Influence of Compaction During Reaction Heat Treatment on the Interstrand Contact Resistances of Nb3Sn Rutherford Cables for Accelerator Magnets
Loading...
Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
IEEE
Abstract
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 stud-ies of Nb3Sn strand, cable, and magnet properties will continue to be needed. Of particular importance is field quality. The amplitudes of multipoles in the bore fields of dipole and quadrupole magnets, in-duced by ramp-rate-dependent coupling currents, are under the control of the interstrand contact resistances – crossing-strand, Rc, adjacent strand, Ra, or a combination of them, Reff. Although two decades ago it was agreed that for the LHC Rc should be in the range 10 - 30 μΩ more recent measurements of LHC quadrupoles have revealed Rc values ranging from 95 μΩ to 230 μΩ. The present paper discusses ways in which these values can be achieved. In a heavily compacted cable Reff can be tuned to some predictable value by var-ying 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 which behaves like an insulating core. If a stain-less steel core is actually present Reff must be independent of core width. Since there is no guarantee that a fixed pre-determined amount of interlayer separation could be reproduced from winding to winding it would be advisable to include a full width core.
Description
Keywords
Nb3Sn, interstrand contact resistance
Citation
Published version: IEEE Transactions on Applied Superconductivity (Volume: 28, Issue: 3, April 2018) Article Sequence Number: 4006504. https://doi.org/10.1109/TASC.2018.2796595