Electromagnetic-wave Absorption And Scattering By A Plasma-filled Enclosure

Unmagnetized, collisional plasmas can be used as broadband EM-wave absorbers or refractors. In the absorption process, plasma electrons are first accelerated by the EM-wave fields and then collide with background-gas molecules, thereby transferring energy from the EM waves to the gas. Two key parameters that control the absorption are the plasma density and the electron collision frequency. Plasma absorbers offer several advantages compared to conventional materials. Plasmas can be turned on and off very rapidly, thereby switching between an absorbing and transparent condition. Calculations indicate that plasma absorbers can be tailored to provide broadband absorption (>40 db) over multiple octaves.