Progress of the Portable Rubidium Atomic Fountain Clock in SIOM
A portable 87Rb atomic fountain clock has been constructed and researched in Shanghai Institute of Optics and Fine Mechanics, and some improvements have been made recently. So far, comparison data with the H-maser shows that, the Allan deviation of the re
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Progress of the Portable Rubidium Atomic Fountain Clock in SIOM Yuanbo Du, Rong Wei, Richang Dong and Yuzhu Wang
Abstract A portable 87Rb atomic fountain clock has been constructed and researched in Shanghai Institute of Optics and Fine Mechanics, and some improvements have been made recently. So far, comparison data with the H-maser shows that, the Allan deviation of the relative frequency stability of this fountain clock is 5.0 9 10-13s-1/2, which reaches 2.6 9 10-15 at the average time of 40000 s, and degenerates for longer time due to the frequency drift of the H-maser. The relative frequency uncertainty has been evaluated with the value of 2.4 9 10-15. In addition, some characteristics technique has been realized on this fountain clock, including ‘‘local-oscillator-locking’’ which gives the error signal back to the local oscillator directly and offers the standard frequency output whose stabilities arrive at the limit determined by the Dick effect, ‘‘health safeguard’’, an improvement used to increase the continuous running time, and suppress the possible faults caused by frequency unlocking and power fluctuation of the laser, and ‘‘self comparing’’, a simple and effective way for the frequency uncertainty evaluation, which is used to evaluate the distributed cavity phase shift, collision shift, and light shift. Keyword Fountain clock locking Health safeguard
Rubidium Frequency stability Local-oscillator Self comparing
Y. Du R. Wei (&) R. Dong Y. Wang Key Laboratory for Quantum Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China e-mail: [email protected] Y. Du R. Wei R. Dong Y. Wang Center for Cold Atom Physics, Chinese Academy of Sciences, Shanghai 201800, China
J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2013 Proceedings, Lecture Notes in Electrical Engineering 245, DOI: 10.1007/978-3-642-37407-4_39, Ó Springer-Verlag Berlin Heidelberg 2013
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39.1 Introduction Atomic fountain clocks (AFC) are the most accurate atomic clocks participating in the UTC and TAI [1], which have been or are being built in most important timing laboratories all over the world. For example, seven rubidium atomic fountain clocks are being constructed to upgrade the timekeeping system in USNO [2]. A portable 87Rb AFC device has been made and researched in Shanghai Institute of Optics and Fine Mechanics since 2003, and early works were reported in the CSNC in 2011 [3]. Since then, a new microwave synthesizer with lower phase noise for a better stability of AFC has been set up and certificated, and the local oscillator locking (LOL) technology is adopted to lock the microwave frequency, namely, error signal given back to the servo local oscillator instead of the DDS in the microwave synthesizer. In addition, certain characteristics technique such as ‘‘health safeguard’’(HS) is applied to increase the continuous running time and suppress the possible faults caused by frequency unlocking and power fluctuation o
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