An invar-based fabry-perot cavity refractometer with a gallium fixed-point cell for assessment of pressure

I. Silander, C. Forssén, J. Zakrisson, M. Zelan, O. Axner


An Invar-based Fabry-Perot cavity refractometer equipped with an automated, miniaturized gallium fixed-point cell for assessment of pressure is presented. The use of an Invar cavity spacer has previously demonstrated pressure assessments with sub-0.1 ppm precision. The fixed-point cell, whose design and implementation are presented here, provides a reference for temperature assessment of the gas inside the cavity with an uncertainty of 4 ppm. This opens up for a self-contained system for realization of the Pascal with an accuracy in the low ppm range. This is an important step towards disseminating the Pascal through fundamental principles.

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