Charged particle generator

The present invention relates to a charged particle beam generator comprising multiple charged particle beam generator units. In particular, the present invention is concerned with apparatus for generating a high- energy, high-current proton beam such as are used in accelerator driven subcritical reactors. The present invention provides a method of generating a composite proton beam using a proton beam generator comprising multiple proton beam generator units. A negative hydrogen ion source is used to generate a beam of negative hydrogen ions in each unit. The negative hydrogen ions are stripped to create a proton beam in each unit, that is accelerated beam and guided to a common point where the beams are merged to form the composite proton beam.