Enhancement of critical current densities by radiation in RE-Ba-Cu-O bulk superconductor

Irradiation of superconducting material with particles, such as electrons, protons, neutrons, ions etc., is known as a valuable tool to introduce pinning centers in a controlled way. Due to its extremely large penetration range, neutron irradiation is thought to be most suitable for the production of randomly distributed defects in bulk materials. Fast neutrons produce spherical cascade defects with a diameter of approximately 5-6 nm. The trapped field of a Y-Ba-Cu-O bulk sample was found to be increased up to 3.7 T at 77 K by fast neutron irradiation, which suggests the practical importance of this technique. On the other hand, by using thermal neutron irradiation, we can create fission tracks in the sample doped with uranium, which causes a dramatic enhancement of Jc. (author)