A Compact, High-Performance Mercury Ion Clock Prototype

NASA’s Deep Space Atomic Clock mission demonstrated the potential of mercury ion clock technology for ground and space applications requiring both high stability and low drift, achieving a stability of 1.5x10^-13/sqrt(tau) and drift below 5x10^-16/day [1].  Building upon this success, a follow-on technology maturation effort has reduced the size, weight, and power of the flight design so that future iterations can be packaged within a 3U footprint (comparable to clocks currently used for GPS) without degrading the stability performance.  These mercury ion clocks have intrinsically low environmental sensitivities along with a high microwave clock transition frequency (40.5 GHz) that enables Q’s from the mid-10¹¹ to low-10¹² range.  Exhibiting coherence times in the tens of seconds, this mercury ion trap could be paired with a photonic local oscillator to create a system capable of e-15 stability at all timescales.  An initial prototype clock using a quartz ultra-stable oscillator has been completed, allowing for the first system-level tests of this updated clock design.  The short- and long-term stability performance results will be reported, along with environmental sensitivities.  

[1] Burt et al., Nature 595, 43 (2021)