The goal of this project is to demonstrate thin film deposited Frequency Selective Surfaces (FSS) on High Power Microwave (HPM) radomes for impedance matching that have low in-band reflection and substantial out-of-band rejection to improve RF transmission. The FSS structures will be applied to radome materials that have ultra-low outgassing properties and are capable of forming vacuum seals. Innovative multilayer dome materials will be used in conjunction with the FSS surfaces to optimize the RF transmission and dome performance. Focusing of the RF beam using the FSS structures will also be explored. Radome, high power microwaves, rf radiation, frequency selective surfaces, Ultra low outgassing, focusing.