Evaluation of the blackbody radiation shift of an Yb optical lattice clock at KRISS

TL;DR

This paper evaluates the blackbody radiation shift in an Yb optical lattice clock at KRISS, achieving precise temperature measurement and uncertainty estimation to improve clock accuracy below 10^{-17}.

Contribution

The study introduces an in-vacuum BBR shield and radiation thermometry to accurately measure the BBR shift in an Yb optical lattice clock.

Findings

Measured temperature at the atom trap site with 13 mK uncertainty

Determined BBR shift uncertainty of 9.5×10^{-19}

Achieved fractional frequency uncertainty of 4.2×10^{-19}

Abstract

As optical clocks are improved to reach the frequency uncertainty below the 10$^{-17}$ level, the frequency shift due to the blackbody radiation (BBR) has been one of the major systematic effects hindering further improvement. To evaluate the BBR shift of an Yb optical lattice clock at KRISS, we installed an in-vacuum BBR shield and made radiation thermometry using a black-coated-sphere thermal probe. After we quantitatively measured the conduction loss of the thermal probe and the effects of all the external radiation sources, we determined the temperature at the atom trap site with an uncertainty of 13 mK, which corresponds to an uncertainty of 0.22 mHz in the clock frequency (a fractional frequency of $4.2\times10^{-19}$). The total uncertainty of the BBR shift including the atomic response is $9.5\times10^{-19}$.