This research aims at developing a novel system that can be used to detect the motion of individual flux lines in high temperature superconducting (HTS) materials in magnetic fields. The instrument will be equipped with HTS thin film transformers with a micrometer-size pickup coil to couple the flux motion signal to a dc SQUID. This probe will be scanned with micrometer control. With this instrument the dynamics of flux line motion will be investigated, especially the depinning process. An objective is to determine information about individual pinning sites in the HTS material. This research may reveal the main pinning mechanism and thus may lead to an improvement in the critical current density in the HTS materials. %%% The discovery of high temperature superconducting materials provides great potential for applications in many types of products. The key problem for many practical applications is the enhancement of the critical current density in magnetic fields that is governed by control of magnetic flux line motion. This grant supports the development of a microscopic probe to detect the motion of flux lines and determine the material properties such as defects or impurities that impede or pin the flux lines. Thus this research may lead to new techniques for the preparation of high-current carrying superconductors. ***
