Emission parameters and coefficients of reflection of heat electrons from tungsten thermo cathodes were investigated under nontraditional for emission electronic conditions, when the surface contacts with highly ionized plasma. For measurements plasma diode electron current-magnetic field strength relations were used. Parameter Dj, which characterizes cathode heterogeneity by work function, and coefficient of reflection for policrystallic tungsten and for face 110 tungsten single crystal were measured. Proportion entering in effective reflection coefficient of electrons, reflected immediately from the surface and from potential barrier of spots field was determinate.
Analytic model for estimating main parameters of the shot glow discharges is presented. Proposed model takes into account as the electrons production in cathode sheath as nonlocal ionization in the negative glow plasma. According the traditional approach, discharge is dividing on different areas by means visual analysis. Discharge gap is dividing on volume charge sheath and quasi-neutral plasma in presented model. Plasmas areas comprise negative glow, Faraday dark space and positive column. Simple expressions for main glow discharge characteristics (voltagecurrent characteristic, cathode sheath) as well as plasmas density profile without volume recombination are deduced. Finding results satisfactorily correspond to the experimental data. Traditional Enghel – Shteenbek model (witch founded on local approach) gives more considerable disar[1]rangement with experiment.
A comparative analysis of the plasma-chemical process in high- and low-pressure glow discharges is presented. Processes that determine parameters of glow discharges have been determined basing on numerical simulation results. Correlations between spatial distribution of the main glow discharge characteristics and distribution of the main plasma chemical processes are presented.
The simple model which allows to make volt-ampere characteristic for the obstructed negative glows, considering non-local ionization in negative glow is developed. Scaling relationship which allow to predict key parameters obstructed glow discharges are received. The basic expressions for calculation of distribution of electrons density along a gap in plasma of a negative glow, distribution of potential and intensity of an electric field (including a point of the electric field reversal) are also presented. Comparison of the received results with data of full-scale modeling has shown the satisfactory consent. Carrying out of preliminary estimations by means of the presented model based on reliable physical principles, allows formulate better a problem for full-scale modeling.
