Abstract
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.
Highlights
Most of improvements in the frequency stability of cesium fountain clock have focused on the accuracy of the quantum detection system and the modification of the microwave electronic circuits
The stability depends on the hydrogen maser itself, so the variation of noise fluctuation characteristics in frequency difference can be boldly corrected because none of this is caused by the hydrogen maser itself
Data process and algorithm modification of the errors of frequency difference in the microwave cavity output is another method to improve the frequency stability of the cesium fountain clock
Summary
Most of improvements in the frequency stability of cesium fountain clock have focused on the accuracy of the quantum detection system and the modification of the microwave electronic circuits.1–4 The frequency stability of the active hydrogen maser is better than that of the cesium fountain clock.
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