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Journal Articles

Progress of divertor simulation research toward the realization of detached plasma using a large tandem mirror device

Nakashima, Yosuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Oki, Kensuke*; Sakamoto, Mizuki*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; Imai, Tsuyoshi*; et al.

Journal of Nuclear Materials, 463, p.537 - 540, 2015/08

 Times Cited Count:18 Percentile:84.56(Materials Science, Multidisciplinary)

Journal Articles

Deuterium retention in tungsten coating layers irradiated with deuterium and carbon ions

Fukumoto, Masakatsu; Nakano, Tomohide; Ueda, Yoshio*; Itami, Kiyoshi; Kubo, Hirotaka

Journal of Nuclear Materials, 462, p.354 - 359, 2015/07

 Times Cited Count:3 Percentile:27.63(Materials Science, Multidisciplinary)

Journal Articles

Meeting report; 18th Plasma Seminar for young researchers

Fukumoto, Masakatsu; Miyata, Yoshiaki; Tojo, Hiroshi

Purazuma, Kaku Yugo Gakkai-Shi, 91(5), P. 371, 2015/05

"18th Plasma Seminar for young researches" (by Department of Advanced Plasma Research, Sector of Fusion Research and Development, Japan Atomic Energy Agency) was held in Naka Fusion Institute, March 3rd through 6th of 2015. The objective of this seminar is that the young researchers in charge of the future fusion research expand their cross-sectoral network. This seminar was entitled "Crystallization of technology of plasma measurement and control" and we invited the lectures not just for fusion plasma but for technology of plasma measurement and control to study the technology of measurement and control of different fields from their fields. There were 8 invited lectures and 17 public lectures and young researchers had an animated discussion.

Journal Articles

Overview of plasma-material interaction experiments on EAST employing MAPES

Ding, F.*; Luo, G.-N.*; Pitts, R.*; Litnovsky, A.*; Gong, X.*; Ding, R.*; Mao, H.*; Zhou, H.*; Wampler, W. R.*; Stangeby, P. C.*; et al.

Journal of Nuclear Materials, 455(1-3), p.710 - 716, 2014/12

 Times Cited Count:24 Percentile:88.84(Materials Science, Multidisciplinary)

Journal Articles

Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Meeting report; 17th plasma seminar for young researchers

Oda, Yasuhisa; Fukumoto, Masakatsu; Uto, Hiroyasu

Purazuma, Kaku Yugo Gakkai-Shi, 90(6), P. 356, 2014/06

no abstracts in English

Journal Articles

The Emission rates of CH, CD and C$$_{2}$$ spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Nakano, Tomohide; Higashijima, Satoru; Kubo, Hirotaka; Asakura, Nobuyuki; Fukumoto, Masakatsu

Nuclear Fusion, 54(4), p.043004_1 - 043004_10, 2014/03

 Times Cited Count:2 Percentile:11.12(Physics, Fluids & Plasmas)

We have determined the CH photon emission rate defined as the number of photons over dissociation and/or ionization event of $$mbox{CH}_4$$, from the ratio of the measured emission intensity of CH spectral band to the $$mbox{CH}_4$$ injection rate into the divertor plasma of JT-60U. Similar photon emission rates of CD for $$mbox{CD}_4$$, CH and $$mbox{C}_2$$ for $$mbox{C}_2mbox{H}_4$$ and $$mbox{C}_2mbox{H}_6$$ have also been determined. Interestingly, during the $$mbox{CH}_4$$ and the $$mbox{CD}_4$$ injection, the $$mbox{C}_2$$ spectral band intensity increases, suggesting that injected $$mbox{CH}_4$$ reacts with the carbon divertor plates to form heavier hydrocarbons. From the determined emission rates, previously published chemical sputtering yields, have been reevaluated. The reevaluated total chemical sputtering yield becomes lower ($$sim6%$$) compared to the original ($$sim8%$$) and the dependence on the incident ion flux and energy becomes weaker.

