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Transient heating in fixed length optical cavities for use as temperature and pressure standards



Jacob Edmond Ricker, Kevin O. Douglass, Jay H. Hendricks, Jack Stone, Sergei Syssoev, Sefer Avdiaj


Optical refractometry techniques can enable realization of both pressure and temperature directly from properties of the gas. For achieving the highest possible accuracy, temperature uniformity across the refractometer must be less than 1 mK. However, the gas dynamics of pressurization cause a temperature increase which effects the uniformity and impedes the ability to make accurate gas temperature measurements. Comparing computer modelling to physical measurements allows us to predict thermal behavior and determine uncertainty of the technique. The measurements and computer modelling show that temperature of the glass elements of the refractometer and copper chamber are equivalent after 3800 s (when going from 1 kPa to 100 kPa) and therefore measurements of the copper chamber provide accurate measurements of the gas temperature to within an uncertainty of 0.5 mK. Here the NIST refractometer is evaluated for operation as temperature standard with direct traceability to the SI.


Optical Thermometer, Pressure, FLOC, Refractive index, Thermal Modeling, Standard


Ricker, J. , Douglass, K. , Hendricks, J. , Stone, J. , Syssoev, S. and Avdiaj, S. (2021), Transient heating in fixed length optical cavities for use as temperature and pressure standards, Metrologia, [online],, (Accessed June 22, 2024)


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Created February 25, 2021, Updated April 21, 2021