Gas flux distribution in a new PTB primary standard for very low pressures

The Physikalisch-Technische Bundesanstalt (PTB), Germany, has recently constructed a new primary standard of Iow pressures based on the continuous expansion method. The paper is concerned with the properties of the gas flow in one of the calibration chambers of this standard. To describe these properties it is essential to know, with the smallest possible uncertainty the local gas densities at points where the tested gauges are installed. The problem was handled by the Monte Carlo method. The gas flux density on the chamber walls and the correction factors for each gauge port were determined (the highest value of the factor was (-32.9š0.6)x10-4 (3 q)).