Journal Articles

Development of Langmuir probes on divertor cassettes in JT-60SA

Fukumoto, Masakatsu; Sakurai, Shinji; Asakura, Nobuyuki; Itami, Kiyoshi

Plasma and Fusion Research (Internet), 8, p.1405153_1 - 1405153_10, 2013/11

Langmuir probes installed in the lower divertor region under high heat flux have been developed and manufactured for JT-60SA. A probe electrode with a head having a rooftop shape is made of a carbon fiber composite and can withstand heat fluxes of up to 10 MW/m$$^2$$ for 5 s and 1 MW/m$$^2$$ for 100 s. This has been achieved by increasing the volume of the probe electrode that is not directly exposed to the plasma. To minimize the reduction of the heat removal performance of the divertor, the Langmuir probes are installed in toroidal gaps with widths of 10mm between the divertor cassettes, without embedding them in the divertor tiles. Aluminum oxide coatings have been applied to insulate the probe electrodes from the divertor cassettes and to limit the toroidal thickness to 8 mm. Brazing of the nickel connectors to the probe electrodes has reduced the toroidal thickness of the Langmuir probes. A minimum spatial resolution of 13.5mm has been achieved to the Langmuir probes installed on the inner and outer divertor targets.

Journal Articles

Chemical binding states of carbon atoms migrated in tungsten coating layer exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Ueda, Yoshio*; Itami, Kiyoshi

Plasma and Fusion Research (Internet), 8, p.1405159_1 - 1405159_8, 2013/11

Journal Articles

Carbon transport and fuel retention in JT-60U with higher temperature operation based on postmortem analysis

Yoshida, Masafumi; Tanabe, Tetsuo*; Adachi, Ayumu*; Hayashi, Takao; Nakano, Tomohide; Fukumoto, Masakatsu; Yagyu, Junichi; Miyo, Yasuhiko; Masaki, Kei; Itami, Kiyoshi

Journal of Nuclear Materials, 438, p.S1261 - S1265, 2013/07

 Times Cited Count:6 Percentile:45.93(Materials Science, Multidisciplinary)

Fuel retention rates and carbon re-deposition rates in the plasma shadowed areas in JT-60U were measured. Distributions of the fuel retention as well as the carbon re-deposition in the whole in-vessel of a large tokamak were clarified for the first time in the world. The fuel retention in the plasma shadowed areas was about two times larger than that in the carbon re-deposited layers on the plasma facing surface, although the amount of the carbon re-deposited on the plasma shadowed areas were about a half of that on the plasma facing surface, because of relatively lower temperature in the shadow areas causing higher hydrogen saturation concentration in the carbon re-deposited layers. The total fuel retention rate in JT-60U, including previously measured for all plasma facing areas, was evaluated to be 1.3$$times$$10$$^{20}$$ H+Ds$$^{-1}$$, which was lower than that in other devices, due to probably to higher temperature operation in JT-60U.

Journal Articles

Investigation of carbon dust accumulation in the JT-60U tokamak vacuum vessel

Asakura, Nobuyuki; Hayashi, Takao; Ashikawa, Naoko*; Fukumoto, Masakatsu

Journal of Nuclear Materials, 438, p.S659 - S663, 2013/07

 Times Cited Count:5 Percentile:40.26(Materials Science, Multidisciplinary)

Dust generated by the plasma-wall interaction is a potential source of the tritium retention in a fusion reactor. Dust samples were collected at 3, 5 and 3 different toroidal locations of the first wall, divertor surface and exhaust route under the divertor, respectively. On the tile surface, large number of dust was found, in particular, at the inner divertor rather upper area of the deposition layers, where recycling neutrals are increased during discharges. On the other hand, significant amount of dust (20-50 times larger) was generally accumulated at the bottom divertor, in particular, the plasma-unexposed area (remote area). It was found that the poloidal distribution is relatively symmetrical in the toroidal direction within a factor of three. Recently, analysis of dust spatial and size distributions, and evaluation of fuel retention in dust have been progressed. The total amount of the hydrogen isotope contained in the dust was estimated.

