Operation and Performance of a Hydrogen Maser with a New State Selector

Abstract

Summary The results of the operation of the hydrogen maser with a ne'v. state selector are described. In the first part of this report, the measurenent results of the magnetic inhomogeneity shift of the maser frequency by the use of a new state selector are described. In the next part, the results of the long-term continuous operation of the masers by the automatic cavlty tuning method are described. Maser structure and Electronics 'The structure of the maser, H3 or H4, is shown in Fig.1. It is of the loboratory type. This apparatus consists of the two ion pumps, the atomic source system, the double focuslng state selector, the four-layer magnetic shields, the microwave cavity and the storage bulb. The shielding factor is about 15000. The loaded Q of the cavity is about 45000 and the cavity temperature 1s controlled within the limits of 10.01 C. the cavity autotuning electronics are shown in Fig.2. The system shown In the upper part of the figure is the phase-locking loop for controlling aMHz quartz crystal oscillator. The system shown in the lower part is the electronics for the automatic cavity tuning1. The beat priod of the two maser frequencies is measured to detect the cavity offset by varying the atomic flux between the two levels. The detected signal is used to correct the cavity frequency. The frequency stability of the free running maser is about 3 x at the averaging time of 500 seconds and that of the autotuned maser is about 1 x at the averaging time from 100 seconds to 1 day. The system of the maser electronics and that of