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16 results on '"Peterson, B. J."'

1. Compatibility between high energy particle confinement and magnetohydrodynamic stability in the inward-shifted plasmas of the Large Helical Device

Author

KANEKO, O., KOMORI, A., YAMADA, H., OHYABU, N., KAWAHATA, K., NAKAMURA, Y., IDA, K., MURAKAMI, S., MUTOH, T., SAKAKIBARA, S., Masuzaki, S., Ashikawa, N., Emoto, M., Funaba, H., Goto, M., Idei, H., Ikeda, K., Inagaki, S., Inoue, N., Isobe, M., Khlopenkov, K., Kubo, S., Kumazawa, R., Minami, T., Miyazawa, J., Morisaki, T., Morita, S., Muto, S., Nagayama, Y., Nakajima, N., Nakanishi, H., Narihara, K., Nishimura, K., Noda, N., Notake, T., Kobuchi, T., Liang, Y., Ohdachi, S., Oka, Y., Osakabe, M., Ozaki, T., Peterson, B. J., Sagara, A., Saito, K., Sakamoto, R., Sasao, M., Sato, K., Sato, M., Seki, T., SHIMOZUKA, T., SHOJI, M., Suzuki, H., Takechi, M., Takeiri, Y., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Torii, Y., Tsumori, K., Yamada, I., Yamamoto, S., Yokoyama, M., Yoshimura, Y., Yoshinuma, M., Watanabe, K.Y., Watari, T., Xu, Y., Itoh, K., Matsuoka, K., Ohkubo, K., Ohtake, I., Satow, T., Sudo, S., Yamazaki, K., Hamada, Y., Motojima, O., Fujiwara, M., O., Kaneko, A., KOMORI, H., YAMADA, N., Ohyabu, K., Kawahata, Y., Nakamura, K., Ida, S., Murakami, T., Mutoh, S., Sakakibara, S., Masuzaki, N., Ashikawa, M., Emoto, H., Funaba, M., Goto, H., Idei, K., Ikeda, S., Inagaki, N., Inoue, M., Isobe, K., Khlopenkov, S., Kubo, R., Kumazawa, T., Minami, J., Miyazawa, T., Morisaki, S., Morita, S., Muto, Y., Nagayama, N., Nakajima, H., Nakanishi, K., Narihara, K., Nishimura, N., Noda, T., Notake, T., Kobuchi, Y., Liang, S., Ohdachi, Y., Oka, M., Osakabe, T., Ozaki, B.J., Peterson, A., Sagara, K., Saito, R., Sakamoto, M., Sasao, K., Sato, M., Sato, T., Seki, T., Shimozuma, M., Shoji, H., Suzuki, M., Takechi, Y., Takeiri, N., Tamura, K., Tanaka, K., Toi, T., Tokuzawa, Y., Torii, K., Tsumori, I., Yamada, S., Yamamoto, M., Yokoyama, Y., Yoshimura, M., Yoshinuma, K.Y., Watanabe, T., Watari, Y., Xu, K., Itoh, K., Matsuoka, K., Ohkubo, I., Ohtake, T., Satow, S., Sudo, K., Yamazaki, Y., Hamada, O., Motojima, and M., Fujiwara

Subjects
Physics, High energy particle, Cyclotron, Plasma, Condensed Matter Physics, Neutral beam injection, Magnetic field, law.invention, Large Helical Device, law, Physics::Plasma Physics, Magnetohydrodynamic drive, Magnetohydrodynamics, Atomic physics
Abstract

The experimentally optimized magnetic field configuration of the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)], where the magnetic axis is shifted inward by 15 cm from the early theoretical prediction, reveals 50% better global energy confinement than the prediction of the scaling law. This configuration has been investigated further from the viewpoints of high energy particle confinement and magnetohydrodynamic (MHD) stability. The confinement of high energy ions is improved as expected. The minority heating of ion cyclotron range of frequency was successful and the heating efficiency was improved by the inward shift. The confinement of passing particles by neutral beam injection was also improved under low magnetic field strength, and there could be obtained an almost steady high beta discharge up to 3% in volume average. This was a surprising result because the observed pressure gradient exceeded the Mercier unstable limit. The observed MHD activities became as high as beta but they did not grow enough to deteriorate the confinement of high energy ions or the performance of the bulk plasma, which was still 50% better than the scaling. According to these favorable results, better performance would be expected by increasing the heating power because the neoclassical transport can also be improved there.

