Calculation of Transmission Probability of Gas Molecule through Vacuum Pipe by Monte-Carlo Method

Abstract

  In this lecture, calculation of the transmission probability of gas molecule through the vacuum pipe by Monte-Carlo simulation is presented. The basic concepts, the computational method of the distribution of scattering angle that follows the cosine law from the homogeneous random distribution and the flow chart of program are shown. The results by Monte-Carlo simulation for the simple cylindrical pipes with various length/diameter (L/D) ratios are compared with those obtained by the approximation formulas and the analytical results. The effect of specular reflection rate in the scattering at the surface of pipe is also presented.