Critical conditions of a high-current vacuum arc

A one-dimensional three-fluid (electrons, slow and fast ions) model of high-current vacuum arc is used to investigate the peculiar features of motion of fast cations and slow anions. The model enables one to calculate the distribution of the concentrations, velocities, and temperatures of the components with due regard for the boundary conditions at the anode and cathode boundaries of plasma. It is demonstrated that, in a three-component plasma, the fast and slow ions have limits restricting the maximum velocity of slow ions from above and the minimum velocity of fast ions from below. In a three-component plasma, these limiting velocities differ from the ion sound velocities of the respective components. The presence of the limiting velocity of slow ions results in the impossibility of their complete flow to the cathode, and the existence of the limiting velocity of fast ions restricts the range of existence of the quasistationary mode of current flow. The calculation results are given, which demonstrate the dependence of the limiting velocities on the parameters of the vacuum arc.