Performance Test and Power-Law Spectrum Analysis of Domestic Cesium Clocks

Abstract

The medium- and short-term stability of hydrogen clocks and the medium- and long-term stability of cesium clocks combine into a time-keeping clock set. This is a common practice in major time-keeping laboratories across the world. Domestic hydrogen clocks have been commercialized, while cesium clocks are subject to key technical bottlenecks. After years of technical research, domestic cesium clocks have achieved a rapid growth and commercialized cesium clocks have become available. In this paper, we observe cesium clocks over a long term, using a hydrogen clock as the reference signal and conduct a power-law spectrum analysis of domestic cesium clocks based on the test data. Results show that cesium clocks have flicker frequency modulation noise within 10 s and white frequency modulation noise from 10 s to 5 days. By using 1pps and frequency measurements, we analyze the consistency between 1pps and frequency signals output by domestic cesium clocks. Results show that the output of 1pps contains 100 ps jitter. The long-term performance is in full accord with that of frequency signals. This paper gives a preliminary assessment on the performance of domestic cesium clocks according to our test data. Cesium Clock A has a second stability of 2.8E−12 and a day stability of 3.4E−14, which is up to the level of 5071A high-performance tube. Cesium Clocks B and C have a second stability of 6.0E−12 and a day stability of 6.0E−14, which is up to the level of 5071A standard performance tube. Also some problems are found in the testing process. To make a comprehensive and accurate assessment of cesium clocks, we need test data over a longer term. In the future, domestic cesium clocks will continue to be tested. With the abundance of test data, domestic cesium clocks will be assessed more accurately, to provide accurate data support for the use of domestic cesium clocks in time-keeping laboratories.