Multipactor Discharge Mitigation in High Power Microwave, HPM, Systems

A multipactor discharge is an electron avalanche supported by secondary electron emission that can couple the HPM field energy to a waveguide dielectric window. The energy deposition can lead to the destruction of the dielectric material and catastrophic window failure. Mitigation approaches for this single surface multipactor at dielectric windows are investigated using Particle-In-Cell simulations. Initially baseline susceptibility diagrams are constructed analytically and compared with self-consistent, dynamic system trajectories. Geometric mitigation is then considered by varying the window orientation with respect to the HPM electric field. Small angular deviations, less than 20 degrees, from the nominal case of the electric field parallel to the surface show dramatic changes in the susceptibility diagram. A materials approach to mitigation is then considered. Titanium Nitride, TiN, coatings applied to the dielectric surface can substantially reduce the secondary emission yield. Representative TiN modifications of the virgin secondary emission yield are simulated and the resulting susceptibility diagrams are discussed.