First accuracy evaluation of NIST-F2
First accuracy evaluation of NIST-F2
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DOI：
10.1088/0026-1394/51/3/174
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发表时间：
2014-06-01
期刊：
影响因子：
2.4
通讯作者：
Jefferts, S. R.
中科院分区：
文献类型：
--
作者：
Heavner, Thomas P.;Donley, Elizabeth A.;Jefferts, S. R.
我们报告了NIST-F2的第一次精度评估，NIST-F2是美国国家标准与技术研究所（NIST）开发的第二代激光冷却铯喷泉一级标准，具有低温（液氮）微波腔和飞行区域。80 K原子询问环境将黑体辐射漂移造成的不确定性降低了50倍以上。此外，Ramsey微波腔在此低温下表现出高品质因数（>50 000），导致减小的分布式腔相移。NIST-F2自2008年首次投入使用以来，经过了多次测试和改进。在过去的几年中，NIST-F2与NIST微波激射器时标和NIST-F1（美国主要频率标准）进行了比较，作为内部精度评估的一部分。我们报告了自2010年以来9次内部比较的结果，重点是最近的准确性评估。本文讨论了物理包、激光和光学系统的设计以及精度评定方法。NIST-F2的B类分数不确定度为0.11 × 10 ~（-15），主要由微波振幅相关效应决定。最近一次评价（2013年8月）的统计（A型）分数不确定度为0.44 x 10（-15）。
We report the first accuracy evaluation of NIST-F2, a second-generation laser-cooled caesium fountain primary standard developed at the National Institute of Standards and Technology (NIST) with a cryogenic (liquid nitrogen) microwave cavity and flight region. The 80K atom interrogation environment reduces the uncertainty due to the blackbody radiation shift by more than a factor of 50. Also, the Ramsey microwave cavity exhibits a high quality factor (>50 000) at this low temperature, resulting in a reduced distributed cavity phase shift. NIST-F2 has undergone many tests and improvements since we first began operation in 2008. In the last few years NIST-F2 has been compared against a NIST maser time scale and NIST-F1 (the US primary frequency standard) as part of in-house accuracy evaluations. We report the results of nine in-house comparisons since 2010 with a focus on the most recent accuracy evaluation. This paper discusses the design of the physics package, the laser and optics systems and the accuracy evaluation methods. The type B fractional uncertainty of NIST-F2 is shown to be 0.11 x 10(-15) and is dominated by microwave amplitude dependent effects. The most recent evaluation (August 2013) had a statistical (type A) fractional uncertainty of 0.44 x 10(-15).