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1. Overview of ASDEX upgrade results in view of ITER and DEMO

Author: H. Zohm, E. Alessi, C. Angioni, N. Arden, V. Artigues, M. Astrain, O. Asunta, M. Balden, V. Bandaru, A. Banon Navarro, M. Bauer, A. Bergmann, M. Bergmann, J. Bernardo, M. Bernert, A. Biancalani, R. Bielajew, R. Bilato, G. Birkenmeier, T. Blanken, V. Bobkov, A. Bock, L. Bock, T. Body, T. Bolzonella, N. Bonanomi, A. Bortolon, B. Böswirth, C. Bottereau, A. Bottino, H. van den Brand, M. Brenzke, S. Brezinsek, D. Brida, F. Brochard, J. Buchanan, A. Buhler, A. Burckhart, Y. Camenen, B. Cannas, P. Cano Megías, D. Carlton, M. Carr, P. Carvalho, C. Castaldo, A. Castillo Castillo, A. Cathey, M. Cavedon, C. Cazzaniga, C. Challis, A. Chankin, A. Chomiczewska, C. Cianfarani, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, L. Colas, G. Conway, S. Costea, D. Coster, T. Cote, A.J. Creely, G. Croci, D.J. Cruz Zabala, G. Cseh, I. Cziegler, O. D’Arcangelo, A. Dal Molin, P. David, C. Day, M. de Baar, P. de Marné, R. Delogu, P. Denner, A. Di Siena, M. Dibon, J.J. Dominguez-Palacios Durán, D. Dunai, M. Dreval, M. Dunne, B.P. Duval, R. Dux, T. Eich, S. Elgeti, A. Encheva, B. Esposito, E. Fable, M. Faitsch, D. Fajardo Jimenez, U. Fantz, M. Farnik, H. Faugel, F. Felici, O. Ficker, A. Figueredo, R. Fischer, O. Ford, L. Frassinetti, M. Fröschle, G. Fuchert, J.C. Fuchs, H. Fünfgelder, S. Futatani, K. Galazka, J. Galdon-Quiroga, D. Gallart Escolà, A. Gallo, Y. Gao, S. Garavaglia, M. Garcia Muñoz, B. Geiger, L. Giannone, S. Gibson, L. Gil, E. Giovannozzi, I. Girka, O. Girka, T. Gleiter, S. Glöggler, M. Gobbin, J.C. Gonzalez, J. Gonzalez Martin, T. Goodman, G. Gorini, T. Görler, D. Gradic, G. Granucci, A. Gräter, G. Grenfell, H. Greuner, M. Griener, M. Groth, O. Grover, A. Gude, L. Guimarais, S. Günter, D. Hachmeister, A.H. Hakola, C. Ham, T. Happel, N. den Harder, G. Harrer, J. Harrison, V. Hauer, T. Hayward-Schneider, B. Heinemann, P. Heinrich, T. Hellsten, S. Henderson, P. Hennequin, M. Herschel, S. Heuraux, A. Herrmann, E. Heyn, F. Hitzler, J. Hobirk, K. Höfler, S. Hörmann, J.H. Holm, M. Hölzl, C. Hopf, L. Horvath, T. Höschen, A. Houben, A. Hubbard, A. Huber, K. Hunger, V. Igochine, M. Iliasova, J. Illerhaus, K. Insulander Björk, C. Ionita-Schrittwieser, I. Ivanova-Stanik, S. Jachmich, W. Jacob, N. Jaksic, A. Jansen van Vuuren, F. Jaulmes, F. Jenko, T. Jensen, E. Joffrin, A. Kallenbach, J. Kalis, A. Kappatou, J. Karhunen, C.-P. Käsemann, S. Kasilov, Y. Kazakov, A. Kendl, W. Kernbichler, E. Khilkevitch, M. Kircher, A. Kirk, S. Kjer Hansen, V. Klevarova, F. Klossek, G. Kocsis, M. Koleva, M. Komm, M. Kong, A. Krämer-Flecken, M. Krause, I. Krebs, A. Kreuzeder, K. Krieger, O. Kudlacek, D. Kulla, T. Kurki-Suonio, B. Kurzan, B. Labit, K. Lackner, F. Laggner, A. Lahtinen, P. Lainer, P.T. Lang, P. Lauber, M. Lehnen, L. Leppin, E. Lerche, N. Leuthold, L. Li, J. Likonen, O. Linder, H. Lindl, B. Lipschultz, Y. Liu, Z. Lu, T. Luda Di Cortemiglia, N.C. Luhmann, T. Lunt, A. Lyssoivan, T. Maceina, J. Madsen, A. Magnanimo, H. Maier, J. Mailloux, R. Maingi, O. Maj, E. Maljaars, V. Maquet, A. Mancini, A. Manhard, P. Mantica, M. Mantsinen, P. Manz, M. Maraschek, C. Marchetto, M. Markl, L. Marrelli, P. Martin, F. Matos, M. Mayer, P.J. McCarthy, R. McDermott, G. Meng, R. Merkel, A. Merle, H. Meyer, M. Michelini, D. Milanesio, V. Mitterauer, P. Molina Cabrera, M. Muraca, F. Nabais, V. Naulin, R. Nazikian, R.D. Nem, R. Neu, A.H. Nielsen, S.K. Nielsen, T. Nishizawa, M. Nocente, I. Novikau, S. Nowak, R. Ochoukov, J. Olsen, P. Oyola, O. Pan, G. Papp, A. Pau, G. Pautasso, C. Paz-Soldan, M. Peglau, E. Peluso, P. Petersson, C. Piron, U. Plank, B. Plaum, B. Plöckl, V. Plyusnin, G. Pokol, E. Poli, A. Popa, L. Porte, J. Puchmayr, T. Pütterich, L. Radovanovic, M. Ramisch, J. Rasmussen, G. Ratta, S. Ratynskaia, G. Raupp, A. Redl, D. Réfy, M. Reich, F. Reimold, D. Reiser, M. Reisner, D. Reiter, B. Rettino, T. Ribeiro, D. Ricci, R. Riedl, J. Riesch, J.F. Rivero Rodriguez, G. Rocchi, P. Rodriguez-Fernandez, V. Rohde, G. Ronchi, M. Rott, M. Rubel, D.A. Ryan, F. Ryter, S. Saarelma, M. Salewski, A. Salmi, O. Samoylov, L. Sanchis Sanchez, J. Santos, O. Sauter, G. Schall, A. Schlüter, J. Scholte, K. Schmid, O. Schmitz, P.A. Schneider, R. Schrittwieser, M. Schubert, C. Schuster, N. Schwarz, T. Schwarz-Selinger, J. Schweinzer, F. Sciortino, O. Seibold-Benjak, A. Shabbir, A. Shalpegin, S. Sharapov, U. Sheikh, A. Shevelev, G. Sias, M. Siccinio, B. Sieglin, A. Sigalov, A. Silva, C. Silva, D. Silvagni, J. Simpson, S. Sipilä, A. Snicker, E. Solano, C. Sommariva, C. Sozzi, M. Spacek, G. Spizzo, M. Spolaore, A. Stegmeir, M. Stejner, D. Stieglitz, J. Stober, U. Stroth, E. Strumberger, G. Suarez Lopez, W. Suttrop, T. Szepesi, B. Tál, T. Tala, W. Tang, G. Tardini, M. Tardocchi, D. Terranova, M. Teschke, E. Thorén, W. Tierens, D. Told, W. Treutterer, G. Trevisan, M. Tripský, P. Ulbl, G. Urbanczyk, M. Usoltseva, M. Valisa, M. Valovic, S. van Mulders, M. van Zeeland, F. Vannini, B. Vanovac, P. Varela, S. Varoutis, T. Verdier, G. Verdoolaege, N. Vianello, J. Vicente, T. Vierle, E. Viezzer, I. Voitsekhovitch, U. von Toussaint, D. Wagner, X. Wang, M. Weiland, D. Wendler, A.E. White, M. Willensdorfer, B. Wiringer, M. Wischmeier, R. Wolf, E. Wolfrum, Q. Yang, C. Yoo, Q. Yu, R. Zagórski, I. Zammuto, T. Zehetbauer, W. Zhang, W. Zholobenko, A. Zibrov, M. Zilker, C.F.B. Zimmermann, A. Zito, S. Zoletnik, the EUROfusion Tokamak Exploitation Team, and the ASDEX Upgrade Team
Subjects: tokamak, MHD stability, transport modelling, radiative exhaust, disruption physics, ELM free scenarios, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: Experiments on ASDEX Upgrade (AUG) in 2021 and 2022 have addressed a number of critical issues for ITER and EU DEMO. A major objective of the AUG programme is to shed light on the underlying physics of confinement, stability, and plasma exhaust in order to allow reliable extrapolation of results obtained on present day machines to these reactor-grade devices. Concerning pedestal physics, the mitigation of edge localised modes (ELMs) using resonant magnetic perturbations (RMPs) was found to be consistent with a reduction of the linear peeling-ballooning stability threshold due to the helical deformation of the plasma. Conversely, ELM suppression by RMPs is ascribed to an increased pedestal transport that keeps the plasma away from this boundary. Candidates for this increased transport are locally enhanced turbulence and a locked magnetic island in the pedestal. The enhanced D-alpha (EDA) and quasi-continuous exhaust (QCE) regimes have been established as promising ELM-free scenarios. Here, the pressure gradient at the foot of the H-mode pedestal is reduced by a quasi-coherent mode, consistent with violation of the high-n ballooning mode stability limit there. This is suggestive that the EDA and QCE regimes have a common underlying physics origin. In the area of transport physics, full radius models for both L- and H-modes have been developed. These models predict energy confinement in AUG better than the commonly used global scaling laws, representing a large step towards the goal of predictive capability. A new momentum transport analysis framework has been developed that provides access to the intrinsic torque in the plasma core. In the field of exhaust, the X-Point Radiator (XPR), a cold and dense plasma region on closed flux surfaces close to the X-point, was described by an analytical model that provides an understanding of its formation as well as its stability, i.e., the conditions under which it transitions into a deleterious MARFE with the potential to result in a disruptive termination. With the XPR close to the divertor target, a new detached divertor concept, the compact radiative divertor, was developed. Here, the exhaust power is radiated before reaching the target, allowing close proximity of the X-point to the target. No limitations by the shallow field line angle due to the large flux expansion were observed, and sufficient compression of neutral density was demonstrated. With respect to the pumping of non-recycling impurities, the divertor enrichment was found to mainly depend on the ionisation energy of the impurity under consideration. In the area of MHD physics, analysis of the hot plasma core motion in sawtooth crashes showed good agreement with nonlinear 2-fluid simulations. This indicates that the fast reconnection observed in these events is adequately described including the pressure gradient and the electron inertia in the parallel Ohm’s law. Concerning disruption physics, a shattered pellet injection system was installed in collaboration with the ITER International Organisation. Thanks to the ability to vary the shard size distribution independently of the injection velocity, as well as its impurity admixture, it was possible to tailor the current quench rate, which is an important requirement for future large devices such as ITER. Progress was also made modelling the force reduction of VDEs induced by massive gas injection on AUG. The H-mode density limit was characterised in terms of safe operational space with a newly developed active feedback control method that allowed the stability boundary to be probed several times within a single discharge without inducing a disruptive termination. Regarding integrated operation scenarios, the role of density peaking in the confinement of the ITER baseline scenario (high plasma current) was clarified. The usual energy confinement scaling ITER98( p,y ) does not capture this effect, but the more recent H20 scaling does, highlighting again the importance of developing adequate physics based models. Advanced tokamak scenarios, aiming at large non-inductive current fraction due to non-standard profiles of the safety factor in combination with high normalised plasma pressure were studied with a focus on their access conditions. A method to guide the approach of the targeted safety factor profiles was developed, and the conditions for achieving good confinement were clarified. Based on this, two types of advanced scenarios (‘hybrid’ and ‘elevated’ q -profile) were established on AUG and characterised concerning their plasma performance.
Published: 2024
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2. Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components

