Lamp Reliability Studies for Improved Satellite Rubidium Frequency Standard

R.P. Frueholz, M. Wun-Fogle, H.U. Eckert, C.H. Volk, P.F. Jones

Abstract:	In response to the premature failure of Rb lamps used In Rb atomic clocks onboard Navstar GPS satellites The Aerospace Corporation has initiated experimental and theoretical investigations into their failure mechanism. The primary goal of these studies is the development of an accelerated life test for future GPS lamps. At this time the primary failure mechanism has been identified as consumption of the lamp's Rb charge via direct interaction between Rb and the lamp's glass surface. The most effective parameters to accelerate the interaction between the Rb and the glass are felt to be rf excitation power and lamp temperature. Differential scanning calorimetry is used to monitor the consumption of Rb within a lamp as a function of operation time. This technique has already yielded base line Rb consumption data for GPS lamps operating under normal conditions. In order to insure acceleration methods do not alter the mechanism of the Rb-glass interaction detailed surface studies yielding information about the mechanism of interaction are in progress. It has been found that penetration profiles of Rb into pyrex surfaces can be analyzed in terms of one-dimensional diffusion models. Diffusion coefficients may be extracted via these models. The Surface studies also indicate that Rb exists in at least two forms in Pyrex, a thin colored surface layer and the major colorless penetration component. Further experiments are in progress to extend these results to a wide variety of glasses.
Published in:	Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 3, 1981 Naval Research Laboratory Washington, DC
Pages:	767 - 790
Cite this article:	Frueholz, R.P., Wun-Fogle, M., Eckert, H.U., Volk, C.H., Jones, P.F., "Lamp Reliability Studies for Improved Satellite Rubidium Frequency Standard," Proceedings of the 13th Annual Precise Time and Time Interval Systems and Applications Meeting, Washington, DC, December 1981, pp. 767-790.
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