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30 results on '"R. Sakamoto"'

1. WEST full tungsten operation with an ITER grade divertor

Author

J. Bucalossi, A. Ekedahl, and the WEST Team, J. Achard, K. Afonin, O. Agullo, T. Alarcon, L. Allegretti, F. Almuhisen, H. Ancher, G. Antar, Y. Anquetin, S. Antusch, V. Anzallo, C. Arnas, J.F. Artaud, M.H. Aumeunier, S.G. Baek, X.Y. Bai, M. Balden, C. Balorin, T. Barbui, A. Barbuti, J. Barlerin, J. Barra, V. Basiuk, T. Batal, O. Baulaigue, A. Bec, M. Becoulet, E. Benoit, E. Bernard, J.M. Bernard, M. Bernert, N. Bertelli, E. Bertrand, P. Beyer, J. Bielecki, P. Bienvenu, R. Bisson, B. Bliewert, G. Bodner, S. Bose, C. Bottereau, C. Bouchand, Y. Boumendjel, F. Bouquey, C. Bourdelle, J. Bourg, S. Brezinsek, F. Brochard, C. Brun, V. Bruno, H. Bufferand, A. Bureau, S. Burles, Y. Camenen, B. Cantone, E. Caprin, M. Carole, S. Carpentier-Chouchana, G. Caulier, F. Causa, N. Cazanave, N. Chanet, O. Chellai, Y. Chen, M. Chernyshova, P. Chmielewski, W. Choe, A. Chomiczewska, G. Ciraolo, F. Clairet, J. Coenen, L. Colas, G. Colledani, J. Colnel, P. Coquillat, E. Corbel, Y. Corre, X. Courtois, T. Czarski, A. Da Ros, R. Daniel, J. Daumas, M. De Combarieu, P. De Vries, C. Dechelle, F. Deguara, R. Dejarnac, J.M. Delaplanche, L.F. Delgado-Aparicio, E. Delmas, L. Delpech, C. Desgranges, P. Devynck, J. Denis, S. Di Genova, R. Diab, A. Diallo, M. Diez, G. Dif-Pradalier, M. Dimitrova, R. Ding, T. Dittmar, L. Doceul, M. Domenes, D. Donovan, D. Douai, L. Dubus, N. Dumas, R. Dumont, F. Durand, A. Durif, F. Durodié, D. Elbeze, S. Ertmer, A. Escarguel, F. Escourbiac, B. Esposito, K. Ezato, F. Faisse, J.L. Farjon, N. Faure, N. Fedorczak, P. Fejoz, F. Felici, C. Fenzi-Bonizec, F. Ferlay, L. Ferrand, L. Fevre, M. Firdaouss, L. Fleury, D. Flouquet, T. Fonghetti, A. Gallo, X. Garbet, J. Garcia, J.L. Gardarein, L. Gargiulo, P. Garibaldi, S. Garitta, J. Gaspar, E. Gauthier, S. Gazzotti, F. Gely, J. Gerardin, G. Gervasini, E. Geulin, M. Geynet, P. Ghendrih, I. Giacalone, C. Gil, S. Ginoux, S. Girard, E. Giroux, G. Giruzzi, M. Goniche, V. Gorse, T. Gray, E. Grelier, C. Grisolia, A. Grosjean, A. Grosman, O. Grover, D. Guibert, D. Guilhem, C. Guillemaut, B. Guillermin, R. Guirlet, J.P. Gunn, Y. Gunsu, T. Gyergyek, S. Hacquin, A. Hakola, J. Harris, J.C. Hatchressian, W. Helou, P. Hennequin, C. Hernandez, L. Hijazi, J. Hillairet, T. Hirai, G.T. Hoang, C. Honoré, M. Houry, A. Huart, G. Huijsmans, P. Huynh, M. Iafrati, F. Imbeaux, N. Imbert, I. Ivanova-Stanik, P. Ivanova, R. Jalageas, A. Jamann, C. Jammes, A. Jardin, L. Jaubert, G. Jiolat, E. Joffrin, C. Johnson, A. Jonas, A. Kirschner, C.C. Klepper, M. Komm, M. Koubiti, S. Kosslow, J. Kovacic, M. Kozeiha, K. Krieger, K. Krol, I. Kudashev, B. Lacroix, L. Laguardia, V. Lamaison, V. Lapleigne, H. Laqua, C. Lau, Y. Lausenaz, R. Lé, M. Le Bohec, N. Lefevre, N. Lemoine, E. Lerche, Y. Lesourd, L. Letellier, M. Lewerentz, Y. Li, A. Liang, P. Linczuk, C. Linsmeier, M. Lipa, X. Litaudon, X. Liu, J. Llorens, T. Loarer, A. Loarte, T. Loewenhoff, G. Lombard, J. Lore, P. Lorenzetto, B. Lu, A. Lumsdaine, R. Lunsford, T. Lunt, G. Luo, P. Magaud, P. Maget, J.F. Mahieu, P. Maini, P. Malard, K. Malinowski, P. Manas, L. Manenc, V. Maquet, Y. Marandet, C. Martin, E.J. Martin, P. Martino, M. Mayer, D. Mazon, S. Mazzi, P. Messina, L. Meunier, D. Midou, G. Miglionico, Y. Mineo, M. Missirlian, R. Mitteau, B. Mitu, D. Moiraf, P. Mollard, G. Momparler, V. Moncada, T. Mondiere, C. Monti, J. Morales, M. Moreau, Ph. Moreau, Y. Moudden, G. Moureau, D. Mouyon, M. Muraglia, T. Nakano, E. Nardon, A. Neff, F. Nespoli, J. Nichols, L. Nicolas, S. Nicollet, R. Nouailletas, M. Ono, V. Ostuni, O. Paillat, C. Parish, H. Park, H. Parrat, J.Y. Pascal, B. Pegourie, F.P. Pellissier, Y. Peneliau, M. Peret, E. Pignoly, G. Pintsuk, R. Pitts, C. Pocheau, A. Podolnik, C. Portafaix, M. Poulos, P. Prochet, A. Puig Sitjes, R. Ragona, M. Rasinski, S. Ratynskaia, G. Raup, X. Regal-Mezin, C. Reux, J. Rice, M. Richou, F. Rigollet, N. Rivals, H. Roche, S. Rodrigues, J. Romazanov, G. Ronchi, C. Ruset, R. Sabot, A. Saille, R. Sakamoto, B. Salamon, F. Samaille, A. Santagiustina, B. Santraine, Y. Sarazin, O. Sauter, Y. Savoie-Peysson, L. Schiesko, M. Scholz, J.L. Schwob, E. Serre, H. Shin, S. Shiraiwa, Ja. Signoret, O. Skalli-Fettachi, P. Sogorb, Y. Song, A. Spring, P. Spuig, S. Sridhar, B. Stratton, C. Talatizi, P. Tamain, R. Tatali, Q. Tichit, A. Torre, L. Toulouse, W. Treutterer, E. Tsitrone, E.A. Unterberg, G. Urbanczyk, G. Van Rooij, N. Varadarajan, S. Vartanian, E. Velly, J.M. Verger, L. Vermare, D. Vezinet, N. Vignal, B. Vincent, S. Vives, D. Volpe, G. Wallace, E. Wang, L. Wang, Y. Wang, Y.S. Wang, T. Wauters, D. Weldon, B. Wirth, M. Wirtz, A. Wojenski, M. Xu, Q.X. Yang, H. Yang, B. Zago, R. Zagorski, B. Zhang, X.J. Zhang, X.L. Zou, and the EUROfusion Tokamak Exploitation Team

Subjects
nuclear fusion, magnetic confinement, tokamak, divertor, WEST, ITER, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation in a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with a focus on testing the ITER actively cooled W divertor in tokamak conditions. Following the successful completion of phase 1 (2016-2021), phase 2 started in December 2022 with the lower divertor made entirely of actively cooled ITER-grade tungsten mono-blocks. A boronization prior the first plasma attempt allowed for a smooth startup with the new divertor. Despite the reduced operating window due to tungsten, rapid progress has been made in long pulse operation, resulting in discharges with a pulse length of 100 s and an injected energy of around 300 MJ per discharge. Plasma startup studies were carried out with equatorial boron nitride limiters to compare them with tungsten limiters, while Ion Cyclotron Resonance Heating assisted startup was attempted. High fluence operation in attached regime, which was the main thrust of the first campaigns, already showed the progressive build up of deposits and appearance of dust, impacting the plasma operation as the plasma fluence increased. In total, the cumulated injected energy during the first campaigns reached 43 GJ and the cumulated plasma time exceeded 5 h. Demonstration of controlled X-Point Radiator regime is also reported, opening a promising route for investigating plasma exhaust and plasma-wall interaction issues in more detached regime. This paper summarises the lessons learned from the manufacturing and the first operation of the ITER-grade divertor, describing the progress achieved in optimising operation in a full W environment with a focus on long pulse operation and plasma wall interaction.

Published
2024
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2. Structure of pellet cloud emission and relation with the local ablation rate

Author

B. Pégourié, E. Geulin, M. Goto, A. Matsuyama, G. Motojima, and R. Sakamoto

Subjects
pellet physics, emission spectrum, ablation rate, LHD, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The experimental reproduction of the conditions of pellet injection expected in future large devices being not possible in present day machines, it is mandatory to validate as thoroughly as possible the available ablation models. Among the different points still under discussion, there is the relation between the spectroscopic measurement of the ablation clouds and the local ablation rate. This relation is investigated by coupling an emission model to the time-dependent simulation of ablation clouds with the HPI2 pellet ablation/deposition code. The simulated quantities are the time-evolution of the cloud visible spectrum ( λ = 400–700 nm) and images in different wavelength domains (e.g. $H_{\alpha}, H_{\beta}$ or the continuum centered at $\lambda = 576\,\mathrm{nm}$ ). It is found that the cloud emission is anisotropic, this is particularly the case for H _α and H _β lines, and that the relation between the cloud emission and the ablation rate depends not only on the conditions of pellet injection, but also on the direction of observation. It follows that, in general, it is not possible to estimate the ablation profile from that of an emission line $\left(H_{\alpha}\right.$ or $\left.H_{\beta}\right)$ . The code predictions are compared with corresponding measurements for a welldocumented pellet injected in LHD, showing a good agreement for global values and main trends. The reasons for observed discrepancies are discussed.

