Optimization of Operation Parameters in a Cesium Atomic Fountain Clock Using Monte Carlo Method

Number of detected atoms and contrast of Ramsey fringe are critical operation parameters in an atomic fountain clock. To optimize these operation parameters, a Monte Carlo method is utilized to simulate the evolution of the atomic cloud. It is found that the physical variables, including atomic temperature, launching direction of the atomic cloud, and the initial position of the atomic cloud, have a large influence on the ratio of the returning atoms to the launching atoms, and consequently the detected atomic number, and the atomic temperature affects the pattern of the Ramsey fringe. In the experiment, these relevant physical variables are optimized and a returning ratio as high as 8.6%±0.4% is obtained for a cesium atomic fountain with a launch height of 1 m. In addition, the Ramsey fringe is experimentally optimized and the contrast of the central Ramsey fringe reaches 90%. The Monte Carlo method we used is also applicable in similar cold atoms experiments.