Theory of applied-B ion diodes

A recently introduced theory of applied-B ion diodes [Phys. Rev. Lett. 59, 2295 (1987)] is developed and presented in detail. The theory incorporates the self-consistent virtual cathode motion to obtain the steady-state ion current as a function of diode voltage. The existence of a limiting voltage at which the ion current diverges is demonstrated. The voltage--current characteristics of the diode are combined with a simple circuit model of the accelerator to calculate the operating point of the diode. The theoretical results are in good agreement with experimental data at peak power. An important consequence of the theory is a relation between the limiting diode voltage and the insulating magnetic flux, suggesting a late-time voltage decay driven by flux penetration into the anode plasma