Toward an international practical pressure scale: A proposal for an IPPS ruby gauge (IPPS-Ruby2020)

ABSTRACT

At the 26^th AIRAPT conference in 2017, a task group was formed to work on an International Practical Pressure Scale (IPPS). This report summarizes the activities of the task group toward an IPPS ruby gauge. We have selected three different approaches to establishing the relation between pressure (P) and ruby R1-line shift (Δλ) with three groups of optimal reference materials for applying these approaches. Using a polynomial form of the second order, the recommended ruby gauge (referred as Ruby2020) is expressed by: $P\left[GPa\right]=1.87\left(\pm 0.01\right)\times {10}^3\left({\displaystyle \frac{\mathrm{\Delta }\lambda }{{\lambda }_0}}\right)\left[1+5.63\left(\pm 0.03\right)\left({\displaystyle \frac{\mathrm{\Delta }\lambda }{{\lambda }_0}}\right)\right]$, where λ₀ is the wavelength of the R1-line near 694.25 nm at ambient condition. In June of 2020, the Executive Committee of AIRAPT endorsed the proposed Ruby2020. We encourage high-pressure practitioners to utilize Ruby2020 within its applicable pressure range (up to 150 GPa), so that pressure data can be directly compared across laboratories and amended consistently as better scales emerge in the future.

KEYWORDS:

• International practical pressure scale
• ruby gauge
• equations of state

Acknowledgment

We thank the AIRAPT Executive Committee for the support of the IPPS task force activities. We thank Dr. Karl Syassen for his contribution to the establishment of Ruby2020. We also thank Drs. Steven Jacobsen and Thomas Duffy for useful discussions. GS acknowledges the support of HPCAT operations by Department of Energy (DOE)-NNSA's Office of Experimental Sciences. YW acknowledges the support of GeoSoilEnviroCARS, which is supported by the National Science Foundation – Earth Sciences (EAR – 1634415) and DOE-GeoSciences (DE-FG02-94ER14466).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Science Foundation: [Grant Number EAR –1634415]; Department of Energy - Department of Energy (DOE)-NNSA’s Office of Experimental Sciences; Department of Energy, Geosciences: [Grant Number DE-FG02-94ER14466].