Resistivity Ratio of Niobium Superconducting Cavities

Abstract

Resistivity measurements have been made on Nb cavities, as well as on Pb and Cu, at 296, 77, and 4.2 °K by means of a contactless induced‐current method. For superconductors, a constant magnetic field drives the material normal below the transition temperature. These measurements provide a simple means for initial material evaluation as well as a direct means of monitoring the effects of material parameters (purity, heat treatment, gas incorporation, etc.) on the electron mean free path. Approximate determinations of H_c, H_c1, and H_c2 can also be derived from these measurements. Normal‐state thermal conductivity and the Ginzburg‐Landau parameter κ are calculated from the resistivity measurements.