3D speckle cooling in a microwave clock

Sub-Doppler laser cooling is studied in an optically polished microwave cavity used as a reflecting cell. Light potential wells due to the speckle field in the cell make Sisyphus cooling mechanisms possible. For a 1 s capture time, about 10⁸ cesium atoms are cooled at temperatures in the microkelvin range from thermal vapor. These results are discussed and compared with the basic theoretical model involving two laser beams lin ⊥ lin polarized. For a microwave clock using such cold atoms, the pulsed operation is precised and the main frequency shifts are evaluated. The short term relative frequency stability is expected to be lower than 10^-12τ^{- 1}2 /.