Geant4 Applications for Modeling Molecular Transport in Complex Vacuum Geometries

TL;DR

This paper demonstrates the novel application of the Geant4 toolkit, originally for particle physics, to simulate molecular transport in complex vacuum geometries, enabling better contamination control in sensitive optical systems.

Contribution

It introduces a new methodology for using Geant4 to model molecular vacuum transport in complex geometries, expanding its application beyond particle physics.

Findings

Validated the approach with simple vacuum geometries against analytical and Monte Carlo methods.

Successfully modeled contaminant transport in the LSST camera cryostat geometry.

Showed potential for improved contamination management in optical systems.

Abstract

We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment, in the molecular flow regime. The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elementary particles within complex detector systems. Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical. The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation. We discuss the use of an application with a very complicated geometry, that of the Large Synoptic Survey Telescope camera cryostat, to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.