COMPUTATIONAL METHODS FOR ANALYZING ELECTRON MULTIPACTING IN RF STRUCTURES

Electron multipacting can cause loss of the the field level in resonat ors or it can break the high power rf components like couplers and win dows. This phenomenon starts if certain resonant conditions for electr on trajectories are fulfilled and if the impacted surface has a second ary yield larger than one. A general cure against multipacting is to a void the resonant conditions. Therefore, we investigated the dynamics of the electron trajectories in order to find rules for these resonanc es. We developed new computational methods which combine the standard trajectory calculations with advanced searching and analyzing methods for multipacting resonances. In numerical experiments we consider diff erent coaxial structures. We are able to find those rf incident power levels at which the multipacting occurs and, thereafter, to locate and identify different multipacting processes. We characterize multipacti ng behavior in straight and tapered lines, and for the straight coaxia l line we give simple scaling laws for the multipacting power bands wi th respect to the diameter, impedance and frequency. Furthermore, the present analysis method turns out to be a powerful tool for optimizing different methods to suppress multipacting. Here, in particular, the biasing DC voltage method is considered.