Investigations of Vapor-Cell Clock Equilibration Following Initial Activation: a Progress Report

S. Herbulock, C. Klimcak, A. Presser, J. Milne, J. Camparo

Abstract:	Over the past several years, anecdotal evidence has grown indicating that Rb gas-cell frequency standards exhibit a long “equilibration” period of somewhere between 30 and 70 days following their initial activation. The mechanism driving this behavior is not well understood and has been the subject of debate. Generally, lamp intensity has also been observed to undergo a slow variation following the clock’s turn-on, and since the clock’s resonant frequency depends on light intensity via the light-shift effect, there has been speculation regarding the light-shift as a possible mechanism for long-term equilibration. However, helium permeation has also been suggested as a contributing mechanism, since the gas cells are manufactured free of He and over time atmospheric He must permeate into the cells changing the clock frequency via the pressure-shift effect. In order to characterize the nature and discern the mechanism of equilibration in Rb clocks, we have initiated a project to study the long-term (i.e., > 100 days) deterministic variations of Rb clocks from different manufacturers. Though our preliminary data confirms the anecdotal findings, the data at present are ambiguous regarding a causal relationship between long-term lamp-intensity change and clock-frequency change.
Published in:	Proceedings of the 35th Annual Precise Time and Time Interval Systems and Applications Meeting December 2 - 4, 2003 Hilton Resort on Mission Bay San Diego, California
Pages:	435 - 443
Cite this article:	Herbulock, S., Klimcak, C., Presser, A., Milne, J., Camparo, J., "Investigations of Vapor-Cell Clock Equilibration Following Initial Activation: a Progress Report," Proceedings of the 35th Annual Precise Time and Time Interval Systems and Applications Meeting, San Diego, California, December 2003, pp. 435-443.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In