期刊
METROLOGIA
卷 59, 期 3, 页码 -出版社
IOP Publishing Ltd
DOI: 10.1088/1681-7575/ac5e7b
关键词
atomic fountain; primary frequency standard; uncertainty evaluation
资金
- JSPS KAKENHI [JP18K04989, 15K21669]
- Grants-in-Aid for Scientific Research [15K21669] Funding Source: KAKEN
In this study, we report the first uncertainty evaluation of NMIJ-F2, the second atomic fountain primary frequency standard at the National Metrology Institute of Japan. By increasing the number of detected atoms and employing an ultra-stable cryogenic sapphire oscillator, the frequency stability has been significantly improved.
We report the first uncertainty evaluation of NMIJ-F2, the second atomic fountain primary frequency standard at the National Metrology Institute of Japan. To improve the frequency stability, we increase the number of detected atoms to 9 x 10(5) using high-power cooling laser beams for vapor-loaded optical molasses and optical pumping into the Zeeman sublevel m (F) = 0. We also employ an ultra-stable cryogenic sapphire oscillator as a local oscillator to prevent the degradation of frequency stability due to the Dick effect. After correcting the collisional frequency shift by alternating atom densities, the frequency stability typically reaches 2.5 x 10(-13)(tau/s)(-1/2). Its value is 1.9 x 10(-16) after 20 days of measurement. Type B uncertainty is typically evaluated at 4.7 x 10(-16); the largest contribution is from a distributed cavity phase shift, followed by a microwave leakage shift. In long-term comparison, the frequency of NMIJ-F2 is found to be consistent with that of the other primary and secondary frequency standards within the uncertainty.
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