title: Effect of Coulomb collision on the negative ion extraction mechanism in negative ion sources.
abstract: To improve the H(-) ion beam optics, it is necessary to understand the energy relaxation process of surface produced H(-) ions in the extraction region of Cs seeded H(-) ion sources. Coulomb collisions of charged particles have been introduced to the 2D3V-PIC (two dimension in real space and three dimension in velocity space particle-in-cell) model for the H(-) extraction by using the binary collision model. Due to Coulomb collision, the lower energy part of the ion energy distribution function of H(-) ions has been greatly increased. The mean kinetic energy of the surface produced H(-) ions has been reduced to 0.65 eV from 1.5 eV. It has been suggested that the beam optics of the extracted H(-) ion beam is strongly affected by the energy relaxation process due to Coulomb collision.
authors.affiliation: Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Goto
authors.affiliation: Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nishioka
authors.affiliation: CERN, 1211 Geneva 23, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Mattei
authors.affiliation: CERN, 1211 Geneva 23, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Lettry
authors.affiliation: Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Abe
authors.affiliation: Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Hatayama