Direct power coupling into a waveguide cavity plasma source

Abstract

For the investigation of a 2.45 GHz magnetron coupled directly to a microwave plasma applicator a simple rectangular waveguide cavity was used. With a six port reflectometer, forward and reflected microwave power and the frequency of the magnetron were measured. It happened that the plasma not only changes the load for the magnetron but also has an influence on the operating point of the magnetron. Since no isolator decouples plasma and magnetron, the phase, amplitude and excitation frequency of the magnetron vary with changing plasma working conditions. To control the magnetron operating point, the current and voltage of the magnetron filament supply and the optical emission of the plasma were measured. To adopt the system for impedance change due to ignition, a simple magnetically controlled two position tuner can be used.