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Journal Articles

Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; Koitaya, Takanori*; Yamamoto, Susumu*; Namba, Yusuke*; Song, C.*; Kim, J.*; Yoshigoe, Akitaka; Koyama, Michihisa*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06

The hydrogen absorption and diffusion mechanisms on cube-shaped Pd nanoparticles (NPs) which are important hydrogen-storage materials were studied using X-ray photoelectron spectroscopy and DFT calculations. In the surface region, hydrogen absorption showed almost similar behavior regardless of the NPs size. It was found that the octahedral sites are more favorable than the tetrahedral sites for hydrogen occupation. We also clarified that the hydrogen atoms absorbing on the smaller-sized Pd NPs diffuse to the subsurface more actively because of the weakened Pd-H bond by the surface disordering, which plays an important role in hydrogen adsorption at a low H$$_{2}$$ pressure.

Journal Articles

Development of a plasma generator for a long pulse ion source for neutral beam injectors

Watanabe, Kazuhiro; Dairaku, Masayuki; Tobari, Hiroyuki; Kashiwagi, Mieko; Inoue, Takashi; Hanada, Masaya; Jeong, S. H.*; Chang, D. H.*; Kim, T. S.*; Kim, B. R.*; et al.

Review of Scientific Instruments, 82(6), p.063507_1 - 063507_6, 2011/06

 Times Cited Count:15 Percentile:61.15(Instruments & Instrumentation)

A long pulse plasma generator for neutral beam injectors has been developed. The plasma generator was designed to produce 65 A at 120 keV from a beam extraction area of 12 cm $$times$$ 46 cm. A type of the plasma generator is a multi-cusp plasma generator with SmCo permanent magnets. A long pulse test of the plasma generator was performed at the KSTAR NBI test stand in Korea under the Japan - Korea Fusion collaboration. It was successfully demonstrated of the long pulse operation of the plasma generator for 200 s at an arc discharge power of 70 kW which can produce 65 A beams. Plasma spatial uniformity at the beam extraction area was confirmed to be smaller than $$pm$$ 8% of the deviation from an averaged ion saturation current density. A high arc efficiency of 0.9-1.1 A/kW was obtained at the beam extraction with 73 keV, 41 A for 5 sec. From these experimental studies, a performance of this plasma generator for long pulse ion sources was confirmed.

JAEA Reports

Information basis for developing comprehensive waste management system; US-Japan Joint Nuclear Energy Action Plan Waste Management Working Group Phase I report (Joint research)

Yui, Mikazu; Ishikawa, Hirohisa; Watanabe, Atsuo*; Yoshino, Kyoji*; Umeki, Hiroyuki; Hioki, Kazumasa; Naito, Morimasa; Seo, Toshihiro; Makino, Hitoshi; Oda, Chie; et al.

JAEA-Research 2010-015, 106 Pages, 2010/05

JAEA-Research-2010-015.pdf:13.58MB

This report summarizes the activity of Phase I of Waste Management Working Group of the United States - Japan Joint Nuclear Energy Action Plan started in 2007. The working group focused on consolidation of the existing technical basis between the U.S. and Japan and the joint development of a plan for future collaborative activities. Firstly, the political/regulatory frameworks related to nuclear fuel cycles in both countries were reviewed. The various advanced fuel cycle scenarios in both countries were surveyed and summarized. Secondly, the waste management/disposal system optimization was discussed. Repository system concepts for the various classifications of nuclear waste were reviewed and summarized, then disposal system optimization processes and techniques were reviewed, and factors to consider in future repository design optimization activities were also discussed. Finally the potential collaboration areas and activities related to the optimization problem were extracted.

Journal Articles

Research and development of imaging bolometers

Peterson, B. J.*; Konoshima, Shigeru; Kostryukov, A. Y.*; Seo, D. C.*; Liu, Y.*; Miroshnikov, I. V.*; Ashikawa, Naoko*; Parchamy, H.*; Kawashima, Hisato; Iwama, Naofumi*; et al.

Plasma and Fusion Research (Internet), 2, p.S1018_1 - S1018_4, 2007/11

An overview of the research and development of imaging bolometers giving a perspective on the applicability of this diagnostic to a fusion reactor is presented. Traditionally the total power lost from a high temperature has been measured using one dimensional arrays of resistive bolometers. The large number of signal wires associated with these resistive bolometers poses hazards not only at the vacuum interface, but also in the loss of electrical contacts that has been observed in the presence of fusion reactor levels of neutron flux. Infrared imaging video bolometers (IRVB), on the other hand, use the infrared radiation from the absorbing metal foil to transfer the signal through the vacuum interface and out from behind a neutron shield. The IRVB can provide hundreds of channels of bolometric signal in an image of the plasma radiation. Recently a prototype IRVB has been deployed on the JT-60U tokamak which demonstrates the ability of this diagnostic to operate in a reactor environment.