Author: O. Grulke, C. Albert, J.A. Alcuson Belloso, P. Aleynikov, K. Aleynikova, A. Alonso, G. Anda, T. Andreeva, M. Arvanitou, E. Ascasibar, E. Aymerich, K. Avramidis, J.-P. Bähner, S.-G. Baek, M. Balden, J. Baldzuhn, S. Ballinger, M. Banduch, S. Bannmann, A. Bañón Navarro, L. Baylor, C.D. Beidler, M. Beurskens, C. Biedermann, G. Birkenmeier, T. Bluhm, D. Boeckenhoff, D. Boeyaert, D. Bold, M. Borchardt, D. Borodin, H.-S. Bosch, H. Bouvain, S. Bozhenkov, T. Bräuer, H. Braune, C. Brandt, S. Brezinsek, K.J. Brunner, C. Büschel, R. Bussiahn, A. Buzás, B. Buttenschoen, V. Bykov, I. Calvo, A. Cappa, F. Carovani, D. Carralero, A. Carls, B. Carvalho, D. Castaño-Bardawil, N. Chaudhary, I. Chelis, S. Chen, D. Cipciar, J.W. Coenen, G. Conway, M. Cornelissen, Y. Corre, P. Costello, K. Crombe, G. Cseh, B. Csillag, H.I. Cu Castillo, G. Czymek, H. Damm, R.J. Davies, C. Day, S. Degenkolbe, R. De Wolf, W. Dekeyser, A. Demby, P. Despontin, C.P. Dhard, A. Dinklage, F.A. d’Isa, T. Dittmar, M. Dreval, M. Drevlak, P. Drews, J. Droste, D. Dunai, C. Dyhring, P. van Eeten, E. Edlund, M. Endler, D.A. Ennis, F.J. Escoto, M.S. Espinosa, T. Estrada, D. Fehling, L. Feuerstein, J. Fellinger, Y. Feng, D.L.C. Fernando, S. Fischer, E.R. Flom, O. Ford, T. Fornal, J. Frank, H. Frerichs, G. Fuchert, G. Gantenbein, Y. Gao, K. Garcia, I. García-Cortés, J.M. García-Regaña, B. Geiger, J. Geiger, P. Geissler, M. Gerard, G. Godino-Sedano, T. Gonda, A. González, A. Goriaev, D. Gradic, M. Grahl, H. Greuner, E. Grigore, M. Gruca, J.F. Guerrero Arnaiz, V. Haak, L. van Ham, K. Hammond, B. Hamstra, X. Han, S.K. Hansen, J. Harris, D. Hartmann, D. Hathiramani, S. Hegedus, S. Heinrich, P. Helander, F. Henke, S. Henneberg, L. Henschke, M. Hirsch, U. Hoefel, K. Hoefler, S. Hoermann, K.-P. Hollfeld, A. Holtz, D. Höschen, M. Houry, J. Huang, M. Hubeny, K. Hunger, D. Hwangbo, K. Ida, Y. Igitkhanov, S. Illy, Z. Ioannidis, M. Jablczynska, S. Jablonski, B. Jabłoński, B. Jagielski, M. Jakubowski, J. Jelonnek, F. Jenko, J. Jin, A. Johansson, G. Jouniaux, S. Kajita, J.-P. Kallmeyer, U. Kamionka, W. Kasparek, C. Kawan, Ye. O. Kazakov, N. Kenmochi, W. Kernbichler, A.K. Kharwandikar, M. Khokhlov, C. Killer, A. Kirschner, R. Kleiber, C.C. Klepper, T. Klinger, J. Knauer, A. Knieps, M. Kobayashi, G. Kocsis, Y. Kolesnichenko, A. Könies, J. Kontula, P. Kornejew, S.A. Korteweg, J. Koschinsky, J. Koster, Y. Kovtun, A. Krämer-Flecken, M. Krause, T. Kremeyer, L. Krier, D.M. Kriete, M. Krychowiak, I. Ksia¸zek, M. Kubkowska, M.D. Kuczyński, D. Kulla, A. Kumar, T. Kurki-Suonio, I. Kuzmych, S. Kwak, V. Lancelotti, A. Langenberg, H. Laqua, H.P. Laqua, M.R. Larsen, S. Lazerson, C. Lechte, B. Lee, A. LeViness, M. Lewerentz, Y. Liang, L. Liao, A. Litnovsky, J. Liu, J. Loizu, R. Lopez-Cansino, L.D. Lopez Rodriguez, A. Lorenz, R. Lunsford, Y. Luo, V. Lutsenko, N. Maaziz, M. Machielsen, R. Mackenbach, D. Makowski, E. Maragkoudakis, O. Marchuk, M. Markl, S. Marsen, J. Martínez, N. Marushchenko, S. Masuzaki, D.A. Maurer, M. Mayer, K.J. McCarthy, P. McNeely, D. Medina Roque, J. Meineke, S. Meitner, S. vaz Mendes, A. Menzel-Barbara, B. van Milligen, A. Mishchenko, V. Moiseenko, A. Möller, S. Möller, D. Moseev, G. Motojima, S. Mulas, P. Mulholland, M. Nagel, D. Nagy, Y. Narbutt, D. Naujoks, P. Nelde, R. Neu, O. Neubauer, U. Neuner, D. Nicolai, S. Nielsen, C. Nührenberg, R. Ochoukov, G. Offermanns, J. Ongena, J.W. Oosterbeek, M. Otte, N. Pablant, N. Panadero Alvarez, A. Pandey, G. Partesotti, E.A. Pasch, R. Pavlichenko, E. Pawelec, T.S. Pedersen, V. Perseo, B. Peterson, F. Pisano, B. Plaum, G. Plunk, L. Podavini, N.S. Polei, P. Poloskei, S. Ponomarenko, P. Pons-Villalonga, M. Porkolab, J. Proll, M.J. Pueschel, A. Puig Sitjes, R. Ragona, K. Rahbarnia, M. Rasiński, J. Rasmussen, D. Refy, F. Reimold, M. Richou, J.S. Riemann, K. Riße, J. de la Riva Villén, G. Roberg-Clark, E. Rodriguez, V. Rohde, J. Romazanov, T. Romba, D. Rondeshagen, M. Rud, T. Ruess, T. Rummel, A. Runov, C. Ruset, N. Rust, L. Ryc, T. Rzesnicki, M. Salewski, E. Sánchez, L. Sanchis Sanchez, G. Satheeswaran, J. Schacht, E. Scharff, J. Schilling, G. Schlisio, K. Schmid, J.C. Schmitt, O. Schmitz, M. Schneider, M. Van Schoor, T. Schröder, R. Schroeder, B. Schweer, S. Sereda, B. Shanahan, G. Sias, S. Simko, L. Singh, Y. Siusko, C. Slaby, M. Śle¸czka, B.S. Smith, D.R. Smith, H. Smith, M. Spolaore, A. Spring, T. Stange, A. von Stechow, I. Stepanov, M. Stern, U. Stroth, Y. Suzuki, C. Swee, L. Syrocki, T. Szabolics, T. Szepesi, R. Takacs, H. Takahashi, N. Tamura, C. Tantos, J. Terry, S. Thiede, H. Thienpondt, H. Thomsen, M. Thumm, T. Thun, S. Togo, T. Tork, H. Trimino Mora, A. Tsikouras, Y. Turkin, L. Vano, S. Varoutis, M. Vecsei, J.L. Velasco, M. Verstraeten, M. Vervier, E. Viezzer, J. Wagner, E. Wang, F. Wang, M. Wappl, F. Warmer, T. Wegner, Y. Wei, G. Weir, N. Wendler, U. Wenzel, A. White, F. Wilms, T. Windisch, A. Winter, V. Winters, R. Wolf, G. Wurden, P. Xanthopoulos, H.M. Xiang, S. Xu, H. Yamada, J. Yang, R. Yi, M. Yokoyama, B. Zamorski, M. Zanini, M. Zarnstorff, D. Zhang, S. Zhou, J. Zhu, J. Zimmermann, A. Zocco, and S. Zoletnik
Subjects: stellarator, long-pulse operation, magnetic fusion confinement, divertor detachment, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first long-pulse operation campaign. A maximum discharge length of 8 min was achieved with a total heating energy of 1.3 GJ. Safe divertor operation was demonstrated in attached and detached mode. Stable detachment is readily achieved in some magnetic configurations but requires impurity seeding in configurations with small magnetic pitch angle within the edge islands. Progress was made in the characterization of transport mechanisms across edge magnetic islands: Measurement of the potential distribution and flow pattern reveals that the islands are associated with a strong poloidal drift, which leads to rapid convection of energy and particles from the last closed flux surface into the scrape-off layer. Using the upgraded plasma heating systems, advanced heating scenarios were developed, which provide improved energy confinement comparable to the scenario, in which the record triple product for stellarators was achieved in the previous operation campaign. However, a magnetic configuration-dependent critical heating power limit of the electron cyclotron resonance heating was observed. Exceeding the respective power limit leads to a degradation of the confinement.
Published: 2024
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3. Recent progress of JT-60SA project toward plasma operation

Author: H. Shirai, K. Takahashi, E. Di Pietro, D. Abate, W. Abdel Maksoud, H. Abe, N. Aiba, T. Abe, M. Akimitsu, J. Ayllon-Guerola, T. Arai, J.-F. Artaud, N. Asakura, N. Ashikawa, L. Balbinot, P. Barabaschi, O. Baulaigue, E. Belonohy, A. Belpane, W. Bin, F. Bombarda, T. Bolzonella, F. Bonne, M. Bonotto, J. Botija, J. Buermans, S. Cabrera-Pérez, A. Cardella, D. Carralero, L. Carraro, J. Cavalier, M. Cavinato, M. Chernyshova, S. Chiba, S. Clement-Lorenzo, V. Cocilovo, S. Coda, R. Coelho, I. Coffey, B. Collin, V. Corato, A. Cucchiaro, T. Czarski, M. Dairaku, S. Davis, C. Day, E. Dela Luna, G. De Tommasi, P. Decool, L. Di Pace, M. Dibon, G. Disset, F. D’Lsa, A. Ejiri, Y. Endo, N. Ezumi, G. Falchetto, A. Fassina, P. Fejoz, A. Ferro, W. Fietz, L. Figini, T. Fornal, G. Frello, T. Fujita, T. Fukuda, K. Fukui, M. Fukumoto, H. Funaba, M. Furukawa, S. Futatani, L. Gabellieri, E. Gaio, K. Galazka, J. Garcia, J. Garcia-Dominguez, J. Garcia-Lopez, M. Garcia-Munoz, L. Garzotti, F. Gasparini, S. Gharafi, L. Giacomelli, G. Ginoulhiac, G. Giruzzi, L. Giudicotti, J. Gonzalez-Martin, R. Guillén-González, N. Hajnal, S. Hall, K. Hamada, K. Hanada, M. Hanada, K. Hasegawa, S. Hatakeyama, V. Hauer, N. Hayashi, T. Hayashi, R. Heller, J. Hidalgo-Salaverri, S. Higashijima, J. Hinata, S. Hiranai, J. Hiratsuka, R. Hiwatari, C. Hoa, H. Homma, A. Honda, M. Honda, K. Hoshino, H. Hurzlmeier, M. Iafrati, K. Ibano, H. Ichige, M. Ichikawa, M. Ichimura, K. Ida, S. Ide, H. Idei, M. Iguchi, T. Iijima, S. Iio, R. Ikeda, Y. Ikeda, T. Imai, R. Imazawa, S. Inagaki, M. Inomoto, S. Inoue, A. Isayama, S. Ishida, Y. Ishii, M. Isobe, F. Janky, E. Joffrin, A. Jokinen, S. Kado, S. Kajita, K. Kajiwara, Y. Kamada, I. Kamata, A. Kaminaga, K. Kamiya, D. Kanapienyte, Y. Kashiwa, M. Kashiwagi, K. Katayama, Y. Kawamata, G. Kawamura, K. Kawano, Y. Kazakov, K. Kimura, F. Kin, M. Kisaki, S. Kitajima, K. Kiyono, K. Kizu, Y. Ko, K. Kobayashi, M. Kobayashi, S. Kobayashi, Ta. Kobayashi, To. Kobayashi, G. Kocsis, A. Kojima, S. Kokusen, M. Komata, K. Komuro, S. Konishi, A. Kovacsik, I. Ksiazek, M. Kubkowska, G. Kühner, M. Kuramochi, K. Kurihara, T. Kurki-Suonio, A.B. Kurniawan, T. Kuwata, B. Lacroix, V. Lamaison, A. Lampasi, P. Lang, P. Lauber, K. Lawson, Q. LeCoz, A. Louzguiti, R. Maekawa, T. Maekawa, S. Maeyama, G. Maffia, P. Maget, J. Mailloux, I. Maione, A. Maistrello, K. Malinowski, A. Mancini, G. Marchiori, J.-L. Marechal, V. Massaut, S. Masuzaki, R. Matoike, G. Matsunaga, S. Matsunaga, A. Matsuyama, Ch Mayri, M. Mattei, M. Medrano, A. Mele, I. Meyer, F. Michel, T. Minami, Y. Miyata, J. Miyazawa, Y. Miyo, T. Mizuuchi, K. Mogaki, J. Morales, P. Moreau, T. Morisaki, S. Morishima, S. Moriyama, A. Moro, H. Murakami, M. Murayama, S. Murakami, K. Nagasaki, O. Naito, N. Nakamura, S. Nakamura, T. Nakano, Y. Nakashima, V. Nardino, E. Narita, Y. Narushima, K. Natsume, S. Nemoto, R. Neu, S. Nicollet, M. Nishikawa, S. Nishimura, T. Nishitani, M. Nishiura, T. Nishiyama, M. Nocente, Y. Nobuta, L. 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Yajima, S. Yamamoto, H. Yamanaka, K. Yamauchi, Y. Yamauchi, H. Yamazaki, K. Yamazaki, R. Yamazaki, S. Yamoto, S. Yanagi, K. Yanagihara, S. Yokooka, M. Yokoyama, T. Yokoyama, M. Yoshida, M. Yoshimura, N. Yoshizawa, K. Yuinawa, L. Zani, and P. Zito
Subjects: JT-60SA, superconducting tokamak, risk mitigation measures, integrated commissioning, maintenance and enhancement, international collaboration, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: Superconducting (SC) tokamak JT-60SA plays an essential role in fusion research and development by supporting and complementing the ITER project, providing directions to the DEMO design activity and fostering next generation scientists and engineers. Since the short circuit incident at the terminal joints of equilibrium field coil #1 during the integrated commissioning (IC) in March 2021, both EU and JA implementing agencies (IAs) have examined how to ensure safe operation of JT-60SA by mitigating the risk of possible discharge occurrence inside the cryostat. Based on the experience of the global Paschen tests, the IAs have established a strategy of risk mitigation measures, which is a combination of (i) reinforcement of insulation, (ii) avoiding unnecessary voltage application to the coil systems and (iii) immediate de-energization of the coils when deteriorated vacuum conditions are detected. Thanks to the considerable efforts of the Integrated Project Team members, the IC restarted in May 2023. After confirmation of the SC state of the coil systems (TF, EF and CS), the coil energization test and the plasma operation phase 1 (OP-1) started. The first plasma was successfully achieved on 23 October 2023 with a limited value of voltage and current applied to the coils. The plasma configuration control was also confirmed with low plasma current and low auxiliary heating power conditions. Based on the IO–F4E–QST collaboration, activities of JT-60SA have been shared with the IO and provided an important lesson for ITER assembly and commissioning, and will provide an outstanding contribution to fusion research at large. After OP-1, maintenance & enhancement phase 1 (M/E-1) starts from January 2024, in which in-vessel components are installed, and heating and diagnostic systems are extensively upgraded to allow a high power heating experiment planned in OP-2. In order to make the best use of JT-60SA, a newly organized JT-60SA experiment team will refine the research plan for the future high heating power operation phase.
Published: 2024
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4. Overview of T and D–T results in JET with ITER-like wall

