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Journal Articles

Structural analyses of HV bushing for ITER heating NB system

Tobari, Hiroyuki; Inoue, Takashi; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Sakamoto, Keishi; Kuriyama, Masaaki*; et al.

Fusion Engineering and Design, 88(6-8), p.975 - 979, 2013/10

 Times Cited Count:1 Percentile:10.81(Nuclear Science & Technology)

The HV bushing, one of the ITER NB components, which is to be procured by JADA, is a multi-conductor feed through composed of five-stage double-layered insulator columns with large brazed ceramic ring and fiber reinforced plastic (FRP) ring. The HV bushing is a bulk head between insulation gas at 0.6 MPa and vacuum. The FRP ring is required to sustain the pressure load, seismic load and dead weight. Brazing area of the ceramic ring with Kovar is required to maintain vacuum leak tightness and pressure tightness against the air filled at 0.6 MPa. To design the HV bushing satisfying the safety factor of $$geq$$ 3.5, mechanical analyses were carried out. As for the FRP ring, it was confirmed that isotropic fiber cloth FRP rings should be used for sufficient strength against shear stress. Also, shape and fixation area of the Kovar sleeve were modified to lower the stress at the joint area. As a result, a design of the insulator for the HV bushing was established satisfying the requirement.

Journal Articles

Compensations of beamlet deflections for 1 MeV accelerator of ITER NBI

Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; Dairaku, Masayuki; Tobari, Hiroyuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Inoue, Takashi; DeEsch, H. P. L.*; Grisham, L. R.*; et al.

AIP Conference Proceedings 1515, p.227 - 236, 2013/02

 Times Cited Count:12 Percentile:96.19

In a five stage multi-aperture multi-grid (MAMuG) accelerator for the ITER neutral beam injector (NBI), 1 MeV, 40 A D$$^-$$ ion beam is required for 1 hour. However, beamlets are deflected due to (1) magnetic field for electron suppression and (2) space charge repulsion between beamlets, and consequently, cause excess grid heat load. A three dimensional beam analysis has been carried out to compensate the beamlet deflections. This paper shows that the beamlet deflections due to (1) and (2) are compensated by an aperture offset of only 0.6 mm applied to the aperture of 17 mm in diameter in the extractor and by a metal bar attached around aperture area beneath the extractor, respectively. When the metal bar is increased to 3 mm in thickness and installed 30 mm away from the aperture area, the beamlet is steered gently by the weaker electric field distortion. The beam optics was confirmed not deteriorated by those compensations. The presentation also discusses application of these compensation techniques to the ITER design.

Journal Articles

Beam optics in a MeV-class multi-aperture multi-grid accelerator for the ITER neutral beam injector

Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; DeEsch, H. P. L.*; Grisham, L. R.*; Boilson, D.*; Hemsworth, R. S.*; Tanaka, Masanobu*; Tobari, Hiroyuki; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 83(2), p.02B119_1 - 02B119_3, 2012/02

 Times Cited Count:11 Percentile:47.28(Instruments & Instrumentation)

In a multi-aperture multi-grid (MAMuG) accelerator of the ITER neutral beam injector (NBI), 1 MeV, 40 A D$$^{-}$$ ion beam is required for 3600 s. Suppression of grid power loading by the direct interception of deflected beamlets is one of the critical issues to realize this accelerator. The beamlets are deflected due to space charge repulsion among beamlets/beam groups and magnetic field. Moreover, the beamlet deflection is influenced by electric field distortion generated by grid supports. To examine such complicated beamlet deflections and design the compensating methods, a three-dimensional beam analysis has been applied to the ITER accelerator. As the simulation model, a 1/4 accelerator model including step/edge of the grid supports is constructed. As results, compensation methods of the beamlet deflection, that it, a metal bar of 1 mm thick around the aperture area, and an aperture offset of 1 mm, were designed.

Journal Articles

1 MV vacuum insulation for the ITER neutral beam injectors

Tanaka, Masanobu*; Hemsworth, R. S.*; Kuriyama, Masaaki*; Svensson, L.*; Boilson, D.*; Inoue, Takashi; Tobari, Hiroyuki; Kashiwagi, Mieko; Taniguchi, Masaki; Umeda, Naotaka; et al.

IEEE Transactions on Plasma Science, 39(6), p.1379 - 1385, 2011/06

 Times Cited Count:6 Percentile:27.45(Physics, Fluids & Plasmas)

In the ITER neutral beam injector (NBI) for plasma heating and current drive, 40 A D$${-}$$ ions are accelerated to 1 MeV with a five-stage electrostatic accelerator. Since the accelerator is immersed in vacuum, vacuum insulation of -1 MV is one of critical issues. In order to sustain high voltage of -1 MV, minimum gap length between the accelerator and the vacuum vessel at ground potential was designed to be more than 900 mm on the basis of previous experimental data. High voltage bushing (HVB) acting as an insulating feed-through supplying electric power and cooling water to the accelerator consists of five stack insulator and each stage is designed to withstand -200 kV. A full-scale and single-stage mockup bushing was manufactured and tested to demonstrate stable voltage holding. As a result, DC -203 kV was sustained stably for 5 hours and the insulation design of HVB has been confirmed.