Published
2002

2. Inter-biome comparison of factors controlling stream metabolism

Author

Mulholland, P. J., Fellows, C. S., Tank, J. L., Grimm, N. B., Webster, J. R., Hamilton, S. K., Martí, Eugènia, Ashkenas, L., Bowden, W. B., Dodds, W. K., McDowell, W. H., Paul, M. J., and Peterson, B. J.

Subjects
Metabolism, Primary production, Respiration, Stream, Inter-biome
Abstract

14 Páginas ; 6 Figuras ; 2 Tablas, 1. We studied whole-ecosystem metabolism in eight streams from several biomes in North America to identify controls on the rate of stream metabolism over a large geographic range. The streams studied had climates ranging from tropical to cool-temperate and from humid to arid and were all relatively uninfluenced by human disturbances. 2. Rates of gross primary production (GPP), ecosystem respiration (R) and net ecosystem production (NEP) were determined using the open-system, two-station diurnal oxygen change method. 3. Three general patterns in metabolism were evident among streams: (1) relatively high GPP with positive NEP (i.e. net oxygen production) in early afternoon, (2) moderate primary production with a distinct peak in GPP during daylight but negative NEP at all times and (3) little or no evidence of GPP during daylight and a relatively constant and negative NEP over the entire day. 4. Gross primary production was most strongly correlated with photosynthetically active radiation (PAR). A multiple regression model that included log PAR and stream water soluble reactive phosphorus (SRP) concentration explained 90% of the variation in log GPP. 5. Ecosystem respiration was significantly correlated with SRP concentration and size of the transient storage zone and, together, these factors explained 73% of the variation in R. The rate of R was poorly correlated with the rate of GPP. 6. Net ecosystem production was significantly correlated only with PAR, with 53% of the variation in log NEP explained by log PAR. Only Sycamore Creek, a desert stream in Arizona, had positive NEP (GPP: R > 1), supporting the idea that streams are generally net sinks rather than net sources of organic matter. 7. Our results suggest that light, phosphorus concentration and channel hydraulics are important controls on the rate of ecosystem metabolism in streams over very extensive geographic areas., The Ecosystems Program, National Science Foundation, to Virginia Tech (DEB-9628860). The research was conducted in part on the Oak Ridge National Environmental Research Park, Environmental Sciences Division, Office of Biological and Environmental Research, U.S. Department of Energy under contract DE-AC05–00OR2725 with University of Tennessee-Battelle LLC.

Published
2008

3. Fluid features of the stochastic layer transport in LHD

Author

Feng, Y., Kobayashi, M., Morisaki, T., Masuzaki, S., Miyazawa, J., Peterson, B. J., Morita, S., Shoji, M., Ida, K., Yamada, I., Narihara, K., Ashikawa, N., Yamada, H., Ohyabu, N., Komori, A., Morojima, O., Sardei, F., Reiter, D., and LHD Experimental Group

Published
2008

4. Factors affecting ammonium uptake in streams - an Inter.-biome perspective

Author

Webster, J. R., Mulholland, P. J., Tank, J. L., Valett, H. M., Dodds, W. K., Peterson, B. J., Bowden, W. B., Dahm, Clifford N., Findaly, S., Gregory, S. V., Grimm, N. B., Hamilton, S. K., Johnson, S. L., Martí, Eugènia, McDowell, W. H., Meyer, J. L., Morrall, D. D., Thomas, S. A., and Wollheim, W. M.

