COMPUTATIONAL OPTIMIZATION OF DIFFUSION PUMP PARAMETERS

The pumping process in a diffusion pump includes the capture of pumped gas molecules on the boundary of a working fluid vapour jet and their transport to the backing line. This process is considered, based on computational modelling of the trajectories of separate pumped gas molecules in the vapour flow field, that is equivalent to the solution of linear Boltzmann equation by the Monte-Carlo method. The distribution of the vapour flow parameters is computed by the continuum approximation. The model allows prediction of the pumping characteristics of the real diffusion pumps as well as optimization of their design.