Non-uniform current distribution in superconducting cables exposed to external magnetic field and its influence on stability

Current distribution in a Rutherford cable made with noninsulated strands was measured with small Hall sensors in an external magnetic field. Eight pairs of Hall sensors were placed around the eight-strand cable. One sensor of each pair was used to cancel the external magnetic field. Nonuniform current distributions induced by the external magnetic field ramp and transporting current were observed with this technique. The current distribution was artificially controlled using heater switches installed at the end of strands to study the influence of a nonuniform current distribution on stability. A local heat pulse was applied to a strand in the cable to determine the minimum quench energy against local disturbance. The initial current distribution varied was varied by the heater switches, and the current redistribution during quench or recovery process and the MQE was studied.