journ é e th é matique dapnia «almants supraconducteurs » high temperature superconductivity...

Y. IWASA (FBML)[email protected]

DAPNIA Day HTS Saclay (03/07/2006)

1

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



2

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



3

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



4

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



5

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



6

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)]



7

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



8

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


Only as TAPE same negative points as Bi-2223

Even AFTER MORE THAN 10 years, still the longest available ~100 m



9

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


[Mike Tomsic (Hyper Tech) (2006)]

Nb barrier

MgB2

Cu

0.87 mm 36-filament wire



10

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



11

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



12

• 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



13

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



14

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”



15

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



16

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



17

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)



18

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]



19

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



20

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)]



21

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



22

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



23

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



24

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 )



25

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



26

• 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



27

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



28

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



29

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



30

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



31

• Develop fail-safe protection techniques

• Develop normal-zone detection techniques

Challenges (continuation)

Protection



32

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



33

• 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



34

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

journ é e th é matique dapnia «almants supraconducteurs » high temperature superconductivity...

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