Author: C.F. Maggi, D. Abate, N. Abid, P. Abreu, O. Adabonyan, M. Afzal, I. Ahmad, M. Akhtar, R. Albanese, S. Aleiferis, E. Alessi, P. Aleynikov, J. Alguacil, J. Alhage, M. Ali, H. Allen, M. Allinson, M. Alonzo, E. Alves, R. Ambrosino, E. Andersson Sundén, P. Andrew, M. Angelone, C. Angioni, I. Antoniou, L. Appel, C. Appelbee, C. Aramunde, M. Ariola, G. Arnoux, G. Artaserse, J.-F. Artaud, W. Arter, V. Artigues, F.J. Artola, A. Ash, O. Asztalos, D. Auld, F. Auriemma, Y. Austin, L. Avotina, J. Ayllón, E. Aymerich, A. Baciero, L. Bähner, F. Bairaktaris, I. Balboa, M. Balden, N. Balshaw, V.K. Bandaru, J. Banks, A. Banon Navarro, C. Barcellona, O. Bardsley, M. Barnes, R. Barnsley, M. Baruzzo, M. Bassan, A. Batista, P. Batistoni, L. Baumane, B. Bauvir, L. Baylor, C. Bearcroft, P. Beaumont, D. Beckett, A. Begolli, M. Beidler, N. Bekris, M. Beldishevski, E. Belli, F. Belli, S. Benkadda, J. Bentley, E. Bernard, J. Bernardo, M. Bernert, M. Berry, L. Bertalot, H. Betar, M. Beurskens, P.G. Bhat, S. Bickerton, J. Bielecki, T. Biewer, R. Bilato, P. Bílková, G. Birkenmeier, R. Bisson, J.P.S. Bizarro, P. Blatchford, A. Bleasdale, V. Bobkov, A. Boboc, A. Bock, G. Bodnar, P. Bohm, L. Bonalumi, N. Bonanomi, D. Bonfiglio, X. Bonnin, P. Bonofiglo, J. Booth, D. Borba, D. Borodin, I. Borodkina, T.O.S.J. Bosman, C. Bourdelle, M. Bowden, I. Božičević Mihalić, S.C. Bradnam, B. Breizman, S. Brezinsek, D. Brida, M. Brix, P. Brown, D. Brunetti, M. Buckley, J. Buermans, H. Bufferand, P. Buratti, A. Burckhart, A. Burgess, A. Buscarino, A. Busse, D. Butcher, G. Calabrò, L. Calacci, R. Calado, R. Canavan, B. Cannas, M. Cannon, M. Cappelli, S. Carcangiu, P. Card, A. Cardinali, S. Carli, P. Carman, D. Carnevale, B. Carvalho, I.S. Carvalho, P. Carvalho, I. Casiraghi, F.J. Casson, C. Castaldo, J.P. Catalan, N. Catarino, F. Causa, M. Cavedon, M. Cecconello, L. Ceelen, C.D. Challis, B. Chamberlain, R. Chandra, C.S. Chang, A. Chankin, B. Chapman, P. Chauhan, M. Chernyshova, A. Chiariello, G.-C. 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Papadopoulos, G. Papadopoulos, G. Papp, V.V. Parail, A. Parsloe, K. Paschalidis, M. Passeri, A. Patel, A. Pau, G. Pautasso, R. Pavlichenko, A. Pavone, E. Pawelec, C. Paz-Soldan, A. Peacock, M. Pearce, I.J. Pearson, E. Peluso, C. Penot, K. Pepperell, A. Perdas, T. Pereira, E. Perelli Cippo, C. Perez von Thun, D. Perry, P. Petersson, G. Petravich, N. Petrella, M. Peyman, L. Pigatto, M. Pillon, S. Pinches, G. Pintsuk, C. Piron, A. Pironti, F. Pisano, R. Pitts, U. Planck, N. Platt, V. Plyusnin, M. Podesta, G. Pokol, F.M. Poli, O.G. Pompilian, M. Poradzinski, M. Porkolab, C. Porosnicu, G. Poulipoulis, A.S. Poulsen, I. Predebon, A. Previti, D. Primetzhofer, G. Provatas, G. Pucella, P. Puglia, K. Purahoo, O. Putignano, T. Pütterich, A. Quercia, G. Radulescu, V. Radulovic, R. Ragona, M. Rainford, P. Raj, M. Rasinski, D. Rasmussen, J. Rasmussen, J.J. Rasmussen, A. Raso, G. Rattá, S. Ratynskaia, R. Rayaprolu, M. Rebai, A. Redl, D. Rees, D. Réfy, R. Reichle, H. Reimerdes, B.C.G. Reman, C. Reux, S. Reynolds, D. Rigamonti, E. Righi, F.G. Rimini, J. Risner, J.F. Rivero-Rodriguez, C.M. Roach, J. Roberts, R. Robins, S. Robinson, D. Robson, S. Rode, P. Rodrigues, P. Rodriguez-Fernandez, S. Romanelli, J. Romazanov, E. Rose, C. Rose-Innes, R. Rossi, S. Rowe, D. Rowlands, C. Rowley, M. Rubel, G. Rubinacci, G. Rubino, M. Rud, J. Ruiz Ruiz, F. Ryter, S. Saarelma, A. Sahlberg, M. Salewski, A. Salmi, R. Salmon, F. Salzedas, F. Sanchez, I. Sanders, D. Sandiford, F. Sanni, O. Sauter, P. Sauvan, G. Schettini, A. Shevelev, A.A. Schekochihin, K. Schmid, B.S. Schmidt, S. Schmuck, M. Schneider, P.A. Schneider, N. Schoonheere, R. Schramm, D. Scoon, S. Scully, M. Segato, J. Seidl, L. Senni, J. Seo, G. Sergienko, M. Sertoli, S.E. Sharapov, R. Sharma, A. Shaw, R. Shaw, H. Sheikh, U. Sheikh, N. Shi, P. Shigin, D. Shiraki, G. Sias, M. Siccinio, B. Sieglin, S.A. Silburn, A. Silva, C. Silva, J. Silva, D. Silvagni, D. Simfukwe, J. Simpson, P. Sirén, A. Sirinelli, H. Sjöstrand, N. Skinner, J. Slater, T. Smart, R.D. Smirnov, N. Smith, P. Smith, T. Smith, J. Snell, L. Snoj, E.R. Solano, V. Solokha, C. Sommariva, K. Soni, M. Sos, J. Sousa, C. Sozzi, T. Spelzini, F. Spineanu, L. Spolladore, D. Spong, C. Srinivasan, G. Staebler, A. Stagni, I. Stamatelatos, M.F. Stamp, Ž. Štancar, P.A. Staniec, G. Stankūnas, M. Stead, B. Stein-Lubrano, A. Stephen, J. Stephens, P. Stevenson, C. Steventon, M. Stojanov, D.A. St-Onge, P. Strand, S. Strikwerda, C.I. Stuart, S. Sturgeon, H.J. Sun, S. Surendran, W. Suttrop, J. Svensson, J. Svoboda, R. Sweeney, G. Szepesi, M. Szoke, T. Tadić, B. Tal, T. Tala, P. Tamain, K. Tanaka, W. Tang, G. Tardini, M. Tardocchi, D. Taylor, A.S. Teimane, G. Telesca, A. Teplukhina, A. Terra, D. Terranova, N. Terranova, D. Testa, B. Thomas, V.K. Thompson, A. Thorman, A.S. Thrysoe, W. Tierens, R.A. Tinguely, A. Tipton, H. Todd, M. Tomeš, A. Tookey, P. Tsavalas, D. Tskhakaya, L.-P. Turică, A. Turner, I. Turner, M. Turner, M.M. Turner, G. Tvalashvili, A. Tykhyy, S. Tyrrell, A. Uccello, V. Udintsev, A. Vadgama, D.F. Valcarcel, A. Valentini, M. Valisa, M. Vallar, M. Valovic, M. Van Berkel, K.L. van de Plassche, M. van Rossem, D. Van Eester, J. Varela, J. Varje, T. Vasilopoulou, G. Vayakis, M. Vecsei, J. Vega, M. Veis, P. Veis, S. Ventre, M. Veranda, G. Verdoolaege, C. Verona, G. Verona Rinati, E. Veshchev, N. Vianello, E. Viezzer, L. Vignitchouk, R. Vila, R. Villari, F. Villone, P. Vincenzi, A. Vitins, Z. Vizvary, M. Vlad, I. Voldiner, U. Von Toussaint, P. Vondráček, B. Wakeling, M. Walker, R. Walker, M. Walsh, R. Walton, E. Wang, F. Warren, R. Warren, J. Waterhouse, C. Watts, T. Webster, M. Weiland, H. Weisen, M. Weiszflog, N. Wendler, A. West, M. Wheatley, S. Whetham, A. Whitehead, D. Whittaker, A. Widdowson, S. Wiesen, M. Willensdorfer, J. Williams, I. Wilson, T. Wilson, M. Wischmeier, A. Withycombe, D. Witts, A. Wojcik-Gargula, E. Wolfrum, R. Wood, R. Woodley, R. Worrall, I. Wyss, T. Xu, D. Yadykin, Y. Yakovenko, Y. Yang, V. Yanovskiy, R. Yi, I. Young, R. Young, B. Zaar, R.J. Zabolockis, L. Zakharov, P. Zanca, A. Zarins, D. Zarzoso Fernandez, K.-D. Zastrow, Y. Zayachuk, M. Zerbini, W. Zhang, B. Zimmermann, M. Zlobinski, A. Zocco, V.K. Zotta, M. Zuin, W. Zwingmann, and I. Zychor
Subjects: magnetic fusion, JET-ILW, D–T, tritium, alpha particles, fusion prediction, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: In 2021 JET exploited its unique capabilities to operate with T and D–T fuel with an ITER-like Be/W wall (JET-ILW). This second major JET D–T campaign (DTE2), after DTE1 in 1997, represented the culmination of a series of JET enhancements—new fusion diagnostics, new T injection capabilities, refurbishment of the T plant, increased auxiliary heating, in-vessel calibration of 14 MeV neutron yield monitors—as well as significant advances in plasma theory and modelling in the fusion community. DTE2 was complemented by a sequence of isotope physics campaigns encompassing operation in pure tritium at high T-NBI power. Carefully conducted for safe operation with tritium, the new T and D–T experiments used 1 kg of T (vs 100 g in DTE1), yielding the most fusion reactor relevant D–T plasmas to date and expanding our understanding of isotopes and D–T mixture physics. Furthermore, since the JET T and DTE2 campaigns occurred almost 25 years after the last major D–T tokamak experiment, it was also a strategic goal of the European fusion programme to refresh operational experience of a nuclear tokamak to prepare staff for ITER operation. The key physics results of the JET T and DTE2 experiments, carried out within the EUROfusion JET1 work package, are reported in this paper. Progress in the technological exploitation of JET D–T operations, development and validation of nuclear codes, neutronic tools and techniques for ITER operations carried out by EUROfusion (started within the Horizon 2020 Framework Programme and continuing under the Horizon Europe FP) are reported in (Litaudon et al Nucl. Fusion accepted), while JET experience on T and D–T operations is presented in (King et al Nucl. Fusion submitted).
Published: 2024
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5. Divertor Tokamak Test facility project: status of design and implementation

