Current developments in SQUID systems-low Tc and high T c-and their application to biomagnetism

Ever since SQUIDs (Superconducting Quantum Interference Devices) were used to demonstrate magnetocardiography in 1969, the promises of biomagnetism have been among the primary forces propelling the technology forward. Recent years have seen continuing advances, with further reductions in device noise, novel approaches to gradiometry, integration of SQUIDS with thin film pick-up coils, and further increases in the number of channels in commercial systems. Perhaps most significant, there have been very rapid developments in SQUIDs based on HTS (high temperature superconductors), which are now showing that they will have a major role to play in several aspects of biomagnetism. The authors briefly survey some of this progress