Controlling the microwave amplitude in optically pumped cesium beam frequency standards

Assuming square wave frequency modulation, the response, versus the amplitu de of the microwave field, of an optically pumped cesium beam tube is consi dered. The properties of the first maximum of this response are analyzed. T he effect of the neighboring lines is taken into consideration, and a model of the profile of the microwave field in each interaction region is valida ted. A symmetry property of the response considered is pointed out. It enab les us to implement a feedback control of the microwave amplitude with a la rge depth of the amplitude modulation. Residual frequency offsets that may occur as a consequence of a spurious amplitude modulation correlated with t he frequency modulation are assessed. And, with a cavity designed such that phi = pi between the two oscillatory fields, it also is possible to measur e the microwave amplitude at the first maximum of the sore contribution of the reference atomic line.