Proton irradiation effects on critical current of bulk single-crystal superconducting YBCO wire

We have investigated the effects of 10 MeV proton irradiation on the magnetization M and critical current density J_c of bulk single-crystal YBa₂Cu₃O_7-δ (YBCO) superconducting thick wire filaments produced through laser-heated floating zone (LHFZ) technique. M and J_c were determined both along the length and perpendicular to the length of the wire. Radiation-induced enhancement of J_c along the length of the wire was observed while there was a small decrease in J_c⊥ to its length. J_c values along the length of the wire up to ~1.4×10⁵ A/cm² at 77 K and ~1.3×10⁶ A/cm² at 30 K and in applied magnetic field H=1 T were observed in the irradiated samples. In the unirradiated sample, the difference in magnetization ΔM at a given field in the magnetic hysteresis loop for increasing and decreasing field applied ⊥ to the sample length was observed to depend on the orientation of the sample about its axis. This indicates anisotropy in J _c along the sample length. This anisotropy increased on irradiation relative to the direction of irradiation. We believe that these J_c values along the length are amongst the highest published J_c values for bulk high temperature superconductor (HTS) thick wire filament