Dielectric-Constant Gas-Thermometry Scale from 2.5 K to 36 K Applying 3He, 4He, and Neon in Different Temperature Ranges

Abstract

New dielectric-constant gas-thermometry (DCGT) measurements were performed at PTB in the temperature range from 23 K to 36 K. For the first time, besides helium, neon was also used as a measuring gas. The measurements with helium and neon yielded thermodynamic temperature data in the range between 27 K and 36 K. A combination of these data, with former measurements in the range between 2.5 K and 26 K made using 3 He and 4 He, lead to a temperature scale which coincides with the ITS-90 within a few tenths of a millikelvin even at highest temperatures. The discussion of the uncertainty budget for neon follows the procedures already proved for helium. Furthermore, a comparison between new highly accurate ab initio calculations for the second and third density virial coefficients of helium, and the extended DCGT results are given. For the third virial coefficient of helium, the presented data allow the first experimental check of the new ab initio calculation for the range above 24 K.

Progress towards the determination of thermodynamic temperature with ultra-low uncertainty

“…Remarkably, the results obtained from all these combinations were found to be consistent with each other. Also, the overall uncertainty was reduced owing to significant improvements of the methods used to determine the compressibility of the capacitors as a function of temperature, leading to a correction of previous results in the temperature range between 2.5 K and 36 K [26]. -The AGT apparatus used at NPL is based on the resonator previously characterized for an extremely accurate determination of the Boltzmann constant k [46] with multiple modifications to the thermostatting system to cover the overall temperature range between 118 K and 303 K. The AGT was operated in relative mode, with measurements of the speed of sound in Ar recorded as a function of pressure along several (20) closely spaced isotherms, including T TPW .…”

“…Triggered by this advance, considerable progress has been made in the following areas, all required to facilitate accurate thermodynamic temperature measurement by the method: (i) pressure balances as primary pressure standards [24]; (ii) the instrumentation used for capacitance measurements [25]; and (iii) the characterization of the elastic properties of the materials used for the construction of the capacitors. Through these improvements, most of which have been made at the Physikalisch-Technische Bundesanstalt (PTB), increasingly accurate determinations of thermodynamic temperature in the low-temperature range have been made [26], and the most accurate, to date, determination of the Boltzmann constant at the triple point of water temperature T TPW by this method [27].…”

Thermophysical properties and collision-induced light scattering as a probe for gaseous helium interatomic potentials

“…The interatomic potentials we provide here are obtained through the analysis of the second and third pressure virial coefficients [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], second acoustic virial coefficients [34] and set of gaseous transport properties [31,32,.…”

“…viscosity (�), thermal conductivity (�), self diffusion coefficient (D) and isotopic thermal factors (S) at different temperatures of helium, obtained via the formulas of Hurly-Mehl [89,90], Bich et al [82] and Hurly-Moldover [30] and their comparison to the accurate experimental results [31,32,. Determination of these properties of a quantum gas requires two major computational steps.…”

Naturkonstanten als solide Basis. Neudefinition der Einheit Kelvin

“…Die Abschätzung aller Faktoren lässt eine mit der akustischen Gasthermometrie vergleichbare Gesamtunsicherheit von etwa 2 · 10 -6 erwarten. Dies wird durch die Ergebnisse gestützt, die vor kurzem bei Messungen im Tieftemperaturbereich von 2,5 K bis 36 K erzielt wurden[7].…”