Rapid response optical RIGT, and relative determination of T - T_90 across (293

Published

October 18, 2024

Author(s)

Patrick Egan

Abstract

A refractive-index gas thermometer has been used to determine T − T90 in the temperature range (293 < T < 433) K within about 3 µK/K relative standard uncertainty. The thermometer is based on an optical resonator operating at 633 nm wavelength. The working principle first measured helium refractivity at known pressure and temperature to determine the temperature-dependent compressibility of the resonator. With accurate knowledge of compressibility, the resonator was then run with argon to determine T − T90 via T = 3*A_R/(2*R) * p/(n-1)⁠. The molar polarizability A_R = 4.195735(13) cm3/mol of argon was dependent on best-knowledge of thermodynamic temperature at the gallium melting-point; consequently, the implementation is relative primary thermometry, with one key-parameter value tied to T − T90 near 303 K. Notable aspects include a settling-time of 1500 s to reach 0.1 mK gradients, and statistical consistency of 0.5 µK/K in the multi-isotherm regression.

Proceedings Title

AIP Conference Proceedings 3230

Volume

3230

Conference Dates

April 3-7, 2023

Conference Location

Anaheim, CA, US

Conference Title

International Temperature Symposium 10. Temperature: Its Measurement and Control in Science and Industry, Vol 9

Pub Type

Conferences

Download Paper

https://doi.org/10.1063/5.0234184

Local Download

Keywords

thermodynamic thermometry, ITS-90 error, refractive-index gas metrology

Citation

Egan, P. (2024), Rapid response optical RIGT, and relative determination of T - T_90 across (293 < T < 433) K, AIP Conference Proceedings 3230, Anaheim, CA, US, [online], https://doi.org/10.1063/5.0234184, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936214 (Accessed October 31, 2024)