The Beam Optics Analysis Based on Monte Carlo Simulation of the Magnetic State Selection and Optical Detection Cesium Beam Clock

Abstract

Compact cesium beam clocks are of great importance in navigation, time-keeping and precision measurements. In traditional cesium clocks, cesium atoms are deflected by strong inhomogeneous magnetic fields, whose velocity distribution and populations of different quantum states are altered. Normally, the distributions are hard to describe with analytical functions. An alternative solution is to apply the Monte Carlo simulation to sample the atoms and calculate the trajectories. We apply the method to cesium beam clocks based on the magnetic state selection and fluorescence detection scheme. The state distributions of the detectable atoms are obtained with Monte Carlo simulation inside the collimator and finite element simulation of the magnetic field. The performance of the cesium beam tube is also estimated via the sampled atoms, such as the signal amplitude and the signal-to-noise ratio (SNR) of atomic shot noise and laser frequency noise. The estimated SNR of the designed cesium beam tube is over 7000 in a 1 Hz detection bandwidth. The influence of the deflection angle of the collimator on the performance of the beam tube is analyzed. The method can be used to guide the design of the cesium beam tube and is easily applied to different cesium beam clocks.