay
lundi 3 juillet 2006
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Outline• Review of LTS & HTS Characteristics
• Challenges
• Important Activities for HTS
• Key issues
• HTS Current Status (Bi-2223; Bi-2212; YBCO; MgB2)
• Opportunities
• Conclusions
HTS R&D Activities in the US
• Market Penetration for HTS
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oHc2 vs.Tc Plots for LTS & HTS
0 20 40 60 80 100 110
150
0
50
100
Tc [K]
oH
c2 [T
]
Nb-Ti ALLOY
Nb3Sn COMPOUND
MgB2 COMPOUND
Bi-2212
Bi-2223
Bi2Sr2Can-1CunO2n+4: (BSCCO)
(n=2)OXIDES
(n=3)
YBCO OXIDE
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0 5 10 15 20 25 30
104
102
10
J c [A
/mm
2 ]
105
0 5 10 15 20 25 30B [T]
Jc Data: LTS @4.2 K
103
Usefulrange formagnet
[Based on graph by P. Lee (12/2002; UW)]
YBCO (4.2; 75)
Bi-2223 (4.2; 20)
Nb-Ti (1.8; 4.2)Nb3Al( 4.2)
Nb3Sn (1.8; 4.2)
Bi-2212 (4.2)
MgB2 (4.2;20)
HTS @4.2 K & Above
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0 10 20 30 40 50 60 70 80 90 100
50
40
30
20
10
0
Top[K]
Bce
nter
[T]
Bcenter vs Top Zones for LTS & HTS Magnets
Nb-Ti
Nb3Sn
MgB2
Bi-2223/2212
YBCO
HTS Opportunities: higher fields over wider Top range
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Bi-2223 Available NOW as “magnet grade conductor”
Only as TAPE
• Difficult to reduce AC losses suitable for DC coils• “Pancake” coils rather than “layered” coils
many joints “large” radial gaps needed in multi-coil inserts
HTS Current Status
0.22 4.2 mm
Sumitomo Electric Bi-2223
[T. Kato (Sumitomo) (2006)]
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Bi-2212
• Easier to minimize AC losses• “Layered” coils
Suitable for multi-coil “inserts”
Available in WIRE form
HTS Current Status (continuation)
0.8 mm18 sub-element each of37 filaments
NEXANS Bi-2212 Wire
[Jean-Michel Rey (2006)]
Still under development
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YBCO
Usable at LN2 temperatures (>64 K)
Considered by many that YBCO less expensive than Bi-2212/2223 low materials costs, e.g., no Ag
HTS Current Status (continuation)
Only as TAPE same negative points as Bi-2223
Even AFTER MORE THAN 10 years, still the longest available ~100 m
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MgB2
Jc (>10 K) still much less than Nb-Ti’s (@4.2 K)
More brittle than Nb-Ti
Available as WIRE same positive points as Bi-2212
Considered by many to be price-competitive against Nb-Ti
HTS Current Status (continuation)
[Mike Tomsic (Hyper Tech) (2006)]
Nb barrier
MgB2
Cu
0.87 mm 36-filament wire
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Key Magnet Issues vs. Top Difficulty or Cost
ProtectionConductor
Mechanical
StabilityCryogenics
0 ~100Top [K]
Range of Operation for LTS Magnets
Range of Operation for HTS Magnets
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Opportunities
• HTS magnets VERY stable immune from disturbances, e.g., mechanical, that still afflict LTS magnets
• Unnecessary to epoxy-impregnate HTS windings?
Saving in production cost
• ALL HTS magnets should be “adiabatic’’
Saving in production cost
→ higher J
Stability
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• ALL HTS magnets, except those combined with LTS magnets, should be dry, cryocooled!
1. HTS magnets CAN operate well above LHe temperatures
• TWO reasons why LHe NOT needed:
2. “Large” temperature margins for HTS magnets
[dT/dt 0]LTS not mandatory for HTS magnets
• ONE serious disadvantage for dry magnets: Nearly ZERO thermal mass for the cold body
ENTER: solid-cryogen-cryocooled “dry” HTS magnets
Opportunities (continuation)
the presence of liquid cryogen in the system tends to make cryogenics too “visible” to the user
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0 10 20 30 40 50 600.0
0.5
1.0
1.5
2.0
Cp
[J/c
m3 K
]
Temperature [K]
SNe SN2 Cu Pb Ag
Phase transition (35.6 K): 8.3 J/cm2SNe
SN2
Pb
AgCu
SNe
CuAg
Pb
SN2
2.0
1.5
1.0
0.5
00 10 20 30 40 50 60
T [K]
Cp [
J/cm
3 K]
Llv = 2.56 J/cm3
for LHe
Cp(T) Plots
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Opportunities (coontinuation)
• When MgB2 can replace Nb-Ti, and Bi-2212/2223 and/or YBCO can replace Nb3Sn, it should be possible to make magnets NMR/MRI; HEP; even FUSION entirely of cryocooled HTS operating >10 K, with ZERO possibility of quenches
“Dry” magnet tends to make cryogenics “invisible”
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Opportunities forLTS & HTSMagnets:Present & Future
Current StatusApplications
HTS (R&D)HTS (R&D)HTS (R&D)
Transmission TransformerFault current limiter
Electric Power Distribution
Crystal (Si) grower LTS (marketplace); HTS (R&D)
LTS (marketplace); HTS (R&D) Medical MRILTS (marketplace); HTS (R&D)Magnetic Separation
HTS (R&D) MotorElectric Power End Use
LTS (marketplace); HTS (R&D) LTS (marketplace); HTS (R&D)
NMR/MRI DC field
RESEARCH MAGNET
LTS (“Teva;” LHC); HTS (R&D) HEP
LTS (TORE SUPRA; ITER); HTS (R&D) FusionElectric Power Conversion & Storage
LTS (R&D); HTS (R&D)LTS (R&D); HTS (R&D)HTS bulk disk (R&D)
GeneratorSMEFlywheel
• DC or ~DC LTS: present HTS: future
LTS (R&D); HTS (R&D) MAGLEV
• DC or ~DC LTS: proven HTS: better?
