CROSSOVER RESISTANCE OF SUPERCONDUCTING CABLE FOR FAST- RAMPING MAGNETS OF PARTICLE ACCELERATORS

Fast-cycling magnetic fields, produced by superconducting magnets of modern accelerators, generate cable losses, which reduce with increase of contact resistance between wires in the cable. On the other hand the contact resistance has to have enough small value in order to provide flow of currents between wires. At IHEP it was carried out the study of crossover resistances in Rutherford type superconducting cable with a different resistive coating of wires in order to find the optimal coating, satisfying both above-mentioned conditions. Values of crossover resistance were measured for 19-strand cables, made from wires with NbTi filaments into copper matrix with a different coating (Ni, Cr and natural oxide). Also dependence of resistance on pressure was studied in the region, corresponding for pressure values, produced in the coils of superconducting magnets for accelerators. Besides the obtained experimental results, the description of features of samples and measuring technique are presented as well as the outcome of calculations of cable component of losses for fast-ramping dipole magnet with two-layer coil.