Published
2024
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3. Overview of Large Helical Device experiments of basic plasma physics for solving crucial issues in reaching burning plasma conditions

Author

K. Ida, M. Yoshinuma, M. Kobayashi, T. Kobayashi, N. Kenmochi, F. Nespoli, R.M. Magee, F. Warmer, A. Dinklage, A. Matsuyama, R. Sakamoto, T. Nasu, T. Tokuzawa, T. Kinoshita, K. Tanaka, N. Tamura, K. Nagaoka, M. Nishiura, Y. Takemura, K. Ogawa, G. Motojima, T. Oishi, Y. Morishita, J. Varela, W.H.J. Hayashi, M. Markl, H. Bouvain, Y. Liang, M. Leconte, D. Moseev, V.E. Moiseenko, C.G. Albert, I. Allfrey, A. Alonso, F.J. Arellano, N. Ashikawa, A. Azegami, L. Bardoczi, M. van Berkel, M. Beurskens, M.W. Binderbaue, A. Bortolon, S. Brezinsek, R. Bussiahn, A. Cappa, D. Carralero, I.C. Chan, J. Cheng, X. Dai, D.J. Den Hartog, C.P. Dhard, F. Ding, A. Ejiri, S. Ertmer, T. Fornal, K. Fujita, Y. Fujiwara, H. Funaba, L. Garcia, J.M. Garcia-Regana, I. Garcia-Cortés, I.E. Garkusha, D.A. Gates, Y. Ghai, E.P. Gilson, H. Gota, M. Goto, E.M. Green, V. Haak, S. Hamaguchi, K. Hanada, H. Hara, D. Hartmann, Y. Hayashi, T. Henning, C. Hidalgo, J. Hillairet, R. Hutton, T. Ido, H. Igami, K. Ikeda, S. Inagaki, A. Ishizawa, S. Ito, M. Isobe, Y. Isobe, M. Ivkovic, Z. Jiang, J. Jo, S. Kamio, H. Kasahara, D. Kato, Y. Katoh, Y. Kawachi, Y. Kawamoto, G. Kawamura, T. Kawate, Ye.O. Kazakov, V. Klumper, A. Knieps, W.H. Ko, S. Kobayashi, F. Koike, Yu.V. Kovtun, M. Kubkowska, S. Kubo, S.S.H. Lam, A. Langenberg, H. Laqua, S. Lazerson, J. Lestz, B. Li, L. Liao, Z. Lin, R. Lunsford, S. Masuzaki, H. Matsuura, K.J. McCarthy, D. Medina-Roque, O. Mitarai, A. Mollen, C. Moon, Y. Mori, T. Morisaki, S. Morita, K. Mukai, I. Murakami, S. Murakami, T. Murase, C.M. Muscatello, K. Nagasaki, D. Naujoks, H. Nakano, M. Nakata, Y. Narushima, A. Nagy, J.H. Nicolau, T. Nishizawa, S. Nishimoto, H. Nuga, M. Nunami, R. Ochoukov, S. Ohdachi, J. Ongena, M. Osakabe, N.A. Pablant, N. Panadero, B. Peterson, J. de la Riva Villén, J. Romazanov, J. Rosato, M. Rud, S. Sakakibara, H.A. Sakaue, H. Sakai, I. Sakon, M. Salewski, S. Sangaroon, S. Sereda, T. Stange, K. Saito, S. Satake, R. Seki, T. Seki, S. Sharapov, A. Shimizu, T. Shimozuma, G. Shivam, M. Shoji, D.A. Spong, H. Sugama, Z. Sun, C. Suzuki, Y. Suzuki, T. Tajima, E. Takada, H. Takahashi, K. Toi, Y. Tsuchibushi, N. Tsujii, K. Tsumori, T.I. Tsujimurai, G. Ueno, H. Uehara, J.L. Velasco, E. Wang, K.Y. Watanabe, T. Wauter, U. Wenzel, M. Yajima, H. Yamada, I. Yamada, K. Yanagihara, H. Yamaguchi, R. Yanai, R. Yasuhara, M. Yokoyama, Y. Yoshimura, M. Zarnstorff, M. Zhao, G.Q. Zhong, Q. Zhou, S. Ziaei, LHD Experiment Group, and the W7-X Team

Subjects
Large Helical Device, basic plasma physics, burning plasma, wave–particle interaction, ion mixing, turbulence spreading, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Recently, experiments on basic plasma physics issues for solving future problems in fusion energy have been performed on a Large Helical Device. There are several problems to be solved in future devices for fusion energy. Emerging issues in burning plasma are: alpha-channeling (ion heating by alpha particles), turbulence and transport in electron dominant heating helium ash exhaust, reduction of the divertor heat load. To solve these problems, understanding the basic plasma physics of (1) wave–particle interaction through (inverse) Landau damping, (2) characteristics of electron-scale (high- k ) turbulence, (3) ion mixing and the isotope effect, and (4) turbulence spreading and detachment, is necessary. This overview discusses the experimental studies on these issues and turbulent transport in multi-ion plasma and other issues in the appendix.

Published
2024
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4. Overview of first Wendelstein 7-X high-performance operation

Author

V. Moncada, S. C. Liu, M. Winkler, P. Pölöskei, A. Tancetti, Naoki Tamura, H. Neilson, M. Krychowiak, Michael Drevlak, K. H. Schlüter, S. A. Henneberg, R. Vilbrandt, N. A. Pablant, M. Schröder, B. van Milligen, Bernd Heinemann, K. Rummel, Jonathan Schilling, Torsten Stange, G. Orozco, Christian Brandt, N. Krawczyk, Suguru Masuzaki, Yunfeng Liang, T. Estrada, Wolfgang Biel, J. H. Harris, B. Unterberg, M. Sleczka, M. Marushchenko, R. Lang, N. Rust, J. P. Kallmeyer, Laurie Stephey, P. Aleynikov, E. Blanco, Hans-Stephan Bosch, B. Buttenschön, D. Mellein, B. Shanahan, M. Vervier, M. Yokoyama, C. Suzuki, Seung Gyou Baek, A. Lücke, Felix Schauer, Ya. I. Kolesnichenko, V. Borsuk, Th. Rummel, B. Gonçalves, R. König, H. P. Laqua, G. Ehrke, K. J. McCarthy, Manfred Zilker, Venanzio Giannella, O. P. Ford, E. Flom, S. Murakami, Andreas Schlaich, P. Xanthopoulos, M. Zanini, E. Ascasíbar, C. Nührenberg, A. Carls, H. Viebke, Y. Feng, A. da Molin, H. Hunger, S. Paqay, Y. Wei, M. Blatzheim, M. W. Jakubowski, F. Köster, T. Wauters, J.C. Schmitt, M. Hubeny, P. van Eeten, H. Damm, Joris Fellinger, Gábor Cseh, Christoph Biedermann, G. Claps, L. Rudischhauser, R. Stadler, J. Mittelstaedt, Matteo Zuin, Z. Szökefalvi-Nagy, M. Knaup, Ch. Linsmeier, Francisco Castejón, J. P. Koschinsky, Bernardo B. Carvalho, L. Wegener, C. Guerard, J.M. Hernández Sánchez, B. Mendelevitch, A. Grosman, S. Pingel, Horacio Fernandes, M. Endler, N. Vianello, Jörg Schacht, Anett Spring, Yu Gao, V. Rohde, Samuel Lazerson, J.H. Matthew, W. Kasparek, R. Neu, R. Burhenn, N. Panadero, Jörg Weggen, P.A. Kurz, Walter H. Fietz, R. Schroeder, Andrea Pavone, G. Offermanns, Ryo Yasuhara, P. Sinha, Massimiliano Romé, José Luis Velasco, Carsten Killer, P. Drewelow, X. Han, T. Windisch, Nengchao Wang, Axel Könies, E.M. Edlund, K. P. Hollfeld, K. Aleynikova, Malte Henkel, Detlev Reiter, S. Brezinsek, Z. Huang, Heinz Grote, S. Langish, Matthias Otte, Alessandro Zocco, Daniel Papenfuß, G. Satheeswaran, Monika Kubkowska, S. Obermayer, G. A. Wurden, Carsten Lechte, F. Wagner, M. Gruca, H. Zhang, Olaf Neubauer, Peter Traverso, T. Ngo, V. Bykov, E. Sánchez, Matt Landreman, Dirk Naujoks, I. Vakulchyk, Andreas Langenberg, E. Wang, B. Hein, I. Ksiazek, S. Valet, Mark Cianciosa, G. Schlisio, Taina Kurki-Suonio, Oliver Schmitz, Adnan Ali, F. Reimold, Shinsuke Satake, Luis Vela Vela, C. Slaby, F. Remppel, David Gates, S. Schmuck, B. Roth, Zhirui Wang, Heinrich P. Laqua, F. Schluck, Olaf Grulke, S. Wadle, A. Runov, Manfred Thumm, Florian Effenberg, G. Fuchert, A. Vorköper, M. Banduch, Jonathan T. Green, J. Nührenberg, F. V. Chernyshev, H. Braune, Ewa Pawelec, David Maurer, A. Winter, A. Charl, Hiroshi Kasahara, T. Mizuuchi, D. Zhang, D. Höschen, J. Riemann, Thomas Klinger, W. Leonhardt, S. Sipliä, Katsumi Ida, T. Jesche, G. Pelka, U. Stridde, Riccardo Nocentini, Alexandra M. Freund, P. McNeely, A. Gogoleva, Victoria Winters, V. Szabó, Wolf-Dieter Schneider, D. A. Hartmann, Fabian Wilde, H. Schumacher, J. Howard, A. van Vuuren, J.L. Terry, M. Nagel, C. Hidalgo, Georg Kühner, S. Wolf, Boyd Blackwell, Michael Cole, Barbara Cannas, D. Rondeshagen, P. Hacker, Torsten Bluhm, J. Kacmarczyk, Kunihiro Ogawa, A. Zeitler, I. Yamada, P. Rong, Tamara Andreeva, Hiroshi Yamada, G. Anda, N. Panadero Alvarez, Wilfried Behr, F. Purps, H. Esteban, Dag Hathiramani, R. Bussiahn, David Ennis, A. H. Reiman, D. R. Mikkelsen, M. Borchardt, B. Israeli, M. Grahl, M. Losert, T. Dittmar, E. Pasch, U. Kamionka, Toru Ii Tsujimura, Gabriel G. Plunk, Felix Warmer, Jeremy Lore, F. Durodié, M. Balden, B.J. Peterson, J.P. Bähner, R. Schrittwieser, Morten Stejner, M.J. Cole, S. Zoletnik, Kian Rahbarnia, O. Marchuk, T. Bräuer, M. Hirsch, R. Riedl, W. Figacz, H. Trimino Mora, S. Degenkolbe, H. Greuner, B. Böswirth, B. Schweer, Dorothea Gradic, S. B. Ballinger, S. Ryosuke, B. Missal, Jiawu Zhu, J. H. E. Proll, M. Czerwinski, A. Cappa, B. Wiegel, J. Loizu Cisquella, Per Helander, Sehyun Kwak, S. Marsen, L. Carraro, T. Ilkei, D. Pilopp, Gábor Náfrádi, S. Récsei, M. Houry, A. de la Peña, Yu. Turkin, T.A. Scherer, T. Schröder, A. Galkowski, P. Drews, H. Frerichs, Benedikt Geiger, A. Krämer-Flecken, M. Dibon, L.-G. Böttger, A. Czarnecka, R. Krampitz, J. Wendorf, N. Chaudhary, T. Kremeyer, A. da Silva, R. Kleiber, R. Sakamoto, J.-M. Travere, I. Abramovic, T. Funaba, Andreas Meier, Fabio Pisano, Holger Niemann, Mirko Salewski, R. Brakel, M. Mayer, X. Huang, Stefan Illy, Ph. Mertens, Naoki Kenmochi, F. Köchl, Peter Lang, J. Geiger, Albert Mollén, A. Hölting, T. Barbui, M. Lennartz, T. Szabolics, Hayato Tsuchiya, S. Renard, A. Lorenz, J. Krom, C. D. Beidler, J. Cai, Andreas Dinklage, Anne White, Ye. O. Kazakov, P. Junghanns, W. Spiess, J. M. García Regaña, S. Elgeti, J. W. Coenen, Thomas Sunn Pedersen, C. Li, T. Mönnich, Miklos Porkolab, R. Laube, Burkhard Plaum, A. Benndorf, Michael Kramer, J. Ongena, J. Svensson, Dmitry Moseev, U. Wenzel, Chandra Prakash Dhard, S. Tulipán, M. C. Zarnstorff, M. Sibilia, A. von Stechow, G. M. Weir, H. Maaßberg, U. Höfel, P. Scholz, Alexey Mishchenko, R. C. Wolf, D. Carralero, G. Kocsis, Ivan Calvo, J. Tretter, Didier Chauvin, Y. Li, J. Boscary, A. Puig Sitjes, Fumimichi Sano, Andrey Samartsev, Tamás Szepesi, A. Kirschner, Dirk Nicolai, Francesco Cordella, M. Rack, A. Alonso, G. Czymek, E. R. Scott, M. E. Puiatti, Stefan Kragh Nielsen, M. Vergote, H. Schmitz, H. Jenzsch, Donald A. Spong, K. Czerski, A. Knieps, Arnold Lumsdaine, L. Ryć, M. N. A. Beurskens, Matthias F. Schneider, Simppa Äkäslompolo, Ulrich Neuner, V. Perseo, Jim-Felix Lobsien, Gerd Gantenbein, Roberto Guglielmo Citarella, L. Pacios Rodriguez, L. Vano, S. Bozhenkov, J. W. Oosterbeek, H. Röhlinger, J. P. Knauer, T. Nishizawa, A.H. Wright, M. Jia, A. Goriaev, H. Brand, D. Böckenhoff, H. M. Smith, J. P. Thomas, T. Fornal, J. Baldzuhn, D. Loesser, K. Risse, John Jelonnek, T. Wegner, S. Jablonski, Martina Huber, V. V. Lutsenko, S. Sereda, J. Ölmanns, Tomohiro Morisaki, H. Thomsen, J. A. Alcuson, P. Kornejew, J M Fontdecaba, Kai Jakob Brunner, A. Werner, T. Kobarg, European Commission, University of Greifswald, Max Planck Institute for Plasma Physics, Technical University of Denmark, Princeton University, National Institute for Fusion Science, CIEMAT, EURATOM HAS, Massachusetts Institute of Technology, University of Wisconsin-Madison, Research Center Julich, Australian National University, Eindhoven University of Technology, University of Cagliari, Consorzio RFX, Universidade de Lisboa, CEA Cadarache, St. Petersburg Scientific Centre, Oak Ridge National Laboratory, University of Salerno, ENEA Frascati Research Center, Institute of Plasma Physics and Laser Microfusion, University of Szczecin, University of Milano-Bicocca, Auburn University, Karlsruhe Institute of Technology, Universidad Carlos III de Madrid, University of Stuttgart, Austrian Academy of Sciences, National Academy of Sciences Ukraine, Technical University of Berlin, Opole University of Technology, Fusion and Plasma Physics, University of Maryland College Park, Consiglio Nazionale delle Ricerche (CNR), Kyoto University, Culham Centre for Fusion Energy, Physikalisch-Technische Bundesanstalt, Los Alamos National Laboratory, Department of Applied Physics, Aalto-yliopisto, and Aalto University

