高精度守时对原子钟性能的要求

The Performance Requirement for Atomic Clocks in high Precision Time Keeping

该文根据NTSC 20多台原子钟的ADEV和HDEV的分析、BIPM发表的TAI系统中原子钟的速率公报和权重报告,讨论了在高精度守时系统中对原子钟频率稳定度的要求。建议用τ≈30 d铯钟的ADEV和氢钟的HDEV至少达到1E-14来作为一个钟能否用于高精度守时的判断标准。

With the analysis of ADEV and HDEV for NTSC＇s more than 20 atomic clocks as well as the BIPM publications of rate and weight,the usability of a clock in high precision time keeping is discussed.The weighting method used in TAI calculation is briefly introduced and its disadvantage is discussed.The way used in TAI calculation to evaluate the quality of a clock is only suitable for a clock without long frequency drift such as cesium clocks（Cs）but not suitable for a hydrogen maser（HM）which is of very small short frequency variation and regular long frequency drift,which may be endued with high weight in the calculation of atomic time scales as long as an appropriate algorithm is used.The statistic analysis of weights endued to Cs and HM in TAI calculation is given in this paper which shows that most of the HM don＇t have contribution to TAI.Therefore,there should be a better method to evaluate quality of atomic clocks for time keeping.It is recommended that HDEV should be used to show whether a clock, especially a HM,could make contribution to high precision timekeeping,and our recommended criterians are that the value should reach at most less than 1E-14 of ADEV for a Cesium clock and HDEV for a maser with the sample time,τ≈30 d,if a clock could be used in time keeping.