Flux Fluctuations and Critical Currents in a Superconducting Ring NearTc

Abstract

Measurements of current fluctuations and critical currents as a function of temperature have been made in a ring of superconducting tin with a current resolution corresponding to about 0.1 quanta of magnetic flux in the cylinder and a temperature resolution of a few microdegrees. The fluctuations occur between neighboring quantum states at a rate which increases rapidly with increasing temperature. The critical currents do not follow the temperature dependence predicted by theory.