世界の時刻を守る新型原子泉時計「NIST-F4」公開（New Atomic Fountain Clock Joins Elite Group That Keeps the World on Time）

2025-04-28 米国国立標準技術研究所 (NIST)

＜関連情報＞

• https://www.nist.gov/news-events/news/2025/04/new-atomic-fountain-clock-joins-elite-group-keeps-world-time
• https://iopscience.iop.org/article/10.1088/1681-7575/adc7bd

一次周波数標準NIST-F4の精度評価 Accuracy evaluation of primary frequency standard NIST-F4

Vladislav Gerginov, Gregory W Hoth, Thomas P Heavner, Thomas E Parker, Kurt Gibble and Jeff A Sherman
Metrologia  Published: 15 April 2025
DOI:10.1088/1681-7575/adc7bd

Abstract

This work describes the apparatus for NIST-F4, an updated cesium atomic fountain at the National Institute of Standards and Technology (NIST), and presents an accuracy evaluation of the fountain as a primary frequency standard. The fountain uses optical molasses to laser cool a cloud of cesium atoms and launch it vertically in a fountain geometry. In high-density mode, the fractional frequency stability of NIST-F4 is σ_y(τ)=1.5×10⁻¹³/τ, where τ is the measurement time in seconds. The short-term stability is limited by quantum projection noise and by phase noise from the local oscillator, an oven-controlled crystal oscillator operating at 5 MHz. Systematic frequency shifts and their uncertainties have been evaluated, resulting in a systematic (type B) fractional frequency uncertainty σ_B=2.2×10⁻¹⁶.