Alternating field losses in a rectangular multifilamentary NbTi superconductor

Abstract

Transverse alternating field losses on a 1 mm × 1.4 mm monolithic multifilamentary composite superconductor were measured calorimetrically at 4.2K for frequencies between 0.1 Hz and 20,000 Hz. The conductor was placed in bias magnetic fields ranging from zero to 50 kOe and subjected to superimposed alternating fields with field amplitudes ranging from 10 Oe to 2 kOe. The classical partial penetration hysteresis loss and full penetration hysteresis loss were observed. Losses were also measured which can be attributed to eddy currents in the composite core. At very high frequencies, eddy current losses were observed resulting from the metallic sheath which encloses the composite core. The magnitude of the eddy current loss in the composite core is explained in terms of the diamagnetism exhibited by the superconducting filaments. The experimental data presented is analyzed using existing loss theories which have been appropriately modified using basic principles to account for the effect of filamentary diamagnetism at low alternating field amplitudes.