Mass measurement of 1 kg silicon spheres to establish a density standard

Abstract

Air buoyancy causes a significant systematic effect in precision mass determination of 1 kg silicon spheres. In order to correct this effect accurately, mass measurement of the silicon sphere was conducted using buoyancy artefacts; additionally, in order to stabilize atmospheric conditions, we used a vacuum chamber in which a mass comparator had been installed. The silicon sphere was also weighed in vacuum to verify the air buoyancy correction. Mass differences measured in air and in vacuum showed good agreement with each other in spite of the desorption effect from weight surfaces. Furthermore, the result of weighing under vacuum conditions demonstrated better repeatability than that obtained in air.

Improved measurement results for the Avogadro constant using a28Si-enriched crystal

“…The BIPM results confirmed those obtained by NMIJ/AIST (Japan) which had measured the adsorption isotherms on SiO 2 /Si(100) plane surfaces [43]. NMIJ conducted mass measurements using an early version of the Mettler-Toledo M_one mass comparator [55]. The measurements under vacuum showed a higher reproducibility than those in air, where air buoyancy and convection effects affected the weighing stability.…”

Electron Paramagnetic Resonance Study on 28Si Single Crystal for the Future Realization of the Kilogram

“…The dimensions of the sample were designed by taking into account the internal dimensions of the microwave cavity resonator and the distribution of the microwave field B 1 in the microwave cavity resonator. The volume of the sample at 20°C was determined to be V s = 0.065 029(5) cm 3 from the crystal density [16] and the mass measured using a vacuum mass comparator [19]. Fig.…”

Experimental testing of a prototype cantilevered liquid-nitrogen-cooled silicon mirror

“…We calculated the areas A r and A c and volume from the mirror CAD-models; uncertainty in these values is related to the manufacturing tolerances of the actual parts. For the material properties of silicon, we assumed a density of 2330 kg m À3 (Peuto et al, 1993;Mizushima et al, 2004), a specific heat capacity of 707 J kg À1 K À1 (Touloukian & Buyco, 1971) and a temperature-dependent emissivity (Constancio Jr et al, 2020).…”