Working for a mobile high accuracy (10<sup>-15</sup>) rubidium atomic fountain clock

Abstract

Fountain clocks, including cesium fountains and rubidium fountains, are the most accurate running atomic clocks in the world. A mobile rubidium clock prototype has been researching at SIOM since 2003, the unique features of the fountain clocks are: less cold-atom loss, higher SNR and less collision-shift were acquired by operating with rubidium, a fold optical path decreased laser power by 2/3, which also made the whole device be more stable, compact, and easier to manufacture. The Ramsey finger of microwave-transition in the fountain clock has been obtained with its SNR of about 100. The fountain clock has been lock to a H-maser, Allan Deviation calculating had shown that the short-term fractional frequency instability was 8×10^-13 at 1 s, and long-term fractional frequency instability was better than 6×10^-15 in 4×10⁴ s. Errors evaluating and system optimizing are in process, the total fractional uncertainties are expected to be less than 4×10^-15 when it is evaluated recently.