Subjects
Metabolism, Nitrogen, Biome, Transient storage, Stable isotope
Abstract

24 Páginas ; 10 Figuras ; 4 Tablas, 1. The Lotic Intersite Nitrogen eXperiment (LINX) was a coordinated study of the relationships between North American biomes and factors governing ammonium uptake in streams. Our objective was to relate inter-biome variability of ammonium uptake to physical, chemical and biological processes. 2. Data were collected from 11 streams ranging from arctic to tropical and from desert to rainforest. Measurements at each site included physical, hydraulic and chemical characteristics, biological parameters, whole-stream metabolism and ammonium uptake. Ammonium uptake was measured by injection of 15N-ammonium and downstream measurements of 15N-ammonium concentration. 3. We found no general, statistically significant relationships that explained the variability in ammonium uptake among sites. However, this approach does not account for the multiple mechanisms of ammonium uptake in streams. When we estimated biological demand for inorganic nitrogen based on our measurements of in-stream metabolism, we found good correspondence between calculated nitrogen demand and measured assimilative nitrogen uptake. 4. Nitrogen uptake varied little among sites, reflecting metabolic compensation in streams in a variety of distinctly different biomes (autotrophic production is high where allochthonous inputs are relatively low and vice versa). 5. Both autotrophic and heterotrophic metabolism require nitrogen and these biotic processes dominate inorganic nitrogen retention in streams. Factors that affect the relative balance of autotrophic and heterotrophic metabolism indirectly control inorganic nitrogen uptake., The LINX study was funded by a grant (DEB-9628860) from the National Science Foundation. Work in Alaska was also funded by the National Science Foundation (OPP-9615949), and the East Fork Little Miami River study was supported by Procter & Gamble. Work at several streams was made possible by collaboration with the U.S. Forest Service and NSF funded LTER studies. Work at Walker Branch, Tennessee, was also partially supported by the Walker Branch Watershed project, Environmental Sciences Division, Office of Biological and Environmental Research, U.S. Department of Energy under contract DE-AC05-00OR22725 with UT-Battelle, LLC.

Published
2003

5. Control of nitrogen export from watersheds by headwater streams

Author

Peterson, B. J., Wolheim, W., Mulholland, P. J., Webster, J. R., Meyer, J. L., Tank, J. L., Grimm, N. B., Martí, Eugènia, Bowden, W. B., Vallet, H. M., Hershey, A. E., McDowell, W. B., Dodds, W. K., Hamilton, S. K., Gregory, S., and D'Angelo, D. J.

Subjects
Geologic Sediments, Nitrogen, chemistry.chemical_element, Fresh Water, STREAMS, Absorption, chemistry.chemical_compound, Nutrient, Nitrate, Animals, Ammonium, Photosynthesis, Ecosystem, Hydrology, geography, Multidisciplinary, geography.geographical_feature_category, Nitrates, Bacteria, Ecology, Fungi, Eukaryota, Estuary, Stream metabolism, United States, Quaternary Ammonium Compounds, chemistry, Biofilms, Nitrification, Seasons, Oxidation-Reduction
Abstract

5 páginas ; 5 Figuras, A comparative 15N-tracer study of nitrogen dynamics in headwater streams from biomes throughout North America demonstrates that streams exert control over nutrient exports to rivers, lakes, and estuaries. The most rapid uptake and transformation of inorganic nitrogen occurred in the smallest streams. Ammonium entering these streams was removed from the water within a few tens to hundreds of meters. Nitrate was also removed from stream water but traveled a distance 5 to 10 times as long, on average, as ammonium. Despite low ammonium concentration in stream water, nitrification rates were high, indicating that small streams are potentially important sources of atmospheric nitrous oxide. During seasons of high biological activity, the reaches of headwater streams typically export downstream less than half of the input of dissolved inorganic nitrogen from their watersheds., NSF grants DEB-9628860, DEB-9810222, and OPP-9615949

