Accurate periodicity measurement of superconducting quantum interference device magnetic flux response

摘要

It is theoretically explained that a response of a superconducting quantum interference device (SQUID) is periodically dependent on total magnetic flux coupling to the SQUID ring (Φ) and its period is a flux quantum (Φo = h/2e, where h and e, respectively, express Planck’s constant and elementary charge). For example, the voltage of an electromagnetically oscillated rf-SQUID or a current biased dc-SQUID is thought to be periodically dependent on Φ with a period of Φo. In this paper, we propose an accurate method to check the periodicity of a SQUID response by using a set of sensing coils covered with a superconducting sheath. As a demonstration, we measured periodicity of a commercially available thin-film type rf-SQUID response in magnetic flux ranging up to approximately 4300Φo. Its flux dependence was periodic below about 3400Φo. © 2010 American Institute of Physics Article Outline INTRODUCTION MEASUREMENT PRINCIPLE AND EXPERIMENTAL SETUP Measurement principle Experimental setup Measurement procedure EXPERIMENTAL RESULTS Detailed experimental setup Results DISCUSSION AND CONCLUSION