• AC or DC Hope hinges on HTS
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HTS R&D Activities in the US• Nearly ALL US superconductivity R&D activities on HTS
• Major federal government HTS R&D activities targeted to devices (electric utilities & military) and YBCO
~$40M/Y1) HTS electric power devices; 2) YBCO DOEBudgetPrincipal AreasSponsor
(lightweight magnets; protection) ~$10M/Y YBCOAir Force
[c] National Institutes of Health
[d] Supports, among others, four HTS NMR/MRI magnet projects currently at MIT
Pays for many LTS NMR & MRI magnets [d] NIH [c]
[b] National Science Foundation
~$25M/Y Operates the NHMFL national facilitiesNSF [b]
[a] Total for two motors, 5MW (2003) & 36.5MW (2006)
$80M [a]Synchronous motors (Bi-2223) for ship propulsionNavy
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Opportunities (continuation)
Selected 1-GHz NMR Magnet Projects
Based entirely on LTS • 1 GHz NRIM (Japan) • 1 GHz Oxford Instruments
Based on LTS/HTS
• 1 GHz: MIT (Bi-2223)• 1.2 GHz: Grenoble/Saclay (Bi-2212)• 1.3 GHz: NHMFL (Bi-2212)
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3-Phase MIT 1-GHz LTS/HTS NMR Magnet Project*
Phase 2 (2003-2007): 700 MHz600 MHz / 100 MHz/ 55 mm RT bore
100 HTS (Bi-2223 @4.2 K)40 Double Pancake Coils
55-mm RT bore
Bi-2223-TapeDouble Pancake Coil
126.5 78.2
401.6
* A US HTS activity (supported by NIH)
600 LTS (Nb-Ti/Nb3Sn @4.2 K)140-mm COLD bore
[JASTEC]
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3-Phase MIT 1-GHz LTS/HTS NMR Magnet Project (cont.)
Phase 3 (2008-20011)*: 1 GHz 760 MHz / 240 MHz / 63 mm RT bore
* NIH yet to approve Phase 3 175
Nb3SnNb-Ti
760 LTS (Nb-Ti/Nb3Sn @4.2 K)175-mm COLD bore
[JASTEC (2005)]
Bi-2223
240 HTS (Bi-2223 @4.2 K)63-mm RT bore64 Double-Pancake Coils
87
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Grenoble/Saclay 1.2-GHz LTS/HTS NMR Magnet Project
Phase 1: 850 Cu/350 HTS
3-Coil HTS (Bi-2212) Insert (Saclay)
136
160
850 (20 T)/20 MW Cu Magnet (Grenoble)
[Jean-Michel Rey (2006)]
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March Towards 1 GHz & 1.2 GHz
: NON-SUPERCONDUCTING [MHz]
3040 60 100
MIT
MIT
YEAR
[Based on Kobe Steel data (1998)]
58 62 66 70 74 78 82 86 90 94 98 02 06 08 10 12 14
: SUPERCONDUCTING—LTS/HTS [GHz]
1
1.2
MIT?
Grenoble/Saclay?
: SUPERCONDUCTING—LTS [MHz]
200220
270
360
500
600
750800
900930
950
1000
Bo [T]
50 54
2
4
6
8
10
12
14
16
18
20
0
22
24
26
28
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Challenges
• Develop “long” (~10 km) conductors• Reduce AC losses in Bi-2223 & YBCO (tapes)• Reduce price/performance ($/kA m)
Conductor
• Develop superconducting joints For NMR/MRI magnets
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Current-Carrying Capacity vs. Price/Length Plots
0.1 1 10 100 1,000 10,000Price [$/m]
10
100
103
104
105I [
A]
Nb-Ti (4.2K; 6T)
$1/kA m
Nb3Sn Tape(10 K; 1 T)
$10/kA m ITERNb3Sn(5.5 K; 13 T)
$100/kA m
Bi-2223 (2006)(77.3 K; s.f.)
$200/kA m
YBCO (2008-2010)(77.3 K; s.f.)
MgB2 (2008-2010)(20 K; 2 T.)
