Determination of the Boltzmann constant with an acoustic quasi-spherical resonator filled with argon

Arnaud Guillou , Laurent Pitre , Fernando Sparasci , Daniel Truong , Lara Risegari , Marc Himbert

There is an important interest in the international metrology community for new accurate determinations of the Boltzmann constant k_B, in order to redefine the unit of thermodynamic temperature, the kelvin. The value of the Boltzmann constant is linked to the speed of sound c in a noble gas. The method described here consists in measuring c inside a quasi-spherical acoustic resonator of inner volume of 0.5 l filled with argon, during an isotherm process at the temperature of the triple point of water (273.16 K) from 0.05 MPa to 0.7 MPa. The determination of k_B at LNE-LCM CNAM with this technique allowed us to obtain the value k_B = 1.380 647 74 (171) \cdot 10^-23 J \cdot K^-1, i.e. with a relative uncertainty of 1.24 \cdot 10^-6. In this paper, we particularly focus on the parameters of the experiment which have an effect on the measurement of c with this method (like gas purity, static pressure, etc) and how they were carefully controlled to get the lowest uncertainty on k_B up to now.

Mots clés: speed of sound; argon; quasi-spherical resonator; Boltzmann constant

Domaines: Acoustique [physics.class-ph]

Arnaud Guillou, Laurent Pitre, Fernando Sparasci, Daniel Truong, Lara Risegari, et al.. Determination of the Boltzmann constant with an acoustic quasi-spherical resonator filled with argon. Acoustics 2012, Apr 2012, Nantes, France. ⟨hal-00811238⟩