AC loss of Nb3Sn-based Rutherford cables with internally and externally added Cu

Calorimetric measurements of AC loss and hence interstrand contact resistances (ICR) were measured on various stabilized (Cu-added) Nb₃Sn Rutherford cables. The cable variations formed two sets; externally added Cu and internally added Cu (mixed strand cables). In the first set, Cu strips were diffusion bonded onto a pre-existing cable. Two distinct variants were made, in the first a Cu strip was added to the "upper" and "lower" cable surfaces and then diffusion bonded during a reaction heat treatment (RHT) of 180 h/650°C under a "cold-applied pressure" of 20 MPa. The second was formed by diffusion bonding a helically wrapped Cu strip along the cable. A control cable with no strip was included in this set. The second set consisted of a cable with approximately 1/3 of the strands replaced with pure Cu wires during the cable winding, and here also a control cable was fabricated for comparison. Calorimetric measurements of AC loss were made on all cables at 4.2 K in a transverse sinusoidal field of amplitude 400 mT, frequency 5 to 90 mHz, applied both parallel and perpendicular to the face of the cable. The loss data were interpreted in terms of an effective interstrand contact resistance, R_⊥,eff.