Plasma Impedance Element in an Active Fabry-Perot Microwave Resonator

Experiments are described in which a plasma is used as an impedance element in an active Fabry-Perot microwave resonator which contains a positive feedback loop. The arrangement functions as a Q multiplier or as an oscillator, with the plasma acting as a power or frequency-determining element. The characteristics of the active Fabry-Perot resonator are discussed in connection with diagnostic methods for pulsed and steady-state plasmas.