Evaluation of Doppler Shifts to Improve the Accuracy of Primary Atomic Fountain Clocks

TL;DR

This paper demonstrates how measuring and modeling Doppler-induced frequency shifts in atomic fountain clocks can significantly reduce their primary uncertainty, enhancing clock precision.

Contribution

It provides the first quantitative evaluation of distributed cavity phase shifts using experimental verification and ab initio calculations, reducing uncertainty in primary atomic fountain clocks.

Findings

Agreement between measurements and calculations of frequency shifts

Uncertainty reduced to 8.4×10^-17

Potential for negligible cavity phase uncertainties in improved clocks

Abstract

We demonstrate agreement between measurements and ab initio calculations of the frequency shifts caused by distributed cavity phase variations in the microwave cavity of a primary atomic fountain clock. Experimental verification of the finite element models of the cavities gives the first quantitative evaluation of this leading uncertainty and allows it to be reduced to delta nu / nu = 8.4\times10^-17. Applying these experimental techniques to clocks with improved microwave cavities will yield negligible distributed cavity phase uncertainties, less than \pm1\times10^-17.