The domestically developed cesium atomic fountain clock from China has been recognized to participate in calibrating international standard time

Recently, the International Bureau of Weights and Measures (BIPM) published Circular T 435, announcing the frequency data of the cesium atomic fountain clock (designated as NTSC-CsF2) for a continuous 18-month period. This marks the recognition of the cesium atomic fountain clock independently developed by the National Time Service Center of the Chinese Academy of Sciences to participate in calibrating Coordinated Universal Time (UTC) and to contribute to International Atomic Time (TAI).

Over nearly 20 years of continuous research and development, the research team led by Dr. Zhang Shougang at the National Time Service Center of the Chinese Academy of Sciences successfully achieved a frequency stability of 2.1×10-13τ-1/2 (high atomic density) and a frequency uncertainty of 4.3×10-16 for the cesium atomic fountain clock device NTSC-CsF2.

To test and verify the frequency performance of the cesium atomic fountain clock, the research team conducted 8 months of comparative measurements between NTSC-CsF2 and other calibrated international atomic time reference clocks using the Global Navigation Satellite System (GNSS) link from August 2022 to March 2023. The results indicated that the independently assessed frequency uncertainty of 4.3×10-16 by the research team is scientifically reasonable.

The National Time Service Center of the Chinese Academy of Sciences utilizes domestically produced hydrogen clocks, self-developed optical pumping cesium clocks, rubidium fountain clocks, cesium fountain primary clocks, and the world time measurement system to autonomously generate the national standard time UTC (NTSC), also known as Beijing Time. The cesium fountain primary clock NTSC-CsF2, as a reference in the national timekeeping system, ensures the accuracy of the national standard time without the need for delayed international comparison data and guarantees the accuracy of the national standard time even in situations where international comparisons are lacking. Cesium atomic fountain clock NTSC-CsF2. Image provided by the National Time Service Center.