Journal Articles

Characteristics of tungsten and carbon dusts in JT-60U and evaluation of hydrogen isotope retention

Ashikawa, Naoko*; Asakura, Nobuyuki; Fukumoto, Masakatsu; Hayashi, Takao; Ueda, Yoshio*; Muroga, Takeo*

Journal of Nuclear Materials, 438, p.S664 - S667, 2013/07

 Times Cited Count:7 Percentile:50.91(Materials Science, Multidisciplinary)

In this study, W concentrations of dusts at P-8 section and hydrogen isotope retentions in dusts are analyzed. Compositions of C including W material dusts were observed in JT-60U. For an enhanced resolution of the XPS measurement to analyze quantitatively the composition of the dust flakes, the new analysis using XPS with indium foil was done and showed that the dust flakes contains about less than 1% of tungsten in carbon. Compositions of tungsten-carbon mixed dusts at different poloidal positions are reported. Produced areas of dust including W is estimated on the outer doom wing by IMPGYRO code. Relative intensities at low temperature regions were smaller than bulk divertor target, which may be caused by the high baking/operation temperature. Amounts of retained Hydrogen/Deuterium in dust particles depend on internal defects and carbon composition of dusts.

Journal Articles

Hydrogen isotopes retention in gaps at the JT-60U first wall tiles

Yoshida, Masafumi; Tanabe, Tetsuo*; Hayashi, Takao; Nakano, Tomohide; Fukumoto, Masakatsu; Yagyu, Junichi; Miyo, Yasuhiko; Masaki, Kei; Itami, Kiyoshi

Fusion Science and Technology, 63(1T), p.367 - 370, 2013/05

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

In this study, the retentions of hydrogen isotopes (H and D) in the gaps in JT-60U are clarified. Carbon tiles used in 1992-2004 were poloidally and toroidally taken out from outboard first wall in JT-60U to measure the retentions. The H and D retentions in the samples were measured by thermal desorption spectrometry (TDS). The H+D retention in the top side was higher than that of the bottom side, which might be due to thicker re-deposited carbon layers on the surface of the top side. The retentions in the surface of the side surfaces were slightly lower than that in the plasma facing surface where the retention was saturated to be 3-4e22 atoms/m$$^{2}$$. The retention rate was evaluated to be 3e17 H+D atoms/m$$^{2}$$/s from the measured retentions in two different discharge times by assuming the retention to increase linearly with the discharge time.

Journal Articles

Effects of carbon impurity on deuterium retention in VPS-tungsten coatings exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Itami, Kiyoshi; Wada, Takaaki*; Ueda, Yoshio*; Tanabe, Tetsuo*

Journal of Nuclear Materials, 415(Suppl.1), p.S705 - S708, 2011/08

 Times Cited Count:5 Percentile:39.92(Materials Science, Multidisciplinary)

Tungsten coating on the first wall in ITER is proposed to reduce in-vessel tritium retention. However, it is possibility that carbon based materials would be used at high heat load components such as limiter. To predict the tritium retention in tungsten coating, it is essential to investigate the effects of carbon impurity on deuterium retention in tungsten coating. In this study, effects of carbon impurity on deuterium retention in the tungsten coating exposed to JT-60U divertor plasmas were investigated. Deuterium was trapped by carbon which was implanted and accumulated in the tungsten coating during the plasma discharge. D/C ration of 0.04-0.08 in the tungsten coating was reached to 1/2-1/4 compared to T/C ration in carbon co-deposition layer. Therefore, simultaneous use of carbon armor materials and tungsten coating would enhance tritium retention in tungsten coating.

Journal Articles

Deuterium retention in tungsten coating on the CFC tiles exposed to JT-60U divertor plasmas

Fukumoto, Masakatsu; Nakano, Tomohide; Masaki, Kei; Itami, Kiyoshi; Ueda, Yoshio*; Tanabe, Tetsuo*

Journal of Plasma and Fusion Research SERIES, Vol.9, p.369 - 374, 2010/08

no abstracts in English

Journal Articles

Experimental studies on in-vessel tritium inventory in complicated environment of fusion reactors

Ueda, Yoshio*; Hino, Tomoaki*; Ono, Noriyasu*; Takagi, Ikuji*; Nakano, Tomohide; Tanabe, Tetsuo*; Kajita, Shin*; Fukumoto, Masakatsu

