An Automated System for Measuring Velocity Distribution in Cesium Beam Tubes

This report describes a completely automated system for measuring the velocity distribution in a cesium Cs beam tube. The measurement system uses the short-pulsed microwave excitation method on Cs beam tubes having separated Ramsey-type interaction regions. This pulsed technique allows for the observation of signals that result from very narrow atomic-velocity groups. The brief theoretical operation of this method is discussed, after which the velocity distributions of six Cs beam tubes from four different manufacturers are presented. Data are presented that show the reproducibility of this measurement on the same beam tube, and comparisons among different tubes are made. Also, velocity distributions have been measured on all seven Zeeman transitions from one tube that exhibits small Rabi pulling. The knowledge of this Cs beam tubes velocity distribution provides considerable insight into the performance and alignment of the beam optics, and thus could be used for the diagnostic testing of Cs beam tubes. We have used this method to characterize a large number of such tubes. Cesium frequency standards, Cesium velocity distributions, Pulsed microwave technique.