Comparison of methods aimed at determining the residual cavity phase shifts in small Cs beam clocks

At the present time, the accuracy of small cesium beam frequency standards is limited by the end to end phase difference Δφ in the Ramsey cavity. As a matter of fact, the design of these small resonators does not allow the use of the beam reversal technique. Some attempts are made to measure Δφ in small cesium beam resonators with methods using only one oven. A new small and symmetrical optically pumped cesium beam resonator (OPCsBR) has been designed. The aim is to compare the classical method of the beam reversal and two other methods. The first one is based on clock frequency measurements at various square wave frequency modulation depths and various microwave levels. The second method is aiming to assess Δφ by means of the slight distortion induced in the Ramsey fringe response