INDUCTIVE RESPONSE OF HTSC PLATELETS AND DISKS DUE TO AC CONDUCTIVITY- ANALYTIC THEORY FOR AXIAL SYMMETRY

The electrodynamic boundary-value problem which is basic for the AC pe netration depth and conductivity measurement of HTSC samples by means of the mutual-induction technique is re-examined, and novel analytic s olutions are presented. In particular, the vector potential from the e xciting current in a circular driving loop and its perturbation due to the induced currents in the neighboring HTSC sample is studied, axial symmetry provided. This paper is mainly concerned with arrangements c haracterized by a strong field perturbation from the sample, combined with a field concentration in certain sample regions, but far from the sample edges, namely disk-shaped samples with radius larger than the driving loop radius. Both the limiting case of the infinite platelet, and/or the AC penetration depth much smaller than the sample thickness (bulk limit) are included. Powerful asymptotic methods are used to ev aluate the complicated integral representations for the infinite-plate let problem. Asymptotic methods are also introduced to solve the integ ral equations for the finite disk. Remainders are given to estimate th e correctness of the analytic approximations.