Thermal diffusion and ac loss in high- Tc superconductors

Abstract

The influence of thermal diffusion and temperature nonuniform distribution on ac loss of high-temperature superconductors has been investigated. Asymptotic solutions of magnetic and electric fields and ac loss are presented in the form of power series of λ h, the normalized frequency of the external ac magnetic field. It reveals that influences of thermal diffusion on the ac loss behavior of high- T c superconductors include: (i) a weak frequency dependence of ac loss per cycle, i.e., ac loss per cycle increases with frequency in the incomplete field penetration, but decreases with frequency in the complete field penetration; (ii) nonuniform temperature distribution in the sample with the highest temperature located in the center; and (iii) existence of a critical frequency at which the superconductivity is destroyed at the hottest point in the sample.