Damping effects and flux kinetics in a type II superconducting disk

Abstract

Magnetooptic techniques coupled with high-speed cinephotography have been used to study flux jumps in a Nb-25 % Zr superconducting disk triggered by the application of an external magnetic field. It is shown that the exponential time constant z u which characterizes the penetration of the magnetic flux and the.flux jumpfield HIj are independent of the sweep rate of the applied magnetic field over three orders of magnitude. It is also demonstrated that magnetic coupling between the disk-shaped superconductor and a high-purity normal metal beneath it can significantly damp the motion of magnetic flux into the superconductor, thus enhancing its stability against flux jumps.

Local threshold field for dendritic instability in superconductingMgB2films

“…1, and 2). Moreover, both instabilities can be suppressed by contacting the superconductor with normal metal so that heat is removed more efficiently 8,14 Furthermore, dynamics in the form of branching flux and temperature distributions has recently been obtained by computer simulations accounting for the heat produced by flux motion, 6,15 and thus support strongly that the flux dendrites indeed results from a thermo-magnetic instability.…”

Vortex avalanches in Nb thin films: Global and local magnetization measurements

“…Measurements performed on YBa 2 Cu 3 O 7 HTS rings show a reduction of the number and amplitude of the magnetization jumps with a short-time magnetic cycling. 19 In some conventional superconductors both the independence of H f j on the sweeping rate 20 and its growth at a high sweeping rate 3,21 were detected.…”

Magnetic instabilities in hard superconductors

“…В целом ряде работ 24 35 , к этому же выводу на основе своих экспериментов пришли Харрисон и др. 30 . Роль переменного внешнего поля сводится лишь к ини-циированию скачков потока.…”