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Journal Articles

Outline of Japan Atomic Energy Agency's Okuma Analysis and Research Center, 3; Laboratory-2

Ito, Masayasu; Ogawa, Miho; Inoue, Toshihiko; Yoshimochi, Hiroshi; Koyama, Shinichi; Koyama, Tomozo; Nakayama, Shinichi

Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 7 Pages, 2017/00

Laboratory-2 of the Okuma Analysis and Research Center will be used for the technological development of techniques to treat and dispose fuel debris, etc. The specific analytical content and its importance has been discussed by an experts committee in FY 2016. The committee regarded fuel debris retrieval and criticality control related topics as the most important content. As a result, it will be a priority to introduce equipment to perform examination such as shape and size measurement, compositional and nuclide analysis, hardness and toughness test, and radiation dose rate measurement. In addition, since sample will have high dose rates (1 Sv/h or more) at the time of reception, hot cells with enough radiation shielding ability will be used. In the hot cell, the pre-processing will be performed, such as cutting and dissolution of samples. Processed samples will be examined in concrete cells, steel cells, glove boxes and fume hoods. Detail design of Laboratory-2 started on FY 2017.

Journal Articles

Long-pulse beam acceleration of MeV-class H$$^{-}$$ ion beams for ITER NB accelerator

Umeda, Naotaka; Kashiwagi, Mieko; Taniguchi, Masaki; Tobari, Hiroyuki; Watanabe, Kazuhiro; Dairaku, Masayuki; Yamanaka, Haruhiko; Inoue, Takashi; Kojima, Atsushi; Hanada, Masaya

Review of Scientific Instruments, 85(2), p.02B304_1 - 02B304_3, 2014/02

 Times Cited Count:10 Percentile:46.06(Instruments & Instrumentation)

In order to realize neutral beam systems in ITER whose target is to produce D$$^{-}$$ ion beam of 1 MeV, 200 A/m$$^{2}$$ during 3600s, the electrostatic five-stages negative ion accelerator has been developed at JAEA. To extend pulse length, heat load of the acceleration grids was reduced by controlling the ion beam trajectory. Namely, the beam deflection due to the residual magnetic filter in the accelerator was suppressed with the newly developed extractor with a 0.5 mm off-set aperture displacement. The use of new extractor improved the deflection angle from 6 mrad to 1 mrad, resulting in the reduction of direct interception of negative ions from 23% to 15% of the total acceleration power, respectively. As a result, the pulse length of 130 A/m$$^{2}$$, 881 keV H$$^{-}$$ ion beam has been successfully extended from a previous value of 0.4s to 8.7s.

Journal Articles

Development of negative ion extractor in the high-power and long-pulse negative ion source for fusion application

Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kojima, Atsushi; Yoshida, Masafumi; Taniguchi, Masaki; Dairaku, Masayuki; Maejima, Tetsuya; Yamanaka, Haruhiko; Watanabe, Kazuhiro; et al.

Review of Scientific Instruments, 85(2), p.02B320_1 - 02B320_3, 2014/02

 Times Cited Count:23 Percentile:20.53(Instruments & Instrumentation)

The negative ion extractor for high power and long-pulse operations is newly developed toward the neutral beam injector (NBI) for heating & current drive of future fusion machines such as ITER, JT-60 Super Advanced (SA) and DEMO reactor. The satisfactory cooling capability is designed in the thermal analysis. A negative ion production and a suppression of electrons are experimentally validated for this new extractor. As the results, the negative ion current shows increases by a factor of 1.3 with suppressing the electron current. The beam divergence angle is also maintained small enough, 4 mrad.

