Measurements on hydrogen masers. I

Two hydrogen masers as high stabilized atomic oscillators were built and investigated at the Heinrich-Hertz-Institut Berlin. Together with a survey of the theory the results of experiments and the methods are given. Especially the maser oscillation's stability as dependent on the signal output, the magnetic polarisation field and the different sources of relaxation is studied in order to find the best operating conditions. The method for the automatic measurement of the relaxation rate and another for the direct registration of the atomic line spectrum is described. The observed fluctuations of the maser frequency are smaller than 10-13 relatively at 10 sec averaging. A long term stability of the maser-frequency of better than +or-2*10-12 relatively is achieved