Study of a bright, slow, and cold cesium source for a continuous beam frequency standard

To achieve a primary frequency standard based on a continuous fountain of laser cooled cesium atoms, we report on the production of a bright, slow and cold continuous atomic beam. Atoms are cooled from a thermal vapor in a 45° laser geometry and launched directly from the optical molasses by the moving molasses technique. The effects of the source fluorescence on the continuous beam (average velocity, temperature and flux) have been observed, and ways to optimize simultaneously the atomic capture and the continuous beam are presented. Flux measurements rise to 2×10⁸ at/s from a 2D magneto-optical trap at 7 m/s. The initial velocity is easily tunable from 1 to 10 m/s. If the longitudinal temperature is about 70 μK, additional transverse cooling even reduces the transverse temperature in one dimension below 30 μK. By extrapolating the obtained atomic flux to the continuous fountain under construction, we expect a short-term stability of 7×10^-14τ^-1/2. Other applications of continuous beams of cold atoms are suggested