提出了一种积分球冷原子钟冷原子数稳定的新方法。该方法通过周期性地监测冷原子的吸收信号,利用反馈控制冷却激光内声光调制器的衍射效率并改变冷却光功率,实现冷原子数的稳定。推导了冷原子数稳定系统的环路方程,分析了稳定环路对冷原子数涨落的抑制作用。稳定后冷原子数的归一化涨落为1±0.001(3 h),其功率谱密度在0.001~0.2 Hz频率范围内的最大抑制量约为30 dB。该涨落被抑制的原因主要是稳定环路除了直接补偿冷却光激光器输出的光功率变化外,还纠正了外界环境引起的冷原子数漂移。冷原子数稳定之后,由冷原子数涨落引起的原子钟频率稳定度可降低至7×10 ^-14τ^-1/2 ( τ 为积分时间)。

A new method for cold atom number stabilization in a integrating sphere cold atom clock is proposed. The stabilization of cold atom number is realized by periodically monitoring the absorption signal of cold atom, adjusting the diffraction efficiency of acoustic optical modulation in cooling laser, and changing the cooling light power. The loop function of the cold atom number stabilization system is deduced, and its suppression effect on the fluctuation of cold atom number is analyzed. The normalized fluctuation of stabilized cold atom number is 1±0.001 in 3 h, and the maximum suppression of power spectral density is about 30 dB in the range of 0.001-0.2 Hz. The reason for fluctuation suppression is that the stabilization loop not only compensates the output light power of cooling laser, but also corrects the cold atom number drift induced by environment. When the cold atom number is stable, the atom clock frequency stability induced by the fluctuation of cold atom number is decreased to 7×10 -14τ-1/2 ( τ is the integral time).