Stability considerations for a Rb87maser oscillator

Self-sustained oscillation has been obtained in an optically pumped rubidium maser operating at the Rb⁸⁷hyperfine transition frequency of 6835 Mc/sec. The entire apparatus can be mounted within the volume of one cubic foot. The operating temperature is60\degC, and the overall power consumption is only a few watts. The anticipated long-term stability is one part in10^{12}. Preliminary estimates also indicate that the device has far better short-term stability than any other existing frequency standard. The present paper explains the basic principles of the rubidium maser and examines the factors affecting the stability of oscillation.