title: Measurement of heat load density profile on acceleration grid in MeV-class negative ion accelerator.
abstract: To understand the physics of the negative ion extraction/acceleration, the heat load density profile on the acceleration grid has been firstly measured in the ITER prototype accelerator where the negative ions are accelerated to 1 MeV with five acceleration stages. In order to clarify the profile, the peripheries around the apertures on the acceleration grid were separated into thermally insulated 34 blocks with thermocouples. The spatial resolution is as low as 3 mm and small enough to measure the tail of the beam profile with a beam diameter of ∼16 mm. It was found that there were two peaks of heat load density around the aperture. These two peaks were also clarified to be caused by the intercepted negative ions and secondary electrons from detailed investigation by changing the beam optics and gas density profile. This is the first experimental result, which is useful to understand the trajectories of these particles.
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Hiratsuka
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Masaya
authors.initials: M
authors.lastname: Hanada
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kojima
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Naotaka
authors.initials: N
authors.lastname: Umeda
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Mieko
authors.initials: M
authors.lastname: Kashiwagi
authors.affiliation: Naruto University of Education, 748 Nakashima, Takashima, Naruto-cho, Naruto-shi, Tokushima 772-8502, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nishikiori
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ichikawa
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Japan Atomic Energy Agency, 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tobari