Diagnostics of a He+ beam extracted from a compact magnetic bucket-type ion sourcea)

Performance of a compact He+ ion source was investigated before installing it to the experiment system developed for studying the efficiency of autodetachment neutralization from He− to He0. Dependence of the extracted ion current upon the plasma parameters and that upon the extraction voltage indicated that the source performance was limited by space charge effect. The beam emittance was measured with a multislit system for various operation conditions. The experimentally determined emittance agreed well with the emittance obtained from ion trajectories calculated with input plasma parameters measured by a Langmuir probe. The beam current density of 60mA∕cm2 and the emittance of less than 25πmmmrad are expected to deliver enough current to the downstream of the He− neutralizer system to clarify factors affecting the final He0 intensity.