Low-Temperature Devices

The basic operating principles of three low-temperature devices the maser, the cryotron, and the cryosar are discussed. In masers the process of stimulated emission of radiation is used to produce an extremely low noise amplifier, with all practical solid state masers thus far employing the electron spins in paramagnetic salts. The cryotron and the cryosar are both primarily intended for computer applications. The former utilizes the phenomenon of superconductivity and its quenching in magnetic fields; the latter uses impact ionization of impurities in semiconductors.