Pressure profile calculation using finite element analysis that exploits the continuity of gas flow

Abstract

We present a numerical method of calculating the pressure profile of a large ultra-high vacuum (UHV) system using finite-element analysis (FEA) that exploits the continuity of gas flow. In this study, we introduce a modified FEA (MFEA) that excludes the redundant count of aperture conductance of the element by the Oatley method and uses a correction factor compensating the beaming effect. Along with the correction and by choosing an appropriate length of the element, we improve the result for a cylindrical tube to show a small difference of 5% or less from that of the test particle Monte Carlo (TPMC) simulation. As an example of a practical application, we calculate the pressure profile of an accelerator vacuum system with a split chamber using the MFEA, and the result is validated by comparison with the TPMC. The MFEA method will be useful to design a large UHV system at an early stage that requires design iteration using a simple and fast calculation procedure.