title: Influence of electric field penetration by a three-electrode beam extraction system on hydrogen negative ion source plasma.
abstract: We study influence of electric field penetration into H(-) ion source plasma with three-electrode beam extraction system. Clear change in the plasma potential due to the field penetration is observed in case of low gap voltage between a plasma electrode and an extraction electrode. Influence of lens voltage on the second electrode, which is normally utilized to focus the extracted beam, on ion source plasma is evaluated separating contributions of H(-) density in the plasma and extraction probability of H(-) ions from the plasma by two kinds of photodetachment techniques. In our operation condition, we found that the lens voltage is also useful to enhance the H(-) density in the plasma, though it negatively affects the extraction probability.
authors.affiliation: Tokushima Bunri University, Nishihama, Yamashiro, Tokushima 770-8514, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Matsumoto
authors.affiliation: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Nishiura
authors.affiliation: RIKEN SPring-8 Center, Hyogo 679-5148, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamaoka
authors.affiliation: Organization for Research Initiatives and Development, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sasao
authors.affiliation: Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Wada