Continuous cathodic Arc sources

Abstract

All the cathodic arc source components and connections need to be designed to handle the high currents required to sustain an arc. Cathode spots (CS) spontaneously extinguish, and can be characterized by an average lifetime, which increases with the arc current. The lifetime is a strong function of cathode material, and is generally longer for the more volatile materials. In addition, the lifetime is a function of the electrical circuit, electrode geometry, and applied magnetic field. As a rule of thumb, the arc current for sustained arcing should be at least as large as the cathode spot splitting current. The energy of the vacuum arc discharge is concentrated in the CS region where practically all the drop of the applied voltage occurs. This energy is removed conductively from the cathode, is spent on electron emission, and leaves the near-cathode region in the kinetic energies of ions and in the thermal energy of electrons moving to the anode. The chapter discusses three categories of control strategies for confining the arc spot to the desired cathode surface. The first two utilize a magnetic field and the acute-angle rule for arc spot drift. The third simply covers all but the desired cathode surface with an insulating material, or electrically isolated metal shields. It is mentioned that coating systems based on the cathodic arc have been used successfully in a great number of applications.