Parametric study of a pin-plane probe in moderately magnetized plasma

Abstract

The application of a planar Langmuir probe in magnetized plasma is found to be problematic due to significant perturbation of plasma along the magnetic field lines intercepting the probe surface. This causes the Ampere–Volts ‘Ie(U)’ characteristics of the probe to deviate from its usual exponential law; in conjunction the electron saturation current Ies is significantly reduced. Moreover estimating the electron temperature Te by considering the entire semi-log plot of Ie(U) gives ambiguous values of Te. To address this problem, Pitts and Stangeby developed a formula for the reduction factor for Ies. This formula depends on a number of uncertain parameters, namely; the ion temperature T+, electron cross-field diffusion coefficient and the local potential hill Vh estimated by applying a floating pin probe in the vicinity of the planar probe. Due to implicit dependence of these parameters on Te, the resulting analysis is not straightforward. This paper presents a parametric study of different parameters that influence the characteristics of a planar probe in magnetized plasma. For this purpose a pin-plane probe is constructed and applied in the magnetized plasma column. A comprehensive discussion is presented that highlights the practical methodology of using this technique for extracting useful information of plasma parameters in magnetized plasmas.