An analysis of the cathode region of a vortex-stabilized arc plasma generator

In an arc plasma generator in air at atmospheric pressure, stabilized by a magnetic field and a vortex flowing gas, with a copper tubular cathode cavity, based on the analysis of forces acting on the cathode region, the shape of the arc column, the direction of the arc current density J near the cathode surface, the position of the cathode spot and its 'jumping' process are studied. The cathode spot's movement over the cathode surface is the result of a repetitious process of birth of new spots and disappearance of old spots provoked by the magnetic field and the gas flow. The spot lifetime is estimated at around (3-4)*10 -4 s. Moreover, following this study, the position of the plane (Z=Z c ) in which the arc cathode spot rotates is determined as a function of arc current I, components of the magnetic field B r and B Z , flowing gas velocities U Z and U theta , the velocity of the arc cathode spot rotation V theta arc and the radius of the arc cathode spot a 0 . The results of this study are in satisfactory agreement with experimental determinations. In this analysis cylindrical coordinates r, theta and Z are used with the symmetrical axis of the cathode tube oriented in the Z direction.