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Journal Articles

Tungsten impurity density in fusion plasma

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*

Journal of Physics B; Atomic, Molecular and Optical Physics, 2 Pages, 2016/01

Collaboration of researchers from Japan Atomic Energy Agency and EUROfusion Consortium (Dutch Institute For Fundamental Energy Research, Max-Planck-Institut f$"{u}$r Plasmaphysik and so on) successfully led to determination of tungsten ion density in high temperature plasmas in Joint European Torus (JET) with an upgraded X-ray spectrometer. The researchers used the FAC code and successfully identified $$mbox{W}^{45+}$$, $$mbox{W}^{46+}$$ and $$mbox{Mo}^{32+}$$ spectral lines. The $$mbox{Mo}^{32+}$$ line identification was confirmed experimentally by Mo injection to the plasma. From the measured absolute intensity of these spectral lines, tungsten and molybdenum ion densities in the plasma core were determined.

Journal Articles

Comparison of Ne and Ar seeded radiative divertor plasmas in JT-60U

Nakano, Tomohide; JT-60 Team

Journal of Nuclear Materials, 463, p.555 - 560, 2015/08

 Times Cited Count:6 Percentile:28.02(Materials Science, Multidisciplinary)

In H-mode plasmas with Ne, Ar and a mixture of Ne and Ar injection, the divertor radiation power fraction amongst these impurities in addition to an intrinsic impurity, C, is investigated. In plasmas with the inner divertor plasma attached, carbon is the biggest radiator, whichever impurites, Ne, Ar or a mixture of Ar and Ne is injected. In contrast, in plasmas with the inner divertor plasma detached, Ne is the biggest radiator due to a significantly high recombination radiation from Ne VIII. Ar is always a minor contributor in plasmas with the innder divertor both attached and detached.

Journal Articles

The Influence of the radial particle transport on the divertor plasma detachment

Hoshino, Kazuo; Shimizu, Katsuhiro; Takizuka, Tomonori*; Asakura, Nobuyuki; Nakano, Tomohide

Journal of Nuclear Materials, 463, p.573 - 576, 2015/08

 Times Cited Count:7 Percentile:22.72(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:2 Percentile:66.76(Materials Science, Multidisciplinary)

Journal Articles

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET with the ITER-like wall configuration

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*; Reinke, M.*; Lawson, K.*; Coffey, I.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G. F.*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 48(14), p.144023_1 - 144023_11, 2015/07

 Times Cited Count:15 Percentile:16.77(Optics)

The $$mbox{W}^{45+}$$ and $$mbox{W}^{46+}$$ 3p-4d inner shell excitation lines in addition to $$mbox{Mo}^{32+}$$ 2p-3s lines have been identified from the spectrum taken by an upgraded high-resolution X-ray spectrometer. It is found from analysis of the absolute intensities of the $$mbox{W}^{46+}$$ and $$mbox{Mo}^{32+}$$ lines that W and Mo concentrations are in the range of $$sim10^{-5}$$ and $$sim10^{-6}$$, respectively, with a ratio of $$sim$$ 5% for ELMy H-mode plasmas with a plasma current of 2.0- 2.5 MA, a toroidal magnetic field of 2.7 T and a neutral beam injection power of 14-18 MW. For the purpose of checking self-consistency, it is confirmed that the W concentration determined from the $$mbox{W}^{45+}$$ line is in agreement with that from the $$mbox{W}^{46+}$$ line within 20% and that the plasma effective charge determined from the continuum of the first order reflection spectrum is also in agreement with that from the second order within 50%. Further, the determined plasma effective charge is in agreement with that determined from a visible spectroscopy, confirming that the sensitivity of the X-ray spectrometer is valid and that probably the W and the Mo concentrations are also valid.

Journal Articles

Analysis of tungsten transport in JT-60U plasmas

Shimizu, Yusuke*; Fujita, Takaaki*; Arimoto, Hideki*; Nakano, Tomohide; Hoshino, Kazuo; Hayashi, Nobuhiko

Plasma and Fusion Research (Internet), 10(Sp.2), p.3403062_1 - 3403062_4, 2015/07

Journal Articles

Issues and approaches for ITER with the full tungsten divertor from Day One

Nakano, Tomohide

Purazuma, Kaku Yugo Gakkai-Shi, 91(3), p.191 - 196, 2015/03

no abstracts in English

Journal Articles

Development of the backflow model for simplified impurity exhaust in Monte-Carlo calculation

Hoshino, Kazuo; Shimizu, Katsuhiro; Kawashima, Hisato; Takizuka, Tomonori*; Nakano, Tomohide; Ide, Shunsuke

Contributions to Plasma Physics, 54(4-6), p.404 - 408, 2014/06

 Times Cited Count:12 Percentile:28.31(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET

Nakano, Tomohide; Shumack, A. E.*; Maggi, C.*; Reinke, M.*; Lawson, K. D.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G.*; Chernyshova, M.*; et al.

