Measurement of critical current and instability threshold of Rutherford-type Nb3Sn cables

As part of a collaboration between FNAL and CERN, Nb3Sn Rutherford-type cables made of different wires (MJR and PIT) have been assembled in the sample holder at FNAL and tested at FRESCA (CERN). All cable samples had 28 strands with 1-mm diameter, and a trapezoidal cross-section with 0.9-1 degree keystone angle. All samples were tested at 4.3 and 1.8 K. After the first series of tests both cables were retested with higher prestress. The PIT sample was extensively retested at 1.9 K. During the second run the MJR sample was also tested at constant current in sweeping field in order to characterize its stability. All samples showed signs of instability and several voltage spikes were detected and recorded. Critical current and instability threshold measurements are presented and compared with previous tests and magnet performances.