Effect of nanostructured layer thickness on tungsten surface on cathode spots dynamics

摘要

Experimental data on the effect of the thickness of a nanostructured layer present on the surface of a tungsten cathode on its arcing properties have been analyzed. It has been found that the key parameters that are responsible for the arc initiation are the electrode potential, which must be no less than -50 V, and a threshold pulsed power of the external action on the cathode, leading to the initiation of explosive emission processes. The potential difference between the electrode and the plasma above the average arc voltage is necessary for the arc discharge to be self-sustaining when the cathode spot cells die off. To model the grouping feature of arc spot cells, an attractive force was introduced into a random walk model based on the Monte Carlo methods. It has been demonstrated that an entanglement of spot cells occurs and the spot cells move together forming a group when the attractive force between them is strong enough. When the entanglement takes place, the spot velocity significantly decreases, whereas the trail width increases.