An Invar-based Fabry-Perot cavity refractometer equipped with an automated, miniaturized galliumfixed-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.
This project (QuantumPascal, 18SIB04) hasreceived funding from the EMPIR programme cofinanced by the Participating States and from theEuropean Union's Horizon 2020 research andinnovation programme. The authors alsoacknowledge support from the Swedish ResearchCouncil (VR) (Project No. 621-2015-04374); theUmeå University Industrial Doctoral School (IDS);the Vinnova Metrology Programme (Project Nos.2018-04570 and 2019-05029); and the KempeFoundations (Project No. 1823, U12).