DC SQUID systems overview

Abstract

SQUID systems consist of three main components: the pick-up circuit (one or more pick-up coils), the SQUID, and the feedback electronics for the linearization of the transfer function. For years, SQUID systems have consisted of wire-wound pick-up coils, all-niobium SQUIDS with thin-film input coils, and feedback electronics using helium temperature impedance matching circuits and flux modulation techniques. The recent world-wide effort to develop biomagnetic multi-channel systems has initiated novel concepts: DC SQUIDS with integrated pick-up loops and alternative (digital, frequency-modulated and directly coupled) read-out schemes leading to more compact and reliable systems. This paper reviews the latest developments of DC SQUID systems suitable for biomagnetic multi-channel applications.