Atomic trajectory characterization in a fountain clock based on the spectrum of a hyperfine transition

TL;DR

This paper introduces a novel spectroscopic method to precisely determine the atomic cloud's position in a fountain clock, aiding in reducing systematic uncertainties from cavity phase gradients.

Contribution

A new spectroscopic technique utilizing hyperfine transition asymmetry to accurately locate atomic clouds in fountain clocks.

Findings

Achieved positional accuracy of about 0.1 mm.

Demonstrated the method's effectiveness through experimental validation.

Provided a means to limit systematic uncertainties in frequency measurements.

Abstract

We describe a new method to determine the position of the atomic cloud during its interaction with the microwave field in the cavity of a fountain clock. The positional information is extracted from the spectrum of the F=3,mF=0 to F=4,mF=-1 hyperfine transition, which shows a position dependent asymmetry when the magnetic C-field is tilted by a few degrees with respect to the cavity axis. Analysis of this spectral asymmetry provides the horizontal center-of-mass position for the ensemble of atoms contributing to frequency measurements. With an uncertainty on the order of 0.1 mm, the obtained information is useful for putting limits on the systematic uncertainty due to distributed cavity phase gradients. The validity of the new method is demonstrated through experimental evidence.