Ion charge state distributions of alloy-cathode vacuum arc plasmas

Ion charge state distributions (CSD´s) of alloy-cathode vacuum arc plasmas have been calculated under the assumption that thermodynamic equilibrium is valid in the vicinity of the cathode spot, and equilibrium CSD´s “freeze” when the plasma is rapidly expanding. In this way, experimental data of titanium-hafnium alloy-cathode plasmas have been simulated using a system of Saha equations generalized for multiple elements. It was found that the CSD´s of titanium and hafnium freeze approximately at the same plasma temperature and density. The freezing parameters depend slightly on the plasma composition. For the example considered, freezing occurs at temperature of T=3.0-3.8 eV and a total heavy particle density of order 10²⁵m^-3