基于离子束流电路直接放大的铯原子钟锁频方法研究

项目名称： 基于离子束流电路直接放大的铯原子钟锁频方法研究

项目编号： No.61471183

项目类型： 面上项目

立项/批准年度： 2015

项目学科： 无线电电子学、电信技术

项目作者： 王骥

作者单位： 兰州空间技术物理研究所

项目金额： 71万元

中文摘要： 电子倍增器的性能衰减严重制约着商品小铯钟的寿命，采用电路直接检测替代电子倍增器实现铯离子束流放大能有效提高小铯钟的寿命，且这项研究工作在国内外迄今为止尚无成功报道。本课题组已利用电子倍增器与电流放大器联合放大铯离子束流获得了Ramsey 跃迁信号，也明确了信噪比是制约离子束流电路检测方法在铯原子钟中应用的关键问题。 本项目提出并建立基于铯离子束流电路直接放大和锁定放大器检测的铯原子钟锁频模型，模拟分析散粒噪声和热噪声对小铯钟信噪比及其输出频率稳定度的影响，进而通过优化放大电路参数和数字锁定放大器改善误差信号信噪比。研究密封pA级信号前置放大电路的真空放气率和噪声特性，并根据锁定放大器的窄带特性提出一种慢方波微波调制新方式并获得利用数字锁定放大器得到频差的检测算法，实现铯原子钟的闭环锁频。本课题探索并阐明电路直接放大铯离子束流小铯钟的稳定锁频方法，为小铯钟完全突破寿命问题提供新途径。

中文关键词： 铯原子钟；信噪比；离子束流；前置放大；锁定放大器

英文摘要： Performance degradation of electron multiplier clearly restricts the lifetime of commercial small cesium atomic clocks. It can effectively prolong the lifetime of small cesium clock by the method of replacing electron multiplier with direct detection circuit to magnify the cesium ion beam flux. Moreover, there is no successful report that with the direct circuit detection method in cesium atomic clocks so far. We have acquired the Ramsey transition signal with the combination of electron multiplier and current amplifier to magnify the cesium ion beam and it is also explicit that signal-to-noise ratio (SNR) is the key question restricting the application of circuit detection method of ion flux in cesium atomic clock. The project brings forward and builds the frequency locking model of a cesium atomic clock based on direct circuit amplification of cesium ion flux and lock-in amplifier detection. With the model, the influences of shot noise and Johnson noise of the small cesium clock on the SNR and stability of output frequency would be simulated and analyzed. Then circuit parameters and digital lock-in amplifier are optimized to improve the SNR of error signal. The vacuum outgassing rate and noise characteristics of the sealed preamplification circuit on pA level signal is investigated. Moreover, according to narrow band characteristics of lock-in amplifier, a new type of slow square wave modulation mode and a detection algorithm of frequency difference are proposed with digital lock-in amplifier to realize close-loop frequency locking of the cesium clock. The goal of the research is to explore and clarify the frequency locking method of small type of the cesium clock with direct circuit amplification of cesium ion flux, and thus provide a new way for absolutely settling the lifetime of small cesium atomic clock.

英文关键词： Cesium atomic clock;signal-to-noise;ion beam flux;preamplification;lock-in amplifier