Experimental and Numerical Investigation on Electromagnetic Absorption and Diffraction by the Plasma-Covered Cavity

To produce a plasma layer (area of 1.3 m² and power of 1.8 kW) covering the inner surface of a metal cavity (diameter of 45 cm and length of 120 cm), a certain number of standard commercial fluorescent lamps were placed directly against one another. Electromagnetic (EM) scattering of a 1- to 3-GHz EM wave has been studied experimentally and theoretically for a metal cavity and a plasma-covered metal cavity. When the EM wave hits the cavity at the front aspect angle, a significant return loss of as large as 10 dB in the frequency of 1-2 GHz and trends to a peak of 20-30 dB near 1.25-1.5 GHz were observed. Using the finite-difference time-domain method, transient scattered fields of EM wave from cavities were achieved. The loss of the EM wave with covered plasma was proved to be a result of the absorption by the plasma, but not from the turning or bending of the wave entering the plasma.