Subjects
Technology, CONFINEMENT, 01 natural sciences, impurities, 010305 fluids & plasmas, law.invention, ECR heating, Divertor, DENSITY LIMIT, law, Data_FILES, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 004 Datenverarbeitung, Informatik, Physics, Glow discharge, Condensed Matter Physics, Content (measure theory), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Electron temperature, Atomic physics, ddc:620, Stellarator, Impurities, Nuclear and High Energy Physics, Technology and Engineering, plasma performance, chemistry.chemical_element, Atmospheric-pressure plasma, PHYSICS, stellarator, Physics::Plasma Physics, NBI heating, 0103 physical sciences, divertor, 010306 general physics, Helium, Plasma performance, turbulence, Física, W7-X, Turbulence, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, chemistry, ddc:004, ddc:600, Energy (signal processing), SYSTEM
Abstract

The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

Published
2019

5. Impact of nonlocal electron heat transport on the high temperature plasmas of LHD

Author

N Tamura, S Inagaki, K Tanaka, C Michael, T Tokuzawa, T Shimozuma, S Kubo, R Sakamoto, K Ida, K Itoh, D Kalinina, S Sudo, Y Nagayama, K Kawahata, A Komori, and the LHD experimental group

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Magnetic confinement fusion, Electron, Plasma, Collisionality, Condensed Matter Physics, law.invention, Large Helical Device, Physics::Plasma Physics, law, Heat transfer, Electron temperature, Atomic physics
Abstract

Edge cooling experiments with a tracer-encapsulated solid pellet in the large helical device (LHD) show a significant rise in core electron temperature (the maximum rise is around 1 keV) as well as in many tokamaks. This experimental result indicates the possible presence of the nonlocality of electron heat transport in plasmas where turbulence as a cause of anomalous transport dominates. The nonlocal electron temperature rise in the LHD takes place in almost the same parametric domain (e.g. in a low density) as in the tokamaks. Meanwhile, the experimental results of LHD show some new aspects of nonlocal electron temperature rise, for example the delay in the nonlocal rise of core electron temperature relative to the pellet penetration time increases with the increase both in the collisionality in the core plasma and the electron temperature gradient scale length in the outer region of the plasma.

Published
2007

6. Repetitive pellet fuelling for high-density/steady-state operation on LHD

Author

R Sakamoto, H Yamada, Y Takeiri, K Narihara, T Tokuzawa, H Suzuki, S Masuzaki, S Sakakibara, S Morita, M Goto, B.J Peterson, K Matsuoka, N Ohyabu, A Komori, O Motojima, and the LHD experimental group

Subjects
Nuclear and High Energy Physics, Steady state, Materials science, Plasma parameters, digestive, oral, and skin physiology, Pellets, Plasma, Radius, Condensed Matter Physics, Large Helical Device, Nuclear magnetic resonance, Pellet, Atomic physics, Penetration depth
Abstract

A repetitive pellet injector has been developed and pellet refuelling experiments have been launched on the Large Helical Device (LHD) in a new regime characterized by high density steady state operation. In order to suppress the disturbance to the core plasma as much as possible, we employ relatively small and slow pellets. The size and velocity of the pellets are typically 2.5?mm in diameter and 250?m?s?1, respectively. The pellets were injected into neutral beam heated plasmas with repetition frequency of 10?Hz. The density rise per pellet is 1.5 ? 1019?m?3 and the pellet penetration depth, which is normalized by the plasma minor radius, is typically less than 0.5. Quasi-steady-state operation was achieved at plasma parameters of , Te = Ti = 1.0?keV. Repetitive pellet fuelling showed improved energy confinement compared with massive gas puff fuelling in the high density regime in common with previous transient pellet injection experiments, and it can sustain such an improved confinement property.

Published
2006

7. Impact of real-time magnetic axis sweeping on steady state divertor operation in LHD

Author

Y Nakamura, S Masuzaki, T Morisaki, H Ogawa, T Watanabe, Y Kubota, R Sakamoto, N Ashikawa, K Sato, H Chikaraishi, K Saito, T Seki, R Kumazawa, T Mutoh, S Kubo, Y Takeiri, B. J Peterson, A Komori, O Motojima, and the LHD experimental group

Subjects
Superconductivity, Nuclear and High Energy Physics, Materials science, Divertor, Cyclotron, Magnetic confinement fusion, Plasma, Condensed Matter Physics, Charged particle, law.invention, Large Helical Device, Heat flux, law, Atomic physics
Abstract

Steady state divertor operation with high performance plasmas (ne ~ 0.7 × 1019 cm−3, Ti ~ 2 keV) was demonstrated for half an hour in the Large Helical Device (LHD), the superconducting helical device (R = 3.6–3.9 m, a = 0.6 m, B = 3 T, l/m = 2/10). The high performance plasmas have been sustained with an averaged heating power of 680 kW and achieved an injected energy of 1.3 GJ. This required both advanced technological integration of heating systems and divertor heat flux control. In particular, optimization of divertor heat flux distribution along the divertor leg trace on divertor plates and real-time magnetic axis sweeping (R = 3.67–3.7 m) have allowed LHD to access a steady state regime with a margin of safety for the actively cooled divertor plates. The distribution of divertor heat load along the traces was investigated with calorimetric measurements and it was found that there was a localized heat load connected with the loss of high-energy ions produced by ion cyclotron radio frequency near-fields. Orbit analysis shows that the behaviour of high-energy ions is qualitatively in good agreement with the experimental result. Long-pulse discharges were terminated by radiation collapse due to penetration of metallic flakes into the plasma.