$2-5/kA m
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Challenges (continuation)Cryogenics
10
100
1000
10000
1
1 W10 W100 W1 kW100 kW
10 20 30 40 50 60 70 800Top [K]
QRT
/Qop
QRT /Qop vs. Top for Selected Qop
CARNOT
• Easier for HTS than for LTS, but its ratio of compressor power QRT to refrigeration power at Top, Qop , needs MUCH (QRT /Qop )
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For an HTS device to compete its Cu counterpart operating at room temperature (RT), its dissipation at Top, PHTS [W/m], multiplied by the refrigerator’s compressor-to-cooling power ratio, QRT /Qop, < Cu’s Joule dissipation, PCu [W/m]
PHTS (QRT /Qop) < PCu PCu /PHTS > QRT /Qop
Challenge: Cryogenics• QRT /Qop , i.e., refrigerator efficiency
Comparison of HTS vs. Cu Devices
Challenge: AC Losses • PHTS to satisfy PCu /PHTS > QRT /Qop
10 kW100 W 1 kW
40018075452010
850380140703015
15005002201105022
8000165060035012055
4.21020305077
Top [K]
1 WQop
QRT /Qop
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• HTS (YBCO) & Cu Transmission “Lines” Based on HTS Refrigeration Power Requirement, Qop PHTS vs. PCu = I2R
w
s
Cu
CuDimensions & Characteristicsof “Basic (Ic =100 A) HTS tape
w = 4x103 m (4 mm) s = 1x106 m (1 µm) = 100
Ic = 100 A (77.3 K, s.f.) Jc = Ic / (ws)= 2.5x1010 A/m2
s = 1x104 m (100 µm)
HTS
w
ss
YBCOSubstrate; stabilizer, etc.
Comparison of Two Systems: An Illustrative Example
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Two-System Comparison (continuation)
Self-Field AC Loss Power/length, PHTS [W/m], of HTS Linecomposed of n 100-A “basic” tapes operated at IT = n (It /Ic)
PHTS
Pcu
Power Density/length, Pcu [W/m], in Cu Tape
w
s
Cu
Figure-Of-Merit (FOM):Pcu
PHTS QRT
Qop
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10000
1000
100
10
10.2 0.4 0.6 0.8 10 i
P cu / P
HTS
33 W/km (PCu/PHTS=6460) 100 W @77 K (QRT / Qop =22)
540 W/km (1600) 1 kW @77 K (QRT / Qop =15); 107
2.8 kW/km (700)
10 kW @77 K (10); 709.1 kW/km (380) 10 kW @77 K (10); 38
FOM=294
77-K operation possible, but, at least in this example, a 10-kA HTS line superior to the Cu line only when the HTS line operated at currents below 5 kA
HTS non-competitive to Cu
Pcu /PHTS & FOM vs. i for 10-kA (nominal) Lines @77 K
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Two-System Comparison (continuation)
Ways to improve FOM:
• Improved YBCO (Jc @77 K )• Thinner substrate ( ) • Improved refrigerator (QRT / Qop)
Challenges: YBCO
Challenge: Cryogenics
Pcu
PHTS QRT
Qop=
LTS’s Failure in Power Applications:
• QRT /Qop @ 4.2 K too large to satisfy PCu /PLTS > [QRT /Qop]4.2 K
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Protection
“Expensive” magnets must be protected from permanent damages
NZPQuenchInitiation
Zone(“Hot spot”)
• LTS magnets generally rely on NZP (normal zone propagation) to spread out the resistive zone to keep the “hot spot” temperature well below 300 K• In HTS magnets, NZP velocities (longitudinal & transverse), compared with those in LTS magnets, very slow, leading to a dangerously high “hot spot” temperature
)()()(
)()(
opcs
mm
cd
m
TTTkT
TCJTU
for HTS Ccd (T) very large UHTS << ULTS
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• Develop fail-safe protection techniques
• Develop normal-zone detection techniques
Challenges (continuation)
Protection
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Important Activities for HTS
• R&D Areas, besides conductor
• Enhance test facilities for evaluation of HTS
Ic measurement (up to: 500 A; 30 T; 100 K; 0.5%)
• BUILD and operate MAGNETS: LTS, LTS/HTS, HTS
Superconducting joints (for NMR/MRI)
Protection
Cryogenics QRT /Qop or efficiency even at 77 K Make cryogenics LESS visible to the user
o solid-cryogen may help achieve this goal
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• HTS applications most likely to succeed and benefit society, i.e., market penetration, include:
If HTS replacing technology to LTS its marketplace penetration to be decided by ECONOMICS Conductor cost/performance ($/ka m); AC losses; Cryogenic efficiency
If HTS enabling technology, e.g., high-field NMR and MRI, its success dictated by HTS PERFORMANCE
DC or nearly DC devices: those already conquered by LTS,e.g., NMR/MRI; HEP; even fusion
Market Penetration for HTS
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Conclusions
• For the most prized application in terms of sheer volume electric power, LTS NOT ENABLING: hope hinges on HTS
• HTS opportunities & challenges will keep ALL of us innovative, relevant, and productive for a long time !
• HTS for NMR/MRI: work already started
• HTS for HEP & fusion: NOT TOO EARLY to begin planning
Merci beaucoup