Interaction of electromagnetic waves with plasma torches

Summary form only given. Scattering of electromagnetic waves by plasma torches is studied experimentally and theoretically in a rectangular waveguide. Up to three plasma torches are placed below an X band waveguide so that the plasma streams through a set of 1/4" holes in the bottom of the guide and out another set of 1/4" holes in the top. The plasma columns of the torch cross the path of propagation of microwaves (-15 dBm, 10 GHz) in the waveguide and cause absorption and scattering losses of the microwaves. The signal received at the other end of the waveguide is monitored with an HP8569B spectrum analyzer. By changing the number of torches (from 0 to 3) appearing in the waveguide, the dependence of the power loss of the wave on the plasma volume, is determined. The theory of the wave scattered by a dielectric post in the rectangular waveguide is extended to a lossy dielectric. Using the plasma density and volume as variable parameters, the attenuation of the wave by the plasma torches (1 to 3) are evaluated. By matching the numerical results with the corresponding experimental results, the plasma density and volume can be determined.