Enhanced Flux Pinning in MOD Second Generation HTS Wires by Silver- and Copper-Ion Irradiation

We have studied the effect of medium-energy ion irradiation on flux pinning in second-generation HTS wires. Irradiation with 74 MeV silver ions and 50 MeV copper ions have produced up to 60% enhancements in critical current. The field-angle dependence shows enhancements over a wide angle range, suggesting that the irradiation defects are point-like defects rather than continuous columns. Such isotropic enhancements are generally preferable over narrow-angle anisotropic effects for wire applications. Ion irradiation can then be used to create a model population of defects to study concentration dependences. We present transport, magnetization, and TEM results to probe the nature of the defects formed by this irradiation.