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The molecular gas flow parameters were evaluated using cosine form of the scattering function of the molecules incident on the surface. This gas scattering model is commonly used for calculating the vacuum system parameters, but it is theoretically valid only if the vacuum system is in equilibrium. This also means that there is no flow in the system. We applied the Maxwell's model of gas scattering...
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 paper presents a new computer program for calculating a conductance with a high precision, based on the Monte-Carlo (MC) method. The high accuracy of the calculations has been obtained by using high-quality random number generators (RNG), specially selected for this purpose. This allows us to extend the application field of the MC simulations and to reduce the uncertainty of the results to below...
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...
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