Dick Effect in the Integrating Sphere Cold Atom Clock

The Dick effect is an important factor limiting the frequency stability of sequentially-operating atomic frequency standards. Here we study the impact of the Dick effect in the integrating sphere cold atom clock (ISCAC). To reduce the impact of the Dick effect, a 5 MHz local oscillator with ultra-low phase noise is selected and a new microwave synthesizer is built in-house. Consequently, the phase noise of microwave signal is optimized. The contribution of the Dick effect is reduced to 2.5\times 10^-13\tau ^-1/2 (\tau is the integrating time). The frequency stability of 4.6\times 10^-13\tau ^-1/2 is achieved. The development of this optimization can promote the space applications of the compact ISCAC.