Frequency shifts in cesium beam clocks induced by microwaveleakages

摘要

The anomalous sensitivity of an optically pumped cesium beam clocknto microwave power and the unexpected frequency shifts observed arendemonstrated to result from microwave leakages outside the arms of thenRamsey cavity. A new design of the cavity associated with a carefulnrealisation provides very weak microwave leakages and negligible relatednfrequency offsets. We have established a theoretical model that allowsnus to calculate the frequency shifts due to microwave field componentsnpropagating along the beam axis in regions which are free-field in annideal Ramsey cavity. This results in first order Doppler effect shifts.nThe order of magnitude of the frequency shift can be predicted andnagrees with the measured one when the amplitude of the leakage magneticnfield is about a 1000 times smaller than the amplitude of the microwaveninterrogation field in the cavity