Title: Специализация: 510405 Физика плазмы
Author: Admin
Last saved by: Yuri Skoblo
Company: Microsoft

Специализация: 010700/05  Физика плазмы
Программа: 010700/05  07 Физика и химия плазмы
Руководитель программы: проф. Ю.Б. Голубовский 
Кафедра оптики
Научные руководитель: доцент к.ф-м.н. Кудрявцев А.А.
Рецензент: д.ф-м.н., проф. Л.Д. Цендин

Studies of cathode space of direct current glow discharge
K.A. Barzilovich

The numerical 2D modeling of a DC glow discharge in argon, with finite element method Comsol Multiphysics software,  is performed. 
The object of modeling is the DC discharge with 1 cm distance between electrodes and 1.5 cm radius. The axial distribution of plasma parameters for such discharge is expected to be close to one in 1D model, especially for growing part of  Voltage-Current Characteristic. The positive column region for such values of gas pressure and interelecrode distance is absent. A self-consistent system of balance equations for densities of electrons, ions Ar^+ and metastable argon atoms Ar^*  and electron energy was used.  The Poisson’s equation was used to find the electric potential. The reaction rate constants and electron transport coefficients were calculated by convolution of Electron Energy Distributuion Function (EEDF) with corresponding electron impact cross sections. The EEDF was assumed to be either Maxwellian and Non-Maxwellian.
The analysis of numerical results had shown that axial distributions of basic plasma parameters are strongly depend from assumed EEDF form. 
The simulation result was that the opposite field phenomenon took place in all cases in Maxwell model, but it didn't take place in any case in calculations with non-Maxwellian EEDF. Besides there was a corelation between opposite field phenomenon and anode space volume charge. Only when the opposite field phenomenon took place, volume charge near anode is positive. In the case of non-Maxwellian EEDF the maximum position of plasma density is turned out strongly shifted toward cathode layer. 
For the case when plasma density at cathode sheath boundary is significantly lower than maximal density, the criterium of existence of electric field reversal point is obtained. It express the condition of reversal electric fied in terms of net fraction of ionizations in cathode field region and ratio of plasma density gradients at cathode sheath and anode.
It is shown that absence of electric field reversal point pointed to realization of Engel-Steenbeck disharge model, in which all ionization localized in cathode sheath.
It is predicted that in case of non-Maxwellian EEDF, the increasing of electric current density, will necessary result in appearance of  a field reversal point.

The list of the publications
1. Dyatko N.A., Ionikh Y.Z, Meshchanov A.V, Napartovich A.P., Barzilovich K.A.. Особенности вольтамперных характеристик диффузной формы тлеющего разряда в смесях Ar:N_2 // Plasma Physics. V. 36, № 12, p. 1104–1129, 2010