Superconducting Magnet Division High Temperature ... · Superconducting Magnet Division USPAS...

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



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)



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.



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)



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:



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.



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).



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)



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.



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



HTS Coil Wound by Hand

Al Bobbin (70 mm radius)(also used, Fe, SS and brass bobbins)



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



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.



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



BSCCO-2212 Cable “Pancake Coils”

HTS cable is carefully wound in large radius pancakecoil for testing at liquid nitrogen temperatures



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@[email protected]

Mix strand cable test, BNL 12/00



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



Ic as a function ofTemperature



Correlation between Tc and Ic

Better cables (withhigher Ic) also havebetter Tc



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



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



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



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



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).



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



Vacuum Impregnation Setup



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.



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



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



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)



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.




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


4 coil halves (2 each of two coils)



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



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)



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).



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.



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.



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.



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.



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).



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

25

30

35

40

0

5

10

15

20

25

30

35

40

0 5 10 15 20 25 30 35 40 45 50 55 60

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



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



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.



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



Cut-away View of the 12 T Magnet

Cut-away view of the 12T Magnet



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.



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

10000

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



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.



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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