INDUCED VOLTAGE, MAGNETIZATION WAVE-FORMS AND THE SPECTRAL RESPONSE AT THE GRAIN-BOUNDARIES OF YBCO SUPERCONDUCTORS AND THE CRITICAL-STATE MODEL

Critical state model for granular superconductors is applied to study the nonlinear a.c. response of Y-Ba-Cu-O superconductors at the grain boundaries. The measured induced voltage waveforms are studied and exp lained at different temperatures and the corresponding calculated wave forms are shown to match the data. The intergranular hysteretic magnet ization losses and the first 10 spectral components of the a.c. harmon ic response are also measured and calculated at different temperatures .