Vacuum transmission lines in the presence of a resistive cathode plasma

A model is introduced to describe the transverse electromagnetic propagation of power in high‐voltage vacuum transmission lines in the presence of a resistive cathode plasma. The model consists of the transmission line equations complemented with a one‐dimensional model for calculating local shunting currents. These equations are self‐consistently solved in the presence of a cathode plasma expanding against the magnetic field. The plasma motion, considered to start at a given point when the local electric field reaches the selected threshold value of 0.3 MV/cm, is described by using one‐dimensional magnetohydrodynamic equations in which the plasma properties at each position along the length of the line are assumed to depend only on the cross cathode‐anode direction. Magnetic diffusion is taken into account in the plasma as well as in the metal cathode. The model is applied to a system for which experimental results are available: a 2‐m vacuum coaxial line of Al walls, driven by a voltage pulse of 130‐ns ...