19./20. September 2007

Current leads for FAIR

Cryogenic Expert Meeting

19./20. September 2007

Birgit Weckenmann

19./20. September 2007

1. Design options for current leads

2. Current leads needed for FAIR

3. HTS leads in LHC at CERN

4. Cooling of HTS leads

5. Adaptation of CERN leads for FAIR

Overview

19./20. September 2007

Conventional vs. HTS leads

met

al

LHe 4.4K

He gas 300K

+ reduction of cryogenic losses (~2.5 W/kA in DC operation)

+ simple (standard) design+ no quench protection+ no additional instrumentation and control

Resistive design HTS design

met

alH

TS

LHe 4.4K

He gas 50K

He gas 300K

19./20. September 2007

Low-current leads

Possible saving in cooling power by using HTS: 1500W => considering the large number of leads no benefit of that design

Magnets Current [A] Number of pairs

SuperFRS dipoles ~200 28

SuperFRS quadrupoles ~300 68

Correctors/ Steerers 50 ÷ 300 503

Total 599

Conventional leads are chosen for all low current circuits with Imax ≤ 300A

Resistive leads are available in optimized design for several currents and can be purchased (Mark & Wedell, American Magnetics)

19./20. September 2007

High-current leads

Saving in cooling power: 3700W => 87% reduction compared to resistive option => 15% of total cryogenic load of FAIR

HTS leads are chosen for all high current circuitswith Imax ≥ 300A

Magnets Current [A] Number of pairs

SIS300 dipoles 8924 7

SIS300 quadrupoles 7830 25

SIS100 dipoles 6600/13000 7

SIS100 quadrupoles 4630 11

Total 50

Adaptation of current lead design of LHC in collaboration with A. Ballarino (CERN)

19./20. September 2007

LHC current leads

Resistive part:copper heat exchangerconvection-cooled by forced flow of helium gas at 20K

HTS part:Stacks of BSCCO-2223 tapes soldered on SS tubeconduction-cooled by liquid helium bath at 4.4K

13000A type:optimized for DC current of 13000A

6000A type:covering currents ranging from3900A to 6900A

19./20. September 2007

Cooling conditions

(mass flow rate in pulsed operation will probably be lower)

FAIRHTS leads

LHC:Cooling of resistive part with 20K Helium gas

=> HTS at 50K

=> m = 0.045 g/(s kA)

FAIR:Cooling with gas at 50K results in a higher temperature of the HTS and a higher mass flow rate

=> HTS at 60K

=> m = 0.065 g/(s kA)

19./20. September 2007

Adaptation of LHC design for FAIR leads

Planned tests of CERN leads at ENEA (Italy) to prove the applicability of the LHC design to FAIR with 6000A type and 13000A type LHC leads provided by CERN

- Redesign of the heat exchanger (diameter)- Variation of HTS stacks (number)

Expected modifications:

1. Test: Stable operation under changed cooling conditions => Cooling of the resistive part with 50K gas DC operation at all currents required by FAIR magnets

2. Test: Stable operation and quench behaviour in pulsed mode => 10 triangular cycles increasing ramp rate and current step by step

19./20. September 2007

SIS100/SIS300 leads

One or more designs for FAIR leads?

• Current range SIS 100: 4600A to 6600A SIS 300: 7900A to 9000A

• Connection HTS to LTS SIS 100: Nuclotron conductor => adapter or change from bath to indirect cooling (???) SIS 300: Rutherford cable => CERN design

=> Two different designs may be reasonable

19./20. September 2007