AC Loss Time Constant Measurements on Nb sub 3 Al and NbTi Multifilamentary Superconductors

摘要

The AC loss time constant is a previously univestigated property of Nb/sub 3/Al, a superconductor which, with recent technological developments, shows some advantages over the more commonly used superconductors, NbTi and Nb/sub 3/Sn. Four Nb/sub 3/Al samples with varying twist pitches and one NbTi sample are inductively measured for their AC loss time constants. The measured time constants are compared to the theoretical time constant limits imposed by the limits of the transverse resistivity found by Carr, and to the theoretical time constants found using the Bean Model as well as to each other. The measured time constants of the Nb/sub 3/Al samples fall approximately halfway between the theoretical time constant limits, and the measured time constants of the NbTi sample is close to the theoretical lower time constant limit. The Bean Model adequately accounts for the variance of the permeability of the Nb/sub 3/Al superconductor in a background magnetic field. Finally, the measured time constant values of the Nb/sub 3/Al samples vary approximately according to the square of their twist pitch. (ERA citation 13:052788)