Author: Francesco Romanelli, on behalf of DTT Contributors, D. Abate, E. Acampora, D. Agguiaro, R. Agnello, P. Agostinetti, M. Agostini, A. Aimetta, R. Albanese, G. Alberti, M. Albino, E. Alessi, S. Almaviva, M. Alonzo, R. Ambrosino, P. Andreoli, M. Angelone, M. Angelucci, C. Angioni, A. Angrisani Armenio, P. Antonini, D. Aprile, G. Apruzzese, M. Aquilini, G. Aragone, P. Arena, M. Ariola, G. Artaserse, L. Aucone, A. Augieri, F. Auriemma, J. Ayllon Guerola, N. Badodi, B. Baiocchi, L. Balbinot, C. Baldacchini, A. Balestri, T. Barberis, G. Barone, L. Barucca, M. Baruzzo, S. Begozzi, V. Belardi, F. Belli, A. Belpane, F. Beone, S. Bertolami, S. Bianucci, S. Bifaretti, S. Bigioni, W. Bin, P. Boccali, B. Boeswirth, E. Bogazzi, R. Bojoi, S. Bollanti, T. Bolzonella, F. Bombarda, M. Bonan, N. Bonanomi, A. Bonaventura, L. Boncagni, M. Bonesso, D. Bonfiglio, R. Bonifetto, D. Bonomi, D. Borgogno, T. Borzone, S. Botti, E. Boz, F. Braghin, M. Brena, S. Brezinsek, M. Brombin, A. Bruschi, S. Buonocore, P. Buratti, D. Busi, G. Calabrò, M. Caldora, G. Calvo, G. Camera, G. Campana, S. Candela, V. Candela, F. Cani, L. Cantone, F. Capaldo, S. Cappello, M. Caponero, S. Carchella, A. Cardinali, D. Carnevale, L. Carraro, C. Carrelli, V. Casalegno, I. Casiraghi, C. Castaldo, A. Castaldo, G. Castro, A. Carpignano, F. Causa, R. Cavazzana, M. Cavedon, M. Cavenago, M. Cecchini, S. Ceccuzzi, G. Celentano, L. Celona, C. Centioli, G.V. Centomani, S. Cesaroni, A.G. Chiariello, R. Chomicz, C. Cianfarani, F. Cichocki, M. Cinque, A. Cioffi, M. Ciotti, M. Cipriani, S. Ciufo, V. Claps, G. Claps, V. Coccorese, D. Coccorese, A. Colangeli, T. Coltella, F. Consoli, F. Cordella, D. Corradini, O. Costa, F. Crea, A. Cremona, F. Crescenzi, F. Crisanti, G. Cristofari, G. Croci, A. Cucchiaro, D. D’Ambrosio, M. Dal Molin, M. Dalla Palma, F. Danè, C. Day, M. De Angeli, V. De Leo, R. De Luca, E. De Marchi, G. De Marzi, G. De Masi, E. De Nardi, C. De Piccoli, G. De Sano, M. De Santis, G. De Tommasi, A. Del Nevo, A. Delfino, A. Della Corte, P. Deodati, S. Desiderati, E. Di Ferdinando, M.G. Di Florio, G. Di Gironimo, L.E. Di Grazia, V. Di Marzo, F. Di Paolo, E. Di Pietro, M. Di Pietrantonio, M. Di Prinzio, A. Di Silvestre, A. Di Zenobio, R. Dima, A. Domenichelli, A. Doria, G. Dose, S. Dubbioso, S. Dulla, I. Duran, M. Eboli, M. Elitropi, E. Emanuelli, B. Esposito, P. Ettorre, C. Fabbri, F. Fabbri, M. Fadone, M.M. Faggiano, F. Falcioni, M.V. Falessi, F. Fanale, P. Fanelli, A. Fassina, M. Favaretto, G. Favero, M. Ferraris, F. Ferrazza, C. Ferretti, A. Ferro, N. Ferron, C. Fiamozzi Zignani, L. Figini, F. Filippi, M. Filippini, A. Fimiani, M. Fincato, F. Fiorenza, D. Fiorucci, D. Flammini, F. Flora, N. Fonnesu, P. Franz, L. Frassinetti, A. Frattolillo, R. Freda, R. Fresa, A. Frescura, P. Frosi, M. Fulici, M. Furno Palumbo, V. Fusco, P. Fusco, L. Gabellier, P. Gaetani, E. Gaio, E. Gajetti, A. Galatà, J. Galdon Quiroga, D.L. Galindo Huertas, S. Gammino, G. Gandolfo, S. Garavaglia, J. Garcia Lopez, M. Garcia Muñoz, P. Gaudio, M. Gelfusa, G. Gervasini, L. Giannini, M. Giarrusso, C. Gil, F. Giorgetti, E. Giovannozzi, G. Giruzzi, L. Giudicotti, M. Gobbin, G. Gorini, G. Granucci, D. Grasso, T. Grasso, S. Grazioso, H. Greuner, G. Griva, G. Grosso, S. Guerini, J.P. Gunn, V. Hauer, J. Hidalgo Salaverri, M. Hoppe, M. Houry, M. Hoelzl, A. Iaboni, M. Iafrati, A. Iaiunese, V. Imbriani, D. Indrigo, P. Innocente, F. Koechl, B. Končar, A. Kryzhanovskyy, L. Laguardia, D.A. Lampasi, C. Lanchi, F. Lanzotti, A. Lanzotti, M. Laquaniti, F. Leone, J. Li, M. Libè, F. Lisanti, D. Liuzza, F. Locati, R. Lombroni, R. Lorenzini, P. Lorusso, L. Lotto, J. Loureiro, F. Lucca, T. Luda Di Cortemiglia, P. Maccari, G. Maddaluno, S. Magagnino, G. Manca, A. Mancini, P. Mandalà, B. Mandolesi, F. Mandrile, G. Manduchi, S. Manfrin, M. Manganelli, P. Mantica, G. Marchiori, N. Marconato, G. Marelli, A. Mariani, A. Marin, R. Marinari, M. Marinelli, F. Marino, P. Marino, D. Marocco, R. Marsilio, E. Martelli, P. Martin, F. Martinelli, G. Martini, R. Martone, A. Marucci, D. Marzullo, V. Masala, D. Mascali, F. Mascari, A. Masi, N. Massanova, S. Mastrostefano, M. Mattei, G. Mauro, S. Mauro, C. Meineri, L. Melaragni, A. Mele, P. Meller, S. Meloni, I. Menicucci, G. Messina, L. Mezi, G. Miccichè, M. Micheletti, S. Migliori, D. Milanesio, F. Milazzo, R. Milazzo, P. Minelli, S. Minucci, F. Mirizzi, M. Missirlian, D. Monarca, C. Monti, M. Mori, A. Moriani, L. Morici, A. Moro, F. Moro, P. Mosetti, R. Mozzillo, A. Murari, A. Muraro, D. Murra, P. Muscente, S. Musumeci, L. Muzzi, G.F. Nallo, F. Napoli, E. Nardon, E. Naselli, R. Neu, M. Nocente, M. Notazio, S. Nowak, E. Ocello, A. Oliva, V. Orsetti, A. Orsini, F.P. Orsitto, M. Ortino, M. Ottavi, G. Paccagnella, D. Pacella, I. Pagani, N. Paganucci, A. Pagliaro, V. Palazzolo, M. Palermo, S. Palomba, F. Panza, D. Paoletti, M. Parisi, R. Pasqualotto, S. Passarello, M. Passoni, T. Patton, L. Pelliccia, A. Peloso, A. Pepato, E. Perelli, A. Perencin, S. Peruzzo, A. Pesenti, N. Pedroni, P. Petrolini, V. Piergotti, A. Pidatella, L. Pigatto, M. Pillon, T. Pinna, S. Pipolo, S. Piras, C. Piron, L. Piron, A. Pironti, M. Pistilli, D. Placido, A. Pizzuto, P. Platania, A. Polimadei, F. Pollastrone, G.M. Polli, N. Pomaro, F. Pompili, C. Ponti, F. Porcelli, V. Prandelli, A. Previti, A. Princiotta, G. Pucino, F. Quaglia, A. Quercia, F. Raffaelli, G. Ramogida, G. Ranieri, B. Raspante, D. Ravarotto, G.L. Ravera, A. Reale, P. Rebesan, M. Recchia, D. Regine, F. Renno, B. Riccardi, D. Ricci, D. Rigamonti, M. Ripani, N. Rispoli, S. Roccella, G. Rocchi, H. Roche, M. Romanato, F. Romanelli, G. Romanelli, R. Romaniello, A. Romano, M. Romano, R. Romano, R. Rossi, G. Rubinacci, G. Rubino, S. Rubino, J. Rueda Rueda, A. Rufoloni, C. Salvia, P. Salvini, M. Scarpari, A. Salvitti, L. Salvò, S. Sandri, F. Santoro, A. Satriano, L. Savoldi, C. Scardino, G. Schettini, S. Schmuck, J. Scionti, M. Scisciò, M. Scungio, K. Sedlak, L. Senni, G. Sias, A. Sibio, A. Simonetto, L. Singh, A. Sirignano, C. Sozzi, I. Spada, S. Spagnolo, L. Spinicci, G. Spizzo, M. Spolaore, C. Stefanini, H. Strobel, F. Subba, F. Taccogna, B. Taheri, C. Tantos, A. Tarallo, M. Tarantino, G. Tardini, M. Tardocchi, P. Tarfila, A. Tenaglia, C. Terlizzi, D. Terranova, D. Testa, E. Testa, R. Testoni, V. Toigo, G. Torrisi, A. Trotta, G. Trovato, E. Tsitrone, A. Tuccillo, O. Tudisco, M. Turcato, S. Turtù, A. Uccello, M. Ugoletti, O. Uras, M. Uras, M. Utili, V. Vaccaro, F. Valentini, L. Valletti, M. Valisa, D. Van Eester, D. Vanzan, E. Vassallo, G. Vecchi, M. Vellucci, I. Venneri, G. Ventura, M. Veranda, L. Verdini, C. Verona, G. Verona Rinati, F. Veronese, N. Vianello, F. Viganò, O. Villano, R. Villari, F. Villone, P. Vincenzi, V. Vitale, F. Vivio, G. Vlad, M. Wischmeier, H.S. Wu, I. Wyss, R. Zanino, B. Zaniol, F. Zanon, A. Zappatore, G. Zavarise, P. Zito, A. Zoppoli, M. Zucchetti, M. Zuin, and P. Zumbolo
Subjects: divertor, exhaust, plasma scenarios, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: An overview is presented of the progress since 2021 in the construction and scientific programme preparation of the Divertor Tokamak Test (DTT) facility. Licensing for building construction has been granted at the end of 2021. Licensing for Cat. A radiologic source has been also granted in 2022. The construction of the toroidal field magnet system is progressing. The prototype of the 170 GHz gyrotron has been produced and it is now under test on the FALCON facility. The design of the vacuum vessel, the poloidal field coils and the civil infrastructures has been completed. The shape of the first DTT divertor has been agreed with EUROfusion to test different plasma and exhaust scenarios: single null, double null, X-divertor and negative triangularity plasmas. A detailed research plan is being elaborated with the involvement of the EUROfusion laboratories.
Published: 2024
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6. Physics basis for the divertor tokamak test facility

