This Research Planning Grant will support the study of the magnetic flux lines in high temperature superconductors. A systematic study is planned of the evolution of the first order melting transition in very clean YBCO single crystals as a function of controlled point disorder created by proton irradiation. The dependence on the critical point, the critical regime, and the scaling exponents on the introduced disorder will be determined. Insight will be gained into the fundamental nature of the vortex-defect interactions, a parameter also important for technological applications. The project is a collaboration between Western Michigan University and Argonne National Laboratory. %%% This Research Planning Grant will support the study of the magnetic flux lines in high temperature superconductors (HTS). A systematic study is planned of the evolution of the flux line motion in very clean single crystals of the yttrium-barium-copper- oxygen HTS as a function of controlled disorder created by proton irradiation. Increased current flow in HTS materials in a magnetic field is important for technological application of these materials. The research will examine how the magnetic field flux lines can be controlled in the HTS to reduce dissipation and thus increase current flow. The project is a collaboration between Western Michigan University and Argonne National Laboratory. ***
