Abstract
Recent developments of SQUID technology are reviewed. First, key elements for the development of high Tc SQUID are briefly shown. Due to these developments, performance of high Tc SQUID has been much improved, and system application is now becoming possible. Second, development of an electronic circuit which makes SQUID robust against environmental noise, is shown. With this circuit, the requirement for magnetic shielding can be reduced. As a result of these developments, constraints in using SQUID, i.e., cooling and shielding, can be relaxed, which is helpful for the extension of the application-field of the SQUID system. Requirements for the SQUID system are briefly mentioned in the application to biomagnetic measurement, nondestructive testing of materials, SQUID microscope and precise measurement. It is emphasized that the requirement for the system is different according to the types of applications. Therefore, it is necessary to develop the system in order to optimize the requirements, including the choice of high Tc or low Tc SQUID. As an example, a nondestructive test of materials using SQUID is shown.
