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