Thermal scanning alternating current susceptometry with multiple pick-up coils for ranging local phenomena in high Tc superconductors

Abstract

We describe a new experimental technique where ac susceptibility is measured simultaneously with three pick-up coils in three different regions along a YBCO ceramic sample, in the presence of strong thermal gradient. Each of the pick-up coils “feels” the shielding currents from the entire sample but with different weight due to geometrical factors. The multiple coil system permits the localization of any particularities (here a local avalanche-like decrease of the susceptibility function). Using this technique we observed experimental evidence of adiabatic flux change in a sintered high Tc superconductive material.