Proton current densities in excess of 1 kA/cm2 have been measured at the cathode in the center of a pinched‐electron‐beam diode. Efficiencies (Ii/I) of about 10% have been achieved to obtain in excess of 12 kA of ions. A surface breakdown plasma on the anode allows attainment of the pinched‐beam equilibrium early in the voltage pulse. The peaking of the ion current density near the pinch roughly follows the theoretical predictions. Measurements were made with biased charge collectors. The theory of these probes has been reconsidered for the high‐current‐density limit, and it is shown that the probe response gives the actual ion current density independent of secondary emission processes on the collector.