Dielectric-constant gas thermometer

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As a special version of the gas thermometer, the dielectric constant gas thermometer (DCGT) exploits the fact that the permittivity (dielectric constant) ε of an ideal gas of low number density N/V or low pressure p is given by ε = ε0 + α0N/V (α0 being the static dipole polarisability of a single gas atom). The equation of state thus can also be written in the form

p = kT(ε - ε0)/α0

and, analogous to the gas thermometer,

T/TTPW = (p/pTPW)(εTPW0)/(ε-ε0)

is obtained. The DCGT serves to determine ε-ε0 by measuring the capacitance variation of a suitable gas-filled capacitor when the gas is pumped off.

References

  1. D Gugan, G W Michel, Metrologia 16, 1980, pp 149-167
  2. H Luther, K Grohmann, B Fellmuth, Metrologia 33, 1996, pp 341-352
  3. B Fellmuth, J Fischer, C Gaiser, N Haft, Dielectric-constant gas thermometry and determination of the Boltzmann constant, Proceedings of TEMPMEKO 2004, to appear
  4. E F May, L Pitre, J B Mehl, M R Moldover, J W Schmidt, Quasi-spherical cavity resonators for metrology based on the relative dielectric permittivity of gases, submitted to Rev Sci Instrum
  5. W Cencek, K Szalewicz, B Jeziorski, Breit-Pauli and direct perturbation theory calculations of relativistic helium polarizability, Phys Rev Lett 86 (25), 2001, pp 5675-5678
  6. G Lach, B Jeziorski, K Szalewicz, Radiative corrections to the polarizability of helium, to be published


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