A d.c. charged particle accelerator comprises accelerator electrodes separated by insulating spacers defining acceleration gaps between adjacent pairs of electrodes. Individually regulated gap voltages are applied across each adjacent pair of accelerator electrodes. In embodiments, the individually regulated gap voltages are generated by electrically isolated alternators mounted on a common rotor shaft driven by an electric motor. Alternating power outputs from the alternators provide inputs to individual regulated d.c. power supplies to generate the gap voltages. The power supplies are electrically isolated and have outputs connected in series across successive pairs of accelerator electrodes. The described embodiment enables an ion beam to be accelerated to high energies and high beam currents, with good accelerator stability.
