Joule heat generation in thermionic cathodes of high-pressure ARCS

Effect of Joule heat generation in the cathode body is investigated in the framework of the model of nonlinear surface heating, which is a widely used tool of simulation of plasma-cathode interaction in high-pressure arc discharges. Special attention is paid to investigation of thermal balance of the cathode and the near-cathode plasma layer. Calculation results are reported for tungsten cathodes and argon arcs under the following conditions, which are typical for experiments with high-pressure arc discharges (e.g., Ref. 2): (1) plasma pressure 2.6 bar, cylindrical cathode of radius 0.75 mm and height 20 mm or 24 mm, current transfer occurs in the spot or diffuse modes; (2) plasma pressure 1 bar, cylindrical cathode with a hemispherical tip of radius 1 mm and height 12 mm, current transfer occurs in the diffuse mode; (3) plasma pressure 1 bar, solitary spot on a large planar cathode.