Published
2001

6. Review on the progress of the LHD experiment

Author

Motojima, O., Yamada, H., Komori, A., Watanabe, K. Y., Mutoh, T., Takeiri, Y., Ida, K., Akiyama, T., Asakura, N., Ashikawa, N., Chikaraishi, H., Cooper, W. A., Emoto, M., Fujita, T., Fujiwara, M., Funaba, H., Goncharov, P., Goto, M., Hamada, Y., Higashijima, S., Hino, T., Hoshino, M., Ichimura, M., Idei, H., Ido, T., Ikeda, K., Imagawa, S., Inagaki, S., Isayama, A., Isobe, M., Itoh, T., Itoh, K., Kado, S., Kalinina, D., Kaneba, T., Kaneko, O., Kato, D., Kato, T., Kawahata, K., Kawashima, H., Kawazome, H., Kobuchi, T., Kondo, K., Kubo, S., Kumazawa, R., Lyon, J. F., Maekawa, R., Mase, A., Masuzaki, S., Mito, T., Matsuoka, K., Miura, Y., Miyazawa, J., More, R., Morisaki, T., Morita, S., Murakami, I., Murakami, S., Mutoh, S., Nagaoka, K., Kazunobu Nagasaki, Nagayama, Y., Nakamura, Y., Nakanishi, H., Narihara, K., Narushima, Y., Nishimura, H., Nishimura, K., Nishiura, M., Nishizawa, A., Noda, N., Notake, T., Nozato, H., Ohdachi, S., Ohkubo, K., Ohyabu, N., Oyama, N., Oka, Y., Okada, H., Osakabe, M., Ozaki, T., Peterson, B. J., Sagara, A., Saida, T., Saito, K., Sakakibara, S., Sakamoto, M., Sakamoto, R., Sasao, M., Sato, R., Seki, T., Shimozuma, T., Shoji, M., Sudo, S., Takagi, S., Takahashi, Y., Takase, Y., Takenaga, H., and Takeuchi, N.

10. Extension of operation regimes and investigation of three-dimensional currentless plasmas in the Large Helical Device

Author

Kaneko, O., Yamada, H., Inagaki, S., Jakubowski, M., Kajita, S., Kitajima, S., Koga, K., Morisaki, T., Morita, S., Mutoh, T., Sakakibara, S., Suzuki, Y., Takahashi, H., Tanaka, K., Toi, K., Yoshimura, Y., Akiyama, T., Asahi, Y., Ashikawa, N., Chikaraishi, H., Cooper, A., Darrow, D. S., Drapiko, E., Drewelow, P., Du, X., Ejiri, A., Emoto, M., Evans, T., Ezumi, N., Fujii, K., Fukuda, T., Funaba, H., Furukawa, M., Gates, D. A., Goto, M., Goto, T., Guttenfelder, W., Hamaguchi, S., Hasuo, M., Hino, T., Hirooka, Y., Ichiguchi, K., Ida, K., Idei, H., Ido, T., Igami, H., Ikeda, K., Imagawa, S., Imai, T., Isobe, M., Itagaki, M., Ito, T., Itoh, K., Itoh, S., Iwamoto, A., Kamiya, K., Kariya, T., Kasahara, H., Kasuya, N., Kato, D., Kato, T., Kawahata, K., Koike, F., Kubo, S., Kumazawa, R., Kuwahara, D., Lazerson, S., Lee, H., Masuzaki, S., Matsuoka, S., Matsuura, H., Matsuyama, A., Michael, C., Mikkelsen, D., Mitarai, O., Mito, T., Miyazawa, J., Motojima, G., Mukai, K., Murakami, A., Murakami, I., Murakami, S., Muroga, T., Muto, S., Nagaoka, K., Nagasaki, K., Nagayama, Y., Nakajima, N., Nakamura, H., Nakamura, Y., Nakanishi, H., Nakano, H., Nakano, T., Narihara, K., Narushima, Y., Nishimura, K., Nishimura, S., Nishiura, M., Nunami, Y. M., Obana, T., Ogawa, K., Ohdachi, S., Ohno, N., Ohyabu, N., Oishi, T., Okamoto, M., Okamoto, A., Osakabe, M., Oya, Y., Ozaki, T., Pablant, N., Peterson, B. J., Sagara, A., Saito, K., Sakamoto, R., Sakaue, H., Sasao, M., Sato, K., Sato, M., Sawada, K., Seki, R., Seki, T., Sergeev, V., Sharapov, S., Sharov, I., Shimizu, A., Shimozuma, T., Shiratani, M., Shoji, M., Sudo, S., Sugama, H., Suzuki, C., Takahata, K., Takeiri, Y., Takemura, Y., Takeuchi, M., Tamura, H., Tamura, N., Tanaka, H., Tanaka, T., Tingfeng, M., Todo, Y., Tokitani, M., Tokunaga, K., Tokuzawa, T., Tsuchiya, H., Tsumori, K., Ueda, Y., Vyacheslavov, L., Watanabe, K. Y., Watanabe, T., Watanabe, T. H., Wieland, B., Yamada, I., Yamada, S., Yamamoto, S., Yanagi, N., Yasuhara, R., Yokoyama, M., Yoshida, N., Yoshimura, S., Yoshinaga, T., Yoshinuma, M., and Komori, A.

