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 densityJ, going to zero asJgoes to a limiting valueJ1. However,J1can be quite large, going to infinity as the diode voltage approaches the limiting voltageV1from below. Thus, it may not always be practical to inject a beam of current density exceedingJ1. The results presented in this paper can be used to determine the fraction of (typically unwanted) ions extracted from the anode foil whenJ≤J1.