An extensive programme
of research work was carried out to produce highly monochromatic stimulated emission at
microwave frequencies. A beam of ammonia molecules was first passed through a charged
enclosure and then through a microwave resonant cavity. The output power from the
microwave stimulated emission was measured to evaluate its use as a frequency
standard. Two ammonia maser assemblies were constructed at SRDE to compare the
stability of the frequency over a period of time.