Pulsed magnetic flux penetration dynamics inside a thin-walled superconducting tube

Abstract

In this work, we present an investigation of transient magnetic field behavior in thin-walled superconducting tubes. It has been determined that if the thickness of the tube wall is significantly less than Bean’s penetration length, the non-linear magnetic field diffusion equation describing the field propagation process inside the tube can be replaced by a simplified lumped-parameter equation. This makes it possible to quickly calculate the current induced in the tube wall and the magnetic field penetrated in the tube cavity. In order to validate this theory, an experimental study of transient magnetic field penetration into a Pb-doped B-2223 (Bi1.8Pb0.26Sr2Ca2Cu3O10+x) tube was conducted. This was done at the temperature of liquid nitrogen using a search coil (B-dot) and a miniature colossal magnetoresistance (CMR)-B-scalar magnetic field sensor made from manganite films, which exhibit a CMR phenomenon. The experimental results were then compared with the datasheet of the superconducting tube manufacturer and the 2D axisymmetric finite element model. It was demonstrated that combining the measurements of the magnetic field outside and inside the tube with the lumped-parameter description allows one to obtain the following information: the screened and trapped magnetic field, the critical current density vs the magnetic field dependence, and the power law index of the superconducting tube material. This enables the development of a fast, non-destructive method for testing the quality of superconducting tubular current leads.