Normal current density effect in RF-discharge according to results of two-dimensional numerical modeling

For the first time, the normal density effect is demonstrated by modeling a two-dimensional cylindrical column of a moderate pressure RF-discharge operating in the α-regime. When the current increases, the discharge column is expanded, with the current density and voltage on the electrodes being unchanged. It is clarified why the boundary between currentless and current (filled with plasma) regions is stabilized. Outside the plasma zone, the gas temperature and the gas density at constant pressure are lower (no Joule's energy release) than those in the plasma zone, therefore the normal voltage is not sufficient to maintain plasma there. It is shown that simple one-dimensional models give quite reasonable results for parameters of the normal discharge.