Generation and geometric focusing of an intense pulsed light-ion beam at Nagaoka

Systematic studies have been carried out on the generation and geometric focusing of an intense pulsed light-ion beam in the Nagaoka ETIGO-I. Using a geometric focusing with magnetically insulated diode, we have studied the focusing properties of the proton beam. Local divergence is found to be less effective on the focusing. Deviation of ion trajectories from the ideal ones (or aberration) strongly affects the focusing. An annular distribution of an ion-current density observed experimentally is found by ion-trajectory calculation to be a space-charge effect. The space-charge neutralization factor is estimated to be more than 99.9 %. (author)