Ion emission from anode foils during multistage acceleration of intense ion beams

Steady-state calculations are presented that show that the ion current density extracted off an anode foil in a multistage ion diode is a monotonically decreasing function of the injected current density J, going to zero as J goes to a limiting value J1. However, J1 can be quite large, going to infinity as the diode voltage approaches the limiting voltage V1 from below. Thus, it may not always be practical to inject a beam of current density exceeding J1. The results presented in this paper can be used to determine the fraction of (typically unwanted) ions extracted from the anode foil when J≤J1