Published
2006

8. Self-sustained detachment in the Large Helical Device

Author

J Miyazawa, S Masuzaki, R Sakamoto, H Arimoto, K Kondo, N Tamura, M Shoji, M Nishiura, S Murakami, H Funaba, B.J Peterson, S Sakakibara, M Kobayashi, K Tanaka, K Narihara, I Yamada, S Morita, M Goto, M Osakabe, N Ashikawa, T Morisaki, K Nishimura, H Yamada, N Ohyabu, A Komori, O Motojima, and the LHD experimental group

Subjects
Nuclear and High Energy Physics, Electron density, Materials science, Rational surface, Divertor, Magnetic confinement fusion, Plasma, Condensed Matter Physics, law.invention, Large Helical Device, Physics::Plasma Physics, law, Atomic physics, Scaling, Stellarator
Abstract

Self-sustained detachment has been obtained in the Large Helical Device (LHD). Strong hydrogen gas puffing of ~200 Pa m3 s−1 after a density feedback phase detaches the plasma from the divertor plates with high reproducibility. High electron density of over 1 × 1020 m−3 is sustained without gas puffing until the heating beam stops and a high-density flat top for 2 s has been demonstrated. Throughout the self-sustained detachment phase, the minor radius of the hot plasma column shrinks to ~90% of the last-closed-flux-surface, which corresponds to the rational surface. This new state has been named the 'Serpens mode', for self-regulated plasma edge 'neath the last-closed-flux-surface. Global energy confinement of the Serpens mode is compared with the international stellarator scaling 1995 (ISS95) and the recently established scaling for high-density LHD plasmas (HD scaling), where shrinking confinement volume and shallow penetration of the heating beams are taken into account. Although the energy confinement of the Serpens mode seems deteriorated compared with ISS95, as in the case of high-density attached plasmas, it is consistent with the HD scaling. This suggests that the energy confinement properties of detached plasmas in LHD are similar to those in high-density attached plasmas.

Published
2006

9. Experimental study of particle transport and density fluctuations in LHD

Author

K Tanaka, C Michael, A.L Sanin, L.N Vyacheslavov, K Kawahata, S Murakami, A Wakasa, S Okajima, H Yamada, M Shoji, J Miyazawa, S Morita, T Tokuzawa, T Akiyama, M Goto, K Ida, M Yoshinuma, I Yamada, M Yokoyama, S Masuzaki, T Morisaki, R Sakamoto, H Funaba, S Inagaki, M Kobayashi, A Komori, and LHD experimental group

Subjects
Convection, Physics, Nuclear and High Energy Physics, Large Helical Device, Electron density, Condensed matter physics, Electron temperature, Diamagnetism, Diffusion (business), Phase velocity, Atomic physics, Condensed Matter Physics, Magnetic field
Abstract

A variety of electron density (ne) profiles have been observed in the Large Helical Device (LHD). The density profiles change dramatically with heating power and toroidal magnetic field (Bt). The particle transport coefficients, i.e. diffusion coefficient (D) and convection velocity (V) are experimentally obtained in the standard configuration from density modulation experiments. The values of D and V are estimated separately in the core and edge. The diffusion coefficients are found to be a function of electron temperature (Te), and vary with Bt. Edge diffusion coefficients are proportional to . Non-zero V is observed, and it is found that the electron temperature gradient can drive particle convection, particularly in the core region. The convection velocity both in the core and edge reverses direction from inward to outward as the Te gradient increases. However, the toroidal magnetic field also significantly affects the value and direction of V. The density fluctuation profiles are measured by a two-dimensional phase contrast interferometer. It was found that fluctuations which are localized in the edge propagate towards the ion diamagnetic direction in the laboratory frame, while the phase velocity of fluctuations around mid-radius is close to the plasma poloidal Er × Bt rotation velocity. The fluctuation level becomes larger as particle flux becomes larger in the edge region.

Published
2005

10. Experiment of magnetic island formation in Large Helical Device

Author

Y Nagayama, K Narihara, Y Narushima, N Ohyabu, T Hayashi, K Ida, S Inagaki, D Kalinina, R Kanno, A Komori, T Morisaki, R Sakamoto, S Sudo, N Tamura, T Tokuzawa, H Yamada, M Yoshinuma, and LHD experimental group

Subjects
Physics, Nuclear and High Energy Physics, Toroid, Condensed matter physics, business.industry, Magnetic confinement fusion, Plasma, Radius, Condensed Matter Physics, Magnetic field, Large Helical Device, Optics, Electron temperature, Electric current, business
Abstract

Magnetic island formation is experimentally investigated in the Large Helical Device. The (m, n) = (1, 1) vacuum magnetic island is generated by using the local island diverter field, where m and n are the poloidal and toroidal mode numbers, respectively. The island width depends on plasma parameters (the electron temperature and the β) and the magnetic axis position. In the case of Rax = 3.53 m the magnetic island in the plasma is larger than that in the vacuum field. Here, Rax is the major radius of the magnetic axis. In the case of Rax = 3.6 m the magnetic island is not generated when the error field is less than the threshold which is increased as the β is increased. Evidence of island current is obtained when the magnetic island is formed due to a small error field. However, the mechanism that generates the island is not yet known.

Published
2005

11. Edge plasma control by local island divertor in LHD

Author

A Komori, T Morisaki, S Masuzaki, M Kobayashi, Y Feng, M Shoji, N Ohyabu, K Ida, K Tanaka, K Kawahata, K Narihara, S Morita, B.J Peterson, R Sakamoto, S Sakakibara, H Yamada, K Ikeda, O Kaneko, S Kubo, J Miyazawa, K Nagaoka, H Nakanishi, K Ohkubo, Y Oka, M Osakabe, D Reiter, F Sardei, T Shimozuma, Y Takeiri, K Tsumori, K.Y Watababe, I Yamada, Y Yoshimura, M Yoshinuma, O Motojima, and LHD Experimental Group

Subjects
Nuclear and High Energy Physics, Materials science, Separatrix, Field line, business.industry, Divertor, High density, Perturbation (astronomy), Plasma, Mechanics, Condensed Matter Physics, Large Helical Device, Optics, business, Plasma control
Abstract

In the Large Helical Device (LHD) programme, one of the key research issues is to enhance helical plasma performance through edge plasma control. For the first time in the LHD programme, the edge plasma control was performed with a local island divertor (LID) that is a closed divertor, utilizing an m/n = 1/1 island generated externally by which 20 small perturbation coils, and fundamental LID functions were demonstrated experimentally. It was found that the outward heat and particle fluxes crossing the island separatrix flow along the field lines to the rear of the divertor head, where carbon plates are placed to receive the heat and particle loads. Accordingly, high efficient pumping was demonstrated, which is considered to be the key in realizing high temperature divertor operations, resulting in an improvement in energy confinement. In this experiment, relatively good energy confinement is achieved in the high density regime at a magnetic axis position, Rax, of 3.75?m. Results of edge modelling are also presented by using the EMC3-EIRENE code.

Published
2005

12. Observation of pellet ablation behaviour on the large helical device

Author

R Sakamoto, H Yamada, K Tanaka, T Tokuzawa, S Murakami, M Goto, S Morita, N Ohyabu, K Kawahata, O Motojima, and the LHD Experimental group

Subjects
Nuclear and High Energy Physics, Toroid, Materials science, business.industry, medicine.medical_treatment, Condensed Matter Physics, Ablation, Neutral beam injection, Ion, Large Helical Device, Optics, Nuclear magnetic resonance, Physics::Plasma Physics, Deflection (engineering), Condensed Matter::Superconductivity, Physics::Space Physics, Pellet, medicine, business, Penetration depth
Abstract

Hydrogen ice pellets have been injected using two different location configurations, namely outer port injection and coil side injection, in the large helical device. The behaviour of the pellet ablation has been observed using a fast camera, which possesses high spatial and time resolution. Striking toroidal deflection of the pellet trajectory is observed. The deflection is in the direction of tangential neutral beam injection. The toroidal velocity ultimately reaches 1000 m s−1 or more. The possibility of a rocket effect due to a unilateral ablation by the fast ions is discussed. The effective penetration depth of the pellet, which is measured by images, agrees with the prediction from the neutral-gas-shielding model. The penetration depth is compared with the measured deposition profile of the pellet.

Published
2004

13. MHD instabilities and their effects on plasma confinement in Large Helical Device plasmas

Author

Katsumi Ida, Shinji Yoshimura, Hiroshi Idei, M. Shoji, S. Ohdachi, Nobuaki Noda, S. Muto, K. Nishimura, R. Sakamoto, Takashi Notake, T. Kobuchi, Tetsuo Watari, K. Narihara, Masahide Sato, S. Yamamoto, I. Ohtake, Kazuo Kawahata, Kiyomasa Watanabe, K. Tanaka, J. Miyazawa, Y. Hamada, T. Ozaki, T. Saida, T. Uda, T. Mito, M. Goto, Y. Oka, T. Shimozuma, Shigeru Sudo, Osamu Kaneko, Hiroshi Yamada, T. Seki, S. Murakami, H. Funaba, J. Li, M. Y. Tanaka, T. Satow, S. Sakakibara, Kimitaka Itoh, A. Sagara, Kunizo Ohkubo, Y. Yoshimura, M. Yokoyama, H. Nakanishi, A. Komori, M. Emoto, Naoki Tamura, T. Mutoh, Kazuo Toi, Shoichi Okamura, Suguru Masuzaki, Y. Xu, Tsuyoshi Akiyama, Shinsaku Imagawa, Y. Liang, K. Ikeda, Y. Narushima, A. Nishizawa, K. Tsumori, Shin Kubo, B. J. Peterson, O. Motojima, Takeshi Ido, N. Nakajima, K. Nagaoka, Shigeru Inagaki, Kozo Yamazaki, R. Kumazawa, Y. Nakamura, A. Weller, X. Ding, Y. Nagayama, Kenji Saito, T. Morisaki, I. Yamada, M. Isobe, Kohnosuke Sato, Masami Fujiwara, Ken Matsuoka, Satoshi Morita, N. Ohyabu, Mamiko Sasao, and N. Ashikawa

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Magnetic confinement fusion, Plasma, Condensed Matter Physics, Ion, law.invention, Large Helical Device, Physics::Plasma Physics, law, Beta (plasma physics), Magnetohydrodynamics, Atomic physics, Edge-localized mode
Abstract

Characteristics of MHD instabilities and their impacts on plasma confinement are studied in current free plasmas of the Large Helical Device. Spontaneous L?H transition is often observed in high beta plasmas close to 2% at low toroidal fields (Bt ? 0.75?T). The stored energy starts to rise rapidly just after the transition accompanying the clear rise in the electron density but quickly saturates due to the growth of the m = 2/n = 3 mode (m and n: poloidal and toroidal mode numbers), the rational surface of which is located in the edge barrier region, and edge localized mode (ELM) like activities having fairly small amplitude but high repetition frequency. Even in low beta plasmas without L?H transitions, ELM-like activities are sometimes induced in high performance plasmas with a steep edge pressure gradient and transiently reduce the stored energy up to 10%. Energetic ion driven MHD modes such as Alfv?n eigenmodes (AEs) are studied in a very wide range of characteristic parameters (the averaged beta of energetic ions, ?b?, and the ratio of energetic ion velocity to the Alfv?n velocity, Vb?/VA), of which range includes all tokamak data. In addition to the observation of toroidicity induced AEs (TAEs), coherent magnetic fluctuations of helicity induced AEs (HAEs) have been detected for the first time in NBI heated plasmas. The transition of a core-localized TAE to a global AE (GAE) is also observed in a discharge with temporal evolution of the rotational transform profile, having a similarity to the phenomenon observed in a reversed shear tokamak. At low magnetic fields, bursting TAEs transiently induce a significant loss of energetic ions, up to 40% of injected beams, but on the other hand play an important role in triggering the formation of transport barriers in the core and edge regions.

