Accuracy Evaluation of NIM5 Cesium Fountain Clock

Liu, Nianfeng; Fang, Fang; Chen, Weiliang; Lin, Pingwei; Wang, Ping; Liu, Kun; Suo, Rui; Li, Tianchu

doi:10.1088/0256-307x/30/1/010601

Cited by 6 publications

(2 citation statements)

References 13 publications

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“…[103] Besides the above two methods, reducing collisional frequency shift ( f L − f H ) will also reduce its uncertainty. Capturing cold atoms in an optical molasses with a much lower atomic density [99,104] is one way to reduce the collisional frequency shift. Another method is to operate Cs fountain clocks at the optimal proportion of the two clock state populations after the first Ramsey pulse to make sure the collisional rates for two clock states |3, 0⟩ and |4, 0⟩ have opposite signs and cancelled with each other, and resulting a much lower collisional induced frequency shift.…”

Section: Collisional Shiftmentioning

confidence: 99%

Cold atom clocks and their applications in precision measurements*

Dai¹,

Zheng²,

Liu³

et al. 2021

Chinese Phys. B

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Cold atom clocks have made remarkable progresses in the last two decades and played critical roles in precision measurements. Primary Cs fountain frequency standards have achieved a total uncertainty of a few parts in 1016, and the best optical clock has reached a type B uncertainty below 10−18. Besides applications in the metrology, navigation, etc., ultra-stable and ultra-accurate atomic clocks have also become powerful tools in the basic scientific investigations. In this paper, we focus on the recent developments in the high-performance cold atomic clocks which can be used as frequency standards to calibrate atomic time scales. The basic principles, performances, and limitations of fountain clocks and optical clocks based on signal trapped ion or neutral atoms are summarized. Their applications in metrology and other areas are briefly introduced.

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Section: Collisional Shiftmentioning

confidence: 99%

Cold atom clocks and their applications in precision measurements*

Dai¹,

Zheng²,

Liu³

et al. 2021

Chinese Phys. B

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“…The design of NIM5 has been described in detail. [16] A Mach-Zehnder interferometric rf switch is built to reduce the leakage field effect. The design of the switch is adopted from LNE-SYRTE, [12] and the performance has been tested and reported in Ref.…”

mentioning

confidence: 99%

Accurate Evaluation of Microwave-Leakage-Induced Frequency Shifts in Fountain Clocks

Fang¹,

Liu²,

Chen³

et al. 2014

Chinese Phys. Lett.

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We report theoretical calculations of the transition probability errors introduced by microwave leakage in Cs fountain clocks, which will shift the clock frequency. The results show that the transition probability errors are affected by the Ramsey pulse amplitude, the relative phase between the Ramsey field and the leakage field, and the asymmetry of the leakage fields for the upward and downward passages. This effect is quite different for the leakage fields presenting below the Ramsey cavity and above the Ramsey cavity. The leakage-field-induced frequency shifts of the NIM5 fountain clock in different cases are measured. The results are consistent with the theoretical calculations, and give an accurate evaluation of the leakage-field-induced frequency shifts, as distinguished from other microwave-power-related effects for the first time.

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Improvement of the frequency stability of the cesium fountain clock by data processing

Yang

Liu

et al. 2021

AIP Advances

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The cesium fountain clock is used as the primary frequency standard to improve the accuracy of the excitation source (active hydrogen maser) through cesium atomic transition frequency. The authors find that the frequency stability of cesium fountain clock is poorer than the active hydrogen maser according to the laws of the frequency stability evaluated by the Allan variance. The cesium fountain frequency stability can only reach 2 × 10−15 after 10 000 s. The traditional stability improvement methods are based on the Ramsey line-width optimization. The correction signal of fountain clock contains error, which can be removed partly by data correction. A new method to improve the frequency stability by modified error factor with statistical theory is presented in this paper. The results of frequency stability can reach 1.03 × 10−14/2 s and 2.78 × 10−16/16 400 s.

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Accuracy Evaluation of NIM5 Cesium Fountain Clock

Cited by 6 publications

References 13 publications

Cold atom clocks and their applications in precision measurements*

Cold atom clocks and their applications in precision measurements*

Accurate Evaluation of Microwave-Leakage-Induced Frequency Shifts in Fountain Clocks

Improvement of the frequency stability of the cesium fountain clock by data processing

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