Fluxoid pinning in bulk Niobium by voids produced during neutron irradiation

Fluxoid pinning due to voids has been studied in niobium irradiated at temperatures from 460 to 1080°C. T
c
decreased slightly and H
c2
increased with irradiation temperature indicating possible O
2
contamination. The J
c
vs H behavior was more complex, with maximum J
c
values obtained in the samples irradiated at 790 and 940°C. With the measured superconducting parameters, and data on void size and distribution, our results were quantitatively compared with expressions for void pinning using the statistical theory of Labusch. Of particular interest in this study was the sample irradiated at 790°C which has an ordered void super-lattice.