Purazuma, Kaku Yugo Gakkai-Shi, 85(10), p.684 - 694, 2009/10

Relation between deuterium retention, wall temperature and hydrocarbon generation in 30-s H-mode discharges of JT-60U was described. In discharges with a density below 50% of the Greenwald density, the trend of the deuterium retention against pulse number depended on the wall temperature: with increasing pulse number, the deuterium retention decreased at a wall temperature of 300 $$^{circ}$$C, decreased gradually at 150 $$^{circ}$$C, and remained constant at 80 $$^{circ}$$C. In contrast, in discharges with high densities above 70% of the Greenwald density, the deuterium retention increased with increasing pulse number at the above three wall temperatures. In the high density discharges, the deuterium retention flux increased with increasing hydrocarbon generation flux, suggesting that the deuterium is retained in co-deposition layers of carbon, which originated from the hydrocarbons.

Journal Articles

Localized tungsten deposition in divertor region in JT-60U

Ueda, Yoshio*; Fukumoto, Masakatsu*; Watanabe, Jun*; Otsuka, Yusuke*; Arai, Takashi; Asakura, Nobuyuki; Nobuta, Yuji*; Sato, Masayasu; Nakano, Tomohide; Yagyu, Junichi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Deposition profiles of tungsten released from the outer divertor were studied in JT-60U. A neutron activation method was used for the first time to accurately measure deposited tungsten. Surface density of tungsten in the thick carbon deposition layer can be measured by this method. Tungsten was mainly deposited on the inner divertor (around inner strike points) and on the outer wing of the dome. Toroidal distribution of the W deposition was significantly localized near the tungsten released position, while other metallic impurities such as Fe, Cr, Ni were distributed more uniformly. These data indicate that inward drift in the divertor region played a significant role in tungsten transport in JT-60U.

Journal Articles

Surface studies of tungsten erosion and deposition in JT-60U

Ueda, Yoshio*; Fukumoto, Masakatsu*; Nishikawa, Masahiro*; Tanabe, Tetsuo*; Miya, Naoyuki; Arai, Takashi; Masaki, Kei; Ishimoto, Yuki*; Tsuzuki, Kazuhiro*; Asakura, Nobuyuki

Journal of Nuclear Materials, 363-365, p.66 - 71, 2007/06

 Times Cited Count:10 Percentile:59.19(Materials Science, Multidisciplinary)

no abstracts in English

Oral presentation

Redeposition distribution of tungsten eroded from the tungsten coated divertor tiles in JT-60U

Fukumoto, Masakatsu*; Otsuka, Yusuke*; Ueda, Yoshio*; Tanabe, Tetsuo*; Sakasai, Akira; Masaki, Kei; Arai, Takashi; Yagyu, Junichi; Nobuta, Yuji; Kubo, Hirotaka; et al.

no journal, , 

no abstracts in English

Oral presentation

Tungsten deposition distribution in divertor region in JT-60U

Watanabe, Jun*; Fukumoto, Masakatsu*; Soga, Yasuyuki*; Otsuka, Yusuke*; Ueda, Yoshio*; Arai, Takashi; Asakura, Nobuyuki; Nakano, Tomohide; Sato, Masayasu; Yagyu, Junichi; et al.

no journal, , 

Tungsten was mainly deposited on the inner divertor (around the inner strike point) and the outer wing of the dome. Tungsten deposition on the dome was found only near the top surface (within depth of a few micron m), while tungsten on the inner divertor was codeposited with carbon to the depth up to about 60 micron m. Discussion on the relation between depth distribution of tungsten and EDX signals are also presented. Significant difference between tungsten and other metallic materials (Fe, Ni, Cr) in terms of toroidal deposition distribution on the outer wing was observed. Tungsten deposition was toroidally localized in the P-8 section, where tungsten coated tiles were installed. On the other hand, other metallic materials (Fe, Ni, Cr) were not toroidally localized compared with the case of tungsten.

56 (Records 1-20 displayed on this page)