rf SQUID’s in the nonhysteretic mode: Detailed comparison of theory and experiment

Abstract

A simple analytic theory for the operation of rf SQUID’s in the regime where the current I in the superconducting ring is a continuous function of the applied flux (nonhysteretic mode) has been extended to include the effects of screening flux LI, where L is the inductance of the ring. A comparison of calculated results with detailed measurements of the response of a rf SQUID using a toroidal Nb ring containing a Nb point contact shows excellent agreement both in cases when screening flux is significant and when it can be neglected.