Investigation of Vortex Pinning Anisotropy in the High Temperature Superconductor YBa$_{2}$Cu$_{3}$O$_{7-\delta }$*

Columnar defects have proven to be highly effective at pinning vortices, but most studies have been performed with the defects oriented either \textit{perpendicular} or at large angles relative to the superconducting Cu-O planes. These studies have shown that the intrinsic pinning anisotropy of the crystal can actually be reversed by sufficiently strong columnar defects oriented \textit{perpendicular} to the Cu-O planes. We have preliminary data that indicate that the pinning anisotropy is actually enhanced for columnar defects introduced \textit{parallel} to the superconducting Cu-O planes. A single crystal of YBa$_{2}$Cu$_{3}$O$_{7-\delta }$ was polished down to a narrow width of 27 $\mu $m, allowing heavy ions to penetrate the crystal along the ab-plane. The crystal was irradiated with 1.4 GeV $^{208}$Pb$^{56+}$ ions to a dose matching field of 1T.