Angular distribution measurement of low-energy beam ions

Abstract

Angular distributions of low-energy ions extracted from a multi-cusp dual- electrode ion source system have been investigated using an electro-static deflection-type angular spread analyzer. The measured angular spreads of the extracted Ar⁺ ions were large near the extractor and became smaller against the increasing distance from the extractor. Initial ion acceleration at the extraction electrode was strongly affected by plasma density and extraction potential. Namely, the sheath formed around the electrodes deflects the adjacent ion trajectories. Energy distribution measurements showed that the energy spread was directly affected by the angular spread which eventually decreased the ion beam current density.