Alternating field losses in mixed matrix multifilament superconductors

Losses were calculated for and measured at 4.2°K in two mixed-matrix superconductors for the cases of transverse applied alternating fields superimposed upon zero or 5T transverse bias fields. The 0.080 in. × 0.160 in. conductors are composites of copper-sheathed Nb-Ti filaments twisted every 5 cm within a copper-nickel matrix, where the copper-nickel to copper to superconductor ratio is nominally 4:4:1. The conductors differ only in the copper-nickel alloy of the matrix and the associated matrix conductivities, sigmamcalorimetric measurements were performed with alternating fields ranging in frequency, f, from 0.3 to 12,800 Hz and from 2500 to 4 oersteds in amplitude Hm. Eddy current losses consistent with the theory and proportional to and were observed. The measured losses were found to be less than the calculated losses and within 45% of the calculated losses in all cases.