A Low Temperature-Sensitive Ramsey Cavity for Rb Fountain Clocks

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A Low Temperature-Sensitive Ramsey Cavity for Rb Fountain Clocks

Zheng, Fasong / Fang, Fang / Wang, Xiumei / Chen, Weiliang / Liu, Kun / Dai, Shaoyang / Cao, Shiying / Zuo, Yani / Li, Tianchu

Abstract

A low temperature-sensitive microwave-vacuum integrated Ramsey cavity (MVIC) used for Rb fountain clocks is proposed to solve the problems that the clocks have a small operating-temperature range and are sensitive to the ambient temperature changes. This cavity mainly consists of a tube made of titanium (Ti) and two end caps made of oxygen-free copper (OFC), forming a cylindrical microwave resonator (CMwR) working at TE₀₁₁ mode. Utilizing the different thermal expansion of the tube and the end caps, the change of the cavity resonance frequency (ReF) to temperature can be self-compensated. To improve this cavity quality factor Q, the tube inner surface is coated by a thin copper film fist and then by a thin gold film on the top. There are two coupling holes (C-holes) face to face on the tube wall for microwave coupling. Each C-hole is vacuum-sealed with a ceramic window (CW) first. And then it is covered by a rectangular waveguide. Two microwaves are fed into the waveguides then coupled into the CMwR through the CWs, respectively. For the prepared MVIC for Rb fountain clocks, its Q-factor is measured to be 11500 and its ReF matches the Rb clock frequency within −49 kHz. And its ReF thermal-coefficient is measured to be −16.3 kHz/℃, which is 7.1 times lower than that of a commonly used OFC Ramsey cavity with the same sizes in the temperature range of 22.48 ℃–34.48 ℃. Additionally, this cavity ReF can be tuned about 130 kHz after performing a further bake-out for the fully assembling clock physical package.

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Document information

Title :

A Low Temperature-Sensitive Ramsey Cavity for Rb Fountain Clocks

Additional title:

Lect. Notes Electrical Eng.

Contributors:

Yang, Changfeng (editor) / Xie, Jun (editor) / Zheng, Fasong (author) / Fang, Fang (author) / Wang, Xiumei (author) / Chen, Weiliang (author) / Liu, Kun (author) / Dai, Shaoyang (author) / Cao, Shiying (author) / Zuo, Yani (author)

Published in:

China Satellite Navigation Conference (CSNC 2022) Proceedings ; Chapter : 35 ; 393-402

Lecture Notes in Electrical Engineering ; 910

Publication date :

2022-05-05

Size :

10 pages

ISBN :

978-981-19-2576-4 , 978-981-19-2575-7

ISSN :

1876-1119 , 1876-1100

DOI :