NUCLEAR TRACK METHOD FOR NEUTRON-INDUCED RADIONUCLIDE MAPPING WITH APPLICATIONS TO URANIUM DISTRIBUTIONS IN SUPERCONDUCTORS

Intermetallic and oxide superconductors can be improved by internal he avy ion irradiation damage produced by doping the materials with urani um followed by neutron-induced fission. The uniformity or the scale of the lack of it in the uranium distribution is critical to whether the superconducting phase is uniformly irradiated and the effect optimize d. In this work we describe, first, how one can measure the distributi on and, second, what it is in recently tested Y-Ba-Cu and Bi-Pb-Sr-Ca- Cu oxide superconductors. The bulk of this work is a primarily tutori al description of the solid-state-track detector method, concentrating on optimizing spatial resolution. It reviews existing work, emphasizi ng examples of doped intermetallic superconductors; it also includes s ome new quantitative aspects of the technique. The second part gives r esults from using these techniques on oxide superconductors, for which the resolution is pushed to its limits. Nevertheless, it is good enou gh to conclude that in Y-Ba-Cu-0 the uranium is mostly within the supe rconducting phase. In Bi-Pb-Ca-Sr-O it can be said only that the urani um is not primarily in minor phases. Resolution in that material is su ch that the uranium could either uniformly coat grains or lie within t hem.