Influence of Compaction During Reaction Heat Treatment on the Interstrand Contact Resistances of Nb₃Sn Rutherford Cables for Accelerator Magnets

Journal Article · 23 January 2018 · IEEE Transactions on Applied Superconductivity

DOI: https://doi.org/10.1109/tasc.2018.2796595 · OSTI ID:1510751

Collings, Edward Collings ^[1]; Sumption, Mike D.  ^[1]; Majoros, Milan ^[1]; Wang, Xiaorong  ^[2]; Dietderich, Daniel R. ^[2]; Yagotyntsev, Konstantin ^[3]; Nijhuis, Arend  ^[3]

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1. The Ohio State Univ., Columbus, OH (United States)
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
3. The Univ. of Twente, Enschede (The Netherlands)

The high field superconducting magnets required for ongoing and planned upgrades to the Large Hadron Collider (LHC) will be wound with Nb₃Sn Rutherford cables for which reason studies of Nb₃Sn strand, cable, and magnet properties will continue to be needed. Of particular importance is field quality. Here, the amplitudes of multipoles in the bore fields of dipole and quadrupole magnets, induced by ramp-rate-dependent coupling currents, are under the control of the interstrand contact resistances-crossing strand, R _c , adjacent strand, R _a , or a combination of them, R _eff. Although two decades ago it was agreed that for the LHC R c should be in the range 10-30 μΩ, more recent measurements of LHC quadrupoles have revealed R_c values ranging from 95 to 230 μΩ. This paper discusses ways in which these values can be achieved. In a heavily compacted cable R _eff can be tuned to some predictable value by varying the width of an included stainless steel (effectively “insulating”) core. But cables are no longer heavily compacted with the result that the crossing strands of the impregnated cable are separated by a thick epoxy layer that behaves like an insulating core. If a stainless steel core is actually present, Reff must be independent of core width. Since there is no guarantee that a fixed predetermined amount of interlayer separation could be reproduced from winding to winding it would be advisable to include a full width core.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1510751
• Journal Information: IEEE Transactions on Applied Superconductivity, Vol. 28, Issue 3; ISSN 1051-8223
• Publisher: Institute of Electrical and Electronics Engineers (IEEE)Copyright Statement
• Country of Publication: United States
• Language: English