Tick tock goes the mercury trapped ion clock

JUL 30, 2021

Only 30 cubic centimeters in size, the physics package of the micro mercury trapped ion clock is one of the smallest, and the most precise and stable to date.

Anashe Bandari

DOI: 10.1063/10.0005840

Tick tock goes the mercury trapped ion clock internal name — Tick tock goes the mercury trapped ion clock lead image

Precise timekeeping is essential for a variety of modern technologies, such as in GPS satellites for navigation systems. These applications need a level of precision that requires the use of atomic clocks. Mercury ion-based clocks have the highest known microwave clock frequency with very low systematic errors, but are not yet ready for certain applications due to practical limitations. To help reduce the size and power consumption of mercury ion clocks while maintaining high stability, Hoang et al. developed a micro mercury trapped ion clock (M2TIC).

M2TIC demonstrated frequency stability capabilities of a few parts per 10¹⁴, an improvement of several orders of magnitude over chip-sized atomic clocks. In tests of its sensitivity against thermal effects, magnetic fields and acceleration, M2TIC also showed promising performance.

“To put in perspective, with one part per 10¹⁴ stability, you won’t lose one second in 1 million years, or 25 billionth of a second in a month,” said author Nan Yu.

At the core of the clock is its atomic physics package, which includes a passively pumped micro vacuum trap tube with a linear trap that can confine up to a few million ions, a low-power field emitter array electron source, a highly efficient mercury microplasma lamp, and various detection and shielding components.

The current clock’s primary limiting factor is its sensitivity to the number of ions, which can be significantly suppressed by longer ion storage times.

“We are continuing to mature the clock technology, and plan to develop a space version in the near future,” Yu said. “The small size and low power of the clock will make its use more ubiquitous in space.”

Source: “Integrated physics package of miro mercury trapped ion clock with 10⁻¹⁴-level frequency stability,” by Thai M. Hoang, Sang K. Chung, Thanh Le, John D. Prestage, Lin Yi, Robert L. Tjoelker, Sehyun Park, Sung-Jin Park, J. Gary Eden, Christopher E. Holland, and Nan Yu, Applied Physics Letters (2021). The article can be accessed at https://doi.org/10.1063/5.0049734 .