Studies on the plasma characteristics of the thermionic anodic vacuum arc in metal vapors

A new type of discharge with heated cathode - in vacuum conditions in the metal vapors of the evaporation anode - has first been reported in 1983. This discharge can be ignited in any kind of pure metal vapors, including refractory metals. Using the computerized complex diagnostics system developed at the University of Essen, full parameters of the expanding metal plasma have been studied, for various working points on volt-ampere characteristics. Even for low thermionic arc currents of the order of 3 A, the degree of ionization was 6%, the deposition rate at 250 mm from the plasma arc was 5 nm/s, plasma density was 6 x 1015 m-3, the metal ion energy was higher than 100 eV, and electron temperature was 10 eV. A deposition rate of metal layer of the order of 5 nm/s has been measured. The obtained layers are very smooth and droplet-free. Very promising technological applications are expected from this new type of discharge. (Author)