Journal Articles

Voltage holding capability of large-size acceleration grid with multiple-apertures and multiple-stage for negative ion source

Kojima, Atsushi; Hanada, Masaya; Inoue, Takashi; NB Heating Technology Group; Yamano, Yasushi*; Kobayashi, Shinichi*

Journal of the Vacuum Society of Japan, 56(12), p.502 - 506, 2013/12

Voltage holding capability of a large negative ion source for fusion application is experimentally examined, which is characterized by multiple-stage acceleration with multiple-apertures over 1000 on large-area grids of 2 m$$^{2}$$ for the multiple-beamlet accelerations. From the observation of the vacuum discharge between the grids, it was found that the aperture generated 10 times larger dark current than the flat region and initiated the vacuum discharge associated with the breakdown. As a result, it was found that the sustainable voltages were dominated by not only the surface area but also the number of the apertures. Because these effects were originated in the area effects by weak and strong electric field profiles, these results implied the surface integration of the electric field were the key parameter for the vacuum insulation.

Journal Articles

Origin of non-uniformity of the source plasmas in JT-60 negative ion source

Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Inoue, Takashi; Kashiwagi, Mieko; Grisham, L. R.*; Akino, Noboru; Endo, Yasuei; Komata, Masao; Mogaki, Kazuhiko; et al.

Plasma and Fusion Research (Internet), 8(Sp.1), p.2405146_1 - 2405146_4, 2013/11

Distributions of H$$^{0}$$ and H$$^{+}$$ in the source plasmas produced at the end-plugs of JT-60 negative ions source were measured by Langmuir probes and emission spectroscopy in order to experimentally investigate the cause of lower density of the negative ions extracted from end-plugs in the source. Densities of H$$^{0}$$ and H$$^{+}$$ in end-plugs of the plasma grid in the source were compared with those in the center regions. As a result, lower density of the negative ion at the edge was caused by lower beam optics due to lower and higher density of the H$$^{0}$$ and H$$^{+}$$.

Journal Articles

Long-pulse production of the negative ion beams for JT-60SA

Kojima, Atsushi; Hanada, Masaya; Yoshida, Masafumi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Grisham, L. R.*; et al.

Fusion Engineering and Design, 88(6-8), p.918 - 921, 2013/10

 Times Cited Count:6 Percentile:46.23(Nuclear Science & Technology)

In this paper, the recent activities are reported toward demonstration of the long pulse production. As for the improvement of uniform beam current profile, a symmetric magnetic field configuration for the source plasma production, a so-called tent-shaped filter, was found to be effective to improve the uniformity of the beam current profile. A similar configuration is applied to the JT-60 negative ion source whose plasma size is 1220 mm $$times$$ 564 mm. An estimation from trajectory calculations of primary electrons with the symmetric magnetic field configuration showed that the primary electrons were distributed uniformly in a longitudinal direction. As for the temperature control of the plasma grid, a prototype of the grid with cooling/heating by circulating a high-temperature fluorinated fluid has been developed. This grid was found to have a capability to control the temperature with a time constant of 10 s by considering the physical properties of the fluid.

Journal Articles

Vacuum insulation of the high energy negative ion source for fusion application

Kojima, Atsushi; Hanada, Masaya; Hilmi, A.*; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.

Review of Scientific Instruments, 83(2), p.02B117_1 - 02B117_5, 2012/02

 Times Cited Count:14 Percentile:37.24(Instruments & Instrumentation)

Production of 500 keV, 3 A beams has been successfully achieved in the JT-60 negative by overcoming the low voltage holding of the accelerator. Toward the design of next ion source, database for the voltage holding capability based on experimental results is required and obtained. As a result, the voltage holding capability was found to vary with 67 N power of -0.15 and with 31.7 S power of -0.125 where N is the aperture number and S is the anode surface area. When N = 1100 and S = 2 m$$^{2}$$ are applied to the design of JT-60SA ion source, the factors C are estimated to be 23 and 29, respectively. Therefore, the influence of the local electric field around the apertures is stronger than that of the surface area.

Journal Articles

Voltage holding study of 1 MeV accelerator for ITER neutral beam injector

Taniguchi, Masaki; Kashiwagi, Mieko; Umeda, Naotaka; Dairaku, Masayuki; Takemoto, Jumpei; Tobari, Hiroyuki; Tsuchida, Kazuki; Yamanaka, Haruhiko; Watanabe, Kazuhiro; Kojima, Atsushi; et al.

