High critical currents due to fission tracks in YBa2Cu3O7-delta

Fission tracks were introduced into uranium containing melt textured YBa2Cu 3O7-delta by inducing fission of the uranium nuclei by thermal neutrons. We measured the critical current densities as a function of the fission track density. They are strongly enhanced at all temperatures (from 5 K up to 77 K) and magnetic fields (up to 14 T) due to the fission tracks. The enhance ment is largest at low magnetic fields and at high temperatures (more than one order of magnitude). The total uranium content, the neutron spectrum an d the amount of the fissionable isotope U-235 Were also varied, in order to optimize the defect structure for high critical currents.