Application of the Monte Carlo method to pressure calculation

The Monte Carlo method, which has been used for simulation of steady‐state molecular flow and estimation of static pressure in relation to vacuum science, is applied to a calculation of the time dependent pressure distribution in a vacuum system. The calculation follows the usual simulation process, but the locations of the test particles are recorded at various values of time. In this way the pressure distribution in a vacuum system can be obtained at any time from the beginning of gas desorption. The pressure propagation along a beam line and the steady‐state pressure distribution in a vacuum system with an orifice and a pump are presented as two examples.