Improving The Medium-Long Term Frequency Stability Of Pulsed Optically Pumped Rubidium Clock

In this paper, we present the improvements of the medium-long term frequency stability of the POP atomic clock. A new temperature servo system with higher temperature stability is developed. The temperature fluctuation of the cavity is 27 K-1 at 104 s, which is improved by approximately one order of magnitude compared to previous result. And the whole physics package is sealed inside a vacuum chamber. With these improvements, the frequency stability of 2.2 x 10(-13) and 7.8 x 10(-15) are achieved at an average time of tau = 1s and tau = 10(4) s, respectively.