title: Analysis of the beam halo in negative ion sources by using 3D3V PIC code.
abstract: The physical mechanism of the formation of the negative ion beam halo and the heat loads of the multi-stage acceleration grids are investigated with the 3D PIC (particle in cell) simulation. The following physical mechanism of the beam halo formation is verified: The beam core and the halo consist of the negative ions extracted from the center and the periphery of the meniscus, respectively. This difference of negative ion extraction location results in a geometrical aberration. Furthermore, it is shown that the heat loads on the first acceleration grid and the second acceleration grid are quantitatively improved compared with those for the 2D PIC simulation result.
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: Faculty 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: Faculty 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: Faculty 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
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukouyama, Naka 319-0913, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hanada
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukouyama, Naka 319-0913, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kojima
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukouyama, Naka 319-0913, Japan.
authors.forename: J
authors.initials: J
authors.lastname: Hiratsuka