Research Progress

NTSC Researchers Developed Rubidium Fountain Clock for Time-keeping

Author:       ArticleSource:       Update time:2023/07/25

Recently, the research team led by Prof. ZHANG Shougang from the National Time Service Center of the Chinese Academy of Sciences successfully developed Rubidium fountain clock for time-keeping with frequency stability and frequency drift rate of 1.91E-13τ-1/2(τ=1~200000 s) and 1.71E-17/d, respectively.

These results published in IEEE Transactions on instrumentation and measurement.

National standard time is a coordinated product of atomic time measured by atomic clocks, and universal time measured by the Earth's rotation. The generation of atomic time is composed of a number of atomic clocks of different kinds and different characteristics, which synthesizes continuous, reliable and stable time signals, and then is calibrated by local primary frequency standard or international comparison data.

At present, the atomic clocks produced and maintained by standard time in various countries or regions mainly include hydrogen clocks and Cesium beam clocks. The frequency stability of Rubidium fountain clocks is one order of magnitude lower than that of Cesium beam clocks, and the frequency drift rate is one order of magnitude lower than that of hydrogen clocks. The combination of three kinds of atomic clocks for time keeping has great potential to improving the stability of national standard time.

The Rubidium fountain clock NTSC-RbF1 developed by the team has been tested and evaluated by the International Bureau of Weights and Measures(BIPM) for 5 months, and has been continuously used for international atomic time calculation since November 2022. It contributes not only to national standard time, but also to international standard time. (

"Now, China can independently develop all kinds of atomic clocks and universal time measurement systems needed for the generation of national standard time, ensuring generation of Beijing time independent and state-of-art", said Prof. ZHANG Shougang.


XIONG Tiantian
National Time Service Center, Chinese Academy of Sciences