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Journal Articles

1 MeV, ampere class accelerator R&D for ITER

Inoue, Takashi; Kashiwagi, Mieko; Taniguchi, Masaki; Dairaku, Masayuki; Hanada, Masaya; Watanabe, Kazuhiro; Sakamoto, Keishi

Nuclear Fusion, 46(6), p.S379 - S385, 2006/06

 Times Cited Count:33 Percentile:75.73(Physics, Fluids & Plasmas)

The JAERI MeV accelerator has been designed extrapolating vacuum insulation design guidelines (the clump theory and Paschen law) to Mega Volt and long vacuum gap. Reduction of electric field concentration at triple junction by a large stress ring was effective to prevent flashover along insulator surface. By the vacuum insulation technology above, the accelerator sustained 1 MV for 8,500 s continuously. Strong enhancement of negative ion surface production has been attained by stopping vacuum leaks due to SF$$_{6}$$ permeation through Viton O rings and a damage of port by backstream ions, followed by increase of the H$$^{-}$$ ion current density without saturation. Operating the KAMABOKO source with high power arc discharge ($$leq$$ 40 kW), H$$^{-}$$ ion beams of 146 A/m$$^{2}$$ (total ion current: 0.2 A) have been obtained stably at the beam energy of 836 keV (pulse length: $$geq$$ 0.2 s). Bremsstrahlung generation in the accelerator is also estimated from EGS4 analysis, and then discussion on the breakdown possibility follows.

Journal Articles

Design study of a neutral beam injector for fusion DEMO plant at JAERI

Inoue, Takashi; Hanada, Masaya; Kashiwagi, Mieko; Nishio, Satoshi; Sakamoto, Keishi; Sato, Masayasu; Taniguchi, Masaki; Tobita, Kenji; Watanabe, Kazuhiro; DEMO Plant Design Team

Fusion Engineering and Design, 81(8-14), p.1291 - 1297, 2006/02

 Times Cited Count:10 Percentile:59.81(Nuclear Science & Technology)

Requirement and technical issues of the neutral beam inejctor (NBI) is discussed for fusion DEMO plant. The NBI for the fusion DEMO plant should be high efficiency, high energy and high reliability with long life. From the view point of high efficiency, use of conventional electrostatic accelerator is realistic. Due to operation under radiation environment, vacuum insulation is essential in the accelerator. According to the insulation design guideline, it was clarified that the beam energy of 1.5$$sim$$2 MeV is possible in the accelerator. Development of filamentless, and cesium free ion source is required, based on the existing high current/high current density negative ion production technology. The gas neutralization is not applicable due to its low efficiency (60%). R&D on an advanced neutralization scheme such as plasma neutralization (efficiency: $$>$$80%) is required. Recently, development of cw high power semiconductor laser is in progress. The paper shows a conceptual design of a high efficiency laser neutralizer utilizing the new semiconductor laser array.

Journal Articles

R&D on a high energy accelerator and a large negative ion source for ITER

Inoue, Takashi; Taniguchi, Masaki; Morishita, Takatoshi; Dairaku, Masayuki; Hanada, Masaya; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; Seki, Takayoshi*; Watanabe, Kazuhiro

Nuclear Fusion, 45(8), p.790 - 795, 2005/08

The R&D of a 1 MeV accelerator and a large negative ion source have been carried out at JAERI. The paper presents following progress as a step toward ITER NB system. (1) Accelerator R&D: According to success in improvement of voltage holding capability, the acceleration test of H$$^{-}$$ ions up to 1 MeV class energy is in progress. H$$^{-}$$ ion beams of 1 MeV, 100 mA class have been generated with a substantial beam current density (100 A/m$$^{2}$$), and the current density is still increasing by the ion source tuning. (2) Large ion source R&D: One of major causes that limited the NB injection performance was spatial unifomity of negative ion production in existing negative-ion based NB systems. The present study revealed that the negative ions produced in the extraction region of the source were locally destructed by fast electrons leaking through magnetic filter. Some countermeasures and their test results are also described.

