| 报告题目： |
An improved NPL Cs fountain primary frequency standard and Searching for variations in α and β through precision spectroscopy of cold CH molecules |
| 报告人： |
Richard James Hendricks |
| 报告人单位： |
英国国家物理实验室 |
| 报告时间： |
2018年8月31日10:00 |
| 报告地点： |
引力中心三楼会议室 |
| 报告摘要： |
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Cs fountains are the primary frequency standards used to define the SI second, and are the most accurate, stable and reliable clocks currently available that are routinely used in high precision time and frequency applications. In this talk I will describe the operating principles of the Cs fountains that steer the UK’s national timescale and provide a frequency reference for microwave and optical clock research at NPL. I will also introduce an improved NPL Cs fountain design that has recently been developed. So far, three of these fountains have been built and shipped to international partners in Canada and Poland, and are currently being evaluated. I will present results showing the performance of the new systems and describe the status of measurements to determine their long-term accuracy.
Some theories trying to explain universal expansion and dark energy invoke new forces that vary as a function of the local matter density. Variations in the values of fundamental constants would be a measurable signature of these new forces. CH molecules are naturally occurring in the low-density environment of space, and possess several transitions that are very sensitive to both the fine structure constant, α, and the electron-proton mass ratio, β. I will describe how we have compared new laboratory measurements with astronomical data to place constraints on the variation of α and β with local matter density at the 10-7 level. |
| 报告人简介： |
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Richard James Hendricks于2001年获得布里斯托尔大学物理学硕士学位；2006年于帝国理工学院获得博士学位，研究方向为潘宁离子阱中激光冷却钙离子的动力学与光谱；2006-2008年在丹麦奥尔胡斯大学从事博士后研究工作，研究方向为微观尺度的RF离子阱加工、激光烧蚀，离子的边带冷却与相干操控等；2008-2015年在帝国理工学院从事博士后研究，研究方向为分子的直接激光冷却、应用于分子协同冷却的原子磁光囚禁，原子、分子的微波囚禁，分子的斯塔克和光学减速，基于超冷分子的精细结构常数变化测量等。2016年加盟国家物理实验室(英国)，研究方向为铯原子喷泉的搭建、优化及系统效应评估，以及光学超稳腔的隔振等。 |