Subjects
Physics::Plasma Physics
Abstract

The progress of physical understanding as well as parameter improvement of net-current-free helical plasma is reported for the Large Helical Device since the last Fusion Energy Conference in Daejeon in 2010. The second low-energy neutral beam line was installed, and the central ion temperature has exceeded 7 keV, which was obtained by carbon pellet injection. Transport analysis of the high-T-i plasmas shows that the ion-thermal conductivity and viscosity decreased after the pellet injection although the improvement does not last long. The effort has been focused on the optimization of plasma edge conditions to extend the operation regime towards higher ion temperature and more stable high density and high beta. For this purpose a portion of the open helical divertors are being modified to the baffle-structured closed ones aimed at active control of the edge plasma. It is compared with the open case that the neutral pressure in the closed helical divertor increased by ten times as predicted by modelling. Studies of physics in a three-dimensional geometry are highlighted in the topics related to the response to a resonant magnetic perturbation at the plasma periphery such as edge-localized-mode mitigation and divertor detachment. Novel approaches of non-local and non-diffusive transport have also been advanced.

11. Long-pulse operation and high-energy particle confinement study in ICRF heating of LHD

Author

Mutoh, T., Kumazawa, R., Seki, T., Saito, K., Watari, T., Torii, Y., Takeuchi, N., Shimpo, F., Nomura, G., Yokota, M., Watanabe, T., Osakabe, M., Sasao, M., Murakami, S., Saida, T., Okada, H., Takase, Y., Fukuyama, A., Ashikawa, N., Emoto, M., Funaba, H., Goncharov, P. R., Goto, M., Hamada, Y., Ida, K., Idei, H., Ikeda, K., Imagawa, S., Inagaki, S., Isobe, M., Kobuchi, T., Kubo, S., Masuzaki, S., Matsuoka, K., Minami, T., Mito, T., Miyazawa, J., Morisaki, T., Morita, S., Muto, S., Nagayama, Y., Nakamura, Y., Hideya Nakanishi, Narihara, K., Narushima, Y., Nishimura, K., Noda, N., Notake, T., Ohdachi, S., Oka, Y., Ozaki, T., Peterson, B. J., Sagara, A., Sakakibara, S., Sakamoto, R., Sato, K., Sato, M., Shimozuma, T., Shoji, M., Suzuki, H., Takeiri, Y., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Tsumori, K., Watanabe, K., Yamada, H., Yamada, I., Yamazaki, K., Yokoyama, M., Yoshimura, Y., Yoshinuma, M., Kaneko, O., Kawahata, K., Ohyabu, N., Ohkubo, K., Komori, A., Sudo, S., and Motojima, O.

