In the proposed pulsed ion source, a steady-state sputtering avalanche sustained by secondary ions locked in phase with an ac voltage applied between plates creates high current bunches with energy monochromaticity and ion purity. In a two-surface cascade, the average current exhibits a Child–Langmuir-like scaling, due to the dynamical constraints on the normalized ac voltage. A single-surface cascade, using a bending magnetic field, operates with unconstrained voltage and exhibits much lower heat load for given current, as well as the ability for average current in excess of the Child–Langmuir limit. The pulsed source is particularly attractive for ion beams of solid materials with high vaporization temperature. ©1998 American Institute of Physics.