Journal Articles

Spatial variation of the foil parameters from in situ calibration of the JT-60U imaging bolometer foil

Araghy, H. P.*; Peterson, B. J.*; Hayashi, Hiromi*; Konoshima, Shigeru; Ashikawa, Naoko*; Seo, D. C.*; JT-60U Team

Plasma and Fusion Research (Internet), 2, p.S1116_1 - S1116_4, 2007/11

We obtain the local foil properties of the JT-60U imaging bolometer foil (a single graphite-coated gold foil with an effective area of 9 $$times$$ 7 cm$$^{2}$$ and a nominal thickness of 2.5 microns) such as the thermal diffusivity and the product of the thermal conductivity and the thickness of the foil by the foil calibration. Calibration of the foil was made in situ using a He-Ne laser ($$sim$$27 mW) as a known radiation source to heat the foil. The thermal images of the foil are provided by an IR camera (micro-bolometer type). The parameters are determined by finite element modeling of the foil temperature and comparing the solution to the experimental results. In this work we apply this calibration technique to investigate the spatial variation of the foil parameters. Significant variation in the local temperature rise of the foil due to local heating by the laser beam indicates a spatial variation of the foil parameters. This variation is possibly due to nonuniformity in the carbon coating and/or the thickness of the foil. In a separate work, the spatial calibration data will be used to produce the bolometer intensity data to be utilized in the tomographic analyses.

Journal Articles

Observation of divertor and core radiation in JT-60U by means of bolometric imaging

Peterson, B. J.*; Konoshima, Shigeru; Parchamy, H.*; Kaneko, Masashi*; Omori, Toshimichi*; Seo, D. C.*; Ashikawa, Naoko*; Sukegawa, Atsuhiko; JT-60 Team

Journal of Nuclear Materials, 363-365, p.412 - 415, 2007/06

 Times Cited Count:12 Percentile:66.47(Materials Science, Multidisciplinary)

Diagnosis of the radiation from both the divertor and core plasma regions is a key issue for the study of impurities resulting from plasma-surface interaction in existing magnetic plasma confinement experiments and future fusion reactors. An infrared imaging video bolometer has been designed, fabricated and installed on the JT-60U tokamak. This diagnostic utilizes an IR camera to image the temperature change of a thin foil which is exposed to plasma radiation through an aperture resulting in an image of the incident plasma radiation absorbed by the foil. In the 2004-2005 experimental campaign intitial data was taken which was limited to 8-bit analog video data from ohmic and hydrogen neutral beam discharges due to inadequate shielding. The semitangential, wide-angle view of the plasma covers the entire poloidal cross-section and the divertor extending over 90 degrees toroidally. This preliminary data showed a strong radiation zone from the divertor that moved up into the core plasma as the discharge terminated in agreement with the data from the resistive bolometer arrays. For the current campaign we have upgraded the system by improving the shielding against neutrons, $$gamma$$ and magnetic field. This has enabled operation of the camera during high magnetic field and some high power deuterium neutral beam discharges. We also improved the triggering and data transmission system to acquire 14-bit digital data. This will allow processing of the IR camera data to produce images of the radiation brightness at the foil which can be viewed as a movie with a frame rate of 30 fps. This data is used to study the toroidal uniformity of the radiation from the divertor in JT-60U.

Journal Articles

Detailed ${it in situ}$ laser calibration of the infrared imaging video bolometer for the JT-60U tokamak

Parchamy, H.*; Peterson, B. J.*; Konoshima, Shigeru; Hayashi, Hiromi*; Seo, D. C.*; Ashikawa, Naoko*; JT-60U Team

Review of Scientific Instruments, 77(10), p.10E515_1 - 10E515_4, 2006/10

 Times Cited Count:13 Percentile:57.01(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Imaging bolometers for steady state fusion experiments

Peterson, B. J.*; Seo, D. C.*; Konoshima, Shigeru; Kawashima, Hisato; Ashikawa, Naoko*; Parchamy, H.*; Liu, Y.*

no journal, , 

Resistive bolometers have problems with signal drift due to the uncompensated change in the background temperature of the detector. The electrical connections are susceptible to large changes in temperature. These characteristics render them ill suited for the application to steady-state fusion experiments. InfraRed imaging Video Bolometers (IRVB), on the other hand, are suited to steady state operation. The radiation is absorbed by the front surface of a thin foil and measured with an infrared camera. Temperature difference is taken with respect to the surrounding frame and no drift in the signal occurs. The materials are all metals and there are no electrical connections. IRVBs have been operated in LHD and JT-60U and are under design for KSTAR and planned for JT-60SA. Foil calibration and tomography techniques have been developed to provide poloidal profiles of the radiation emissivity.

Oral presentation

Design of an imaging bolometer upgrade for JT-60U

Peterson, B. J.*; Konoshima, Shigeru; Kostryukov, A. Y.*; Kawashima, Hisato; Seo, D. C.*; Miroshnikov, I. V.*; Ashikawa, Naoko*; Parchamy, H.*; Liu, Y.*; JT-60 Team

no journal, , 

Oral presentation

Comparison of the Au and Ta foil parameters from laser calibration of imaging bolometer foils

Parchamy, H.*; Peterson, B. J.*; Hayashi, Hiromi*; Konoshima, Shigeru; Ashikawa, Naoko*; Seo, D. C.*; Kawashima, Hisato; JT-60 Team

no journal, , 

10 (Records 1-10 displayed on this page)
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