Published
2004

14. Ion cyclotron range of frequencies heating and high-energy particle production in the Large Helical Device

Author

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

Subjects
Nuclear and High Energy Physics, Range (particle radiation), High energy particle, Materials science, Cyclotron, Magnetic confinement fusion, Plasma, Condensed Matter Physics, law.invention, Large Helical Device, Helicon, Physics::Plasma Physics, law, Dielectric heating, Atomic physics
Abstract

Significant progress has been made with ion cyclotron range of frequencies (ICRF) heating in the Large Helical Device. This is mainly due to better confinement of the helically trapped particles and less accumulation of impurities in the region of the plasma core. During the past two years, ICRF heating power has been increased from 1.35 to 2.7 MW. Various wave-mode tests were carried out using minority-ion heating, second-harmonic heating, slow-wave heating and high-density fast-wave heating at the fundamental cyclotron frequency. This fundamental heating mode extended the plasma density range of effective ICRF heating to a value of 1×1020 m−3. This use of the heating mode was its first successful application in large fusion devices. Using the minority-ion mode gave the best performance, and the stored energy reached 240 kJ using ICRF alone. This was obtained for the inward-shifted magnetic axis configuration. The improvement associated with the axis-shift was common for both bulk plasma and highly accelerated particles. For the minority-ion mode, high-energy ions up to 500 keV were observed by concentrating the heating power near the plasma axis. The confinement properties of high-energy particles were studied for different magnetic axis configurations, using the power-modulation technique. It confirmed that with the inward-shifted configuration the confinement of high-energy particles was better than with the normal configuration. By increasing the distance of the plasma to the vessel wall to about 2 cm, the impurity influx was sufficiently reduced to allow sustainment of the plasma with ICRF heating alone for more than 2 min.

Published
2003

15. Behaviour of ion temperature in electron and ion heating regimes observed with ECH, NBI and ICRF discharges of LHD

Author

S. Morita, M. Goto, S. Kubo, S. Murakami, K. Narihara, M. Osakabe, T. Seki, Y. Takeiri, K. Tanaka, H. Yamada, H. Funaba, H. Idei, K. Ida, K. Ikeda, S. Inagaki, O. Kaneko, K. Kawahata, A. Komori, R. Kumazawa, S. Masuzaki, J. Miyazawa, T. Morisaki, O. Motojima, S. Muto, T. Mutoh, Y. Nagayama, Y. Nakamura, K. Nishimura, S. Ohdachi, N. Ohyabu, Y. Oka, T. Ozaki, B.J. Peterson, S. Sakakibara, R. Sakamoto, M. Sasao, K. Sato, T. Shimozuma, M. Shoji, H. Suzuki, K. Toi, T. Tokuzawa, K. Tsumori, K.Y. Watanabe, T. Watari, I. Yamada, and LHD Experimental Group

Subjects
Nuclear and High Energy Physics, Electron density, Large Helical Device, Materials science, Helicon, Electron temperature, Plasma diagnostics, Plasma, Atomic physics, Condensed Matter Physics, Doppler broadening, Ion
Abstract

Ion temperature at the plasma centre has been measured from Doppler broadening of Ti XXI (2.61 A) and Ar XVII (3.95 A) x-ray lines using a newly installed crystal spectrometer with CCD detector in ECH, NBI and ICRF plasmas of Large Helical Device (LHD). The ion temperature obtained in a range of 0.6 and 3.5 keV was analysed with electron density and compared with electron temperature. A new parameter range of Ti>Te was found in low-density (ne

Published
2002

16. The divertor plasma characteristics in the Large Helical Device

Author

S. Masuzaki, T. Morisaki, N. Ohyabu, A. Komori, H. Suzuki, N. Noda, Y. Kubota, R. Sakamoto, K. Narihara, K. Kawahata, K. Tanaka, T. Tokuzawa, S. Morita, M. Goto, M. Osakabe, T. Watanabe, Y. Matsumoto, O. Motojima, and the LHD Experimental group

Subjects
Nuclear and High Energy Physics, Materials science, Tokamak, Field line, Divertor, Magnetic confinement fusion, Plasma, Condensed Matter Physics, law.invention, symbols.namesake, Large Helical Device, Physics::Plasma Physics, law, symbols, Langmuir probe, Plasma diagnostics, Atomic physics
Abstract

Divertor plasma characteristics in the Large Helical Device (LHD) have been investigated mainly by using Langmuir probes. The three-dimensional structure of the helical divertor, which is naturally produced in the heliotron-type magnetic configuration, is clearly seen in the measured particle and power deposition profiles on the divertor plates. These observations are consistent with the numerical results of field line tracing. The particle flux to the divertor plates increases almost linearly with the line averaged density. The high-recycling regime and divertor detachment, which are observed in tokamaks, have not been observed even during high density discharges with low input power. Both electron density and temperature decrease with increasing radius in the stochastic layer with open field lines, and at the divertor plate they become fairly low compared with those at the last closed flux surface. This means the reduction of pressure along the magnetic field lines occurs in the open field line region in LHD.

Published
2002

17. Overview of LHD experiments

Author

M. Fujiwara, K. Kawahata, N. Ohyabu, O. Kaneko, A. Komori, H. Yamada, N. Ashikawa, L.R. Baylor, S.K. Combs, P.C. deVries, M. Emoto, A. Ejiri, P.W. Fisher, H. Funaba, M. Goto, D. Hartmann, K. Ida, H. Idei, S. Iio, K. Ikeda, S. Inagaki, N. Inoue, M. Isobe, S. Kado, K. Khlopenkov, T. Kobuchi, A.V. Krasilnikov, S. Kubo, R. Kumazawa, F. Leuterer, Y. Liang, J.F. Lyon, S. Masuzaki, T. Minami, J. Miyajima, T. Morisaki, S. Morita, S. Murakami, S. Muto, T. Mutoh, Y. Nagayama, N. Nakajima, Y. Nakamura, H. Nakanishi, K. Narihara, K. Nishimura, N. Noda, T. Notake, S. Ohdachi, Y. Oka, S. Okajima, M. Okamoto, M. Osakabe, T. Ozaki, R.O. Pavlichenko, B.J. Peterson, A. Sagara, K. Saito, S. Sakakibara, R. Sakamoto, H. Sanuki, H. Sasao, M. Sasao, K. Sato, M. Sato, T. Seki, T. Shimozuma, M. Shoji, H. Sugama, H. Suzuki, M. Takechi, Y. Takeiri, N. Tamura, K. Tanaka, K. Toi, T. Tokuzawa, Y. Torii, K. Tsumori, K.Y. Watanabe, T. Watanabe, T. Watari, I. Yamada, S. Yamaguchi, S. Yamamoto, M. Yokoyama, N. Yoshida, Y. Yoshimura, Y.P. Zhao, R. Akiyama, K. Haba, M. Iima, J. Kodaira, T. Takita, T. Tsuzuki, K. Yamauchi, H. Yonezu, H. Chikaraishi, S. Hamaguchi, S. Imagawa, A. Iwamoto, S. Kitagawa, Y. Kubota, R. Maekawa, T. Mito, K. Murai, A. Nishimura, K. Takahata, H. Tamura, S. Yamada, N. Yanagi, K. Itoh, K. Matsuoka, K. Ohkubo, I. Ohtake, S. Satoh, T. Satow, S. Sudo, S. Tanahashi, K. Yamazaki, Y. Hamada, and O. Motojima

Subjects
Nuclear and High Energy Physics, Materials science, Tokamak, Thermonuclear fusion, Plasma, Condensed Matter Physics, law.invention, Ion, law, Beta (plasma physics), Atomic physics, Magnetohydrodynamics, Scaling, Stellarator
Abstract

During the first two years of the LHD experiment the following results have been achieved: (i) higher Te (Te(0) = 4.4 keV at ne = 5.3 × 1018 m-3 and Pabs = 1.8 MW); (ii) higher confinement (τE = 0.3 s, Te(0) = 1.1 keV at ne = 6.5 × 1019 m-3 and Pabs = 2.0 MW); (iii) higher stored energy, Wpdia = 880 kJ at B = 2.75 T. High performance plasmas have been realized in the inward shifted magnetic axis configuration (R = 3.6 m) where helical symmetry is recovered and the particle orbit properties are improved by a trade-off of MHD stability properties due to the appearance of a magnetic hill. Energy confinement was systematically higher than that predicted by the International Stellarator Scaling 95 by up to a factor of 1.6 and was comparable with the ELMy H mode confinement capability in tokamaks. This confinement improvement is attributed to configuration control (inward shift of the magnetic axis) and to the formation of a high edge temperature. The average beta value achieved reached 2.4% at B = 1.3 T, the highest beta value ever obtained in a helical device, and so far no degradation of confinement by MHD phenomena has been observed. The inward shifted configuration has also led to successful ICRF minority ion heating. ICRF powers up to 1.3 MW were reliably injected into the plasma without significant impurity contamination, and a plasma with a stored energy of 200 kJ was sustained for 5 s by ICRF alone. As another important result, long pulse discharges of more than 1 min were successfully achieved separately with an NBI heating of 0.5 MW and with an ICRF heating of 0.85 MW.

