SQUIDS and their applications in the measurement of weak magnetic fields

The development of weak magnetic field measurement techniques based on the superconducting devices known as SQUIDS has led to both an increase in interest in this traditional area and the opening up of new areas of application. In particular, the weak fields associated with the human body are being increasingly studied. This review first outlines both the theory and operation of SQUID systems. After a brief survey of alternative instruments some experiments representing possible major applications of SQUID systems are discussed. Finally a forecast is made of the progress to be expected in the next few years.