Recent improvements on the atomic fountain clock at SIOM**Project supported by the National Natural Science Foundation of China (Grant Nos. 61275204 and 91336105).

Abstract

We report the recent advance in our rubidium atomic fountain clock (AFC). The parameters of the Ramsey cavity are optimized by balancing the coupling from the two ports. The temperature control system of the Ramsey interaction region is renovated, and the resonant temperature of the Ramsey cavity is regulated to be slightly above the room temperature. The quality of magnetic environment in the Ramsey interaction region is also improved. A new digital-to-analog converter (DAC) circuit that controls the local oscillator is adopted to decrease the noise of the oven-controlled crystal oscillator output. As a result, the short-term fractional frequency stability of 2.7 × 10−13τ−1/2 and the long-term fractional frequency stability of 1.6 × 10−15 at the average time of 32800 s are achieved.