Determination of the Planck constant using a watt balance with a superconducting magnet system at the National Institute of Standards and Technology

Abstract

For the past two years, measurements have been performed with a watt balance at the National Institute of Standards and Technology (NIST) to determine the Planck constant. A detailed analysis of these measurements and their uncertainties has led to the value $h=6.62606979(30)\times 10^{-34}$Js. The relative standard uncertainty is $45\times 10^{-9}$. This result is $141\times 10^{-9}$ fractionally higher than $h_{90}$. Here $h_{90}$ is the conventional value of the Planck constant given by $h_{90}\equiv 4/(K_{\mathrm{J}-90}^2{R}_{\mathrm{K}-90})$, where $K_{\mathrm{J}-90}$ and $R_{\mathrm{K}-90}$ denote the conventional values of the Josephson and von Klitzing constants, respectively.

22 pages, 8 figures, published in metrologia

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