Pyrometric and spectroscopic investigations of lanthanated tungsten cathode in argon arc plasma discharge at atmospheric pressure are reported. The distribution of the surface cathode temperature was measured. Calculations and estimates of the emission current density are performed. Experimental data of the total current density are compared with the obtained results of estimation. The possible reasons for the discrepancy between the experimental and theoretical values of the total current were discussed.
In this work the destruction mechanism of a pure tungsten cathode during the initiation of direct current arc is studied. The experimental work shows that the cathode resides in liquid form during the initiation of the arc, and the process of its destruction happens by ejecting droplets from its surface with the following explosion. The average speed of the ejection and the temperature at the explosion points microseconds before the explosion were registered. A mathematical model is proposed explaining the reason behind the droplets formation.
Spectroscopic and thermometric measurements were performed on the hafnium cathode in argon plasma at atmospheric pressure in a stable burning mode of the arc. The distribution of temperatures on the cathode and distribution of electron temperatures in plasma near the cathode are presented. It was shown that the obtained theoretical range of values for the voltage drop in the volume charge layer is in good agreement with experimental results. Based on the numerical simulations, a range of values were obtained for the current densities of ions and electrons and electric field strength on the cathode tip.
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