Improved model for multipactor in low pressure gas

The effect of electron-neutral collisions on the multipactor threshold in a low pressure gas is analyzed using a model that takes into account the friction force from the electron impacts with the neutrals, the thermalization of the electrons, as well as the contribution from impact ionization to the total number of electrons. It is found that the friction force is most important for first-order multipactor for materials with a low first cross-over energy and leads to an increased threshold. For higher-order modes with the same material, the thermalization effect dominates and results in a lowered threshold. The contribution to the total number of electrons from impact ionization for such materials is insignificant, but for materials with a high first cross-over energy this contribution dominates the behavior and a decreased threshold is obtained for all orders of multipactor.