Microwave Applications of Superconductivity

In this invited paper the author gives an overview of microwave applications of superconductivity. For many years after the discovery of superconductivity in 1911, the phenomenon remained largely a laboratory curiosity. For over 40 years physicists worked with only moderate success to gain a theoretical uncle rstanding of superconductivity. In recent years , however, the situation has ch~nged rapidly. An adequate theory has now been developed (the BCS theory), and superconductivity has become a useful tool in many fields of pure and applied research. As an outstanding example, superconducting magnets are now available commercially which can generate dc fields up to 100 kilogauss.