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 3He and 4He, 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.