Interstrand contact resistance and magnetization of Nb3Sn Rutherford cables with cores of different materials and widths

Rutherford cables with cores of E-glass and S-glass woven tape and types AISI-316 and AISI-304 stainless steel (SS) ribbon were subjected to calorimetric AC loss measurement in transverse magnetic fields of amplitude 400 mT and frequencies of up to 90 mHz applied in the face-on (FO) and edge-on (EO) orientations. The results yielded the effective interstrand con- tact resistances (ICR), Reff (to be defined), and corresponding estimates of the FO coupling magnetizations generated by fields ramping at the LHC-specified 6.5 mT/s. Detailed analysis of the results indicated: 1) a cable with a full-width 316-SS core and a satisfactory Reff value would be suitable for magnet winding; 2) a cable with an off-center partial-width core had a very low Reff and an excessively large coupling magnetization; 3) The cables with glass-tape cores although characterized by large Reffs and very small coupling magnetizations turned out to have mostly uncoupled strands with intermittent points of low resistance contact. In order to achieve the target ICR values, the level of glass insulation insert should be reduced and cable compaction adjusted.