REBCO WG meeting

Thursday 11 Mar 2021, 11:00 → 12:20 US/Pacific

Anis Ben Yahia (Brookhaven National Laboratory), Ernesto Bosque (NHMFL), Paolo Ferracin, Ramesh Gupta (BNL), Reed Teyber (LBNL), Stephen Gourlay (LBNL), Vadim Kashikhin (Fermilab), Vito Lombardo (Fermilab), Xiaorong Wang (LBNL)

• What performances and parameters should the conductor have? How can we make magnets using these conductors? 
• What is the maximum dipole field a REBCO magnet can generate?  
• What is the magnet performance? How does it quench? How to protect the magnet during a quench? What is the field quality? 
• How can we characterize the performance for long conductors? 

11:00 → 11:15 Feedback from the CM and our thoughts to proceed

Speakers: Anis Ben Yahia (Brookhaven National Laboratory), Ernesto Bosque (NHMFL), Paolo Ferracin, Ramesh Gupta (BNL), Reed Teyber (LBNL), Stephen Gourlay (LBNL), Vadim Kashikhin (Fermilab), Vito Lombardo (Fermilab), Xiaorong Wang (LBNL)

HTS magnets, cable, conductor

• The US-MDP program for HTS accelerator magnets encompasses both Bi2212 multifilamentary round wires and REBCO tapes.
• Both types are being studied for application to CCT magnets and to SMCT magnets. 
• The wide, thin, and flat geometry of the REBCO requires other cabling methods.
• The R&D reported here is focused solely on the CORC© cable configuration.

Comments:

• REBCO has been supplied from a single vendor, who has been an excellent partner to improve performance and modify tape design for a single CORC© cable concept.
• Great progress in increasing CORCO cable Je as well as reducing degradation from coil winding and operating stresses.
• There are several REBCO vendors also making high quality REBCO tapes, in relatively large production amounts driven by the fusion program.
• Several other conductor/cable concepts using some type of stacked tapes are being developed outside this program. It could be worthwhile to include different cable types.

Recommendations:

1. Investigate additional suppliers for REBCO tape and other REBCO cable concepts.
   1. Note for the WG from today's discussion: consider and compare alternative REBCO cable concepts such as STAR, stacked-tape, and Roebel cables. 
2. Look for opportunities to obtain additional sufficient lengths of HTS conductors to make model magnets.

11:15 → 11:45 A first discussion on the quench detection and protection of the subscale CORC common coil magnet

Speaker: Anis Ben Yahia (Brookhaven National Laboratory)

1. Quench detection needs to neglect the possible voltage spikes from the CORC common coil. Filtering? Validation time window?
2. Reed/Maxim/Anis to follow up on 1) the definition of instrumentation wires that is compatible for the BNL header; and 2) the DAQ needs for the advanced diagnostics during the test.
3. Anis/Ramesh to determine the feasibility of a center tap to create the voltage signals over two half coils to cancel the inductive signals. 
4. Isolation amplifiers will be critical to protect the instruments during discharge. Any opportunities to use the cryogenic amplifiers here prior to the isoamp?
5. Consider performing the spot-heater experiments at different current plateaus from low current with high margin to high current with low margin on CORC. This may allow to characterize and determine the magnitude of the flux-flow voltage before runaway that can be used to protect the magnet.