Author: F. Crisanti, R. Ambrosino, M.V. Falessi, L. Gabellieri, G. Giruzzi, G. Granucci, P. Innocente, P. Mantica, G. Ramogida, G. Vlad, R. Albanese, E. Alessi, C. Angioni, P. Agostinetti, L. Aucone, F. Auriemma, B. Baiocchi, L. Balbinot, A. Balestri, T. Barberis, M. Baruzzo, T. Bolzonella, N. Bonanomi, D. Bonfiglio, S. Brezinsek, G. Calabrò, F. Cani, I. Casiraghi, A. Castaldo, C. Castaldo, M. Cavedon, S. Ceccuzzi, F. Cichocki, M. Ciotti, C. Day, C. De Piccoli, G. Dose, E. Emanueli, L. Frassinetti, L. Figini, V. Fusco, E. Giovannozzi, M. Gobbin, F. Koechi, A. Kryzhanovskyy, Y. Li, R. Lombroni, T. Luda, A. Mariani, P. Martin, C. Meineri, A. Murari, P. Muscente, F. Napoli, E. Nardon, R. Neu, M. Nocente, M. Notazio, S. Nowak, L. Pigatto, C. Piron, F. Porcelli, S. Roccella, G. Rubino, M. Scarpari, C. Sozzi, G. Spizzo, F. Subba, F. Taccogna, C. Tantos, D. Terranova, E. Tsitrone, A. Uccello, D. Van Eester, N. Vianello, P. Vincenzi, M. Wischmeier, and F. Zonca
Subjects: plasma, experiment, theory, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: This paper is dealing with the physics basis used for the design of the Divertor Tokamak Test facility (DTT), under construction in Frascati (DTT 2019 DTT interim design report (2019)) Italy, and with the description of the main target plasma scenarios of the device. The main goal of the facility will be the study of the power exhaust, intended as a fully integrated core-edge problem, and eventually to propose an optimized divertor for the European DEMO plant. The approach used to design the facility is described and their main features are reported, by using simulations performed by state-of-the-art codes both for the bulk and edge studies. A detailed analysis of MHD, including also the possibility to study disruption events and Energetic Particles physics is also reported. Eventually, a description of the ongoing work to build-up a Research Plan written and shared by the full EUROfusion community is presented.
Published: 2024
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7. 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

8. Active conditioning of ASDEX Upgrade tungsten plasma-facing components and discharge enhancement through boron and boron nitride particulate injection

Author: Alessandro Bortolon, A. Nagy, R. M. McDermott, D.K. Mansfield, Florian Laggner, R. Neu, A. Drenik, R. Dux, A. Herrmann, V. Rohde, A. Kallenbach, E. Wolfrum, Robert Lunsford, R. Maingi, P. David, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Nuclear and High Energy Physics, Materials science, Divertor, Analytical chemistry, chemistry.chemical_element, Magnetic confinement fusion, Nitride, Tungsten, Collisionality, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, chemistry.chemical_compound, chemistry, ASDEX Upgrade, Boron nitride, 0103 physical sciences, 010306 general physics, Boron
Abstract: The injection of boron (B) and boron nitride (BN) powders into ASDEX Upgrade H-mode discharges have demonstrated effective control of tungsten influx in low density/collisionality operational regimes, similar to conventional boronization methods. Sub-mm powder particles are gravitationally accelerated into the upper edge of a lower single null H-mode plasma with a boundary shape roughly conforming to the shape of the poloidal midplane limiters. Visible spectroscopy measurements at one of the outer limiter showed increases in both B and N signal levels, as well as elevated B levels in the divertor, and an increase in total radiated power by greater than a factor of two during BN injection. Globally the BN injection improved energy confinement by 10%–20%, associated with improvements in pedestal performance similar to gaseous N injection. Following conditioning discharges with B powder injection, three low gas-fueling discharges with magnetic perturbations for ELM suppression were successfully conducted. These first results suggest that the application of B containing powders can be used to both improve plasma performance in real-time, and to improve overall wall conditions for subsequent discharges.
Published: 2019

9. Determination of the tolerable impurity concentrations in a fusion reactor using a consistent set of cooling factors

Author: E. Fable, Th. Pütterich, R. Dux, M. G. O'Mullane, R. Neu, and Mattia Siccinio
Subjects: Nuclear and High Energy Physics, Materials science, Nuclear engineering, Atmospheric-pressure plasma, Plasma, Fusion power, Parameter space, Effective radiated power, Condensed Matter Physics, ASTRA, 7. Clean energy, 01 natural sciences, 010305 fluids & plasmas, 0103 physical sciences, Nuclear fusion, 010306 general physics, Scaling, QC
Abstract: In the present work, the tolerable impurity level and composition for a reactor plasma using several sets of model assumptions are evaluated. Special care was taken to evaluate a comprehensive and consistent set of atomic data for 35 different elements, such that the impurity level for various elements may be studied as a function of their nuclear charge. The data set may not only be useful for the presented work or for system codes which design fusion reactors, but also for interpretation of bolometric measurements. Additionally, the predictions of the spectral distribution of the radiated power is of high quality such that soft x-ray broadband measurements may be interpreted. In the present work the data is used for predicting the radiated power in a reactor plasma, using a 0D, several variants of a 0.5D model and a realistic 1D ASTRA modelling of a DEMO plasma, i.e. the EU DEMO1 2015 design. The maximal or appropriate impurity content of a reactor plasma for all models can be determined, such that the predictions from a simplistic 0D model can be compared to less simplistic models and a proper reactor simulation. These comparisons suggest that with the simplistic models the impurity content may be estimated within a factor of about 1.5, independent of the realization of the reactor plasma. At the same time this study underlines the sensitivity of the reactor performance on the impurity mixture and especially of the He content of the plasma. Additionally, an extended 0.5D model is presented which is able to predict variations of the fusion yield Q and the He concentration, when both is known for a reference scenario. These predictions prove to be of high accuracy when compared to the 1D ASTRA modelling and thus, allow the net impact of an increased dilution and a simlutaneous temperature rise at constant plasma pressure to be evaluated. Furthermore, the parameter space is scanned with more than 105 model reactor plasmas demonstrating that the use of a low-Z impurity diminishes the possibility of an economical feasible reactor plasma. The main results of the parameter scan are made available via scaling formulae.
Published: 2019

10. Interaction of metal dust adhered on castellated substrates with the ELMy H-mode plasmas of ASDEX-Upgrade

Author: M. De Angeli, D. Ripamonti, E. Thoren, A. Herrmann, R. Neu, G. Riva, Ladislas Vignitchouk, K. Krieger, Panagiotis Tolias, B. Sieglin, Svetlana V. Ratynskaia, V. Rohde, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team
Subjects: Nuclear and High Energy Physics, Materials science, droplets, transient heat loads, Divertor, Metallurgy, Refractory metals, chemistry.chemical_element, Plasma, metallic dust, Tungsten, equipment and supplies, Condensed Matter Physics, complex mixtures, 01 natural sciences, Copper, castellated PFC, respiratory tract diseases, 010305 fluids & plasmas, Chromium, chemistry, ASDEX Upgrade, 0103 physical sciences, Beryllium, 010306 general physics
Abstract: Castellated substrates with adhered micron dust have been exposed in the outer ASDEX-Upgrade divertor to ELMy H-mode discharges. Beryllium proxy (chromium, copper) and refractory metal (tungsten, molybdenum) dust has been deposited on the plasma-facing and plasma-shadowed sides of the monoblocks as well as the bottom of the gaps. Interaction with time-averaged transient heat loads up to 5 MWm(-2) led to dust remobilization, clustering, melting and wetting-induced coagulation. The amount of dust released in the vessel has been quantified and remobilized dust trajectories inferred. Gaps can efficiently trap locally adhered dust, but dust detaching from adjacent monoblocks does not preferentially move inside the gaps implying that they do not constitute a dust accumulation site. Heat transfer simulations of melting events are also reported taking into account heat constriction due to the finite contact area and the presence of surface roughness.
Published: 2018

11. The performance of improved H-modes at ASDEX Upgrade and projection to ITER

Author: A. Gude, C. F. Maggi, O. J. W. F. Kardaun, G. Tardini, V. Igochine, A. C. C. Sips, A. Stäbler, O. Gruber, J. Stober, G. V. Pereverzev, Cary Forest, Patrick J. McCarthy, W. Suttrop, R. Neu, A. G. Peeters, V. Mertens, M. Maraschek, L. D. Horton, and ASDEX Upgrade Team
Subjects: Nuclear physics, Nuclear and High Energy Physics, Materials science, ASDEX Upgrade, Beta (plasma physics), Thermal, Extrapolation, Plasma, Fusion power, Collisionality, Condensed Matter Physics, Scaling
Abstract: Since 1998 ASDEX Upgrade has developed stationary H-modes that routinely obtain confinement enhancement factors H98(y,2) > 1 and normalized beta, βN = 2–3. These discharges are characterized by a q-profile with low magnetic shear in the centre and q(0) ~ 1. New results presented here concentrate on extending the operational range of these improved H-modes at ASDEX Upgrade and extrapolating the results to ITER. Discharges are obtained at high density, over a wide range of plasma collisionality and with a first wall predominantly covered by tungsten coated carbon tiles. The performance is optimized for q95 ranging from 3 to 5. At q95 ~ 3 real time control of βN is used and in some cases ECCD to suppress NTM activity at low βN ~ 2. For the extrapolation to ITER, the fusion power is calculated using the same thermal beta (βN,th) and kinetic profile shapes as obtained in ASDEX Upgrade and setting ne/nGW = 0.85. The fusion gain that could be obtained is evaluated using different confinement scaling expressions. The results indicate that improved H-modes are a candidate for an ITER hybrid scenario or could extend ITER operation beyond what is currently foreseen using standard H-modes.
Published: 2007

12. Overview of transport, fast particle and heating and current drive physics using tritium in JET plasmas

Author: P. Belo, T.T.C. Jones, R. J. Pearce, Luciano Bertalot, L. Worth, D. C. McDonald, P. de Vries, Sergey Popovichev, L. Garzotti, R. Neu, J. Brzozowski, D. N. Borba, M. G. O'Mullane, Sean Conroy, Pierre Dumortier, M. F. F. Nave, M.F. Stamp, D. Ciric, J. Mailloux, D. Stork, K-D. Zastrow, P. U. Lamalle, J. Ongena, N. C. Hawkes, I. Voitsekhovitch, H. Weisen, S. E. Sharapov, V. G. Kiptily, T. C. Hender, E. Joffrin, J. Stober, Elizabeth Surrey, M. J. Mantsinen, A. D. Whiteford, C. D. Challis, Jet-Efda Contributors, V.A. Yavorskij, M.R. de Baar, Yu.F. Baranov, and M. Valovic
Subjects: Physics, Nuclear and High Energy Physics, Jet (fluid), Astrophysics::High Energy Astrophysical Phenomena, Transport coefficient, Magnetic confinement fusion, Plasma, Condensed Matter Physics, law.invention, Nuclear physics, Ignition system, Physics::Plasma Physics, law, Orbit (dynamics), Particle, Tritium, Atomic physics
Abstract: Results are presented from the JET Trace Tritium Experimental (TTE) campaign using minority tritium (T) plasmas (n(T)/n(D) 2 MA) and monotonic q-profiles. In CH discharges the gamma-ray emission decay times are much lower than classical (tau(Ts) + tau(alpha s)), indicating alpha confinement degradation, due to the orbit losses and particle orbit drift predicted by a 3-D Fokker-Planck numerical code and modelled using TRANSP.
Published: 2005

