No abstract

Vacuum arcs can be initiated without external means of power enhancement at the cathode surface (by using a high-voltage trigger, laser triggering, and so on). Arc initiation by simply applying the relatively low voltage of the arc power supply is possible if the cathode-anode-separating insulator is coated with a conducting layer and the current at the layer-cathode interface is concentrated at one or a few contact points. The local power density at these contact points can exceed which is sufficient for plasma production and thus arc initiation. This `triggerless' principle has been tested successfully with a large number of cathode materials. One extended test was performed with titanium and more than pulsed vacuum arc initiations have been obtained.

We have developed several different embodiments of repetitively pulsed vacuum arc metal plasma gun, including miniature versions, multicathode versions that can produce up to 18 different metal plasma species between which one can switch, and a compact high-duty cycle well-cooled version, as well as a larger dc gun. Plasma guns of this kind can be incorporated into a vacuum arc ion source for the production of high-energy metal ion beams, or used as a plasma source for thin film formation and for metal plasma immersion ion implantation and deposition. The source can also be viewed as a low-energy metal ion source with ion drift velocity in the range 20–200 eV depending on the metal species used. Here we describe the plasma sources that we have developed, the properties of the plasma generated, and summarize their performance and limitations.