Published
2001

18. Impact of heat deposition profile on global confinement of NBI heated plasmas in the LHD[Original title in FEC2002, Lyon: response of temperature and density profiles to heat deposition profile and its impact on global scaling in LHD.].

Author

H. Yamada, S. Murakami, K. Yamazaki, O. Kaneko, J. Miyazawa, R. Sakamoto, K.Y. Watanabe, K. Narihara, K. Tanaka, S. Sakakibara, M. Osakabe, B.J. Peterson, S. Morita, K. Ida, S. Inagaki, S. Masuzaki, T. Morisaki, G. Rewoldt, H. Sugama, and N. Nakajima

Published
2003

19. New approach to the control of particle recycling using divertor pumping in the Large Helical Device.

Author

G. Motojima, S. Masuzaki, T. Morisaki, H. Tanaka, R. Sakamoto, T. Murase, S. Oliver, M. Kobayashi, M. Shoji, M. Tokitani, Y. Tsuchibushi, H. Yamada, Y. Takeiri, and Group, L. H. D. Experiment

Subjects
FUSION reactor divertors, WOOD pellets, PLASMA density, GAS injection, PUMPING machinery, PRESSURE control
Abstract

The effect of the divertor pumping on plasmas has been investigated in the Large Helical Device (LHD). A divertor pump which reaches high pumping speed (67  ±  5 m3 s−1 in hydrogen) and high pumping capacity (58 000 Pa m3 in hydrogen) has been developed at LHD. The global particle confinement time (), which is expressed as τp/(1  −  R), where τp is the particle confinement time and R is the global recycling coefficient, is used for comparison of operation with and without divertor pumping. After the fueling was stopped, shorter values were obtained in low density plasmas with divertor pumping in comparison with the values without divertor pumping. In this paper, the acceleration of RF wall conditioning by the divertor pumping is also discussed. The effect of the divertor pumping on high density plasmas has been investigated. In high density plasmas obtained by pellet fueling, not only edge density but also core density is reduced by the divertor pumping due to shallower pellet penetration. The control of neutral pressure by the feedback operation of pellet injection and gas puffing likely will be a candidate for the edge density control. [ABSTRACT FROM AUTHOR]

Published
2019
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20. Conceptual design of a compact helical fusion reactor FFHR-c1 for the early demonstration of year-long electric power generation.

Author

T. Goto, J. Miyazawa, H. Tamura, T. Tanaka, R. Sakamoto, C. Suzuki, R. Seki, S. Satake, M. Nunami, M. Yokoyama, N. Yanagi, A. Sagara, and Group, the FFHR Design

Subjects
ELECTRIC power production, FUSION reactors, CONCEPTUAL design, SUPERCONDUCTING magnets
Abstract

Conceptual design of a compact large helical device (LHD)-type helical fusion reactor FFHR-c1 has been conducted. This design focuses on a year-long electric power generation with as small a reactor size as possible by adopting the operation with auxiliary heating and innovative ideas for the design of the superconducting magnet, divertor and blanket system. The primary design parameters, which have been selected by extrapolation from the previous design FFHR-d1B using simple scalings, has been examined by the systems code and the 1D integrated physics analysis code from the viewpoint of plant power balance and the achievable plasma operation regime. The design feasibility of the proposed design point has been confirmed with the physics parameters that are consistent with the LHD experiment. Further improvement of the plasma performance is expected by the optimisation of the helical coil winding law. Although intensive R&D is needed to realise the innovative ideas of the engineering design, this design ensures the path to helical commercial power plants and provides more options and increases the probability of solving critical issues of fusion reactors. [ABSTRACT FROM AUTHOR]

Published
2019
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21. The isotope effect on impurities and bulk ion particle transport in the Large Helical Device.

Author

K. Ida, R. Sakamoto, M. Yoshinuma, K. Yamazaki, T. Kobayashi, Y. Fujiwara, C. Suzuki, K. Fuji, J. Chen, I. Murakami, M. Emoto, R. Mackenbach, H. Yamada, G. Motojima, S. Masuzaki, K. Mukai, K. Nagaoka, H. Takahashi, T. Oishi, and M. Goto

Subjects
*DEUTERIUM, *ION transport (Biology), *ISOTOPES, *CHARGE exchange, *THERMAL diffusivity, *DEUTERIUM plasma
Abstract

The isotope effect on impurities and bulk ion particle transport is investigated by using the deuterium, hydrogen, and isotope mixture plasma in the Large Helical Device (LHD). A clear isotope effect is observed in the impurity transport but not the bulk ion transport. The isotope effects on impurity transport and ion heat transport are observed as a primary and a secondary effect, respectively, in the plasma with an internal transport barrier (ITB). In the LHD, an ion ITB is always transient because the impurity hole triggered by the increase of ion temperature gradient causes the enhancement of ion heat transport and gradually terminates the ion ITB. The formation of an impurity hole becomes slower in the deuterium (D) plasma than the hydrogen (H) plasma. This primary isotope effect on impurity transport contributes the longer sustainment of the ion ITB state because the low ion thermal diffusivity can be sustained as long as the normalized carbon impurity gradient R/Ln,c, where , is above the critical value (∼−5). Therefore, the longer sustainment of the ITB state in the deuterium plasma is considered to be a secondary isotope effect due to the mitigation of the impurity hole. The radial profile of H and D ion density is measured using bulk charge exchange spectroscopy inside the isotope mixture plasma. The decay time of H ion density after the H-pellet injection and the decay time of D ion density after D-pellet injection are almost identical, which demonstrates that there is no significant isotope effect on ion particle transport. [ABSTRACT FROM AUTHOR]

Published
2019
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22. Establishment of a low recycling state with full density control by active pumping of the closed helical divertor at LHD.

Author

G. Motojima, S. Masuzaki, H. Tanaka, T. Morisaki, R. Sakamoto, T. Murase, Y. Tsuchibushi, M. Kobayashi, O. Schmitz, M. Shoji, M. Tokitani, H. Yamada, Y. Takeiri, and Group, The L. H. D. Experiment

Subjects
RECYCLING equipment, PUMPING machinery, DIVERTERS (Electronics), PLASMA density, TOROIDAL plasma
Abstract

Superior control of particle recycling and hence full governance of plasma density has been established in the Large Helical Device (LHD) using largely enhanced active pumping of the closed helical divertor (CHD). In-vessel cryo-sorption pumping systems inside the CHD in five out of ten inner toroidal divertor sections have been developed and installed step by step in the LHD. The total effective pumping speed obtained was 67  ±  5 m3 s−1 in hydrogen, which is approximately seven times larger than previously obtained. As a result, a low recycling state was observed with CHD pumping for the first time in LHD featuring excellent density control even under intense pellet fueling conditions. A global particle confinement time () is used for comparison of operation with and without the CHD pumping. The was evaluated from the density decay after the fueling of hydrogen pellet injection or gas puffing in NBI plasmas. A reliably low base density before the fueling and short after the fueling were obtained during the CHD pumping, demonstrating for the first time full control of the particle balance with active pumping in the CHD. [ABSTRACT FROM AUTHOR]

Published
2018
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23. Major results from the first plasma campaign of the Wendelstein 7-X stellarator

