G121 シリコン球体を用いた気体密度計測による気体定数の決定

Abstract

Within a few years, definintion of thermodynamic temperature T may be replaced by a definition, E = kT, using the Boltzmann constant, k, or the universal gas constant, R(= kN_A), where N_A is the Avogadro constant. A gaseous speed-of-sound measurement (AGT, acoustic gas thermometry) reported by Moldover et al. in 1988 is the most promising approach to determine R within a relative uncertainty beging 1.8 ppm. Other experimental approaches such by a dielectric constant or refractive index, uncertainties are still several times larger than AGT. Gas density thermometry (GDT) is also a possible experimental approach, due to an improving measurement performance realized by a silicon single-crystal sphere as a solid density standard. In this paper, feasibility of the GDT using a silicon single-crystal was examined and concluded that it is possible to determine the universal gas constant with a relative uncertainty of 3.5 ppm by pressures, densities, temperatures and molar mass of argon.