Studies on the mid-term effects of the double-modulation CPT clock

We present recent studies on a continuous compact atomic clock based on the double modulation coherent 1 population trapping (DM-CPT) technique. A short term frequency stability of 2.9x10^-13_τ-1/2 up to 100 s averaging time is reported. A new technique and time sequence in order to gain in stability in the 1000 s is presented, allowing a frequency stability of 2.0x10⁻¹³ at this averaging time, which is better by almost an order of magnitude than the previously published results.