Current realisations of the pascal rely on piston gauges (also known as pressure balances) and liquid manometers containing toxic mercury, both of which measure force per area. Their performance however has remained essentially unchanged over the past few decades and they suffer from practical and environmental limitations. This project aims to develop photon based standards, which determine the pressure via gas density using the gas law. Recent advances in optical, microwave, dielectric and spectroscopic measurement techniques have paved the way for the development of novel and improved means of assessing the number density and pressure of gases. Combined with quantum-based calculations of gas parameters such as the permittivity, and thus the refractivity, novel, powerful, and user-friendly methods can be envisioned, having the potential to become new primary standards of the pascal over the wide pressure range from 1 Pa to 3 MPa and beyond.
In the framework of the project, INRiM has developed a pioneering system for gas density/pressure measurements based on Rayleigh scattering (RAY), an optical pressure standard realized through a multi-reflection homodyne interferometer (UINT) and a pressure standard based on the determination of the refractivity of monatomic gases as a function of density, using a microwave cavity (RIGT technique). Furthermore, within a collaboration with LNE, a prototype of a superconducting microwave cavity is under development. In addition to the fundamental range related to atmospheric pressure, altogether, these methods are able to cover a wide pressure interval from vacuum up to 3 MPa.
Contributing scientific sectors
