Reaching a few 10−13 τ−1/2 stability level with the compact cold atom clock HORACE

HORACE is a compact cold cesium atom clock which is being developed in LNE-SYRTE for space applications and onboard systems. The operation of this clock is different from fountains since the laser cooling, the microwave interrogation and the detection are sequentially performed inside the spherical microwave cavity. The entire simplified operation sequence is described. A short term relative frequency stability of 2.2 10
^-13
tau
^-1/2
is achieved. Preliminary results on mid term show that a level of 4 10
^-15
is reached after 5 10
³
s of integration. Limitations are investigated.