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The effect of the magnetic field having axial and radial components on the vacuum arc stability and arc extinction was studied experimentally. It has been demonstrated that the magnetic field configuration affects the arc discharge channel shape. It has been shown also that there is a critical current value in the external magnetic field. With the current values below the critical value, high-frequency voltage oscillations appeared on the arc indicating the arc instability. The critical current value depends on the value of each of the magnetic field components. The effect of the magnetic field component values on the conditions of the vacuum arc current breaking was investigated. A physical model has been suggested, and a mathematical 3-D-model has been developed that describes the current channel shape in the external nonuniform magnetic field. The trajectories of ion motion in the vacuum arc current channel have been calculated. It has been demonstrated that when some part of ion trajectories go beyond the bounds of the anode, it can result in the arc burning instability.
Date of Publication: Aug. 2009