Flux jumping phenomena in sputtered cylindrical niobium films

Abstract

Measurements of the critical temperature and resistance ratio of cylindrical niobium films, prepared by getter sputtering, indicate that their purity is high. Magnetic measurements on the superconducting films show that flux penetrates to the bore of the cylinder, either in the form of regular jumps or continuously, in a manner resulting in regular hysteresis. The variation of the magnitude of the jumps with applied field and temperature is reported, and the magnitude is also found to be proportional to the square root of film thickness. The latter result is also obtained from a thermodynamic energy balance calculation, but predictions of the flux jump height as a function of the applied field and temperature yield only partial agreement with experiment.