13. Overview of ASDEX Upgrade results—development of integrated operating scenarios for ITER

Author: F. Serra, R. Pugno, S. Klose, A. Herrmann, B. Kurzan, K. Mank, R. Narayanan, Garrard Conway, E. Würsching, O. Gehre, Q. Yu, P. Merkel, U. Seidel, R. Kochergov, T. Eich, K. Krieger, A. Bergmann, M. G. Pacco-Düchs, F. Ryter, C. F. Maggi, M. Balden, P. Martin, R. Riedl, Philipp Lauber, Frank Jenko, I. Radivojevic, L. Giannone, M. Maraschek, B. Zaniol, G. Haas, A. Mück, Gerhard Raupp, C. Tichmann, R. Merkel, H. F. Meyer, E. Strumberger, Martin Jakobi, D. Zasche, G. Becker, M. Garcia Munoz, K. Lackner, Y.P. Chen, W. Sandmann, O. J. W. F. Kardaun, K.-H. Steuer, Analiza M. Silva, F. Braun, A. G. Peeters, O. Gruber, F. Leuterer, A. Lyssoivan, W. Suttrop, A. Kallenbach, V. Mertens, K. K. Kirov, Bruce D. Scott, F. Wesner, Y.-S. Na, M. Münich, E. Quigley, C. Angioni, R. Lorenzini, Ivan Bizyukov, Michael Kaufmann, S. Kálvin, H. P. Zehrfeld, K.H. Behringer, W. Becker, Yasutaro Nishimura, A. Carlson, Daisuke Nishijima, M. Mayer, Hajime Urano, S. Cirant, A. Manini, T. Ribeiro, D. Borba, K. Engelhardt, B. Streibl, Junghee Kim, K. Dimova, H. Meister, M. Troppmann, S. Saarelma, Ursel Fantz, J. Hobirk, S. D. Pinches, F. Monaco, Emanuele Poli, Sheena Menmuir, Marco Brambilla, W. Kraus, A. Geier, H. Maier, S. Schweizer, G. Schramm, D. Merkl, S. W. Yoon, R. Neu, E. Speth, R. Bilato, A. V. Chankin, Thomas Zehetbauer, M. Tsalas, Julia Fuchs, M. Huart, J. Gafert, Fernando Meo, Alexander Kendl, T. Bolzonella, R. Drube, R. Dux, G. Tardini, K. Borrass, B. Heger, G. Pautasso, H. D. Murmann, Th. Pütterich, J. Chen, D. Meisel, K. Behler, J. Schirmer, V. Rohde, Wolf-Dieter Schneider, A. Lohs, G. Gantenbein, K. F. Mast, C. V. Atanasiu, G. Schall, A. Stäbler, A. Buhler, H. W. Müller, P. Varela, D. Strintzi, V. Bobkov, K. Gal, A. C. C. Sips, A. Jacchia, H. Kollotzek, Peter Lang, J. M. Santos, W. Treutterer, M. Apostoliceanu, M. Zilker, J. Neuhauser, M. Reich, P. Franzen, Tilman Dannert, J. Roth, H.-U. Fahrbach, Bernd Heinemann, M. E. Manso, D. A. Hartmann, C. Sihler, J. Stober, L. Fattorini, Isabel L. Nunes, H. Zohm, M. Kick, D. Wagner, A. Keller, Martin Laux, Jari Likonen, Taina Kurki-Suonio, E. Posthumus-Wolfrum, D. P. Coster, J. Schweinzer, G. Kocsis, M. Y. Ye, H. Hohenöcker, H. B. Schilling, C. Konz, P. Mantica, V. Igochine, G. Neu, Sibylle Günter, G. V. Pereverzev, L. D. Horton, Patrick J. McCarthy, M. Foley, A. Lorenz, and J.-M. Noterdaeme
Subjects: Nuclear and High Energy Physics, Materials science, Tokamak, Nuclear engineering, Automatic frequency control, fusion reactors, Electron, Parameter space, 7. Clean energy, 01 natural sciences, Particle transport, Electron cyclotron resonance, 010305 fluids & plasmas, ASDEX Upgrade, ITER, 0103 physical sciences, 010306 general physics, plasma, Magnetic confinement fusion, Condensed Matter Physics, fusion energy, ___, JET, Atomic physics, Control methods
Abstract: Significant progress has been made on ASDEX Upgrade during the last two years in the basic understanding of transport, in the extension of the improved H-mode in parameter space and towards an integrated operating scenario and in the development of control methods for major performance limiting instabilities. The important features were the understanding of particle transport and the control of impurity accumulation based on it, the satisfactory operation with predominantly tungsten-clad walls, the improved H-mode operation over density ranges and for temperature ratios covering (non-simultaneously) the ITER requirements on ν*, n/nGW and Te/Ti, the ELM frequency control by pellet injection and the optimization of NTM suppression by DC-ECCD through variation of the launching angle. From these experiments an integrated scenario has emerged which extrapolates to a 50% improvement in n T τ or a 30% reduction of the required current when compared with the ITER base-line assumptions, with moderately peaked electron and controllable high-Z density profiles.
Published: 2005

14. Modelling of tungsten migration during limiter ramp-down in the ASDEX Upgrade divertor tokamak

Author: A Geier, K Krieger, R Neu, D.P Coster, J.D Elder, R Pugno, V Rohde, and the ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Tokamak, Materials science, Nuclear engineering, Divertor, Magnetic confinement fusion, chemistry.chemical_element, Tungsten, Condensed Matter Physics, law.invention, Nuclear physics, chemistry, ASDEX Upgrade, law, Limiter, Deposition (law), Plasma-facing material
Abstract: The suitability of tungsten as a plasma facing material in magnetic fusion devices is currently under investigation at the ASDEX Upgrade divertor tokamak. Recently, the complete central column, which is also used as a ramp-up and ramp-down limiter was covered with W coated carbon tiles. Experimentally, the transient limiter phases were identified to dominate the gross influx of eroded tungsten and thus they could have an effect on the post-campaign surface analysis measurements. Therefore, the migration of W during limiter contact was assessed using the DIVIMP impurity transport code. The results indicate that most of the tungsten eroded during the limiter phases is redeposited locally on the central column and that only an average of less than 10% of the eroded W is deposited somewhere else on the wall. Accordingly, campaign integrated surface analysis measurements of tungsten deposition in the divertor are not influenced by tungsten deposited during ramp-up or ramp-down. Moreover, the comparison of tungsten migration during the limiter phases and the much longer flat-top divertor phases is not contradictory to the experimental result that only about 10% of the tungsten, eroded at the central column, is found in the divertor by post-campaign tile analysis.
Published: 2005

15. Studies of the ‘Quiescent H-mode’ regime in ASDEX Upgrade and JET

Author: W Suttrop, V Hynönen, T Kurki-Suonio, P.T Lang, M Maraschek, R Neu, A Stäbler, G.D Conway, S Hacquin, M Kempenaars, P.J Lomas, M.F.F Nave, R.A Pitts, K.-D Zastrow, the ASDEX Upgrade team, and contributors to the JET-EFDA workprogramme
Subjects: Physics, Larmor precession, Nuclear and High Energy Physics, ASDEX Upgrade, Physics::Plasma Physics, Joint European Torus, Atomic physics, Magnetohydrodynamics, Condensed Matter Physics, Edge-localized mode, Plasma oscillation, Neutral beam injection, Pressure gradient
Abstract: The stationary edge localized mode (ELM)-free 'Quiescent H-mode' (QH-mode) regime, obtained with counter neutral beam injection, is studied in ASDEX Upgrade and Joint European Torus. QH-mode plasmas have high pedestal and core ion temperatures together with good High-confinement mode (H-mode). ELMs are replaced by continuous MHD oscillations, the 'edge harmonic oscillation' (EHO) and the 'high frequency oscillation'. Stationarity of particle and impurity densities is linked to the occurrence of these MHD modes. The EHO location in the steep-gradient region and its appearance with increasing edge pressure points towards the edge pressure or pressure gradient as possible drivers for the EHO. Injection of small cryogenic pellets can raise the plasma density to about 40% of the Greenwald density limit without triggering ELMs. Orbit following calculations of the slowing-down distribution show the presence of an enhanced fast particle density in the H-mode barrier region despite the large loss currents with counter-injection. The radial electrical field in the edge barrier region, about twice as large in QH-mode as in ELMy H-mode, is large enough to reverse the precession drift direction of injected beam ions, leading to a resonance of the EHO with the drift precession frequency.
Published: 2005

16. The improved H-mode at ASDEX Upgrade: a candidate for an ITER hybrid scenario

Author: A Staebler, A.C.C Sips, M Brambilla, R Bilato, R Dux, O Gruber, J Hobirk, L.D Horton, C.F Maggi, A Manini, M Maraschek, A Mück, Y.-S Na, R Neu, G Tardini, M.R Wade, and ASDEX Upgrade Team
Subjects: Physics, Mode number, Nuclear physics, Nuclear and High Energy Physics, Toroid, Amplitude, ASDEX Upgrade, Gyroradius, Tearing, Magnetic confinement fusion, Plasma, Condensed Matter Physics
Abstract: A stationary regime with improved confinement (H98(y, 2) > 1) and, simultaneously, improved stability (βN > 2.5) compared to standard H-mode has been investigated on ASDEX Upgrade for many years. This so-called 'improved H-mode' is characterized by a q-profile with low central magnetic shear and q0 ≥ 1 that is obtained by early heating during the current ramp. Studies of this discharge scenario have been continued. New results are presented concerning the existence domain in the q95 range, the dependence on the normalized Larmor radius and initial experiments showing that high performance improved H-modes can be obtained with strong central ion cyclotron resonance heating (ICRH). In addition, the present status of understanding of the improved H-mode is reviewed. Improved H-mode plasmas are documented for 3.2 1 sawteeth as the main trigger of large amplitude neoclassical tearing modes are avoided. The stability is eventually limited by the occurrence of a mode with poloidal mode number m = 2 and toroidal mode number n = 1 at typically βN ~ 3. As far as the reactor relevance of this regime is concerned, its compatibility with significant central electron heating by ICRH, with high edge densities and low amplitude edge localized modes is of importance. The improved H-mode is, therefore, seen as a candidate for a long pulse ITER 'hybrid' operation.
Published: 2005

17. Integrated exhaust scenarios with actively controlled ELMs

Author: P.T Lang, A Kallenbach, J Bucalossi, G.D Conway, A Degeling, R Dux, T Eich, L Fattorini, O Gruber, S Günter, A Herrmann, J Hobirk, L.D Horton, S Kalvin, G Kocsis, J Lister, M.E Manso, M Maraschek, Y Martin, P.J McCarthy, V Mertens, R Neu, J Neuhauser, I Nunes, T Pütterich, V Rozhansky, R Schneider, W Schneider, I Senichenkov, A.C.C Sips, W Suttrop, W Treutterer, I Veselova, H Zohm, and the ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Materials science, ASDEX Upgrade, Nuclear engineering, Divertor, Radiative transfer, Magnetic confinement fusion, Plasma, Effective radiated power, Atomic physics, Condensed Matter Physics, Plasma oscillation, Neutral particle
Abstract: An integrated radiative high performance scenario has been established at ASDEX Upgrade based on simultaneous feedback control of the average divertor neutral particle and power flux in combination with a high, pellet induced frequency of edge localized modes (ELMs). This approach is fully compatible with the present tungsten wall coating covering about 65% of the plasma facing components and is intended for application in the envisaged full-tungsten experiment. In these experiments, divertor recycling and effective divertor temperature (derived from thermoelectric currents) were tuned by acting on fuel gas puff and argon injection rates. The ELM frequency (f(ELM)) was kept high by repetitive injection of small cryogenic deuterium pellets to avoid the radiative instabilities seen at low f(ELM) and high radiated power, and to control the ELM energy. No confinement loss is observed in this radiative type-I ELMy scenario with relatively flat density profiles. In contrast, similar type-III ELM scenarios achieved in hydrogen show a confinement loss of 25% as compared to the type-I phase. In parallel to pellets, alternative ELM trigger techniques have been investigated as well. Fast vertical plasma oscillations are able to synchronize the ELM frequency to values higher and lower than the intrinsic f(ELM), but remain to be tested in the integrated scenario. Supersonic gas injection showed better fuelling efficiencies than usual gas puffing but instantaneous ELM release has not been achieved. A particular experimental challenge for AUG conditions is to obtain a high pace making frequency, to establish scalings of confinement and energy loss as a function of controlled ELM frequency.
Published: 2005