Review of Scientific Instruments, 83(2), p.02B121_1 - 02B121_3, 2012/02

 Times Cited Count:11 Percentile:45.14(Instruments & Instrumentation)

JAEA has developed the MeV accelerator to demonstrate 1 MeV, 200 A/m$$^{2}$$ H$$^{-}$$ ion beam acceleration required for ITER NBI. A key to realize such a high power accelerator is improvement of voltage holding capability. Based on detailed investigation of the voltage holding characteristics, MeV accelerator was modified to reduce electric field concentration by extending gaps between the grid supports and increasing curvature radiuses at the support corners. After the modifications, accelerator succeeded in sustaining -1 MV in vacuum without beam acceleration. Moreover, beam deflection due to the magnetic field for electron suppression and space charge repulsion was compensated by aperture displacement technique. As the result, beam deflection was compensated and voltage holding during the beam acceleration was improved. Beam parameter of the MeV accelerator was increased to 980 keV, 185 A/m$$^{2}$$, which is close to the requirement of ITER accelerator.

Journal Articles

First neutral beam injection experiments on KSTAR tokamak

Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; In, S. R.*; Lee, K. W.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Review of Scientific Instruments, 83(2), p.02B102_1 - 02B102_3, 2012/02

 Times Cited Count:18 Percentile:29.94(Instruments & Instrumentation)

The first NB (neutral beam) injection system of the KSTAR tokamak was partially completed in 2010 with only 1/3 of its full design capability, and NB heating experiments were carried out during the 2010 KSTAR operation campaign. The ion source is composed of a JAEA bucket plasma generator and a KAERI large multi-aperture accelerator assembly. Before the beam injection experiments, characteristics of the ion source were investigated. A minimum beam divergence angle was 0.8 $$^{circ}$$. The ion species ratio was D$$^{+}$$:D$$_{2}$$$$^{+}$$:D$$_{3}$$$$^{+}$$=75:20:5. The arc efficiency is more than 1.0 A/kW. In the 2010 KSTAR campaign, the deuterium NB power of 0.7-1.5 MW was successfully injected into the KSTAR plasma with the beam energy of 70-90 keV. L-H transitions were observed within a wide range of beam powers relative to a threshold value. In every deuterium NB injection, a burst of D-D neutrons was recorded, and increases in the ion temperature and the plasma stored energy were found.

Journal Articles

Detailed analyses of key phenomena in core disruptive accidents of sodium-cooled fast reactors by the COMPASS code

Morita, Koji*; Zhang, S.*; Koshizuka, Seiichi*; Tobita, Yoshiharu; Yamano, Hidemasa; Shirakawa, Noriyuki*; Inoue, Fusao*; Yugo, Hiroaki*; Naito, Masanori*; Okada, Hidetoshi*; et al.

Nuclear Engineering and Design, 241(12), p.4672 - 4681, 2011/12

 Times Cited Count:10 Percentile:31.15(Nuclear Science & Technology)

A five-year research project has been initiated in 2005 to develop a code based on the MPS (Moving Particle Semi-implicit) method for detailed analysis of key phenomena in core disruptive accidents (CDAs) of sodium-cooled fast reactors (SFRs). The code is named COMPASS (Computer Code with Moving Particle Semi-implicit for Reactor Safety Analysis). The key phenomena include (1) fuel pin failure and disruption, (2) molten pool boiling, (3) melt freezing and blockage formation, (4) duct wall failure, (5) low-energy disruptive core motion, (6) debris-bed coolability, (7) metal-fuel pin failure. Validation study of COMPASS is progressing for these key phenomena. In this paper, recent COMPASS results of detailed analyses for the several key phenomena are summarized. The present results demonstrate COMPASS will be useful to understand and clarify the key phenomena of CDAs in SFRs in details.

Journal Articles

Progress in development and design of the neutral beam injector for JT-60SA

Hanada, Masaya; Kojima, Atsushi; Tanaka, Yutaka; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Akino, Noboru; et al.

