Low-Frequency Impedance Characteristics of a Langmuir Probe in a Plasma

Abstract

Measurement of the low‐frequency impedance of a Langmuir probe in a plasma can give the local electron density and temperature. Such diagnostic methods have been employed in ionospheric probing, but the interpretation of the results based on simplified theory has not been entirely satisfactory. This paper describes laboratory plasma studies designed to investigate the validity of the simplified theory. Good agreement is obtained between results obtained by two different impedance techniques, and conventional Langmuir probe data reduction. It is concluded that the methods could provide additional methods of measurement in laboratory plasmas, with some inherent advantages, but that a more detailed theory and extensive experimental verification are required before they can be applied with confidence to more complicated conditions in the ionosphere.