Improvement Of Frequency Stability In Fountain Clock

The cesium atom fountain clock is a frequency reference source defined by the International Bureau of Standards and Metrology.It participates in basic research fields such as time standard generation,basic physical constant measurement,and relativity inspection.With the development of science and technology,improving the stability performance of the cesium atomic fountain clock and making use of the accuracy potential of the fountain clock are the hotspots and difficulties of the current fountain clock research.This article studies the quantization noise or errors that cause the fountain clock’s short-term or mid-and long-term frequency stability,such as:quantum projection noise,photon shot noise,electronic detection noise,local crystal noise and Dick effect,etc.,and correct the noise source or modify the fountain clock Various methods of internal structure to improve frequency stability.This article directly focuses on the frequency data output by the fountain clock,and makes attempts from two aspects:data processing and frequency-phase conversion processing.In this paper,a frequency-phase processing conversion device is designed in the aspect of frequency-phase conversion processing.The device is a frequency-locked processing device composed of frequency differences using a phase coincidence detection method.And by adding the analogue atomic clock frequency differences as one input of the device,and selecting the locked source of the atomic clock as the locked source of the device,the high frequency accuracy of the clock is preserved.Change the resolution of the quantized phase shift between signals,and explore the conversion relationship between frequency lock and phase lock.Experimental results show that when the phase synchronization accuracy between signals reaches the order of E-14,the stability of the output frequency can be converted,revealing the regularity of frequency stability output,and realizing the frequency control result to the phase control result conversation.This paper also designs a scheme to convert the output frequency difference of the cesium fountain clock into a phase output effect based on the experimental results.This paper compares the instantaneous relative frequency difference sequence and frequency stability of the input active hydrogen clock and the output frequency difference of the cesium atomic fountain clock,and analyzes the difference between the output frequency stability of the cesium atomic fountain clock and the change of the input hydrogen clock.The fluctuation of the cesium atom fountain clock relative to the frequency difference sequence is not concentrated,and the range is too large,which will cause sudden changes in frequency stability in a short interval.Therefore,on the basis of not destroying the long-term characteristics of the frequency stability of the input hydrogen clock and not reducing the accuracy of the cesium atom transition frequency,this paper adopts methods such as data frequency phase conversion,gross error correction,bin smoothing,and changing bin interval.The output frequency data of the cesium atomic fountain clock.The output frequency stability of the cesium atom fountain clock has been removed from the protrusion at about 20s,and the frequency stability has been improved to 7.30E-16/32800s.