Journal Articles

Development of full-size mockup bushing for 1 MeV ITER NB system

Tobari, Hiroyuki; Inoue, Takashi; Hanada, Masaya; Dairaku, Masayuki; Watanabe, Kazuhiro; Umeda, Naotaka; Taniguchi, Masaki; Kashiwagi, Mieko; Yamanaka, Haruhiko; Takemoto, Jumpei; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

High voltage (HV) bushing in the ITER NBI is one of critical components, which acts as a feedthrough for electric power and cooling water from the -1 MV power supply in SF$$_{6}$$ gas to beam source inside vacuum. JAEA has overcome a longstanding issue on manufacturing of a large bore ceramic ring with 1.56 m in diameter as the insulator of the five-stage HV bushing. Joining method of the ceramic and metal flange with thick Kovar plate to form vacuum boundary was also developed. By assembling components, a full-size mockup bushing simulating one stage of the HV bushing was successfully manufactured. In the voltage holding test, the high voltage of 240 kV including the margin of 20 % of a rated voltage was sustained for 3600 s without breakdown, and the voltage holding capability required in ITER was successfully verified.

Journal Articles

1 MV holding and beam optics in a multi-aperture multi-grid accelerator for ITER NBI

Kashiwagi, Mieko; Taniguchi, Masaki; Kojima, Atsushi; Dairaku, Masayuki; Hanada, Masaya; Hemsworth, R. S.*; Mizuno, Takatoshi*; Takemoto, Jumpei; Tanaka, Masanobu*; Tanaka, Yutaka*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

At JAEA, a multi-aperture multi-grid accelerator has been developed for the ITER neutral beam system. A target is H$$^{-}$$ ion beam acceleration of 0.5 A (200 A/m$$^{2}$$) at 1 MeV. In real accelerators, it was found that the voltage holding was about a half of that obtained in an ideal small electrode. After applying necessary gap length and radii of edges of grid supports to lower local electric field concentrations, the accelerator succeeded in sustaining 1 MV for 4000 s. As a result, beam parameters were increased to 879 keV, 0.36 A (157 A/m$$^{2}$$) at perveance matched condition from 796 kV, 0.32 A (140 A/m$$^{2}$$) reported in FEC2008. In the beam acceleration, the beamlet deflections due to magnetic field and space charge repulsion caused direct interceptions, that resulted in limitations in the beam energy and current. Compensation of these beamlet deflections has been tested applying aperture offset and field shaping plate, which were examined in a three-dimensional beam analysis.

Journal Articles

Progress on the heating and current drive systems for ITER

Jacquinot, J.*; Albajar, F.*; Beaumont, B.*; Becoulet, A.*; Bonicelli, T.*; Bora, D.*; Campbell, D.*; Chakraborty, A.*; Darbos, C.*; Decamps, H.*; et al.

Fusion Engineering and Design, 84(2-6), p.125 - 130, 2009/06

 Times Cited Count:24 Percentile:82.52(Nuclear Science & Technology)

The electron cyclotron (EC), ion cyclotron (IC), neutral beam (NB) and, lower hybrid (LH) systems for ITER have been reviewed in 2007/2008 in light of progress of physics and technology. Although the overall specifications are unchanged, notable changes have been approved. Firstly, the full 73MW should be commissioned and available on a routine basis before the D/T phase. Secondly, the possibility to operate the NB at full power during the hydrogen phase requiring new shine through protection; IC with 2 antennas with increased robustness; 2 MW transmission systems to provide an easier upgrading of the EC power; the addition of a building dedicated to the RF power sources and to a testing facility for acceptance of diagnostics and heating port plugs. Thirdly, the need of a plan for developing, in time for the active phase, a CD system such as LH suitable for very long pulse operation of ITER was recognized.

Journal Articles

Status of the ITER heating neutral beam system

Hemsworth, R. S.*; Decamps, H.*; Graceffa, J.*; Schunke, B.*; Tanaka, Masanobu*; Dremel, M.*; Tanga, A.*; DeEsch, H. P. L.*; Geli, F.*; Milnes, J.*; et al.

Nuclear Fusion, 49(4), p.045006_1 - 045006_15, 2009/04

 Times Cited Count:381 Percentile:99.75(Physics, Fluids & Plasmas)

The ITER neutral beam (NB) injectors are the first injectors that will be operated under conditions and constraints similar to those in a fusion reactor. These injectors will be operated in a radiation environment and they will be activated due to the neutron flux from ITER. The injectors uses a single large ion source and accelerator that will produce 40 A 1 MeV D$$^{-}$$ beams for pulse lengths of up to 3600 s. Design changes have been made to the ITER NB injectors over the past 4 years as follows: (1) Modifications to allow installation and maintenance of the beamline components with an overhead crane. (2) The RF driven negative ion source has replaced the filamented ion source. (3) The ion source power supplies will be located in an air insulated high voltage (-1 MV) deck located outside the tokamak building instead of inside an SF6 insulated HV deck located above the injector. This paper describes the status of the design as of December 2008 including the above mentioned changes.

