Determining Optimum C-Field Settings that Minimize Output Frequency Variations in Cesium Atomic Frequency Standards.

摘要

De Marchi at the National Institute of Standards and Technology (NIST) performed an experiment on Hewlett-Packard cesium (Cs) frequency standards, in which he showed that there exist optimum values of the C-field that make the output frequency insensitive to variations in microwave power. Moreover, and most important, De Marchi demonstrated that the long-term stability of the Cs standard was improved at these optimum values of the C-field. To see if these results could be obtained with standards made by different manufacturers and having different modulation schemes and Cs tube designs, we performed a similar study using a completely automated measurement system on four Cs standards made by two other manufacturers. Our results, similar to those of De Marchi, showed that there are similar optimum C-field settings in these standards; furthermore, they showed that it may be more important to tune the microwave cavity precisely to the center Cs resonance frequency (fo) than it is to set the C-field at an optimum value. The best procedure, of course, is to do both, i.e., tune the cavity to the Cs resonance frequency as well as set an optimum C-field. C-Field, Cesium frequency standards, Cavity tuning.