Realization of Quantum Pascal Using Natural Fundamental Physical Constants
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Realization of Quantum Pascal Using Natural Fundamental Physical Constants V. N. Thakur1,2, S. Yadav1,2 and A. Kumar1,2* 1
CSIR-National Physical Laboratory, Dr. K. S. Krishnan Marg, New Delhi 110012, India 2
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India Received: 16 September 2020 / Accepted: 02 November 2020 Ó Metrology Society of India 2020
Abstract: The acceptance of the redefinition of SI units on 20 May 2019, based on fundamental physical constants of nature led to significant changes in the field of metrology. The National Institute of Standards and Technology (NIST), USA has developed a quantum pressure standard, i.e. optical interferometer manometer (OIM), which is based on the change in the refractive index/polarizability/density of gas molecule that measures the pressure by calculating the change in fractional frequencies of monochromatic laser light passing through the medium compared to the vacuum. Theoretically, as per the ideal gas equation, pressure may be derived from fundamental physical constants either by Boltzmann’s constant or Avogadro number. The NIST, USA has developed fixed and variable-length optical cavity (FLOC and VLOC) OIM, which is based on the change in the resonance frequency of laser-molecule interaction depending on the pressure inside the cavity. Worldwide, most national metrology institutes (NMIs) have been working to realize the quantum Pascal based on the principle mentioned earlier; however, their design and configuration might differ. The national physical laboratory has also initiated the OIM project to realize the quantum Pascal in India. For that, we have reviewed the pressure standards based on the laser refractometer developed by NMIs. Keywords: Primary pressure standard; Optical interferometer manometer; SI Units based on fundamental constants; Refractive index 1. Introduction Redefinition of SI units has taken place on 20 May 2019, such as kilogram is redefined in terms of fundamental Planck’s constant, mol is redefined using Avogadro numbers, Kelvin based on Boltzmann constant (kB), Ampere in terms of electronic charge, etc. [1–3]. After redefining Kelvin and Mol, the gas laws can be defined in terms of universal fundamental constants for the realization of derived SI units. Last several years, various national metrology institutes (NMIs), such as the National Institute of Standards and Technology (NIST), USA, Physikalisch-Technische-Bundesanstalt (PTB), Germany, National Institute of Advanced Industrial Science and Technology (AIST), Japan, Industrial Technology Research Institute (ITRI) Taiwan, Korea Research Institute of Standards and Science (KRISS) Korea, etc. have been pursuing research to realize Pascal using
*Corresponding author, E-mail: [email protected]
optical interferometry by calculating the gas density; however, only a few NMIs have accomplished the quantum Pascal [4–22]. The gas laws are used to calculate the pressure by calculating gas density inside a high fineness enclosure. NIST, USA has alre
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