Miniaturized Mercury Ion Clock for Ultra-Stable Deep Space Applications

John D. Prestage, Sang Chung, Lawrence Lim, Thanh Le

Abstract:	We have recently completed a prototype ion-clock physics package based on Hg ions shuttled between a quadrupole and a 16-pole rf trap. With this architecture, we have demonstrated short-term stability ~2-3x10-13 at 1 second, averaging to 10-15 at 1 day. This development shows that H-maser quality stabilities can be produced in a small clock package, comparable in size to an ultra-stable quartz oscillator required for holding 1-2x 10-13 at 1 second. This performance was obtained in a sealed vacuum configuration, where only a getter pump was used to maintain vacuum. The vacuum tube containing the traps has now been under sealed vacuum conditions for nearly 1.5 years with no measurable degradation of ion trapping lifetimes or clock short-term performance. Because the tube is sealed, the Hg source and Neon buffer gas are held indefinitely, for the life of the tube. There is no consumption of Hg in this system, unlike in a Cs beam tube where the lifetime is often limited by Cs depletion. This approach to the vacuum follows the methods used in flight vacuum tube electronics, such as flight TWTA’s where tube operation lifetime and shelf life of up to 15 years is achieved. We use neon as a buffer gas with 2-3 times less pressure induced frequency pulling than traditional helium and, being heavier, negligible diffusion losses will occur over the operation lifetime.
Published in:	Proceedings of the 38th Annual Precise Time and Time Interval Systems and Applications Meeting December 7 - 9, 2006 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	95 - 104
Cite this article:	Prestage, John D., Chung, Sang, Lim, Lawrence, Le, Thanh, "Miniaturized Mercury Ion Clock for Ultra-Stable Deep Space Applications," Proceedings of the 38th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 2006, pp. 95-104.
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