AC losses in commercial Bi:2223/Ag tape

Abstract

We have investigated the effect of temperature, field amplitude, frequency and orientation of the field on AC losses in a commercial Bi:2223/Ag tape. The measurements were performed using an AC susceptometer. The experimental results show that the losses depend on field amplitude, temperature, and strongly on frequency. Due to the strong dependence of AC losses on frequency, measurements were pursued at several frequencies between 20 Hz and 10 kHz, at both 20 and 30 K. The strong frequency dependence at these low temperatures is attributed to eddy current losses or/and inter-filamentary coupling losses. At higher temperatures and low frequencies, the main contribution to AC losses comes from hysteresis losses due to the flux entry into and exit from the superconducting tape during the up and down swings of the magnetic field. We have calculated the hysteresis losses in the critical state framework, as a function of AC field amplitudes and temperature, for planar geometry. Experimental data are analyzed by comparing them with the calculated curves.