Diffuse vacuum arc with heated cathode made of ceramic (CeO2) and metal (Cr) mixture

The paper presents a diffuse vacuum arc with heated cathode made of ceramic (CeO2) and metal (Cr) mixture, initiated and studied for the first time. Plasma sources of multicomponent mixtures are demanded for plasma based methods of rare-earths recycling and spent nuclear fuel reprocessing, which are currently under development. The discharge current-voltage characteristic was measured for different cathode temperatures (1950-2250 K); in the range of the arc current 30-100 A the voltage varied from 6 to 11 V. A cooling effect of the mixed cathode due to the thermionic emission at presence of the arc plasma was found; the effect reached about 150 W at the arc current of 30 A. The cooling effect and the current-voltage characteristic distinguish the discharge from the diffuse vacuum arcs with single-component cathodes made of cerium dioxide and chromium. The plasma parameters and optical emission spectra were analyzed for various cathode temperatures and arc currents (electron temperature was 0.4-0.6 eV, local particle densities in plasma near the cathode were in range 1011-1013 cm−3). The study is of interest for plasma sources development and increase of their efficiency as well as for the tasks aimed at ionization of multicomponent mixtures.