Plasma Mismatching with Microwave Transmission Characteristics for Diagnostic Purposes

Many remote diagnostic systems rely on the transmission and reflection of electromagnetic waves. In diagnostics facilities such as microwave reflectometers which operate in the cut-off frequency range, the collisionality of the plasma can affect the transmission and reflection characteristics of electromagnetic waves. In this paper, plasma mismatching and reflection properties of microwave propagation through partially ionized, uniform, and cold plasma were studied. Using the simplified Lorentz model of the plasma and associated dispersion relation of electromagnetic wave propagation through collisional, cold plasma, propagation characteristics of the electromagnetic waves were investigated in different collisional regimes of single-interface and double-interface, bounded plasma. It was found that in the cut-off frequency range, the propagation coefficients of the electromagnetic wave can be significantly affected depending on the collision frequency of the plasma. It was also found that in the double-interface case, the thickness of the plasma can cause multiple reflections in the plasma slab, and such reflections can be suppressed in the high-loss collisional regime.