Atomic frequency standards: Cesium primary frequency standard. Development of atomic fountain primary frequency standard at CRL

Abstract

Communications Research Laboratory has been conducting the development of a Cesium atomic fountain primary frequency standard. Cs atoms are cooled to below 2 micro-K by a magneto-optical trap and polarization gradient cooling, and launched vertically by moving molasses method. The launched atoms pass through a microwave cavity twice, on the way upward and downward, and give rise to Ramsey resonance whose linewidth is less than 1 Hz. The atomic fountain standard based on the cold atoms is expected to achieve the uncertainty of the order of 10(exp -15). The atomic fountain has also been developed to aim at an operational primary frequency standard with the frequency uncertainty of 1 x 10(exp -15). In this chapter, the present status of development of atomic fountain at CRL is reported.