The gas flux distribution in the XHV chamber of the vacuum primary standard developed by PTB

摘要

The ultimate pressure in the XHV calibration chamber of the PTB primary standard CE3, whose operation is based on the continuous expansion of gas, has been reduced by the use of a relatively large orifice area. Thus, the gas density and flux distributions cannot be taken as uniform in the calibration chamber. To eliminate this drawback we examined the gas flux distribution by Direct Simulation using the Monte Carlo method. This paper describes the gas flux distribution over the chamber walls, which was simulated, recorded and related to the idealized conditions. This allows determining the gauge position correction factor K-gi for each of the gauge ports. Using these factors, it is possible to eliminate the systematic deviation of the gas flow parameters from those under the idealized Maxwellian conditions and to improve the uncertainty budget. (C) 2004 Elsevier Ltd. All rights reserved. [References: 9]