Construction of Cs atomic fountain frequency standard at NRLM

Summary form only given, as follows. Towards the primary frequency standard with the accuracy of 10/sup -16/ level, we are developing a Cs atomic fountain at NRLM. The Cs atoms are trapped in a magneto-optical trap (MOT), cooled in the optical molasses and then launched upward. Among the six beams comprising the MOT, two beams are in the horizontal plane and other beams are oriented 45° to the vertical axis. This geometry enables multi-pulse operation, which is useful to reduce the frequency shifts due to cold collisions and the down conversion of the local oscillator noise. Recent progress in the development this frequency standard is reported.