Hall probe magnetometer for SSC magnet cables: effect of transport current on magnetization and flux creep

A Hall probe magnetometer has been constructed to measure the magnetization hysteresis loops of Superconducting Super Collider magnet cables. The instrument uses two Hall-effect field sensors to measure the applied field H and the magnetic induction B. Magnetization M is calculated from the difference of the two quantities. The Hall probes are centered coaxially in the bore of a superconducting solenoid with the B probe against the sample's broad surface. An alternative probe arrangement, in which M is measured directly, aligns the sample probe parallel to the field. M was measured as a function of H and field cycle rate both with and without a DC transport current. Flux creep as a function of current was measured from the dependence of AC loss on the cycling rate and from the decay of magnetization with time. Transport currents up to 20% of the critical current have a minimal effect on magnetization and flux creep.