SQUID: Superconducting Quantum Interference Device

Abstract

The SQUID , " Superconducting Quantum Interference Device " , was first built in the sixties. Since then numerous scientists have been working and developing this incredible device. In this paper I will try to give a glimpse of this wonderful world of superconducting devices. This paper is mainly based on two books (Barone Antonio and Gianfreanco Paterno (1982))[7] and (T. Van Duzer and C. W. Turner (1999))[6] and a few papers. First I will give a brief explanation of the basic aspects of superconductivity regarding SQUIDs, such as Meissner effect, Cooper pair tunneling and Josephson junction. Further, We will discuss one junction and multi junction SQUIDs. And last but not least SQUID magnetometers. I. THEORY A. The Meissner effect The Meissner experiment was a milestone in the history of superconduction, done by Meissner and Ochsenfeld[5] in 1933. They had been working on per-fectly pure crystals of a normal metal in which resistance vanishes at T = 0 because of the elimination of phonon scattering. In this experiment they compared the behav-ior of this kind of metal to superconductors. In this section we will examine the behavior of a con-ductor subject to an ac field. In an electron gas with an applied electric field − → E , there are two opposing influences on the momenta of the electrons. Therefor the differen-tial equation for the average x-directed electron velocity can be written as m d x dt + m x τ (1)