Abstract:

Vapor cell’s helium permeation is considered to be one of the reasons for the frequency drift of rubidium (Rb) clocks. In this study, we measured the helium permeability for both commonly used Pyrex Rb cell and newly developed anti-helium aluminosilicate Rb cell. Their helium permeabilities at operating temperatures (~60 ℃) are 2E-19 m²/(Pa•s) and ≤3E-22 m²/(Pa•s), respectively. The analysis shows that the Pyrex Rb cells causes clock drift from helium permeation to be about E-13/day in the first four years and E-14/day in the next six years, and the aluminosilicate Rb cell can suppress the drift from helium permeation to E-16/day. The results are instructive for improving Rb clock’s long-term frequency drift performance.

Key words: Rubidium atomic clock, Atomic vapor cells, Helium permeation, Atomic clock frequency drift