Abstract
A new active technique for electron density measurements in ionized gas plasmas is described. The technique employs an amplitude modulated carrier signal to probe the plasma. The modulation frequency is determined by the effective length of a delay-line oscillator's feedback path, part of which includes the plasma. In contrast with other active diagnostic techniques, adjacent-mode competition is avoided by allowing the modulating signal's wavelength to be equal to the effective delay-line length. Fabry-Perot reflections occurring in the modulated segment which lead to fringes in the oscillator's frequency data are analyzed. A microwave carrier is used for experimental verification of the predicted results, although IR or visible carriers are expected to give improved performance.