18. Tungsten: an option for divertor and main chamber plasma facing components in future fusion devices

Author: R Neu, R Dux, A Kallenbach, T Pütterich, M Balden, J.C Fuchs, A Herrmann, C.F Maggi, M O'Mullane, R Pugno, I Radivojevic, V Rohde, A.C.C Sips, W Suttrop, A Whiteford, and the ASDEX Upgrade team
Subjects: Nuclear and High Energy Physics, Materials science, Divertor, Magnetic confinement fusion, chemistry.chemical_element, Plasma, Tungsten, Condensed Matter Physics, chemistry, ASDEX Upgrade, Dielectric heating, Limiter, Plasma diagnostics, Atomic physics
Abstract: The tungsten programme in ASDEX Upgrade is pursued towards a full high-Z device. The spectroscopic diagnostic of W has been extended and refined and the cooling factor of W has been re-evaluated. The W coated surfaces now represent a fraction of 65% of all plasma facing components (24.8 m(2)). The only two major components that are not yet coated are the strikepoint region of the lower divertor as well as the limiters at the low field side. While extending the W surfaces, the W concentration and the discharge behaviour have changed gradually pointing to critical issues when operating with a W wall: anomalous transport in the plasma centre should not be too low, otherwise neoclassical accumulation can occur. One very successful remedy is the addition of central RF heating at the 20-30% level. Regimes with low ELM activity show increased impurity concentration over the whole plasma radius. These discharges can be cured by increasing the ELM frequency through pellet ELM pacemaking or by higher heating power. Moderate gas puffing also mitigates the impurity influx and penetration, however, at the expense of lower confinement. The erosion yield at the low field side guard limiter can be as high as 10(-3) and fast particle losses from NBI were identified to contribute a significant part to the W sputtering. Discharges run in the upper W coated divertor do not show higher W concentrations than comparable discharges in the lower C based divertor. According to impurity transport calculations no strong high-Z accumulation is expected for the ITER standard scenario as long as the anomalous transport is at least as high as the neoclassical one.
Published: 2005

19. Nonlinear pertubative electron heat transport study in the ASDEX Upgrade tokamak

Author: A Jacchia, F. De Luca, F Ryter, A Bruschi, F Leuterer, R Neu, G Pereverzev, W Suttrop, D Wagner, and ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Tokamak, Materials science, Condensed matter physics, Magnetic confinement fusion, Electron, Condensed Matter Physics, Thermal conduction, law.invention, Temperature gradient, ASDEX Upgrade, law, ____, Electron temperature, Plasma diagnostics, Atomic physics
Abstract: Electron heat transport properties have been investigated by means of localized steady-state and modulated electron cyclotron heating in the ASDEX Upgrade tokamak. The experimental findings have been successfully compared with the electron temperature with the model assumption of a threshold gradient length, L-Tc, (1/L-T = -delT(e0)/T-e0), T-e0 below which the electron thermal conductivity measured under steady-state conditions, chi(ePB), shows a sudden increase and the heat conduction 'seen' by a temperature perturbation, chi(eHP), switches from low to high values. In this work electron cyclotron heating (ECH) power is used both to modify the steady-state gradient length and to induce a nonlinear transition from low to high electron heat transport at the position where the temperature gradient crosses its critical (or threshold) value. Steady-state ECH has been injected at different radial positions and the changes induced in electron heat transport have been studied by means of cold pulses launched from the plasma boundary. Cold pulses, obtained by injecting radiating impurities by means of laser blow off of silicon, have proved to be a flexible tool for investigating both the radial position of the step in chi(eHp) and the dependence on local plasma parameters of the underlying physical mechanism.
Published: 2004

20. Diverted tokamak carbon screening: scaling with machine size and consequences for core contamination

Author: H. Meister, J. D. Strachan, G. Corrigan, V. Rohde, J. Spence, G. F. Matthews, R. Neu, and A. Kallenbach
Subjects: Nuclear and High Energy Physics, Jet (fluid), Tokamak, Materials science, Divertor, Nuclear engineering, chemistry.chemical_element, Magnetic confinement fusion, Plasma, Condensed Matter Physics, Methane, law.invention, chemistry.chemical_compound, chemistry, ASDEX Upgrade, Physics::Plasma Physics, law, Atomic physics, Carbon
Abstract: Plasma impurity content depends on the impurity sources, fuelling efficiency, and confinement. In JET, carbon is the primary impurity, and its fuelling efficiency has been studied using methane gas injection and modelled with the scrape-off-layer (SOL) codes: DIVIMP and EDGE2D. In this paper, EDGE2D modelling of similar ASDEX Upgrade experiments and projections to ITER are described. The parameters that govern the size scaling of carbon screening have been identified.Size scaling is complex. For carbon injected from the main chamber, the important factors include: the SOL temperature, the magnitude of the thermal force at the divertor entrance, and the parallel distance to the divertor. For carbon injected at the strike points, the intersection of the carbon ionization region with the region of strong thermal force determines the carbon fuelling efficiency.ITER projects to have much better carbon screening than JET. The ITER SOL is hotter so that main chamber carbon is ionized further from the separatrix making the calculated carbon fuelling efficiency lower. Also, the carbon originating near the strike point has less chance of escaping the divertor since the ITER divertor is larger. The carbon sputtering is projected to be larger, making the ITER core contamination difficult to estimate. A general result is that the core contamination at fixed total sputtering rate and core impurity confinement increases when the fraction of carbon ionized in the main chamber SOL increases, and decreases for larger machine size and higher density operation.
Published: 2004

21. Recent ECRH results in ASDEX Upgrade

Author: F. Ryter, R. Neu, A. G. Peeters, M. Maraschek, G. Tardini, R. Dux, A. Keller, G. Gantenbein, Aug Team, F. Leuterer, J. Hobirk, A. Mück, G. V. Pereverzev, W. Suttrop, K. K. Kirov, J. Stober, and H. Zohm
Subjects: Nuclear and High Energy Physics, Materials science, Turbulence, Cyclotron, Magnetic confinement fusion, Electron, Condensed Matter Physics, Electron cyclotron resonance, law.invention, Nuclear physics, ASDEX Upgrade, Heat flux, Physics::Plasma Physics, Power Balance, law
Abstract: This paper provides an overview on recent experimental results obtained in ASDEX Upgrade using electron cyclotron heating and current drive. The following topics are covered: determination of the power deposition profile, modulated power deposition, studies of the electron heat transport via power balance and heat wave analysis and a comparison with turbulent transport theory, generation of an internal transport barrier for the electron heat flux, impact of electron cyclotron resonance heating (ECRH) on particle and impurity transport, and studies related to neoclassical tearing modes and to sawteeth.
Published: 2003

22. Dependence of particle transport on heating profiles in ASDEX Upgrade

Author: J Stober, R Dux, O Gruber, L Horton, P Lang, R Lorenzini, C Maggi, F Meo, R Neu, J.-M Noterdaeme, A Peeters, G Pereverzev, F Ryter, A.C.C Sips, A Stäbler, H Zohm, and the ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Materials science, ASDEX Upgrade, Heat flux, Physics::Plasma Physics, Pinch, Magnetic confinement fusion, Electric current, Atomic physics, Condensed Matter Physics, Instability, Flattening, Bootstrap current
Abstract: The behaviour of the density profiles in ASDEX Upgrade can be described well with the assumption D χ and a pinch of the order of the neoclassical Ware pinch. The latter is estimated from slowly equilibrating density profiles. The assumption D χ has been succesfully tested by varying the heat deposition profile, making use of on-/off-axis ICRH and ECRH: due to the generally observed self-similarity of the temperature profile, such variations in the heat flux profile have a strong effect on the χ-profile and on the D-profile if the above assumption is correct. The corresponding variations in the density profiles have indeed been observed. The model is also capable of describing the decay of the density profile after injecting a train of pellets. The anomalous transport of impurities is also increased with central heating, and the corresponding flattening of the density profile leads to a significant reduction of the neoclassical impurity pinch. Central ICR or ECR heating are therefore now routinely used to control density peaking and its negative effect on the stability of neoclassical tearing modes as well as to control the impurity transport in ASDEX Upgrade.
Published: 2003

23. ELM frequency control by continuous small pellet injection in ASDEX Upgrade

Author: P.T Lang, J Neuhauser, L.D Horton, T Eich, L Fattorini, J.C Fuchs, O Gehre, A Herrmann, P Ignácz, M Jakobi, S Kálvin, M Kaufmann, G Kocsis, B Kurzan, C Maggi, M.E Manso, M Maraschek, V Mertens, A Mück, H.D Murmann, R Neu, I Nunes, D Reich, M Reich, S Saarelma, W Sandmann, J Stober, U Vogl, and the ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Range (particle radiation), Materials science, ASDEX Upgrade, Pellet, Pellets, Magnetic confinement fusion, Plasmoid, Plasma, Mechanics, Atomic physics, Condensed Matter Physics, Edge-localized mode
Abstract: Injection of cryogenic deuterium pellets has been successfully applied in ASDEX Upgrade for external edge localized mode (ELM) frequency control in type-I ELMy H-mode discharge scenarios. A pellet velocity of 560 m s−1 and a size of about 6 × 1019 D-atoms was selected for technical reasons, although even lower masses were found sufficient to trigger ELMs. A moderate repetition rate close to 20 Hz was chosen to avoid over-fuelling of the core plasma. Pellet sequences of up to 4 s duration were injected into discharges close to the L–H threshold, intrinsically developing large compound ELMs at a rate of 3 Hz. With pellet injection, these large ELMs were completely replaced by smaller type-I ELMs at the much higher pellet frequency, accompanied by a slight increase of density and even of stored energy. This external ELM control could be repeatedly switched on and off by just interrupting the pellet train. ELMs were triggered in less than 200 µs after pellet arrival at the plasma edge, at which time only a fraction of the pellet has been ablated, forming a rather localized, three-dimensional plasmoid, which drives the edge unstable well before the deposited mass is spread toroidally. The pellet controlled case has also been compared with a discharge at a somewhat lower density, but with otherwise rather similar data, developing spontaneous 20 Hz type-I ELMs. Despite the different trigger mechanisms, the general ELM features turn out to be qualitatively similar, possibly because of the similarity of the two cases in terms of ELM relevant parameters. The scaling with background plasma, heating power, pellet launch parameters, etc over a larger range still remains to be investigated.
Published: 2003

24. Overview of ASDEX Upgrade results

Author: O. Gruber, R. Arslanbekov, C. Atanasiu, A. Bard, G. Becker, W. Becker, M. Beckmann, K. Behler, K. Behringer, A. Bergmann, R. Bilato, D. Bolshukin, K. Borrass, H.-S. Bosch, B. Braams, M. Brambilla, R. Brandenburg, F. Braun, H. Brinkschulte, R. Brückner, B. Brüsehaber, K. Büchl, A. Buhler, H. Bürbaumer, A. Carlson, M. Ciric, G. Conway, D.P. Coster, C. Dorn, R. Drube, R. Dux, S. Egorov, W. Engelhardt, H.-U. Fahrbach, U. Fantz, H. Faugel, M. Foley, P. Franzen, P. Fu, J.C. Fuchs, J. Gafert, G. Gantenbein, O. Gehre, A. Geier, J. Gernhardt, E. Gubanka, A. Gude, S. Günter, G. Haas, D. Hartmann, B. Heinemann, A. Herrmann, J. Hobirk, F. Hofmeister, H. Hohenöcker, L. Horton, L. Hu, D. Jacobi, M. Jakobi, F. Jenko, A. Kallenbach, O. Kardaun, M. Kaufmann, A. Kendl, J.-W. Kim, K. Kirov, R. Kochergov, H. Kollotzek, W. Kraus, K. Krieger, B. Kurzan, G. Kyriakakis, K. Lackner, P.T. Lang, R.S. Lang, M. Laux, L. Lengyel, F. Leuterer, A. Lorenz, H. Maier, K. Mank, M.-E. Manso, M. Maraschek, K.-F. Mast, P.J. McCarthy, D. Meisel, H. Meister, F. Meo, R. Merkel, V. Mertens, J.P. Meskat, R. Monk, H.W. Müller, M. Münich, H. Murmann, G. Neu, R. Neu, J. Neuhauser, J.-M. Noterdaeme, I. Nunes, G. Pautasso, A.G. Peeters, G. Pereverzev, S. Pinches, E. Poli, R. Pugno, G. Raupp, T. Ribeiro, R. Riedl, S. Riondato, V. Rohde, H. Röhr, J. Roth, F. Ryter, H. Salzmann, W. Sandmann, S. Sarelma, S. Schade, H.-B. Schilling, D. Schlögl, K. Schmidtmann, R. Schneider, W. Schneider, G. Schramm, J. Schweinzer, S. Schweizer, B.D. Scott, U. Seidel, F. Serra, S. Sesnic, C. Sihler, A. Silva, A. Sips, E. Speth, A. Stäbler, K.-H. Steuer, J. Stober, B. Streibl, E. Strumberger, W. Suttrop, A. Tabasso, A. Tanga, G. Tardini, C. Tichmann, W. Treutterer, M. Troppmann, N. Tsois, W. Ullrich, M. Ulrich, P. Varela, O. Vollmer, U. Wenzel, F. Wesner, R. Wolf, E. Wolfrum, R. Wunderlich, N. Xantopoulos, Q. Yu, M. Zarrabian, D. Zasche, T. Zehetbauer, H.-P. Zehrfeld, A. Zeiler, and H. Zohm
Subjects: Nuclear and High Energy Physics, 0103 physical sciences, 010306 general physics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas
Published: 2001