Author

H. Maaßberg, M. Grahl, V. Moncada, Marek Scholz, Naoki Tamura, H. Neilson, R. Koziol, M. Krychowiak, A. Lücke, T. Estrada, R. Munk, M. Marushchenko, K. Toi, Heinrich P. Laqua, S. Paqay, Olaf Grulke, K. Baumann, A. Czermak, Ivan Calvo, Yasuhiro Suzuki, P.J. Heitzenroeder, H. Hölbe, G. Offermanns, Gintautas Dundulis, U. Stridde, H. Hunger, S. Valet, P. Denner, N. Krawczyk, O. Mishchenko, Andrey Samartsev, Mantas Povilaitis, Andrea Pavone, H. Schumacher, P. Aleynikov, H. P. Laqua, U. Wenzel, M. Sibilia, J. Ongena, Kian Rahbarnia, A. Galkowski, T.A. Scherer, C. Slaby, J. Nührenberg, H.-J. Roscher, Martin Köppen, L.-G. Böttger, A. Czarnecka, R. Krampitz, M. Zilker, T. Kremeyer, J. Wendorf, V. Bykov, A. Goriaev, Josef Preinhaelter, A. Alonso, Peter Titus, G. Czymek, Andreas Langenberg, Matteo Zuin, A. Gogoleva, F. Musielok, A. Zeitler, Andreas Schlaich, P. Xanthopoulos, Victoria Winters, M. Losert, D. A. Hartmann, Roberto Guglielmo Citarella, L. Pacios Rodriguez, Boyd Blackwell, E. Blanco, Hans-Stephan Bosch, R. König, R. Stadler, J. Mittelstaedt, Ch. Linsmeier, U. Höfel, N. Panadero Alvarez, E. Pasch, Francesco Cordella, M. Knaup, Fabian Wilde, M. C. Zarnstorff, B. Mendelevitch, Toru Ii Tsujimura, T. Szabolics, Hayato Tsuchiya, J.C. Schmitt, Tadas Kaliatka, Sadayoshi Murakami, Samuel Lazerson, W. Spiess, J. M. García Regaña, P. Junghans, María Sánchez, A. Grosman, I. Yamada, K. P. Hollfeld, K. Aleynikova, Gábor Náfrádi, T. Krings, Daniel Papenfuß, José Luis Velasco, P. Drewelow, N. A. Pablant, S. Renard, Alessandro Zocco, F. Wagner, D. Böckenhoff, S. Ryosuke, Michael Kramer, A. Vorkörper, M. Turnyanskiy, R. Riedl, W. Figacz, H. Trimino Mora, A. da Silva, D. Gradic, M. Keunecke, A. Pieper, M. Houry, S. Pingel, K. H. Schlüter, J. Loizu Cisquella, L. Carraro, S. Schmuck, M. Banduch, Sehyun Kwak, T. Ilkei, X. Huang, Stefan Illy, N. Fahrenkamp, I. Vakulchyk, G. Kocsis, Ph. Mertens, T. Morizaki, K. Czerski, F. V. Chernyshev, Bernd Heinemann, L. Lewerentz, B.J. Peterson, Francisco Castejón, Olaf Neubauer, D. Zhang, Torsten Bluhm, F. Köchl, C.P. von Thun, Michael Cole, Fabio Pisano, R. Brakel, Peter Traverso, G. Orozco, Wolf-Dieter Schneider, A. A. Ivanov, S. Sipliä, V. Szabó, D. Pilopp, A. Cappa, G. Anda, H. Braune, A. Krämer-Flecken, R. Sakamoto, A. Charl, Hiroshi Kasahara, Massimiliano Romé, J.-H. Feist, Mark Cianciosa, M. Führer, G. Schlisio, Taina Kurki-Suonio, F. Purps, H. Esteban, A. H. Reiman, J. Krom, C. D. Beidler, D. Loesser, H. M. Smith, Nengchao Wang, Axel Könies, Oliver Schmitz, T. Bräuer, M. Hirsch, Gabriel G. Plunk, Felix Warmer, R. Karalevicius, Riccardo Nocentini, J.L. Terry, John Jelonnek, Arnold Lumsdaine, L. Ryć, M. N. A. Beurskens, H. Jenzsch, Z. Sulek, Donald A. Spong, A. Khilchenko, P. Marek, R. Schroeder, T. Schröder, B. Standley, Manfred Thumm, B. Brünner, T. Fornal, Benedikt Geiger, H. Frerichs, R. Kleiber, T. Funaba, Andreas Meier, S. Degenkolbe, P. Rong, Dag Hathiramani, Matthias F. Schneider, Simppa Äkäslompolo, M. R. Stoneking, A. Dudek, Jiawu Zhu, X. Han, T. Windisch, Y. Wei, Detlev Reiter, J. Tretter, N. Rust, J. P. Kallmeyer, J. Baldzuhn, P. Bolgert, Dirk Timmermann, Shinsuke Satake, Luis Vela Vela, Yu. Turkin, Z. Szökefalvi-Nagy, Sigitas Rimkevicius, Naoki Kenmochi, Ulrich Neuner, M. Garcia-Munoz, V. Perseo, Matthias Otte, A. Puig Sitjes, Tamás Szepesi, A. da Molin, Alexis Terra, C. Guerard, J.M. Hernández Sánchez, A. Rodatos, J. Assmann, D. Höschen, Albert Mollén, A. Hölting, Tom Wauters, Adnan Ali, Ewa Pawelec, W. Kasparek, Ryo Yasuhara, D. Kinna, P. Sinha, B. Wiegel, Horacio Fernandes, M. E. Puiatti, S. Récsei, E. Ascasíbar, J.-M. Travere, C. Hidalgo, Joris Fellinger, H. Schmitz, Suguru Masuzaki, Katsumi Ida, G. Pelka, Jim-Felix Lobsien, S. Wolf, Jörg Schacht, J. Koshurinov, Han Zhang, P. Kornejew, J M Fontdecaba, T. Ngo, E. Wang, B. Hein, Gerd Gantenbein, Michael Drevlak, M. Vervier, J. W. Oosterbeek, H. Röhlinger, J. P. Knauer, B. Schweer, Jakub Urban, David Maurer, I. Ksiazek, David Gates, S. C. Liu, S. Massidda, F. Remppel, A.H. Wright, G. Satheeswaran, Monika Kubkowska, K. Rummel, Kai Jakob Brunner, Torsten Stange, J. Riemann, Thomas Klinger, S. Obermayer, H. Brand, Christine Hennig, A. Werner, N. Gierse, S. A. Henneberg, R. Vilbrandt, J. Wolowski, T. Sunn Pedersen, M. Dostal, G. A. Wurden, I. Abramovic, Carsten Lechte, R. Lang, S. A. Bozhenkov, G. Ehrke, K. J. McCarthy, Egidijus Urbonavicius, M. Schröder, S. Jablonski, Martina Huber, M. Nagel, Yunfeng Liang, O. P. Ford, Barbara Cannas, T. Mizuuchi, Anatoly Panin, Jan Skodzik, V. V. Lutsenko, R. Koslowski, R. Laube, Jonathan T. Green, B. Unterberg, Jeremy Lore, Laurie Stephey, J. H. E. Proll, M. Czerwinski, Venanzio Giannella, Jörg Weggen, S. Marsen, Clifford M Surko, Grzegorz Gawlik, B. Roth, D. Birus, Ch. Brandt, M. Mardenfeld, K. Riße, Y. Feng, Alexandra M. Freund, M. Vergote, S. Wadle, H. Thomsen, Wilfried Behr, A. Runov, L. Wegener, Burkhard Plaum, J. Svensson, Dmitry Moseev, Łukasz Ciupiński, G. M. Weir, E. Winkler, W. Pan, E. Erckmann, D. Mellein, B. Shanahan, Th. Kobarg, Marek Barlak, John Howard, Günter Dammertz, M. Endler, D.P. Dhard, N. Vianello, L. V. Lubyako, R. Burhenn, J. Thomas, N. Panadero, M. Gruca, T. Mönnich, J. Majano-Brown, Wolfgang Biel, S. Tulipán, J. H. Harris, C. Nührenberg, A. Carls, H. Viebke, Walter H. Fietz, L. Haiduk, S. Brezinsek, Heinz Grote, S. Langish, V. Huber, Jacek Jagielski, David Ennis, P. Kraszewsk, J. Kacmarczyk, Kunihiro Ogawa, U. Kamionka, O. Bertuch, F. Durodié, B. Missal, A. de la Peña, Robertas Alzbutas, Anett Spring, Yu Gao, Matt Landreman, Dirk Naujoks, Florian Effenberg, P. McNeely, Ya. I. Kolesnichenko, B. Gonçalves, B. van Millingen, M. Blatzheim, X. Peng, F. Harberts, M. W. Jakubowski, F. Köster, Gábor Cseh, Ph. Drews, Christoph Biedermann, G. Claps, L. Rudischhauser, Bernardo B. Carvalho, M. Yokoyama, Seung Gyou Baek, Felix Schauer, V. Borsuk, Th. Rummel, J. Boscary, Fumimichi Sano, J. R. Danielson, M. Rack, G. Fuchert, H.-J. Hartfuß, W. Leonhardt, Georg Kühner, D. R. Mikkelsen, M. Borchardt, A. Benndorf, P. Scholz, R. C. Wolf, I.V. Shikhovtsev, Holger Niemann, Andreas Zimbal, J. Geiger, T. Barbui, M. Lennartz, A. Lorenz, Andreas Dinklage, G. Krzesiński, J. Zajac, B. Israeli, R. Schrittwieser, M.J. Cole, S. Zoletnik, O. Marchuk, Per Helander, B. Buttenschön, P. van Eeten, Tamara Andreeva, Hiroshi Yamada, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Max-Planck-Institut fur Plasmaphysik Teilinstitut Greifswald, Wendelsteinstr. 1, 17491 Greifswald, Germany, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), KFKI Research Institute for Particle and Nuclear Physics (KFKI-RMKI), Forschungszentrum Julich GmbH, Institut fur Energie- und Klimaforschung---Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), Wilhelm-Johnen-Strase, 52428 Julich, Germany, University of Maryland, Princeton, Laboratory for Plasma Physics of the Ecole Royale Militaire/Koninklijke Militaire School (LPP-ERM/KMS), Avenue de la Renaissance 30, 1000 Bruxelles, Belgien, Los Alamos National Laboratory (LANL), Institute of Physics, Massachusetts Institute of Technology, Cambridge, University of Wisconsin-Madison, National Centre for Nuclear Research (NCBJ), Institut für Experimentelle Kernphysik, Universität Karlsruhe (IEKP), Geoscience Australia, Max Planck Institut für Plasma Physik and Excellence Cluster, Eindhoven University of Technology, Università degli Studi di Cagliari = University of Cagliari (UniCa), Consorzio Interuniversitario per la Fisica Spaziale (CIFS), Instituto Superior Técnico, Universidade de Lisboa (IST), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Computer Science and Mathematics Division, Oak Ridge National Laboratory, Università di Milano, Warsaw University of Technology, ENEA-Frascati, IPPLM Institute of Plasma Physics and Laser Microfusion, 23 Hery Str., 01-497 Warsaw, Poland, Institute of Nuclear Physics PAN, University of Szczecin, 70-453, aleja Papieza Jana Pawla II 22A, Szczecin, Poland, Milano, University of California [San Diego] (UC San Diego), University of California (UC), International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Brandenburg University of Technology Cottbus-Senftenberg, Universitatsplatz 1, 01968 Senftenberg, Germany, National Institute for Fusion Science (NIFS), 322-6 Oroshicho, Toki, Gifu Prefecture 509-5202, Japan, Universidad Carlos III de Madrid (UC3M), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Budker Institute of Nuclear Physics (BINP), 11, akademika Lavrentieva prospect, Novosibirsk, 630090, Russian Federation, Institut für Raumfahrtsysteme, Universität Stuttgart (IRS), Fraunhofer-Institut fur Schicht- und Oberflachentechnik IST, Bienroder Weg 54 E, 38108 Braunschweig, Germany, Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften (IWF), Kiev Institute for Nuclear Research, A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP), Institut für Optik und Atomare Physik, Technische Universität Berlin, University of Opole, plac Kopernika 11a, 45-001 Opole, Poland, School of Electrical Engineering, Aalto University, Physikalisch-Technische Bundesanstalt (PTB), Kyoto University, Institute of Plasma Physics, Chinese Academy of Sciences, 350 Shushanhu Rd., Hefei, Anhui 230031, People's Republic of China, Institute of Plasma Physics of the Czech Academy of Science, Za Slovankou 1782/3, 182 00 Prague 8---Liben, Czechia, Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche (IFP-CNR), Fraunhofer-Institut fur Werkzeugmaschinen und Umformtechnik IWU, Reichenhainer Strase 88, 09126 Chemnitz, Germany, Universität Rostock, Wayne State University, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro, 7, 00185 Roma, Italy, Max Planck Institute for Plasma Physics, CIEMAT, Wigner Research Centre for Physics, Jülich Research Centre, University of Maryland, College Park, Princeton University, Royal Military Academy, Los Alamos National Laboratory, Lithuanian Energy Institute, Massachusetts Institute of Technology, Narodowe Centrum Badań Jadrowych, Karlsruhe Institute of Technology, Australian National University, University of Cagliari, National Research Council of Italy, Instituto Superior Tecnico Lisboa, Ioffe Institute, Oak Ridge National Laboratory, University of Salerno, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, Soltan Institute for Nuclear Studies, The Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences, University of Szczecin, University of Milan - Bicocca, University of California San Diego, Auburn University, Brandenburg University of Technology, National Institute for Fusion Science, Universidad Carlos III de Madrid, CEA, Culham Centre for Fusion Energy, RAS - Budker Institute of Nuclear Physics, University of Stuttgart, Fraunhofer Institute for Surface Engineering and Thin Films, Austrian Academy of Sciences, NASU - Institute of Nuclear Research, RAS - Institute of Applied Physics, Technical University of Berlin, University of Opole, Department of Applied Physics, Physikalisch-Technische Bundesanstalt, CAS - Institute of Plasma Physics, Czech Academy of Sciences, Istituto di Fisica Del Plasma Piero Caldirola, Fraunhofer Institute for Machine Tools and Forming Technology, University of Rostock, Lawrence University, Aalto-yliopisto, Aalto University, Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, Claps, G., and Cordella, F

Subjects
Magnetic confinement, Nuclear and High Energy Physics, Technology and Engineering, Plasma heating, Cyclotron resonance, CONFINEMENT, 01 natural sciences, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, PHYSICS, Nuclear physics, stellarator, current drive, magnetic confinement, plasma heating, Condensed Matter Physics, law, 0103 physical sciences, ddc:530, 010306 general physics, tellarator, Stellarator, Physics, Magnetic confinement fusion, Plasma, 530 Physik, TRANSPORT, Current drive, Electron temperature, Plasma diagnostics, Atomic physics, Wendelstein 7-X, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 1019 m−3 , central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre. EURATOM 633053

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24. Two conceptual designs of helical fusion reactor FFHR-d1A based on ITER technologies and challenging ideas.

