The Edge Effect on the EEDF Measurements of Magnetized DC Plasma

Abstract

The localized plasma parameters at the edge of the discharge electrodes cell have been investigated for axial distribution, such as the electric field distribution, the electron energy distribution functions (EEDF), the electron temperature (Te) and the electron density (Ne), all have been determined with and without the applications of external magnetic field using Langmuir single probe in the three regions of the discharge. The EEDF was investigated using two different methods e.g. the graphical method and the electron current second derivative method. The electron energy distribution functions are maxwellian only in the positive column region (P.C.) and non- maxwellian in the cathode fall (C.F) and the negative glow (N.G.) regions, where two groups of electrons were observed. The diffusion coefficients and the electron temperatures are lower in the presence of the magnetic field, where Te decreased from 6.5 to 3 eV for C.F, from 5.18 to 2.6 eV for N.G., and from 4.2 to 1.1 eV for P.C. Furthermore, sharp axial increments for potential distribution and electron density in the presence of the magnetic field were measured, whereas in the border between C.F and N.G regions, Ne increased from 4 x109 to 9.5 x109 cm-3 and 4.97 x109 to 11.6 x109 cm-3, respectively. In contrast, an axial decrement of the electron density in P.C. region due to the electron capture by the anode in P.C. region was also found.