IEEE Trans Ultrason Ferroelectr Freq Control. 2017 Mar;64(3):623-633. doi: 10.1109/TUFFC.2016.2636088. Epub 2016 Dec 19.
Linear ion trap frequency standards are among the most stable continuously operating frequency references and clocks. Depending on the application, they have been operated with a variety of local oscillators (LOs), including quartz ultrastable oscillators, hydrogen-masers, and cryogenic sapphire oscillators. The short-, intermediate-, and long-term stability of the frequency output is a complicated function of the fundamental performances, the time dependence of environmental disturbances, the atomic interrogation algorithm, the implemented control loop, and the environmental sensitivity of the LO and the atomic system components. For applications that require moving these references out of controlled lab spaces and into less stable environments, such as fieldwork or spaceflight, a deeper understanding is needed of how disturbances at different timescales impact the various subsystems of the clock and ultimately the output stability. In this paper, we analyze which perturbations have an impact and to what degree. We also report on a computational model of a control loop, which keeps the microwave source locked to the ion resonance. This model is shown to agree with laboratory measurements of how well the feedback removes various disturbances and also with a useful analytic approach we developed for predicting these impacts.
线性离子阱频率标准是最稳定的连续工作频率基准和时钟之一。根据应用的不同，它们已经使用了各种本地振荡器 (LO) 进行操作，包括石英超稳定振荡器、氢 maser 和低温蓝宝石振荡器。频率输出的短、中、长期稳定性是基本性能、环境干扰的时间依赖性、原子询问算法、实现的控制回路以及 LO 和原子系统组件的环境敏感性的复杂函数。对于需要将这些参考从受控实验室空间移动到稳定性较差的环境（例如现场工作或太空飞行）的应用，需要更深入地了解不同时间尺度的干扰如何影响时钟的各个子系统，并最终影响输出稳定性。在本文中，我们分析了哪些干扰有影响以及影响程度。我们还报告了一个控制回路的计算模型，该模型使微波源锁定在离子共振上。该模型与实验室测量结果吻合良好，反馈能够很好地消除各种干扰，并且与我们开发的用于预测这些影响的有用分析方法吻合。
