4C4 - Modulation effects in an ammonia beam maser oscillator

Modulation of the amplitude of oscillation of an ammonia beam maser is discussed for those cases where the molecular beam passes through a single cavity and two cavities in succession. It is shown that experiments using a single cavity in which the molecular beam flux is modulated by variations of the EHT applied to the state separator can yield information about the velocities of the molecules which contribute to the oscillation power. In the cascaded cavity case complex behavior is observed when either the molecular flux or the matching to the first cavity is modulated. These effects are interpreted in terms of the static characteristics of the cascaded cavity system. A self-modulation phenomenon and unusual variations of the oscillation amplitude are also reported for the cascaded cavity system which is obtained for a beam flux just above the oscillation threshold. These results and their interpretation in terms of the resolved hyperfine structure of N¹⁴H3are discussed.