Studies of dielectrically loaded cavities for small size hydrogen masers

A dielectrically loaded cavity made of a hollow alumina cylinder, which is used to reduce hydrogen maser size, is considered. The results of a theoretical study of the effect of the cavity geometry on the frequency stability capability of the maser are reported. The active mode as well as the passive mode of operation are considered and the achievable performances are compared. It is shown that the frequency stability capabilities do not differ very much for both modes of operation with, however, a slight advantage to the active mode