Fusion Engineering and Design, 86(6-8), p.835 - 838, 2011/10

 Times Cited Count:8 Percentile:38.85(Nuclear Science & Technology)

Neutral beam (NB) injectors for JT-60 Super Advanced (JT-60SA) have been designed and developed. Twelve positive-ion-based and one negative-ion-based NB injectors are allocated to inject 30 MW D$$^{0}$$ beams in total for 100 s. Each of the positive-ion-based NB injector is designed to inject 1.7 MW for 100s at 85 keV. A part of the power supplies and magnetic shield utilized on JT-60U are upgraded and reused on JT-60SA. To realize the negative-ion-based NB injector for JT-60SA where the injection of 500 keV, 10 MW D$$^{0}$$ beams for 100s is required, R&Ds of the negative ion source have been carried out. High-energy negative ion beams of 490-500 keV have been successfully produced at a beam current of 1-2.8 A through 20% of the total ion extraction area, by improving voltage holding capability of the ion source. This is the first demonstration of a high-current negative ion acceleration of $$>$$1 A to 500 keV. The design of the power supplies and the beamline is also in progress. The procurement of the acceleration power supply starts in 2010.

Journal Articles

Acceleration of 500 keV negative ion beams by tuning vacuum insulation distance on JT-60 negative ion source

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Kobayashi, Shinichi*; et al.

AIP Conference Proceedings 1390, p.466 - 475, 2011/09

 Times Cited Count:2 Percentile:43.75

Voltage holding tests by using JT-60 negative ion source and small electrodes was carried out because JT-60 negative ion source had a critical problem about low voltage holding capability for long time. As a result, the voltage holding capability is decreased with the increase of area where local electric field is generated, as well as the surface area according to existing scaling low about surface area. Therefore, in order to improve the voltage holding without changing the existing accelerator, the voltage holding test was carried out by extending gap lengths of the negative ion source. In order to improve the voltage holding, beam radiation shield needs to be optimized additionally. As a result, the voltage holding has been improved to 500 kV and stabilized. By using this modified ion source, negative ion beams of 500 keV up to 3A has been successfully produced.

Journal Articles

Development of the JT-60SA Neutral Beam Injectors

Hanada, Masaya; Kojima, Atsushi; Inoue, Takashi; Watanabe, Kazuhiro; Taniguchi, Masaki; Kashiwagi, Mieko; Tobari, Hiroyuki; Umeda, Naotaka; Akino, Noboru; Kazawa, Minoru; et al.

AIP Conference Proceedings 1390, p.536 - 544, 2011/09

 Times Cited Count:5 Percentile:20.64

no abstracts in English

Journal Articles

Improvement of voltage holding and high current beam acceleration by MeV accelerator for ITER NB

Taniguchi, Masaki; Kashiwagi, Mieko; Inoue, Takashi; Umeda, Naotaka; Watanabe, Kazuhiro; Tobari, Hiroyuki; Dairaku, Masayuki; Yamanaka, Haruhiko; Tsuchida, Kazuki; Kojima, Atsushi; et al.

AIP Conference Proceedings 1390, p.449 - 456, 2011/09

 Times Cited Count:2 Percentile:43.75

At JAEA, MeV accelerator has been developed as a proof-of-principle accelerator for ITER NBI. To achieve the acceleration of 1 MeV, 200 A/m$$^{2}$$ beam required for ITER, improvement of the voltage holding capability is essential. Review of voltage holding results ever obtained with various geometries of the accelerators showed that voltage holding capability was about a half of that for ideal small electrode. This is due to local electric field concentration in the accelerators, such as edge and corner between grids and its support structures. Based on these results, accelerator was modified to reduce the electric field concentration by reshaping the support structures and expanding the gap length. After the modifications, voltage holding capability in vacuum was increased from 835 kV to 1 MV. Voltage holding progressed the energy and current to 879 keV, 0.36 A (157 A/m$$^{2}$$).

