Abstract

A self-comparison method with closely interleaved switching states is analyzed and used to evaluate some type-B uncertainties of an Rb87 atomic fountain clock. Free from additional frequency reference, the method can be applied to a running fountain to reach a precision beyond its uncertainty. A verification experiment proves an uncertainty of 9.2×10⁻¹⁶ at an averaging time of 242500 s. Further, the method is applied to measure light shift, and no visible relative frequency shift is found in the fountain within the uncertainty of 2.1×10⁻¹⁵. When applied to the evaluation of a cold collisional shift, the result gives a −2.2×10⁻¹⁵ shift with a 9.5×10⁻¹⁶ uncertainty.

© 2016 Chinese Laser Press

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