Progress in the LPTF cesium beam frequency standard

The present short term stability of our optically pumped frequency standard is /spl sigma//sub y/(/spl tau/)=3.8/spl middot/10/sup -13/ /spl tau//sup - 1/2 /. A great deal of work has been performed in order to reduce the uncertainties of this standard. An example is given with two of them, associated to the second order Doppler effect and to the presence of a microwave field outside the Ramsey cavity.