Journal Articles

Positive and negative ion sources for magnetic fusion

Hemsworth, R. S.*; Inoue, Takashi

IEEE Transactions on Plasma Science, 33(6), p.1799 - 1813, 2005/12

 Times Cited Count:88 Percentile:92.87(Physics, Fluids & Plasmas)

The positive or negative ion sources which form the primary components of neutral beam injection systems used in magnetic fusion have to meet simultaneously several demanding requirements. This paper describes the underlying physics of modern positive ion sources, which provide the required high proton fraction ($$>$$90%) and high current density ($$approx$$2 kA/m$$^{2}$$) at a low source pressure (0.4 Pa) with a high electrical efficiency and uniformity across the accelerator grids. The development of negative ion sources, which are required if high energy neutral beams are to be produced, is explained. The paper reports that negative ion sources have achieved many of the parameters required of sources for the neutral beam injectors of future fusion devices and reactors, $$>$$200 A/m$$^{2}$$ of D$$^{-}$$ at low pressure, $$<$$0.3 Pa, with low co-extracted electron content. The development needed to meet all the requiremens of future systems is briefly discussed.

Journal Articles

Long pulse production of high density negative(H$$^{-}$$/D$$^{-}$$) ion beams in negative ion source development for NBI

Kashiwagi, Mieko; Amemiya, Toru*; Iga, Takashi*; Inoue, Takashi; Imai, Tsuyoshi; Okumura, Yoshikazu; Takayanagi, Tomohiro; Hanada, Masaya; Fujiwara, Yukio; Morishita, Takatoshi; et al.

Dai-12-Kai Ryushisen No Sentanteki Oyo Gijutsu Ni Kansuru Shimpojiumu (BEAMS 2001) Hobunshu, p.37 - 40, 2001/11

no abstracts in English

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:64 Percentile:96.64(Nuclear Science & Technology)

no abstracts in English

Journal Articles

ITER R&D: Auxiliary systems; Neutral beam heating and current drive system

Inoue, Takashi; Hemsworth, R. S.*; Kulygin, V.*; Okumura, Yoshikazu

Fusion Engineering and Design, 55(2-3), p.291 - 301, 2001/07

 Times Cited Count:25 Percentile:84.44(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Neutral beams for the International Thermonuclear Experimental Reactor

Inoue, Takashi; Di Pietro, E.*; Mondino, P. L.*; Bayetti, P.*; Hemsworth, R. S.*; Massmann, P.*; Fujiwara, Yukio; Hanada, Masaya; Miyamoto, Kenji; Okumura, Yoshikazu; et al.

Review of Scientific Instruments, 71(2), p.744 - 746, 2000/02

 Times Cited Count:17 Percentile:67.98(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Physics assessment of the NBI capability in ITER plasmas

Oikawa, Toshihiro; Polevoi, A. R.*; Mukhovatov, V.*; Sakamoto, Yoshiteru; Kamada, Yutaka; Shimada, Michiya*; Campbell, D. J.*; Chuyanov, V.*; Schunke, B.*; Tanga, A.*; et al.

no journal, , 

In the ITER design review, reducing the NBI energy is proposed for increasing the plasma rotation in terms of suppressing MHD instabilities. NBI capability has been assessed for various design possibilities. In D-T operation, the planned auxiliary heating power makes possible reliable operation well above the H-L transition boundary. In hydrogen operation the beam energy should be limited to 500keV due to the NBI shinethrough. However, reduction of the NBI central heating at high density necessary for the ITER mission is significant at 500keV, confirming the need for higher energy in DT operation. Although the rotation increases by 13% at 750keV relative to 1MeV at constant power, NB current drive decreases by 20%, which would be problematic for the development of steady-state scenarios. Therefore it is concluded that the beam energy should be kept 1MeV in DT operation. The beam energy variation in a pulse enables the plasma beta control for avoiding the stability boundary.

Oral presentation

Development of DC ultra-high voltage insulation technology for ITER NBI

Tobari, Hiroyuki; Hanada, Masaya; Watanabe, Kazuhiro; Kashiwagi, Mieko; Kojima, Atsushi; Dairaku, Masayuki; Seki, Norikatsu; Abe, Hiroyuki; Umeda, Naotaka; Yamanaka, Haruhiko; et al.

no journal, , 

Progress on technical development on ITER and JT-60SA neutral beam injector (NBI) were reported. In development of a 1 MV insulating transformer for ITER NB power supply, a bushing extracting 1 MV required a huge insulator that was impossible to manufacture. To solve this issue, a composite bushing with FRP tube and a small condenser bushing with insulation gas was newly developed. In development the HV bushing as an insulating feed through, voltage holding in large cylindrical electrodes inside the HV bushing was investigated. The scaling for vacuum insulation design of large cylindrical electrodes was obtained. Toward long pulse production and acceleration of negative ion beam, active control system of plasma grid temperature and a new extractor consisting of the extraction grid with high water cooling capability and aperture offset were developed. As a result, 15 negative ion beam has been achieved for 100 s. Also beam energy density has been increased two orders of magnitude.

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