Vacuum Outgassing Study of Candidate Materials for Next Generation Pulsed Power and Accelerators: Improving the Boundary Conditions for Molecular Flow Simulations

Abstract

Next generation pulsed power (NGPP) machines and accelerators require a better understanding of the materials used within the vacuum vessels to achieve lower base pressures (P << 10−5 Torr) and reduce the overall contaminant inventory while incorporating various dielectric materials which tend to be unfavorable for ultra-high vacuum (UHV) applications. By improving the baseline vacuum, it may be possible to delay the onset of impedance collapse, reduce current loss on multi-mega Amp devices, or improve the lifetime of thermionic cathodes, etc [3]. In this study, we examine the vacuum outgassing rate of Rexolite® (cross-linked polystyrene) and Kel-F® (polychlorotrifluoroethylene) as candidate materials for vacuum insulators [1]. These values are then incorporated into boundary conditions for molecular flow simulations using COMSOL Multiphysics® and used to predict the performance of a prototypical pulsed power system designed for 10−8 Torr operations.