Broadband Plasma Impedance Measurements and Determination of Plasma Parameters

摘要

A small spherical probe is used in conjunction with a network analyzer to determine the impedance of the probe-plasma system over a wide frequency range. Impedance curves are in good agreement with accepted circuit modes with plasma-sheath and electron plasma frequency resonances easily identifiable. Phase measurements show clear transitions between capacitive and inductive modes as predicted by the model. Sheath thickness and absolute electron density are determined from the location of these transitions. In addition, much larger power absorption is observed at the sheath plasma resonance than is predicted by collisional absorption.