磁场对冷镱原子光钟稳定度影响的仿真分析

Simulation Analysis of the Influence of the Magnetic Field on the Stability of 171Yb Optical Lattice Clocks

在光晶格钟运行时,不停起伏的杂散磁场会引入一阶塞曼频移和二阶塞曼频移,从而影响光晶格钟的频率不稳定度。此外,突变的磁场可能导致激光频率参考到钟跃迁频率的伺服闭环过程发生不可恢复的失锁,从而阻碍光钟的持续运行。在实验中,光钟进行频率闭环锁定前,通常通过控制三维线圈对光钟主腔中心原子处的杂散磁场进行补偿。首先使用三维磁强计,对真空主腔附近的磁场进行监测和记录,以分析杂散磁场对光钟性能的影响。然后利用正态分布模型和二项分布模型等,对光钟频率伺服锁定过程的阿伦偏差进行仿真拟合。在引入实际磁场监测数据的基础上,模拟光钟频率的伺服锁定过程,分析其仿真结果可以得出:减小杂散磁场起伏和控制磁场漂移,在提高冷镱原子光钟的短期稳定性和长期稳定性方面,具有重要意义。

The magnetic field, which is not elaborately controlled, will inevitably deteriorate the frequency instability of the optical lattice clocks through the first-and second-order Zeeman shifts. Furthermore, unrecoverable servo failures on the laser resonant with the clock transition may occur in the presence of the transient magnetic fields, thus hindering the long-term reliable clock operation. In experiment, the three-dimensional coils are used to compensate the stray magnetic field before the clock frequency locking. To analyse the effect of the magnetic field, the three-dimensional magnetometer is utilized for detection around the vacuum cavity. Meanwhile, the normal distribution model and the binomial probability distribution model are employed to simulate the Allan deviation of the optical lattice clock frequency servo lock process. On the basis of introducing the actual magnetic field monitoring data, the servo locking process of the optical clock frequency is simulated, and the simulation results show that reducing the fluctuation of stray magnetic field and controlling the magnetic field drift are of great significance in improving the short-term and long-term stability of the 171Yb optical lattice clocks.