A. A. Kordyuk, V. V. Nemoshkalenko
IEEE Trans. Appl. Supercond. 7 (no.2), 928-931 (1997).
We investigated physical mechanisms for flux pinning and energy losses due to inter- and intragrain flux motion by the high-accuracy experimental technique that uses the levitation effect. Low-power self-stabilizing magnetic rotors with HTS bearings have been designed on the basis of obtained results. Its rotation speed may be up to 200,000 r.p.m. The low energy consumption of the rotor enabled us to determine the energy losses in any sample in alternating magnetic field with an accuracy down to 10-11 W. By this method we investigated magnetic flux dynamics in Y-123 and Bi-2223 granular superconducting samples and determined that flux motion in a Y-123 sample is described by intragranular thermally assisted flux flow with viscosity equal 8 105 kg/(m sec). We have also studied the frequency dependencies of energy losses for rotors with non-ideal magnetic symmetry and found the optimization criterion for rotor designing.
presented at the ASC'96, Pittsburgh, USA