Journal Articles

R&D on a high energy accelerator and a large negative ion source for ITER

Inoue, Takashi; Taniguchi, Masaki; Morishita, Takatoshi; Dairaku, Masayuki; Hanada, Masaya; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; Seki, Takayoshi*; Watanabe, Kazuhiro

Nuclear Fusion, 45(8), p.790 - 795, 2005/08

 Times Cited Count:22 Percentile:60.74(Physics, Fluids & Plasmas)

The R&D of a 1 MeV accelerator and a large negative ion source has been carried out at JAERI for the ITER NB system. The R&D is in progress at present toward: (1) 1 MeV acceleration of H$$^{-}$$ ion beams at the ITER relevant current density of 200 A/m$$^{2}$$, and (2) improvement of uniform negative ion production over wide extraction area in large negative ion sources. Recently, H$$^{-}$$ ion beams of 1 MeV, 140 mA level have been generated with a substantial beam current density (100 A/m$$^{2}$$). In the uniformity study, it has been clarified that electron temperature in the ion extraction region is locally high ($$>$$ 1 eV), which resulted in destruction of negative ions at a high reaction rate. Interception of fast electrons leaking through a transverse magnetic field called "magnetic filter" has been found effective to lower the local electron temperature, followed by an improvement of negative ion beam profile.

JAEA Reports

Research and development plan of fusion technologies in JAERI toward DEMO reactors

Department of Fusion Engineering Research

JAERI-Review 2005-011, 139 Pages, 2005/03

JAERI-Review-2005-011.pdf:11.95MB

no abstracts in English

JAEA Reports

R&D on high power negative ion sources and accelerators for a neutral beam injector

Inoue, Takashi

JAERI-Research 2005-006, 87 Pages, 2005/03

JAERI-Research-2005-006.pdf:10.53MB

Negative ion sources and accelerators have been developed toward the ITER neutral beam injector (NBI). According to an analysis of negative ion surface production, the "KAMABOKO" ion source has been developed maximizing its volume/surface ratio, for fast electron confinement followed by enhancement of atomic density. An "external filter" is equipped in the source, to suppress ion destruction by the fast electrons with efficient diffusion of the atoms to ion extraction region. H$$^{-}$$ ions of 300 A/m$$^{2}$$ was extracted at the pressure of 0.3 Pa. For the accelerator, vacuum insulation technology has been developed since insulation gas such as SF$$_{6}$$ is not applicable under radiation environment. Considering pressure in the accelerator (0.02$$sim$$0.2 Pa), insulation guideline has been developed for both vacuum arc and glow discharges. Reduction of electric field stress at triple junction was effective to prevent flashover along insulator surface. H$$^{-}$$ ion beams of 900 keV and 80 A/m$$^{2}$$ (total ion current: 0.11 A) were obtained for several hundred shots.

Journal Articles

Investigation of photo neutralization efficiency of high intensity H$$^{-}$$ beam with Nd:YAG laser in J-PARC

Tomisawa, Tetsuo; Akikawa, Hisashi; Sato, Susumu; Ueno, Akira; Kondo, Yasuhiro; Oigawa, Hiroyuki; Sasa, Toshinobu; Hasegawa, Kazuo; Lee, S.*; Igarashi, Zenei*; et al.

Proceedings of 7th European Workshop on Beam Diagnostics and Instrumentation for Particle Accelerators (DIPAC 2005), p.275 - 277, 2005/00

The photo neutralization method with Nd:YAG laser for negative hydrogen ions has been expected as an available candidate for the transverse beam profile measurement. The fraction of photo detached electron can also be used for charge exchange procedure to extract very low power proton beam for Transmutation Experimental Facility in J-PARC. The laser system has advantages of maintenance and radiation hardness in high intensity proton accelerators. In order to establish the low power beam extraction system and beam profile monitor, the photo neutralization efficiency must be surveyed in practical beam line with high intensity H$$^{-}$$ beam. In this paper, an experimental set-up and preliminary results of photo neutralization method for intense H$$^{-}$$ beam in J-PARC MEBT1 are described.

JAEA Reports

Manufacture of high-speed neutral atomic and molecular beam apparatus and its characterization

Hachiue, Shunsuke; Teraoka, Yuden

JAERI-Tech 2004-066, 69 Pages, 2004/11

JAERI-Tech-2004-066.pdf:7.44MB

In order to progress chemical reaction studies at verious material surfaces using high speed and reactive ions and neutral particles beams, a high-speed neutral atomic and molecular beam apparatus has been developed. In this report, details of the apparatus and characteristics of actually-generated oxygen atomic and molecular ion/neutral beams are discribed. This apparatus is a ultra-high vacuum system consisting of a plasma ion source, electrostatic lens systems, a mass separator, and a charge transfer chamber. Total oxygen ion currents of 52 microamps at accerelation energy of 8 keV and 17 microamps even at 20 eV were obtained. Mass separation was also good so that an oxygen molecular ion beam of 11 microamps and an oxygen atomic ion beam of 5.5 microamps were obtained even at 20 eV. A neutral oxygen atomic or molecular beam was also generated with the flux density of 10$$^{12}$$ particles/cm$$^{2}$$/s.

