Uncertainty Evaluation of the Caesium Fountain Primary Frequency Standard NIM6

TL;DR

This paper presents the development and comprehensive uncertainty evaluation of the NIM6 caesium fountain clock, demonstrating high stability and agreement with other primary standards through advanced techniques and meticulous analysis.

Contribution

The paper introduces a new caesium fountain clock NIM6 with innovative design features and a detailed uncertainty assessment, advancing precision timekeeping technology.

Findings

Achieved a short-term stability of 1.0x10^-13 τ^-1/2

Estimated an overall fractional type-B uncertainty of 2.3x10^-16

Demonstrated agreement with other Cs fountain standards within uncertainties

Abstract

A new caesium (Cs) fountain clock NIM6 has been developed at the National Institute of Metrology (NIM) in China, for which a comprehensive uncertainty evaluation is presented. A three-dimensional magneto-optical trap (3D MOT) loading optical molasses is employed to obtain more cold atoms rapidly and efficiently with a tunable, uniform density distribution. A heat pipe surrounding the flight tube maintains a consistent and stable temperature within the interrogation region. Additionally, a Ramsey cavity with four azimuthally distribution feeds is utilized to mitigate distributed cavity phase shifts. The Cs fountain clock NIM6 achieves a short-term stability of 1.0x10-13 {\tau}-1/2 at high atomic density, and a typical overall fractional type-B uncertainty is estimated to be 2.3x10-16. Comparisons of frequency between the Cs fountain NIM6 and other Cs fountain Primary Frequency Standards (PFSs) through Coordinated Universal Time (UTC) have demonstrated an agreement within the stated uncertainties.