| In this work, the dependence of the vacuum arc spot velocity on physical and electrical properties of different graphite cathode materials is investigated in the presence of a variable magnetic field. A pulsed arc system is used to perform preliminary experiments on the arc mobility for the different types of graphite for the selection of proper material morphology and the design of a continuous vacuum arc system. The characteristics of arc mobility, erosion rate, and carbon ion flux emitted from the continuous carbon source are then evaluated in view of particle-free diamond-like protective coatings. Results show that the arc spot velocity on graphite cathodes is larger on cathodes having larger grain size, lower electrical resistivity and higher apparent density. The spot velocity is also lower for cathodes having larger pore sizes and total porosity. The arc spot velocity is also found to be increased by increasing the magnetic field intensity over the surface of any graphite type. Reduced residence time of the spot on a given site of the cathode resulting from arc velocity increase should lead to a reduction in the heat load input in the cathode spot. This correlates with results on the number of emitted particles, the film thickness and roughness, and the erosion rate that are found to decrease, while the ion flux emission is increased. Diamond-like carbon (DLC) films free of particles are produced in a continuous arc ion plating (AIP) system. The ion energy in the continuous AIP system is found to vary with the graphite surface properties and the intensity of a plasma confining magnetic field in front of the cathode. The ion energies measured vary between 39.8 eV to 62.6 eV. |
