Session P2b: Present and Future Space Clocks for Space Applications

Preliminary Investigation of a Life-Limiting Mechanism in RF-Discharge Lamps for Hg+ Atomic Clocks
Kaitlin Harpenau, Arielle Little, Charles Klimcak, and James Camparo, The Aerospace Corporation
Location: Seaview A/B
Date/Time: Wednesday, Jan. 29, 11:26 a.m.

The mercury-ion (Hg+) atomic clock is a viable candidate for PNT applications that require long autonomy periods between ground station synchronizations (i.e., deep space, submarine, or in a cislunar PNT architecture). The Deep Space Atomic Clock (DSAC) flight demo elevated the TRL to 7, showing real promise for this technology as a future flight clock. The UV light source for the clock, an RF-discharge lamp containing a small amount of Hg, is an identified pain point in technology transfer and scalability. Hg contained within the lamp may be consumed by the glass bulb during normal lamp operation, resulting in failure of the lamp, and, consequently, the clock, due to a decrease in the 194 nm emission line intensity that drives the clock signal. Hg consumption can occur via diffusion into the glass or by chemical reactions with contaminants evolved from the glass during lamp operation. To study lamp failure modes, we procured several lamps with suprasil envelopes and varying Hg fill. The lamps were operated in a custom RF-driver for a period of several months. DSC and UV spectroscopy were performed throughout the test period to determine degradation of the lamp. Here we present the preliminary results of this lifetime test study of Hg discharge lamps to determine light source-related limitations to the lifetime of the Hg+ atomic clocks, valuable information for technology transfer to potential clock manufacturers.