Journal Articles

Arc discharge characteristics of a long pulse ion source for the KSTAR neutral beam injector

Chang, D. H.*; Jeong, S. H.*; Jin, J. T.*; Chang, D. S.*; Kim, T. S.*; Lee, K. W.*; In, S. R.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Journal of the Korean Physical Society, 59(2), p.275 - 280, 2011/08

 Times Cited Count:3 Percentile:69.22(Physics, Multidisciplinary)

A long pulse ion source (LPIS) for the neutral beam injector (NBI) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) superconducting tokamak. The arc discharge characteristics of the ion source were investigated on the first KSTAR neutral beam injector (NBI-1). The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of prototype tetrode accelerators with circular apertures. Stable and efficient arc plasmas up to an arc power of 70 kW have been produced by using a constant power-mode operation of the arc power supply. The reliable operation region of the arc discharges has been investigated for various filament heating voltages, arc powers, and amounts of injected deuterium gas.

Journal Articles

Achievement of 500 keV negative ion beam acceleration on JT-60U negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08

 Times Cited Count:40 Percentile:10.75(Physics, Fluids & Plasmas)

Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.

Journal Articles

Thickness and density of additive adsorbed layer on metal surface measured by neutron reflectometry and its effect on tribological properties

Hirayama, Tomoko*; Torii, Takashi*; Konishi, Yohei*; Maeda, Masayuki*; Matsuoka, Takashi*; Inoue, Kazuko*; Hino, Masahiro*; Yamazaki, Dai; Takeda, Masayasu

Nippon Kikai Gakkai Rombunshu, C, 77(779), p.2884 - 2893, 2011/07

Journal Articles

Event structure and double helicity asymmetry in jet production from polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07

 Times Cited Count:22 Percentile:28.74(Astronomy & Astrophysics)

We report on the event structure and double helicity asymmetry ($$A_{LL}$$) of jet production in longitudinally polarized $$p + p$$ collisions at $$sqrt{s}$$ = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured $$A_{LL}$$ = -0.0014 $$pm$$ 0.0037 at the lowest $$P_T$$ bin and -0.0181 $$pm$$ 0.0282 at the highest $$P_T$$ bin. The measured $$A_{LL}$$ is compared with the predictions that assume various $$Delta G(x)$$ distributions.

Journal Articles

Results of beam extraction performance for the KSTAR neutral beam injector

Chang, D. H.*; Jeong, S. H.*; Kim, T. S.*; Lee, K. W.*; In, S. R.*; Jin, J. T.*; Chang, D. S.*; Oh, B. H.*; Bae, Y. S.*; Kim, J. S.*; et al.

Japanese Journal of Applied Physics, 50(6), p.066302_1 - 066302_7, 2011/06

 Times Cited Count:9 Percentile:56.53(Physics, Applied)

A stable ion beam extraction of the LPIS-1 was achieved up to 85 kV/32 A for a 5 s pulse length and 80 kV/25 A for a 14 s pulse length. An optimum beam perveance of 1.15 $$mu$$perv was observed at an acceleration voltage of 60 kV. Neutralization efficiency was measured by a water-flow calorimetry (WFC) method using a calorimeter and the operation of a bending magnet. The full-energy species of ion beams were detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6-1.1 A/kW depending on the operating conditions of arc discharge. A neutral beam power of 1.0 MW must be sufficiently injected into the KSTAR plasmas from the LPIS-1 at a beam energy of 80 keV.

Journal Articles

Identified charged hadron production in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

 Times Cited Count:140 Percentile:0.67(Physics, Nuclear)

Transverse momentum distributions and yields for $$pi^{pm}, K^{pm}, p$$, and $$bar{p}$$ in $$p + p$$ collisions at $$sqrt{s}$$ = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different $$sqrt{s}$$ collisions. We also present the scaling properties such as $$m_T$$ and $$x_T$$ scaling and discuss the mechanism of the particle production in $$p + p$$ collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

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