Measurement of the Planck constant at the National Institute of Standards and Technology from 2015 to 2017

Abstract

Researchers at the National Institute of Standards and Technology(NIST) have measured the value of the Planck constant to be h = 6.626 069 934(89) × 10 −34 J s (relative standard uncertainty 13 × 10 −9 ). The result is based on over 10 000 weighings of masses with nominal values ranging from 0.5 kg to 2 kg with the Kibble balance NIST-4. The uncertainty has been reduced by more than twofold relative to a previous determination because of three factors: (1) a much larger data set than previously available, allowing a more realistic, and smaller, Type A evaluation; (2) a more comprehensive measurement of the back action of the weighing current on the magnet by weighing masses up to 2 kg, decreasing the uncertainty associated with magnet nonlinearity; (3) a rigorous investigation of the dependence of the geometric factor on the coil velocity reducing the uncertainty assigned to time-dependent leakage of current in the coil.

The ampere and the electrical units in the quantum era

“…Adoption of the theoretical relationships K J = 2e/h and R K = h/e 2 in the SI provides a direct link between mass and Planck constant according to m = h A 4gv , where A is a quantity involving Josephson frequencies, number of Josephson junctions and Hall plateau index. After participating in h determinations [99], it is now a question of using Kibble's balances, notably those having participated in the 49 determination of h from NIST [263], NRC [264] and LNE ( fig.29b) [265], to calibrate mass standards with a 10 −8 relative uncertainty from the Planck constant value[98] h = 6.62607015 × 10 −34 J.s. This extension of the application of solid-state quantum effects beyond electrical metrology is to benefit from the user-friendly graphene-based quantum resistance standard and cryogen-free cooling techniques.…”

Single‐Electron Pumps and Quantum Current Metrology in the Revised SI

“…This progress was enabled by recent advances in the watt balance (aka Kibble balance; see refs. [] and references herein) and silicon‐sphere (aka XRCD or Avogadro; see refs. [] and references herein) experiments, which helped to remove inconsistencies that had been revealed in the intermediate CODATA adjustments from 2010 .…”

The Planck Constant for the Definition and Realization of the Kilogram

“…The Planck and Avogadro results of this adjustment are shown in Figure . These results include four Avogadro results (IAC‐11, IAC‐15, IAC‐17, and NMIJ‐17) shown in red and four Kibble balance results (NIST‐15, NRC‐17, NIST‐17, and LNE‐17) shown in blue, all with their stated standard uncertainties . The four Kibble balance results come from four distinct balances, each of different design.…”