Study on Helium Permeation in Rubidium Clock’s Vapor Cell

doi:10.11938/cjmr20243093

Abstract

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

CLC Number:

O455+.1

ZUO Yulong, LI Dou, XU Junqiu, ZHU Weihang, WANG Pengfei, MING Gang, WANG Fang, WANG Chen, KANG Songbai, ZHAO Feng, MEI Ganghua. Study on Helium Permeation in Rubidium Clock’s Vapor Cell[J]. Chinese Journal of Magnetic Resonance, 2024, 41(4): 469-475.

Figures/Tables 5

Fig. 1

Fig. 2

Table 1

The size of the glass cell, helium pressure, frequency drift fitting results and calculated helium permeability

编号	外径/mm	高度/mm	厚度/mm	氦气压强/Torr	$k f$ /(Hz/s)^*	K/(m²/(Pa•s))@60 ℃
Prex1	13.84±0.10	15.60±0.20	1±0.10	785±1	0.00549±9.3E-8	1.982E-19±2.0E-20
Prex2	14.10±0.10	15.70±0.20	1±0.10	780±1	0.00542±1.1E-7	2.003E-19±2.1E-20
Prex3	13.84±0.10	16.46±0.20	1±0.10	782±3	0.00536±3.8E-7	1.978E-19±2.0E-20
Prex4	13.90±0.10	15.70±0.20	1±0.10	787±1	0.00571±4.6E-8	2.068E-19±2.1E-20
A^**[7]						5.0E-19
B^**[8]						2.5E-19
C^**[9]						4.6E-19
ASG cell01	20.02±0.10	17.04±0.20	1±0.10	786±2	1.21E-5	≤6E-22
ASG cell02	19.92±0.10	16.98±0.20	1±0.10	784±1	5.23E-6	≤3E-22

Table 1

Fig. 3

Fig.4

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