Evaluation and Operation of Atomic Beam Tube Frequency Standards Using Time Domain Velocity Selection Modulation

Abstract

Pulsed excibtion of atomic and molecular beam devices with separated Ramsey-type interaction regions allows the observation of signals due to very narrow atomic velocity groups. The theoretical background of this method is discussed. Experimental operation of a near mono-velocity cesium beam tube is demonstrated. The velocity distribution of a commercial cesium beam tube is obtained using the pulse method. The normal R,amsey pattern of this beam tube is calculated from the velocity distribution and compared with the measured Ramsey pattern. The pulse method allows the direct determination of the cavity phase shift and of the second-order Doppler correction in beam devices. The pulse method thus shows promise for the evaluation of existing laboratory as well as commercial cesium beam tubes with respect to these effects.

Status report on primary frequency standards

“…These lower than the current frequency of TAI [5,7,8], Thus, we may conclude at this point in time that TAI runs at a frequency too high with respect to the definition of the second by about 1 part in 10 Similarly designed cesium beam frequency standards are nearing completion and evaluation in Japan and in the United Kingdom.…”

“…Present. devices have not yet demonstrated better than 1 part in 10 in accuracy. However, no real physical limit down to 10 appears to be known.…”

“…They may permit an evaluation of most existing cesium beam standards, whether they were designed for evaluation or not, including commercial beam tubes [9,10]. Thus, many more laboratories could join the group of laboratories owning primary frequency standards provided they go through certain electronic test procedures with existing cesium beam standards found suitable for the application of these techniques.…”

Impact of Lasers on Primary Frequency Standards and Precision Spectroscopy

“…The experiments and experimental techniques are f a r too numerous t o l i s t i n an a r t i c l e o f t h i s length, but there are many excellent reviews and conference proceedings [36,40]. T r a n s i t time broadening can a1 so be reduced by longitudinal i n t e r a c t i o n schemes [Hall, J. L., p Second-order Doppler broadening can be reduced only by decreasing the speed o f the atoms under study o r by i n t e r a c t i n g w i t h a single-vector v e l o c i t y group (e.g., longitudinal i n t e r a c t i o n w i t h a well-collimated atomic beam o r by pulsedl a s e r method [15,41]). Decreasing the speed i s possible by cryogenic cooling, b u t many materials condense i f they are cooled much below room temperature.…”

Accuracy Evaluation and Stability of the NBS Primary Frequency Standards

“…Some rewiring is necessary as well. Since this is a fairly long procedure, and since beam reversal data have been obtained and evaluated from NBS-5 (in the light of the pulse method and power-shift method [2]), the beam has not been reversed in NBS-4. However, independent accuracy data on NBS-4 were obtained solely by the powershift method.…”