Journal Articles

Acceleration of 1 MeV, 100 mA class H$$^{-}$$ ion beams in a proof-of-principle accelerator for ITER

Inoue, Takashi; Taniguchi, Masaki; Dairaku, Masayuki; Hanada, Masaya; Kashiwagi, Mieko; Morishita, Takatoshi; Watanabe, Kazuhiro; Imai, Tsuyoshi

Review of Scientific Instruments, 75(5), p.1819 - 1821, 2004/05

 Times Cited Count:11 Percentile:53.04(Instruments & Instrumentation)

The paper reports progress of proof-of-principle test of negative ion accelerator for ITER. The accelerator structure is immersed in vacuum, surrounded by a FRP insulator column as the vacuum boundary. So far, the beam energy has been limited due to poor voltage holding capability of the FRP insulator column. By lowering the electric field strength at the triple junction (interface of FRP insulator, metal flange and vacuum) with large stress ring installed inside the insulator column, high voltage of 1 MV was stably sustained for more than 2 hours. In the following beam test, acceleration of 900 keV, 100 mA H$$^{-}$$ ion beam was succeeded. Although the current was lower (70 mA) at 1 MeV, the beam of this level has been stably accelerated for 6 days, 130 shots in total (each pulse length: 1 s).

Journal Articles

Formation of a charge-exchange target for fast ions in the plasma of large-scale toroidal devices under NBI conditions

Mironov, M. I.*; Khudoleev, A. V.*; Kusama, Yoshinori

Plasma Physics Reports, 30(2), p.164 - 168, 2004/02

 Times Cited Count:0 Percentile:0.02(Physics, Fluids & Plasmas)

High-energy charge-exchange diagnostics can determine the distribution function of fast atoms produced via the neutralization of hydrogen ions by hydrogen-like impurity ions. Deriving the distribution function requires to know the composition and spatial distribution of the target ions in a plasma. A charge-exchange target forms as a result of the interaction between impurity nuclei and beam atoms. Depending on the arrangement of heating beams with respect to the diagnostics, it is necessary to calculate their trajectories. A model which takes into account elementary processes resulting in the ionization equilibrium of the ions of impurities in a specific tokamak configuration is proposed. The model is applied to the JT-60U plasma. Mechanisms for the formation of charge-exchange atomic flows are considered. The relative contributions of different heating injectors to the charge-exchange flow are estimated. Based on the calculated results, a method is proposed for local measurements of the ion distribution function with a stationary analyzer.

Journal Articles

Accelerator R&D for JT-60U and ITER NB systems

Inoue, Takashi; Hanada, Masaya; Iga, Takashi*; Imai, Tsuyoshi; Kashiwagi, Mieko; Kawai, Mikito; Morishita, Takatoshi; Taniguchi, Masaki; Umeda, Naotaka; Watanabe, Kazuhiro; et al.

Fusion Engineering and Design, 66-68, p.597 - 602, 2003/09

 Times Cited Count:21 Percentile:80.27(Nuclear Science & Technology)

The neutral beam (NB) injection has been one of the most promising methods for plasma heating and current drive in tokamak fusion devices. JAERI has developed high energy electrostatic accelerators for the NB systems in JT-60U and ITER. Recent progress on this R&D are as follows: 1) In the JT-60U NB system, some of the beams has been deflected due to distorted electric field in the accelerator, resulting in an excess heat load on the NB port. By correcting the electric field, a continuous injection of H$$^{0}$$ beam was succeeded for 10 s with the NB power of 2.6 MW at 355 keV. 2) To increase the beam energy, a metal structure called stress ring was designed. The ring reduces electric field concentration at the triple junction point (interface between metal and dielectric insulator inside vacuum). Initial test of the accelerators with the stress rings has shown higher voltage hold off performance in both accelerators for JT-60U and ITER R&D than that without rings.