Author

A. Sagara, J. Miyazawa, H. Tamura, T. Tanaka, T. Goto, N. Yanagi, R. Sakamoto, S. Masuzaki, H. Ohtani, and Group, The FFHR Design

Subjects
FUSION reactors, HELICAL gears, HIGH temperature metallurgy, SUPERCONDUCTORS, ELECTRIC reactors
Abstract

The Fusion Engineering Research Project (FERP) at the National Institute for Fusion Science (NIFS) is conducting conceptual design activities for the LHD-type helical fusion reactor FFHR-d1A. This paper newly defines two design options, ‘basic’ and ‘challenging.’ Conservative technologies, including those that will be demonstrated in ITER, are chosen in the basic option in which two helical coils are made of continuously wound cable-in-conduit superconductors of Nb3Sn strands, the divertor is composed of water-cooled tungsten monoblocks, and the blanket is composed of water-cooled ceramic breeders. In contrast, new ideas that would possibly be beneficial for making the reactor design more attractive are boldly included in the challenging option in which the helical coils are wound by connecting high-temperature REBCO superconductors using mechanical joints, the divertor is composed of a shower of molten tin jets, and the blanket is composed of molten salt FLiNaBe including Ti powers to increase hydrogen solubility. The main targets of the challenging option are early construction and easy maintenance of a large and three-dimensionally complicated helical structure, high thermal efficiency, and, in particular, realistic feasibility of the helical reactor. [ABSTRACT FROM AUTHOR]

Published
2017
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25. The effect of transient density profile shaping on transport in large stellarators and heliotrons.

Author

A. Dinklage, R. Sakamoto, M. Yokoyama, K. Ida, J. Baldzuhn, C.D. Beidler, S. Cats, K.J. Mc Carthy, J. Geiger, M. Kobayashi, H. Maaßberg, S. Morita, G. Motojima, M. Nakata, M. Nunami, N. Pablant, K. Ogawa, J.H.E. Proll, S. Satake, and K. Tanaka

Subjects
*STELLARATORS, *PLASMA flow, *ELECTRIC fields, *THERMODYNAMICS, *TEMPERATURE effect
Abstract

Transport studies of pellet fuelling experiments on LHD are reported. Spatio-temporal evolutions after pellet injection into LHD discharges show cases where central density increases on the time scale of particle transport processes. Both the temperature gradient and the density gradient change during the density relaxation, the latter even in sign. The resulting thermodynamic forces influence radial electric fields—both as a driving term but also by, e.g. affecting the Er dependence of ion transport. Magnetic fluctuations have been found to be induced by pellet injection but die out with the relaxation of the pressure profile. [ABSTRACT FROM AUTHOR]

Published
2017
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26. Observation of the ballooning mode that limits the operation space of the high-density super-dense-core plasma in the LHD.

Author

S. Ohdachi, K.Y. Watanabe, K. Tanaka, Y. Suzuki, Y. Takemura, S. Sakakibara, X.D. Du, T. Bando, Y. Narushima, R. Sakamoto, J. Miyazawa, G. Motojima, T. Morisaki, and Group, L. H. D. Experiment

Subjects
MAGNETOHYDRODYNAMICS, SHEAR (Mechanics), SCIENTIFIC observation, NUCLEAR excitation, PLASMA gases
Abstract

The central beta of the super-dense-core (SDC) plasma in the large helical device (LHD) is limited by a large scale MHD event called ‘core density collapse’ (CDC). The detailed measurement reveals that a new type of ballooning mode, quite localized in space and destabilized from the 3D nature of Heliotron devices, is the cause of the CDC. It is the first observation of an unstable mode in a region with global negative magnetic shear. Avoidance of the excitation of this mode is a key to expand the operational limit of the LHD. [ABSTRACT FROM AUTHOR]

Published
2017
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27. Development of a real-time simulation tool towards self-consistent scenario of plasma start-up and sustainment on helical fusion reactor FFHR-d1.

Author

T. Goto, J. Miyazawa, R. Sakamoto, Y. Suzuki, C. Suzuki, R. Seki, S. Satake, B. Huang, M. Nunami, M. Yokoyama, A. Sagara, and Group, the FFHR Design

Subjects
SELF-consistent field theory, NUCLEAR reactors, FUSION reactors, MAGNETOHYDRODYNAMICS, SIMULATION methods & models, PLASMA gases
Abstract

This study closely investigates the plasma operation scenario for the LHD-type helical reactor FFHR-d1 in view of MHD equilibrium/stability, neoclassical transport, alpha energy loss and impurity effect. In 1D calculation code that reproduces the typical pellet discharges in LHD experiments, we identify a self-consistent solution of the plasma operation scenario which achieves steady-state sustainment of the burning plasma with a fusion gain of Q ~ 10 was found within the operation regime that has been already confirmed in LHD experiment. The developed calculation tool enables systematic analysis of the operation regime in real time. [ABSTRACT FROM AUTHOR]

Published
2017
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28. Progress of long pulse discharges by ECH in LHD.

Author

Y. Yoshimura, H. Kasahara, M. Tokitani, R. Sakamoto, Y. Ueda, S. Ito, K. Okada, S. Kubo, T. Shimozuma, H. Igami, H. Takahashi, T.I. Tsujimura, R. Makino, S. Kobayashi, Y. Mizuno, T. Akiyama, N. Ashikawa, S. Masuzaki, G. Motojima, and M. Shoji

Subjects
ICR heating, ELECTRON cyclotron resonance heating, STEADY state conduction, STELLARATORS, ELECTRON density, GYROTRONS
Abstract

Using ion cyclotron heating and electron cyclotron heating (ECH), or solo ECH, trials of steady state plasma sustainment have been conducted in the superconducting helical/stellarator, large helical device (LHD) (Ida K et al 2015 Nucl. Fusion55 104018). In recent years, the ECH system has been upgraded by applying newly developed 77 and 154 GHz gyrotrons. A new gas fueling system applied to the steady state operations in the LHD realized precise feedback control of the line average electron density even when the wall condition varied during long pulse discharges. Owing to these improvements in the ECH and the gas fueling systems, a stable 39 min discharge with a line average electron density ne_ave of 1.1  ×  1019 m−3, a central electron temperature Te0 of over 2.5 keV, and a central ion temperature Ti0 of 1.0 keV was successfully performed with ~350 kW EC-waves. The parameters are much improved from the previous 65 min discharge with ne_ave of 0.15  ×  1019 m−3 and Te0 of 1.7 keV, and the 30 min discharge with ne_ave of 0.7  ×  1019 m−3 and Te0 of 1.7 keV. [ABSTRACT FROM AUTHOR]

Published
2016
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29. Conceptual design of high resolution and reliable density measurement system on helical reactor FFHR-d1 and demonstration on LHD.

Author

T. Akiyama, R. Yasuhara, T. Tanaka, M. Isobe, R. Sakamoto, T. Goto, K. Kawahata, K. Nakayama, S. Okajima, and A. Sagara

Subjects
PLASMA instabilities, NEODYMIUM lasers, VIBRATION (Mechanics), ELECTRON density, NUCLEAR fusion, LASER interferometers
Abstract

This paper describes a conceptual design of the density measurement system on the helical reactor FFHR-d1 based upon its quantitative operation scenario. The density measurement is necessary to satisfy the reactor design, and to have a high density resolution of the order of 1017 m−3 with a time resolution of 10 ms. High reliability that avoids measurement failures is also necessary. A combined system of ‘a dispersion interferometer’ and a polarimeter is designed and a prototype of the dispersion interferometer with an Nd:YAG laser is tested. The dispersion interferometer with a CO2 laser is also installed on LHD, which can realize a demo relevant density plasma. The prototypes demonstrate the feasibility on a demo reactor. [ABSTRACT FROM AUTHOR]

Published
2015
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30. Integrated physics analysis of plasma start-up scenario of helical reactor FFHR-d1.

Author

T. Goto, J. Miyazawa, R. Sakamoto, R. Seki, C. Suzuki, M. Yokoyama, S. Satake, A. Sagara, and Group, The FFHR Design

Subjects
PLASMA instabilities, PLASMA gases, NUCLEAR reactors, NUCLEAR physics experiments, MAGNETOHYDRODYNAMICS, PHASE equilibrium, TRANSPORT theory
Abstract

1D physics analysis of the plasma start-up scenario of the large helical device (LHD)-type helical reactor FFHR-d1 was conducted. The time evolution of the plasma profile is calculated using a simple model based on the LHD experimental observations. A detailed assessment of the magnetohydrodynamic equilibrium and neo-classical energy loss was conducted using the integrated transport analysis code TASK3D. The robust controllability of the fusion power was confirmed by feedback control of the pellet fuelling and a simple staged variation of the external heating power with a small number of simple diagnostics (line-averaged electron density, edge electron density and fusion power). A baseline operation control scenario (plasma start-up and steady-state sustainment) of the FFHR-d1 reactor for both self-ignition and sub-ignition operation modes was demonstrated. [ABSTRACT FROM AUTHOR]

Published
2015
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