12. OVERVIEW OF LHD PLASMA DIAGNOSTICS

Author

Kawahata, K., Peterson, B. J., Akiyama, T., Ashikawa, N., Emoto, M., Funaba, H., Hamada, Y., Katsumi Ida, Inagaki, S., Ido, T., Isobe, M., Goto, M., Mase, A., Masuzaki, S., Michael, C., Morisaki, T., Morita, S., Muto, S., Nagayama, Y., Nakamura, Y., Nakanishi, H., Sakamoto, R., Narihara, K., Nishiura, M., Ohdachi, S., Okajima, S., Osakabe, M., Sakakibara, S., Sanin, A., Sasao, M., Sato, K., Shimizu, A., Shoji, M., Sudo, S., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Veshchev, E. V., Vyacheslavov, L. N., Yamada, I., Yoshinuma, M., and Lhd, Expt Grp

13. Recent diagnostic developments on LHD

Author

Sudo, S., Nagayama, Y., Peterson, B. J., Kawahata, K., Akiyama, T., Ashikawa, N., Emoto, M., Goto, M., Hamada, Y., Ida, K., Ido, T., Iguchi, H., Inagaki, S., Isobe, M., Kobuchi, T., Komori, A., Liang, Y., Masuzaki, S., Minami, T., Morisaki, T., Morita, S., Muto, S., Nakamura, Y., Nakanishi, H., Narushima, M., Narihara, K., Nishiura, M., Nishizawa, A., Ohdachi, S., Osakabe, M., Ozaki, T., Pavlichenko, R. O., Sakakibara, S., Sato, K., Shoji, M., Tamura, N., Tanaka, K., Toi, K., Tokuzawa, T., Watanabe, K. Y., Watanabe, T., Yamada, H., Yamada, I., Yoshinuma, M., Pavel Goncharov, Kalinina, D., Kanaba, T., Sugimoto, T., Ejiri, A., Ono, Y., Hojo, H., Ishii, K., Iwama, N., Kogi, Y., Mase, A., Sakamoto, M., Kondo, K., Nagasaki, H., Yamamoto, S., Nishino, N., Okajima, S., Saida, T., Sasao, M., Takeda, T., Tsuji-Iio, S., Darrow, D. S., Takahashi, H., Liu, Y., Lyon, J. F., Kostrioukov, A. Yu, Kuteev, V. B., Sergeev, V., Viniar, I., Krasilnikov, A. V., Sanin, A., Vyacheslavov, L. N., Stutman, D., Finkenthal, M., and Motojima, O.

14. Recent progress in large helical device experiments

Author

Komori, A., Morisaki, T., Mutoh, T., Sakakibara, S., Takeiri, Y., Kumazawa, R., Kubo, S., Ida, K., Morita, S., Narihara, K., Shimozuma, T., Tanaka, K., Watanabe, K. Y., Yamada, H., Yoshinuma, M., Akiyama, T., Ashikawa, N., Emoto, M., Funaba, H., Goto, M., Ido, T., Ikeda, K., Inagaki, S., Isobe, M., Igami, H., Itoh, K., Kaneko, O., Kawahata, K., Kobuchi, T., Masuzaki, S., Matsuoka, K., Minami, T., Miyazawa, J., Muto, S., Nagayama, Y., Nakamura, Y., Nakanishi, H., Narushima, Y., Nishimura, K., Nishiura, M., Nishizawa, A., Noda, N., Ohdachi, S., Oka, Y., Osakabe, M., Ohyabu, N., Ozaki, T., Peterson, B. J., Sagara, A., Saito, K., Ryuichi Sakamoto, Sato, K., Seki, T., Shoji, M., Sudo, S., Tamura, N., Toi, K., Tokuzawa, T., Tsumori, K., Uda, T., Watari, T., Yamada, I., Yokoyama, M., Yoshimura, Y., Motojima, O., Beidler, C. D., Fujita, T., Isayama, A., Sakamoto, Y., Takenaga, H., Goncharov, P., Ishii, K., Sakamoto, M., Kawazome, H., Torii, Y., Murakami, S., Notake, T., Takeuchi, N., Okajima, S., Sasao, M., and Exp Group, L. H. D.

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