Europhysics Conference Abstracts (Internet), 38F, p.P1.019_1 - P1.019_4, 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

 Percentile:100(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 advanced inductive scenarios for ITER

Luce, T. C.*; Challis, C. D.*; Ide, Shunsuke; Joffrin, E.*; Kamada, Yutaka; Politzer, P. A.*; Schweinzer, J.*; Sips, A. C. C.*; Stober, J.*; Giruzzi, G.*; et al.

Nuclear Fusion, 54(1), p.013015_1 - 013015_15, 2013/12

 Times Cited Count:14 Percentile:23.25(Physics, Fluids & Plasmas)

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

Hydrogen isotope effects on ITG scale length, pedestal and confinement in JT-60 H-mode plasmas

Urano, Hajime; Takizuka, Tomonori*; Aiba, Nobuyuki; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Nuclear Fusion, 53(8), p.083003_1 - 083003_8, 2013/08

 Times Cited Count:15 Percentile:26.34(Physics, Fluids & Plasmas)

Dependence of heat transport, edge pedestal and confinement on isotopic composition was investigated in conventional H-mode plasmas. Identical profiles for the electron density, electron temperature, and ion temperature were obtained for hydrogen and deuterium plasmas, whereas the required power clearly increased for hydrogen, which resulted in reduction of heat diffusivity for deuterium. The inverse of the ion-temperature-gradient (ITG) scale length which is required for a given ion heat diffusivity increased by a factor of approximately 1.2 for deuterium compared with that for hydrogen.

Journal Articles

Contribution of Ne ions to radiation enhancement in JT-60U divertor plasmas

Nakano, Tomohide; Asakura, Nobuyuki; Kubo, Hirotaka; JT-60 Team

Journal of Nuclear Materials, 438, p.S291 - S296, 2013/07

 Times Cited Count:13 Percentile:15.14(Materials Science, Multidisciplinary)

It is already concluded that neon injection is more effective than argon injection in order to enhance the radiative power from the divertor plasmas in JT-60U. In this study, we have investigated radiation processes of neon ions in low-temperature and high-density divertor plasmas with spectroscopic technique. It was observed that the emission intensities of Ne VII spectral lines became high during plasma detachment. A collisional-radiative model analysis with the intensity ratio of Ne VII emission lines gave an electron temperature of 100 eV and a radiative power of only 5% of total radiative power, measured with a bolometer. Because C IV emission intensity was low, it is probable that the radiative power of C IV was also low. Therefore, it is possible that neon and carbon ions at other charge states contribute much to the total radiative power from the divertor plasma.

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:5 Percentile:53.77(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

Spatial characterization of a divertor in the presence of an X-point MARFE by collisional-radiative modeling and line profile calculations

Koubiti, M.*; Nakano, Tomohide; Marandet, Y.*; Mekkaoui, A.*; Mouret, L.*; Rosato, J.*; Stamm, R.*

Journal of Nuclear Materials, 438, p.S599 - S601, 2013/07

 Times Cited Count:2 Percentile:72.96(Materials Science, Multidisciplinary)

We have measured a profile of C IV spectral line emitted from the detached diverter plasma of JT-60U with a high-wavelength resolution spectrometer, and analyzed it with PPP code. In the previous analysis, the measured spectral profile was compared with the spectral profile calculated by the PPP code with one pair of electron density and temperature. With this method, the spectral profiles measured around the X-point were well reproduced, but the spectral profile measured at a very center of the X-point was not reproduced. In the present analysis, we have succeeded to reproduce the spectral profile measured at the very center of the X-point by synthesizing two spectra calculated with two pairs of electron densities and temperatures. One pair was 1$$times$$10$$^{20}$$ m$$^{-3}$$ and 23.0 eV, and the other 1$$times$$10$$^{20}$$ m$$^{-3}$$ and 2.5 eV. The contribution to the intensity of C IV spectral line of the first pair was 65% and that of the second 35%.

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

 Percentile:100(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

Optimization of JT-60SA plasma operational scenario with capabilities of installed actuators

Ide, Shunsuke; Aiba, Nobuyuki; Bolzonella, T.*; Challis, C. D.*; Fujita, Takaaki; Giruzzi, G.*; Joffrin, E.*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Honda, Mitsuru; et al.

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Journal Articles

Dependence of heat transport and confinement on isotopic composition in conventional H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/01

Dependence of heat transport on isotopic composition is investigated in conventional H-mode plasmas for the application to ITER. The identical profiles of $$n_mathrm{e}$$, $$T_mathrm{e}$$ and $$T_mathrm{i}$$ are obtained for hydrogen and deuterium plasmas while the required power becomes clearly larger for hydrogen, resulting in the reduction of the heat diffusivity for deuterium. The result of the identical temperature profiles in spite of different heating power suggests that the characteristics of heat conduction differs essentially between hydrogen and deuterium even at the same scale length of temperature gradient. On the other hand, the edge stability is improved by increased total $$beta_mathrm{p}$$ regardless of the difference of the isotropic composition.

Journal Articles

Information of ITPA (International Tokamak Physics Activity) meeting, 38

Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Isayama, Akihiko; Honda, Mitsuru; Urano, Hajime; Nakano, Tomohide

Purazuma, Kaku Yugo Gakkai-Shi, 88(12), p.763 - 767, 2012/12

no abstracts in English

222 (Records 1-20 displayed on this page)