Persistent-Current Magnetization of Strands: Influence of Applied Field Angle and Transport Current

For many accelerator magnets field quality at the bore is a critical requirement for which reason it is necessary to fully characterize the persistent-current magnetization of strands of the kind under consideration for these magnets. The magnetization of a strand is generally measured in a magnetometer. However, certain effects can differentiate such measurements from the true magnetizations of strands in magnets. This report focuses on persistent-current magnetization: 1) measured by vibrating-sample magnetometer on segments of strand extracted from a section of heat treated Nb₃Sn cable as functions of angle of the applied field, and 2) calculated as function of applied transport current. It is found that the magnetization of a strand in a cable increases by ~10% as the field applied to the cable is shifted from edge-on to face-on, and that the difference between the current-on and current-off magnetizations is not significant until close to the operational field of a magnet.