Atomic frequency standards: A survey

The last comprehensive survey on atomic frequency standards was done by McCoubrey [1]. This survey reviews the more recent historical background of atomic frequency standards leading to the present developments. A discussion of the underlying physical and engineering principles is given. Modern atomic frequency standards, including their performance, are compared quantitatively, and projections are attempted at likely future developments and performance characteristics. As in 1966, the standards principally used in technical and scientific applications are rubidium gas cell devices, cesium beam tubes, and hydrogen maser oscillators. However, substantial advances in physical and performance characteristics can be reported. New developments include passive hydrogen devices, saturated absorption stabilized lasers, ion storage devices, and atomic beams in the far infrared and infrared region, as well as new techniques to evaluate frequency biases such as those encountered in cesium and hydrogen standards. The survey includes a discussion of the effects of past and current developments in atomic frequency standards on the technical and scientific user community.