It would be great for you to do some work on this. But there is a big literature to look at because getting energy from a pusled beam to a cirucit is what hihg power microwave design is all about–gryotrosn etc. Except they use elctron, not ion beams. It is not a simple problem to get high efficiency, since not all the ions are traveling with the exact same velosity. The energy storage devices are going to be fast capacitors.
