Magnetic Measurements of Interstrand Contact Resistance in Cables in Response to Variation of Pre-Heat-Treatment Condition

Inductive (pickup-coil) magnetometry was used to measure AC loss in uncored Nb₃Sn Rutherford cables in the perpendicular and parallel orientations of the applied field. The four cables selected for study had widths of 8, and 13 mm and strand counts of 20 and 30, respectively. Under various surface conditions they were reaction heat treated (RHT) then vacuum impregnated with resin in preparation for measurement. The magnetic measurements were made at 4.2 K in sinusoidal fields of amplitude 400 mT and frequencies of 5 to 90 mHz, The total per-cycle loss so obtained was used to deduce the "crossover" interstrand contact resistance (ICR). Attention is focused on the ICRs of one particular 8-mm/20-strand cable measured in this and previous studies under several pre-RHT conditions: (i) as-received, (ii) acetone-degreased, and (iii) acetone-degreased then HCl-deoxidized then acetone rinsed. A comparison is also made to the ICR of a sub-size cored Nb₃Sn cable