Understanding Langmuir probe characteristics of a magnetized plasma column in partial contact with grounded probe reference

Abstract

The article presents an experimental investigation on Langmuir probe measurements in a magnetized plasma column which exhibits two-temperature electron populations. It is a known fact that probe I(U) traces follow the usual exponential law if the measurements are performed with a reference electrode in good contact with plasma; which is usually a grounded discharge electrode. However in the present case, as the grounded probe reference is not a part of the discharge circuit the resulting I(U) analysis is not straightforward. It is found that owing to the high impedance between bulk plasma and probe reference, the probe measurement results in lower values of electron saturation current as compared to the ideal scenario. An appropriate correction is thus required to account actual electron saturation current and thereby to extract subsequent plasma parameters. Therefore, a simple analysis technique has been proposed to interpret probe I(U) traces resulting from such magneto-plasma devices, where reference to the probe is in partial/ poor contact with the bulk plasma.