The influence of characteristics of an HF discharge on the oscillation level of a hydrogen maser

Hydrogen maser excitation by means of an HF discharge was examined for the feasibility of using a low power oscillator such as a transistor. Measurements were made of the discharge luminosity, the reflected and incident power between the generator and resonator, the power dissipated in the cavity, and the coupling in the worst conditions. The resonator was excited at frequencies between 370-525 MHz. The maser oscillation level was monitored as a function of the discharge power, the pressure, and the discharge luminosity. A critical power level was identified where the oscillation level remains constant while the discharge luminosity increases monotonously. The oscillation threshold, however, could not be determined with certainty.