The observed laws to be explained by the change in the size of the "cathode spot" formed by the plasma discharge torch on the surface of the solution in the plasma--chemical reactor.
In the course of experiments on measuring the area of the "cathode spot" it was found that the variation of the current strength of the plasma discharge affects its size (Fig.
It was also found that in addition to the current strength of the plasma discharge, the area of the "cathode spot" defines the distance from the anode to the surface of the solution.
The generation of high power is determined by the bombardment of the zone of the cathode spot with the ions of the sputtered material.
It is well known that the method of microarc evaporation with ion bombardment is based on the initiation of a microarc discharge in vacuum on the cathode surface and the subsequent formation of cathode spots having exceptionally high density and temperature [5-7].
Thus, for commanded pulses and positive polarity, the temperature on cathode spot
, [t.sub.spot] was 2550[degrees]C and its radius [R.sub.cs] = 2.5 [micro]m.
At the very first ignition of the arc active insert is subjected to the process of sintering under action of heat flow, which enters into the active insert from the cathode spot.
Temperature of cathode spot on emission oxide film, consisting of pure de-stoichiometrized zirconium oxide, achieves, approximately, 4000 K .
When inspecting non-etched film at high magnification of the cathode spot, one can see on screen of a scanning microscope granular structure with streaks of eutectics (Figure 5, a).
It turned out that it was impossible to use ingenious development of Wenelt in cathodes of welding electric arc, because for stable work of the welding arc it is necessary that mean density of current on the surface of a non-consumable cathode of welding arc, in addition to the current density in the cathode spot
, exceeded mentioned density in the tubes at least by three orders .
For a second or two, the process behaves as a typical cathodic arc as bright, tiny "cathode spots
" race around on the carbon, the plasma in the chamber being of the whitish hue characteristic of that element.