Accurate determination of the phase space evolution of a laser-cooled atomic beam

A laser-cooled atomic beam apparatus employing a frequency modulated ring dye laser has been developed which permits continuous monitoring of the fluorescence at any point along the beam. The laser frequency is modulated by the counterrotation of two intracavity glass plates mounted on scanning galvo drivers. Hermetically sealed photodiode assemblies have been mounted inside the vacuum system along the length of the atomic beam in a 1.6-m section of uniform magnetic field. This permits the characterization of the density and velocity distribution of the atomic beam at any spatial or temporal point during the cooling process as a function of various experimental parameters. Observations of the fluorescence from the atomic beam during a complete cycle including optical pumping, deceleration, and velocity profile compression are currently in progress with sodium. Spatial profiles of the beam are also being measured using a hot wire detector. The authors anticipate extension to other alkali atom beams using frequency modulated laser diodes