Simulation of Multipactor Effect through the Individual Simulation of Electrons

In the context of the ESA Program AO 4025 Surface Treatment and Coating, we have developed a simulator called MEST for the prediction of the multipactor effect. The simulator has been developed using a micro level object-oriented approach, where each electron in the simulation is an independent object. This approach differs from other models described in the literature, which are macro level or intermediate, handling electrons in packages rather than individually. MEST works with a simplified model of a waveguide, where a radiofrequency potential is applied to the plates. The space between the plates is assumed to be a vacuum, except for the presence of a number of free electrons. The individual trajectories of all the electrons in the RF field are computed, although no space charge effects are assumed. When electrons collide with the plates, secondary emission of electrons is simulated. The secondary electron emission yield (SEY) is computed with a detailed Monte Carlo model, which has been validated using experimental data. It depends on the surface material (bulk), but also on surface finish properties, such as air contamination, cleanliness or surface treatments. If certain conditions hold, the number of electrons between the plates may increase out of control, until a multipactor discharge occurs and the waveguide becomes unusable. The object of the simulator is to predict the occurrence (or not) of this phenomenon for different surface materials. The simulator has been validated using experimental data from ESTEC (ESA), UAM and TESAT. Several materials have been tested. The results show good agreement with the experimental data.