铷同位素的精密标定及对精细结构常数变化的测试

The project will research the atomic fountain clocks group of rubidium isotopes and its application on measuring the variation of α, the fine structure constant. We have pointed out that the variation can been detected by comparing related variation between two clock frequencies of the isotopes, and the idea has been proved as one of the most effective methods by theory. One part of research is improvements of a rubidium 87 atomic fountain clock, the stability will become better by adding a cold atoms loading system, and adjusting microwave system will restrict the error of distributed cavity phase, so as to reduce the total uncertainty of the clock to less than 1.3E-15. Many adjustments, such as adding a loading system of cold atoms and fine magnetic shield, are used at building of atomic fountain of rubidium 85, which will make the device run continuously with best indexes. The microwave synthesizer of atomic fountain of rubidium 85 is attached to the microwave system of rubidium 87 fountain clock, the fountain clock groups runs by the way of same source, which decreases comparing time of two fountain clocks greatly. The uncertainties of fountain clock of rubidium 85 and its measuring result of clock frequency will less than 3E-15, and the result of long-time comparing of two clocks will use to detect the variation of α. Common-view method will been used to validating the measuring result and issuing the frequency signal of fountain clocks will high uncertainty index.

本项研究将开展铷同位素喷泉钟组的研究并且利用它测试精细结构常数α的变化。我们提出了利用两种铷同位素钟频率的相对变化测试α的变化，理论预期这是最有效的方案之一。我们将开展Rb87喷泉钟的改进研究，通过增加装载系统，改善喷泉钟稳定度指标，通过改进微波系统，抑制分布腔相移的影响，使喷泉钟的不确定度降低到1.3E-15以下，在搭建Rb85喷泉装置时，通过增加精密磁屏蔽和冷原子装载系统等手段，使该系统达到可运行精密原子钟的要求，在Rb87喷泉钟微波系统的基础上搭建Rb85喷泉的微波综合器，利用同源法实现喷泉钟组运行并显著降低钟组间的比对时间。Rb85喷泉的不确定度和钟频率测试误差将低于3E-15，钟频率的长期比较用于测试α的变化。利用共视法验证测试结果并发布高不确定度指标的喷泉钟频率信号。

本项目开展了铷的两种同位素喷泉钟的研究，目的是建立铷87-85的喷泉钟组，利用两台钟的相互比对，高精度计量铷85钟频率，测试精细结构常数随时间的变化，探索喷泉钟性能指标极限和改进方法，同时探索钟组协同工作下获得更高精度频率信号的方法。.在本项目中，完成了铷87喷泉钟的技术改进，实现短稳2.5E-13τ^-0.5，长稳优于1.2E-15，不确定度优于2E-15的标准频率输出，大于98%的准连续运行。我们搭建了铷85喷泉钟装置。多项创新性技术应用于该系统的设计，装置实现1E8-1E9冷原子数的原子装载，获得飞行时间信号，由Dick效应估算的喷泉钟短期稳定度为2E-13τ^-0.5。搭建了共视比对平台，实现了基于精密单点定位的长期共视比对。.在喷泉钟实验平台上，我们完成了多项创新性成果，弱磁敏跃迁拓展磁场测试动态范围近3个量级；基于塞曼频谱的相对跃迁强度实现磁场矢量测试；磁场动态补偿法将喷泉钟的微波作用区磁场均匀性提高1个数量级（5nT到0.4nT）。我们利用直接锁定本机振荡器的方法实现了喷泉钟频率信号输出；“自比对”法用于评估原子钟不确定度，测试误差优于7E-16@30万秒；“噪声实时分辨”方法可以将某些效应对喷泉钟的不确定度贡献压制约1个数量级。.本项目搭建的铷同位素喷泉钟组实验平台将开展精密计量物理实验、喷泉钟物理问题的研究和工程应用方面的研究，项目中探索的创新方法增加了我们对喷泉钟的操控手段，加深了我们对喷泉钟的理解，促进了喷泉钟的性能提升。