A UME Kibble balance displacement measurement procedure

Abstract

<p>The redefinition of the kilogram in terms of Planck constant came into effect on 20 May 2019. The National Metrology Institute of Turkey (UME) realised the new definition by means of the oscillating magnet Kibble balance. The novel dynamical measurement procedure developed for Kibble balance in Turkey has the advantage of being less sensitive to environmental disturbances compared to the traditional Kibble balance experiments. Precise displacement measurements are performed either with Michelson or Fabry-Perot interferometers in worldwide Kibble balances. Moreover, most of them operate in a global vacuum. A commercial Michelson interferometer has been used in UME’s Kibble balance experiment. In this article, we determine the contribution of ultra-small oscillations to the Planck constant by taking simultaneous displacement measurements on two back-to-back mirrors attached to the piezoelectric transducer, undergoing an oscillatory motion with the Michelson and Fabry-Perot interferometers. The following novel measurement procedure makes such measurements possible in a regular laboratory environment. Otherwise, the experiment needs to be performed in a global vacuum. This is why we were required to investigate the resolution performances of these devices in laboratory conditions. As the expected relative uncertainty in the redefinition of kilogram is above the resolution uncertainties of both interferometers, we may conclude that a commercial Michelson interferometer will serve our purposes in our route to the redefinition of a kilogram by means of local vacuum.</p>

UME Kibble balance operating in air

“…As a result, an additional uncertainty may arise in the displacement measurements due to the temporal variations of the air refraction index. In [26] it has been shown that, these variations are negligibly small provided that the duration of the measurement is much larger than the fundamental period of the magnet assembly.…”