Abstract :
A model of near-electrode processes is applied here to describe the behavior of cathode spots on graphite cathode in vacuum arc. The physical model is based on a kinetic treatment of cathode evaporation, electron emission from the cathode, and plasma production. The model consists of physical assumptions and a system of equations that are formulated in the paper. Spot parameters, such as cathode erosion rate, cathode potential drop, cathode surface temperature, current density, electric field, and plasma density, temperature, and velocity in the near-electrode region are calculated numerically. The calculation includes the dependence of spot parameters on spot current and spot lifetime. The variation of spot parameters as a function of spot lifetime are very strong at lifetimes shorter than 10 μs. The calculations indicate that Joule heating in the cathode body is significant, and may exceed cathode heating by the ion heat flux. Calculated spot parameters are compared with the corresponding experimental data for relatively low arc currents (<100 A) and their agreement is discussed
Keywords :
cathodes; electron emission; evaporation; graphite; plasma production; plasma-wall interactions; vacuum arcs; Dushman relationship; Joule heating; cathode body; cathode erosion; cathode erosion rate; cathode evaporation; cathode heating; cathode potential drop; cathode surface temperature; current density; electric field; electron emission; graphite cathode; ion heat flux; kinetic treatment; near-electrode processes; near-electrode region; nonequilibrium layer; physical model; plasma density; plasma production; plasma temperature; plasma velocity; relatively low arc current; relaxation zone; return atom flux; spot current; spot lifetime; spot parameters; vacuum arc cathode spot model; Cathodes; Electron emission; Equations; Heating; Kinetic theory; Plasma applications; Plasma density; Plasma temperature; Production; Vacuum arcs;
