ANALYSIS OF THE OUTGASSING IN AN OPTICAL PRESSURE STANDARD

Yuanchao Yang, Kun Ma, Tom Rubin, Xiaojuan Feng, Bowen Wang

Abstract

Outgassing effects in a Fabry-Perot cavity based optical pressure standard (OPS) developed at NIM were studied at low pressures using a pressure rising method. The pressure rising curves were recorded by the OPS and a calibrated pressure transducer simultaneously. The pressure values assessed by the OPS were dependent on the gas refractivity parameters and deviated from the transducer values. From the difference, the effective molar polarizability of the accumulated gases was deduced and found to be close to the parameter of water vapour and increased with time. It supported that the accumulated gas in the OPS was composed of water vapor from outgassing and a small amount of air from leakage. To lower the outgassing effects, an external large vacuum chamber was attached to the OPS manifold. Finally, the pressure increase rate was reduced to ~ 50 mPa/h for a period of ~ 140 h, and ~ 27 mPa/h for the first 20 h.

Keywords

optical pressure standard; outgassing; refractometry; molar polarizability

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IMEKO-TC16-2022-150.pdf

DOI

10.21014/tc16-2022.150

IMEKO TC

TC16 - Pressure and Vacuum Measurement

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