小型化钙离子光钟的黑体辐射频移研究

With the rapid development of the optical clock recently, several kinds of optical clock ‘s uncertainty have been reached to E-18 Level in the world. In our minimized portable single ion optical clock case , The black body radiation shift(BBR) is the largest one among all of the error effects in the budget table. It has become the most difficult obstacle for improving the uncertainty of the whole portable optical clock. The BBR uncertainty comes from two factors, one is the coefficient uncertainty of BBR Δα,The other one is the uncertainty of the environment temperature in the center of the ion trap. The Δα is the difference of statistic polarization rate between the two clock states .Its uncertainty is mainly determined by the theory calculation precision. While the environment temperature uncertainty is determined by the experiment measurement precision. In this projection application, A kind of Finite Element method will be used to analyze and simulate the BBR model of the temperature distribution in the center of ion trap center of our minimized portable ca+ ion optical clock. According to the simulation results, We can optimize our ion trap structure to improve the BBR uncertainty, We also can do the precision measurement of the coefficient of the difference of statistic polarization rate between the two clock states by beat frequency measurement of the two optical clock .Finally, We can get the BBR uncertainty is better than 2E-18 level. So the uncertainty of the portable optical clock can be greatly improved..This Finite Element research method can be used in other optical clock BBR research as well.

近年来，随着光频标的发展突飞猛进，世界上已有多种光钟不确定度进入E-18水平。而在可搬运离子光钟的系统误差评估误差表中，黑体辐射(BBR)频移及其不确定度成为误差最主要的贡献者，是提高可搬运光钟指标的最大障碍。对于可搬运钙离子光频标，黑体辐射频移不确定度的主要来源是黑体辐射频移系数Δα的不确定度以及离子所处环境黑体辐射场的温度的不确定度。前者中的Δα为钙离子钟跃迁所涉及两个能级的静态极化率之差，其不确定度主要取决于理论计算精度，而后者主要受限于射频对离子阱零部件加热达到的平衡温度的实验测量。本项目拟采用基于有限元分析方法的黑体辐射模型对可搬运钙离子光钟的中心温度分布进行模拟，并根据模拟结果改进实验装置；采用两台光钟比对实验对黑体辐射频移系数进行精确测量，最终使得可搬运钙离子光钟系统中黑体辐射频移因素优于2E-18，从而整体提高光钟指标。此研究方法对其他光钟黑体辐射研究也具有重要的参考意义。

作为下一代原子钟，基于囚禁原子/离子的光钟由于具有更好的性能发展迅速。在众多光钟候选体系中，40Ca+ 离子光钟因其便于小型化和集成化的方案优势使其成为研制可搬运光钟的最佳选择之一。迄今为止，黑体辐射（Blackbody Radiation，BBR）频移不确定度成为制约着研制E-18精度可搬运40Ca+离子光钟最关键的因素之一。本项目选择可搬运钙离子光钟为研究对象，针对钙离子光钟黑体辐射频移评估开展了系统研究。研究工作总结如下：.1、基于有限元方法（Finite element method, FEM），结合红外成像仪真空腔内测温的校准技术，发展了离子光钟BBR温度评估方法。利用该方法，分别对实验室三套钙离子光钟系统的BBR温度进行了评估，结果分别是295.27 (0.77) K、294.95 (0.40) K、296.88 (0.83) K。相应BBR频移不确定度分别达到9.1E-18、4.7E-18、1.0E-18。.2、为了抑制可搬运40Ca+离子光钟BBR频移不确定度，通过调控离子阱系统各部件有效立体角，结合BBR屏蔽层，研制了一套可搬运光钟囚禁离子新装置。经评估，新系统的BBR温度不确定度为0.17 K，对应BBR频移不确定度已接近2 E-18，解决了室温下可搬运40Ca+离子光钟系统不确定度进入E-18水平的最大难题。. 通过该项目的执行，成功掌握了小型化可搬运钙离子光钟黑体辐射频移不确定度评估方法，将此方法成功应用于多台光钟上。同时申请多项国家发明专利，并且发表了多篇学术论文。很好地完成项目研究任务和研究目标。