Losses in superconducting magnets under fast ramp rate operation

AC losses in superconducting Pulse magnets have been investigated in order to establish a method which yields a quantitative calculation of the losses. The pulse magnets, A and T, wound from different kinds of Nb-Ti multifilament superconductors, were operated at the ramp rate over the range from 0.1T/sec to 40T/sec. The associated losses were measured by the calorimetric method. The conductor types employed in the present magnets were a monolith with Cu-matrix, a monolith with Cu-Ni barriers and a stranded cable. The transient losses in the magnet wound with the Cu-matrix monolithic conductor were found to be saturated at the ramp rate in excess of 0.25T/sec. In these experiments, no quench was observed. The results were discussed in terms of our loss model: The parameter which characterizes the loss is a dimensionless sweep rate , where τ is the relaxation time for the coupling current, is the external field and Bpis the full-penetration field for the composite. For , the composite behaves like a solid conductor, so that the AC loss is expected to be saturated as observed.