title: Development of negative ion extractor in the high-power and long-pulse negative ion source for fusion application.
abstract: High power and long-pulse negative ion extractor, which is composed of the plasma grid (PG) and the extraction grid (EXG), is newly developed toward the neutral beam injector for heating and current drive of future fusion machines such as ITER, JT-60 Super Advanced and DEMO reactor. The PG is designed to enhance surface production of negative ions efficiently by applying the chamfered aperture. The efficiency of the negative ion production for the discharge power increased by a factor of 1.3 against that of the conventional PG. The EXG is also designed with the thermal analysis to upgrade the cooling capability for the long pulse operation of >1000 s required in ITER. Though the magnetic field for electron suppression is reduced to 0.75 of that in the conventional EXG due to this upgrade, it was experimentally confirmed that the extracted electron current can be suppressed to the allowable level for the long pulse operation. These results show that newly developed extractor has the high potential for the long pulse extraction of the negative ions.
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kashiwagi
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Umeda
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tobari
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kojima
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Taniguchi
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Dairaku
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Maejima
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Yamanaka
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Inoue
authors.affiliation: Japan Atomic Energy Agency (JAEA), 801-1 Mukoyama, Naka 311-0193, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hanada