Perturbation diagnostics of microwave resonant cavities

Summary form only given. A new perturbation analysis which accounts for the complex electromagnetic fields in microwave resonant cavities is introduced. This is done by modeling the discharge as a lossy dielectric, and allowing the microwave frequency to become complex. It is shown that the imaginary portion of the frequency represents the change in the cavity quality factor due to the discharge while the real portion is simply the change in the resonant frequency of the cavity. By measuring these two quantities, the electron density and collision frequency of the discharge may be obtained. The results of the diagnostic are applied to an Asmussen-style microwave cavity operating in the TM/sub 012/ mode. The electron densities determined from this technique have been compared to those measured from double Langmuir probes. The densities agreed from 10/sup 11/ to 10/sup 12/ cm/sup -3/.