JAEA Reports

Conceptual design of cesium removal device for ITER NBI maintenance

Oka, Kiyoshi; Shibanuma, Kiyoshi

JAERI-Tech 2003-004, 57 Pages, 2003/03

JAERI-Tech-2003-004.pdf:2.36MB

Cesium is required in order to generate a stable negative ion of hydrogen in an ion source of the neutral beam injector (NBI), which is one of the plasma-heating devices for International Thermonuclear Experimental Reactor (ITER). After long time operation of NBI, the cesium deposits to the insulators supporting the electrode. Due to the deterioration of the insulation resistance, the continuous operation of the NBI will be difficult. In addition, the NBI device is activated by neutron from D-T plasma, so that a periodic removal and cleaning of the cesium on the insulators by remote handling is required. A study of the cesium removal scenario and device is therefore required considering remote handling. In this report, a cesium removal procedure and conceptual design of the cesium removal device using laser ablation technique are studied, and the feasibility of laser ablation is shown.

Journal Articles

Effects of finite radial excursion on the slowing-down distribution of toroidally circulating energetic ions produced by tangential neutral beam injection

Wang, S.*; Ozeki, Takahisa; Xie, J.*; Hayashi, Nobuhiko

Physics of Plasmas, 9(11), p.4654 - 4663, 2002/11

 Times Cited Count:0 Percentile:0.02(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Operation and develoment on the positive-ion based neutral beam injection system for JT-60 and JT-60U

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Mogaki, Kazuhiko; Oga, Tokumichi; Ohara, Hiroshi; Umeda, Naotaka; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.424 - 434, 2002/09

 Times Cited Count:15 Percentile:69.46(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Neutral beam injectors for ITER and tokamak fusion reactors

Inoue, Takashi

Purazuma, Kaku Yugo Gakkai-Shi, 78(5), p.398 - 404, 2002/05

Neutral beam (NB) heating and current drivesystem for ITER fires the energetic particle beams of 1 MeV, 33 MW (16.5 MW/NB injector) into the fusion plasma. The design allows late installation of third NB injector for upgrade in current drive experiment toward steady state operation. The ITER NB system has been designed to fulfill requirements of the plasma physics, including advanced scenario achieved with off-axis current drive by NB. A design overview of the ITER NB system is described. The paper also reports recent R&D status of ion source and accelerator, as key components of the NB system, toward ITER construction. NB heating and current drive performance required in future tokamak reactors are discussed together with the necessary R&D issues.

Journal Articles

Design of neutral beam system for ITER-FEAT

Inoue, Takashi; Di Pietro, E.*; Hanada, Masaya; Hemsworth, R. S.*; Krylov, A.*; Kulygin, V.*; Massmann, P.*; Mondino, P. L.*; Okumura, Yoshikazu; Panasenkov, A.*; et al.

Fusion Engineering and Design, 56-57, p.517 - 521, 2001/10

 Times Cited Count:59 Percentile:96.52(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Study of increasing the beam power on the negative ion based neutral beam injector for JT-60U

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Kusaka, Makoto*; et al.

Fusion Engineering and Design, 56-57(Part.A), p.523 - 527, 2001/10

 Times Cited Count:5 Percentile:40.34(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Steering of H$$^{-}$$ ion beamlet by aperture displacement

Inoue, Takashi; Suzuki, Yasuo*; Miyamoto, Kenji; Okumura, Yoshikazu

JAERI-Tech 2000-051, 16 Pages, 2000/09

JAERI-Tech-2000-051.pdf:2.27MB

no abstracts in English

JAEA Reports

Steering of high energy negative ion beam and design of beam focusing/deflection compensation for JT-60U large negative ion source

Inoue, Takashi; Miyamoto, Kenji; Nagase, Akihito*; Okumura, Yoshikazu; Watanabe, Kazuhiro

JAERI-Tech 2000-023, p.27 - 0, 2000/03

JAERI-Tech-2000-023.pdf:1.18MB

no abstracts in English

Journal Articles

Power flow in the negative-ion based neutral beam injection for JT-60

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Kusaka, Makoto*; et al.

Review of Scientific Instruments, 71(2), p.751 - 754, 2000/02

 Times Cited Count:17 Percentile:69.07(Instruments & Instrumentation)

no abstracts in English

89 (Records 1-20 displayed on this page)