Radiation damage effects on flux pinning and current dissipation in the high temperature superconductor yttrium-barium-copper-oxide

A comprehensive explanation of defect size dependence of radiation induced Jc enhancements in the high temperature superconductor YBa2Cu3O7 (Y123) is presented. The effects of fast neutron, 100 MeV electron, 60 MeV 4He1+, 560 MeV 16O6+, and 770 MeV 129Xe17+ irradiation are studied. A new parameter (q), the flux pinning enhancement per unit displacement damage, is introduced to compare the effectiveness of different radiation damages on an equivalent basis. Cluster type defects are found to be more effective flux pinners than point defects. Positron annihilation measurements of fast neutron irradiated Y123 were in good agreement with this result. 100 MeV electron irradiation of Y123 carried out at four angles to the c-axis indicates that extended defects are deleterious when oriented in the flux motion direction. A new classification scheme for particle radiation is introduced. A new ac permeability data analysis technique has been developed, allowing an investigation of the resistive response above the irreversibility (IRL). The result of this investigation on unirradiated samples favors a vortex glass interpretation, in agreement with other experimental investigations. Investigations of the high energy O ion irradiated sample show little change in the IRL or the extracted linear resistivity. The high energy Xe ion irradiated sample show an enhanced IRL, a changed temperature dependence of the IRL, and a more complicated linear resistivity function. Irradiation with 100 MeV electrons was also used to study the effect of radiation damage on transport properties of the high quality melt-processed Y123 material. Evidence of weak link effects were visible in the E-J characteristics of all the irradiated samples. A model based on point defect migration is proposed to explain the result