Lifetime-Study Results of Mercury RFDischarge Lamps for Ion Atomic Clocks

Romas Jatulis, Kaitlin Harpenau, Arielle Little, Charles Klimcak, In-Tae Bae, Bernardo Jaduszwiler, James Camparo, Daniele Monahan

Abstract:	The mercury-ion (Hg+ ) atomic clock is a promising candidate for next-generation PNT applications where long-term periods of autonomy are required. Here, we present updated results on our long-term study of the UV light source for the clock: the rf-discharge lamp. The Hg+ atomic clock was successfully demonstrated in space by NASA JPL’s Deep Space Atomic Clock mission, increasing its potential for space-system timekeeping. While there are no documented lamp failures in flight-quality Hg+ clocks, the lamp has nonetheless been identified as a potential life-limiting component for the clock. In particular, similar to a lamp-failure mechanism in Rb rf-discharge lamps employed in GPS atomic clocks, the mercury fill of the lamp could be completely consumed after an extended period of operation. In the work discussed here, mercury lamp bulbs were acquired from a commercial atomic clock manufacturer and operated in our lab in custom-built rf drivers. Lamp envelopes were fabricated from Corning Suprasil-310 UV-transparent glass, and these were filled with natural abundance elemental mercury. A wide range of initial mercury mass fills from 0.1 mg to 1.4 mg were used in this study. Throughout the lamps’ operation, the bulb health was monitored via detection of the emission intensity of the relevant clock wavelength, 194 nm, in comparison to the strong neutral mercury emission line at 254 nm. At periodic intervals throughout operation, each bulb was turned off and the Hg mass in the bulb was non-destructively measured using Differential Scanning Calorimetry (DSC) In this report we discuss both mass consumption and mercury oxide formation as potential lamp failure mechanisms for Hg+ atomic clocks.
Published in:	Proceedings of the 57th Annual Precise Time and Time Interval Systems and Applications Meeting January 26 - 29, 2026 Hyatt Regency Orange County Anaheim, California
Pages:	1 - 11
Cite this article:	Jatulis, Romas, Harpenau, Kaitlin, Little, Arielle, Klimcak, Charles, Bae, In-Tae, Jaduszwiler, Bernardo, Camparo, James, Monahan, Daniele, "Lifetime-Study Results of Mercury RFDischarge Lamps for Ion Atomic Clocks," Proceedings of the 57th Annual Precise Time and Time Interval Systems and Applications Meeting, Anaheim, California, January 2026, pp. 1-11. https://doi.org/10.33012/2026.20482
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In