Metamaterial Survivability in the High-Power Microwave Environment

Artificial materials offer several advantages to high-power microwave (HPM) source design, but most importantly, they offer the possibility of exploiting new forms of interaction previously unavailable for microwave source design, and can offer an approach to reduce the dimensions of standard HPM sources and components. However, this all hinges on the ability to identify suitable subwavelength, structures in a configuration that can withstand the harsh operating environment of an HPM device.
In this chapter, we investigate the ability of these artificial materials to survive in the harsh HPM environment and lay the framework for considering the application of these materials in HPM devices. Artificial materials, such as metamaterials (MTMs), are composites consisting of many subwavelength metallic/dielectric constructs that collectively, when averaged over many unit cells, act as a homogeneous material defined by effective (macroscopic) constitutive parameters. In this chapter, we use the original Walser definition for a MTM; a subclass of artificial materials that exhibit both a simultaneous negative permittivity (휖) and permeability (휇). The permittivity and permeability define how the electric and magnetic components of an electromagnetic (EM) wave interact with a material, including losses experience by the wave as it propagates and interacts in the material. These materials offer highly tailorable electric/magnetic responses defined by the subwavelength geometry rather than the atomic makeup of the material. The extreme environment inside a HPM device is an interesting place to consider placing any material, let alone a series of subwavelength geometries consisting of multiple elements, and possibly multiple materials. The risk of material outgassing in the vacuum environment places constraints on the materials that can be used, let alone the risks presented from a kV electron beam passing close to these structures that could lead to localized charging and breakdown. Then, of course, we have the issues surrounding the interaction of these geometries and the EM wave coupling to them, that can lead to localized heat and the associated difficulties of heat dissipation from these structures. To explore this, we consider the case where artificial materials are loaded into waveguides, using both simulations and experiments to investigate the effects on artificial material function.