Phase transient measurement at the micro radian level for atomic fountain clocks

This paper focuses on two effects due to the microwave interrogation signal imperfection. The first one deal with cycle synchronous phase transients due to the sequential operation of the atomic fountain. For the search of such a phase variations deeply buried in the synthesizer phase noise we have developed a triggered transient phase analyzer able to process the microwave signal in order to extract the phase in a synchronous fashion. With this device we check “in vivo” the FO2 interrogation signal with a resolution approaching 1microradian. Using this device we investigate a new generation of microwave switches able to reduce drastically the microwave leakage without inducing any phase transient on the microwave signal and we measure the microwave leakages on the FO2 atomic fountain at the 10^-16.