1985 年 54 巻 3 号 p. 278-285
The laboratory-type hydrogen masers were operated continuously for about 200 days by using the automatic cavity tuning system. In this paper, the structure of the masers, the auto-tuning system and the results of the continuous operation are described. In the auto-tuning system, the state selection exchange method was used to vary the atomic flux for cavity tuning. It became clear that this system is stable and operates with high reliability for a considerable period of time. The frequency differences between each of the hydrogen masers as well as each maser and each of the several commercial cesium frequency standards were measured during the period of the continuous operation. As a result of frequency comparison, a linear drift was observed in the maser frequency. It is considered that this linear drift is due to a change in the wall shift.