25. Video analysis of dust events in full-tungsten ASDEX Upgrade

Author: G. Pautasso, C. Vorpahl, R. Neu, A. Shalpegin, T. Lunt, S. Bardin, J.L. Briançon, Volker Rohde, F. Brochard, Institut Jean Lamour (IJL), Université de Lorraine (UL)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Universität Stuttgart [Stuttgart], Dutch Institute for Fundamental Energy Research [Nieuwegein] (DIFFER), Max-Planck-Institut für Plasmaphysik [Garching] (IPP), ITER organization (ITER), Technische Universität Munchen - Université Technique de Munich [Munich, Allemagne] (TUM), Institut de Chimie du CNRS (INC)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: [PHYS]Physics [physics], Nuclear and High Energy Physics, Tokamak, Meteorology, Nuclear engineering, [SPI.PLASMA]Engineering Sciences [physics]/Plasmas, Dust particles, chemistry.chemical_element, Plasma, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Tungsten, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, chemistry, ASDEX Upgrade, 13. Climate action, law, 0103 physical sciences, Environmental science, Vertical displacement, 010306 general physics
Abstract: International audience; Fast video data recorded during seven consecutive operation campaigns (2008-2012) in full-tungsten ASDEX Upgrade have been analyzed with an algorithm developped to automatically detect and track dust particles. A total of 2425 discharges have been analyzed, corresponding to 12204 seconds of plasma operation. The analysis aimed at precisely identifying and sorting the discharge conditions responsible of the dust generation or remobilization. Dust rates are found to be significantly lower than in tokamaks with carbon PFCs. Significant dust events occur mostly during off-normal plasma phases such as disruptions and particularly those preceded by vertical displacement events (VDEs). Dust rates are also increased but to a lower extent during type-I ELMy H-modes. The influences of disruption energy, heating scenario, vessel venting and vessel vibrations are also presented.
Published: 2016

26. Propagation of cold pulses and heat pulses in ASDEX Upgrade

Author: F Ryter, R Neu, R Dux, H.-U Fahrbach, F Leuterer, G Pereverzev, J Schweinzer, J Stober, W Suttrop, ASDEX Upgrade Team, F. De Luca, A Jacchia, and J.E Kinsey
Subjects: Nuclear and High Energy Physics, Materials science, Tokamak, Plasma, Electron, Tore Supra, Condensed Matter Physics, Laser, law.invention, ___, ASDEX Upgrade, Physics::Plasma Physics, law, Electron temperature, Atomic physics, Bandwidth-limited pulse
Abstract: Experiments on electron heat transport were performed in the tokamak ASDEX Upgrade, mainly in ohmically heated plasmas, applying either edge cooling with laser blow-off impurity injection or edge heat pulses with ECRH. Repetitive pulses within one plasma discharge were made allowing Fourier transformation of the temperature perturbation, yielding a good signal to noise ratio up to high harmonics and a detailed investigation of the pulse propagation. For densities lower than 1.8 x 10(19) m(-3), an increase of central electron temperature was found as the response to edge cooling via impurity injection similar to observations made in the TEXT, TFTR, RTP and Tore Supra tokamaks. The inversion does not appear instantaneously, but with a time delay roughly compatible with diffusion. Modelling of the propagation of the cold pulses in the framework of the IFS-PPPL model yields qualitative agreement. However, the predicted increase of ion temperature is not observed experimentally on a fast timescale. The response to ECRH heat pulses is not perfectly symmetrical to cold pulse experiments, but the similarities suggest a common underlying physical mechanism. No inversion of the heat pulse is found, instead the initial pulse from the edge is associated with a second, much slower, heat pulse in the centre. This central reaction is in fact quite similar (and not symmetrical) to that of the cold pulses. By varying the position of the ECRH deposition it could be shown that the central increase is related to the arrival of the pulse close to the inversion radius and not to the initial pulse. Modelling was performed to investigate the possible physics mechanisms and for comparison with the cold pulses.
Published: 2000

27. Zdependence of the core impurity transport in ASDEX Upgrade H mode discharges

Author: R Dux, A.G Peeters, A Gude, A Kallenbach, R Neu, and ASDEX Upgrade Team
Subjects: Physics, Convection, Nuclear and High Energy Physics, Drift velocity, Density gradient, ASDEX Upgrade, Physics::Plasma Physics, Impurity, Flux, Plasma, Diffusion (business), Atomic physics, Condensed Matter Physics
Abstract: The dependence of core plasma impurity transport on the Z number has been investigated for ASDEX Upgrade H?mode discharges. For the elements Ne, Ar, Kr and Xe the diffusion coefficient in the centre is D ? 6 ? 10-2m2/s and rises with the radial distance from the centre. With increasing Z number the transport becomes strongly convective with inward directed drift velocities that produce very peaked impurity densities for high Z. The inward drift decreases with decreasing deuterium density gradient. Neoclassical transport of the impurities has been calculated numerically. The calculated diffusion coefficient and drift velocity are close to the experimental values for the lower-Z elements Ne and Ar. However, for high Z, the calculated diffusion coefficient is smaller by a factor of up to 2.5 and the inward drift velocity is too small by a factor of 10. Toroidal rotation of the plasma that leads to an increased impurity density on the outboard side of the flux surfaces is not taken into account by the neoclassical calculations. Inboard/outboard asymmetries are not present for Ar and Ne with toroidal Mach number Mtor around 1. However, for heavier elements than Kr with Mtor ? 2 and an outboard/inboard ratio of ? 1.5, poloidal variation of the impurity density is important and might account for the discrepancy between the measured and calculated transport coefficients.
Published: 1999

28. Overview of ASDEX Upgrade results

Author: O Gruber, H.-S Bosch, S Günter, A Herrmann, A Kallenbach, M Kaufmann, K Krieger, K Lackner, V Mertens, R Neu, F Ryter, J Schweinzer, A Stäbler, W Suttrop, R Wolf, K Asmussen, A Bard, G Becker, K Behler, K Behringer, A Bergmann, M Bessenrodt-Weberpals, K Borrass, B Braams, M Brambilla, R Brandenburg, F Braun, H Brinkschulte, R Brückner, B Brüsehaber, K Büchl, A Buhler, H.P Callaghan, A Carlson, D.P Coster, L Cupido, S. de Peña Hempel, C Dorn, R Drube, R Dux, S Egorov, W Engelhardt, H.-U Fahrbach, U Fantz, H.-U Feist, P Franzen, J.C Fuchs, G Fussmann, J Gafert, G Gantenbein, O Gehre, A Geier, J Gernhardt, E Gubanka, A Gude, G Haas, K Hallatschek, D Hartmann, B Heinemann, G Herppich, W Herrmann, F Hofmeister, E Holzhauer, D Jacobi, M Kakoulidis, N Karakatsanis, O Kardaun, A Khutoretski, H Kollotzek, S Kötterl, W Kraus, B Kurzan, G Kyriakakis, P.T Lang, R.S Lang, M Laux, L.L Lengyel, F Leuterer, A Lorenz, H Maier, M Manso, M Maraschek, M Markoulaki, K.-F Mast, P.J McCarthy, D Meisel, H Meister, R Merkel, J.P Meskat, H.W Müller, M Münich, H Murmann, B Napiontek, G Neu, J Neuhauser, M Niethammer, J.-M Noterdaeme, G Pautasso, A.G Peeters, G Pereverzev, S Pinches, G Raupp, K Reinmüller, R Riedl, V Rohde, H Röhr, J Roth, H Salzmann, W Sandmann, H.-B Schilling, D Schlögl, K Schmidtmann, H Schneider, R Schneider, W Schneider, G Schramm, S Schweizer, R.R Schwörer, B.D Scott, U Seidel, F Serra, S Sesnic, C Sihler, A Silva, E Speth, K.-H Steuer, J Stober, B Streibl, A Thoma, W Treutterer, M Troppmann, N Tsois, W Ullrich, M Ulrich, P Varela, H Verbeek, O Vollmer, H Wedler, M Weinlich, U Wenzel, F Wesner, R Wunderlich, N Xantopoulos, Q Yu, D Zasche, T Zehetbauer, H.-P Zehrfeld, H Zohm, and M Zouhar
Subjects: Nuclear and High Energy Physics, 0103 physical sciences, 010306 general physics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas
Published: 1999

29. Spectroscopic investigations of tungsten in the EUV region and the determination of its concentration in tokamaks

Author: K Asmussen, K.B Fournier, J.M Laming, R Neu, J.F Seely, R Dux, W Engelhardt, J.C Fuchs, and ASDEX Upgrade Team
Subjects: Nuclear and High Energy Physics, Laser ablation, Materials science, Extreme ultraviolet lithography, Divertor, chemistry.chemical_element, Plasma, Tungsten, Condensed Matter Physics, Ion, ASDEX Upgrade, chemistry, Extreme ultraviolet, Atomic physics
Abstract: Tungsten was injected by means of laser ablation in both ohmic and additionally heated plasmas of the ASDEX Upgrade tokamak experiment. Spectroscopic investigations were performed in the extreme ultraviolet (EUV) wavelength region, 4 to 140 nm. Besides the quasi-continuum structure at ? 5 nm emitted by tungsten ions around W27+, isolated lines of tungsten were observed in the same spectral region and also in the range from 12 to 14 nm. By comparison with calculations from the HULLAC and RELAC codes, these lines could be identified as transitions of bromine to nickel-like tungsten ions. The concentration cW of tungsten after laser ablation was determined from comparisons between the total tungsten radiation PW and the calculated radiation losses. Calibration of the quasi-continuum intensity with the help of the PW measurements allows the tungsten concentration to be determined from spectroscopic observations, which are more sensitive. Both concentration measurements (quasi-continuum, PW) agree well in discharges with laser ablation. From a comparison of the intensity of the isolated lines with code results, cW could be estimated in the central region of hot, additionally heated plasmas. The lower detection limit of the spectroscopic method allows the extraction of cW during the tungsten divertor experiment of ASDEX Upgrade.
Published: 1998

30. Tearing mode formation and radiative edge cooling prior to density limit disruptions in ASDEX upgrade

Author: K. Büchl, M. Schittenhelm, K. Lackner, M. Sokoll, R. Neu, H. Zohm, M. Maraschek, Julia Fuchs, V. Mertens, W. Suttrop, and Michael Kaufmann
Subjects: Nuclear and High Energy Physics, Electron density, Materials science, Tokamak, Flux, Electron, Condensed Matter Physics, law.invention, ASDEX Upgrade, law, Tearing, Radiative transfer, Atomic physics, Ohmic contact
Abstract: Tearing mode formation is investigated for ohmic density limit discharges on the ASDEX Upgrade tokamak at medium and high safety factors (q95=3.8, 4.9, 6.0). Low electron temperatures inside magnetic islands and the observation of localized C III impurity radiation suggest that a thermal instability, as proposed by Rebut and Hugon, destabilizes the (m, n)=(3,1) and (4,1) islands, which grow during the current profile contraction phase. In contrast, the (2,1) islands appear to be thermally stable. Minor disruptions lead to step-wise loss of confinement, first localized at the 4 2 surface, then after a time delay comparable to the resistive time-scale, at the q=3 surface and after a second time delay, at the q=4 surface. It is found that (3,1) islands, unlike (2,1) islands, are quenched by the high heat flux during minor disruptions
Published: 1997

31. The contribution of chemical erosion to the carbon content in the ASDEX Upgrade tokamak

Author: W. Poschenrieder, R. Neu, and A. Kallenbach
Subjects: Nuclear and High Energy Physics, Materials science, Divertor, Analytical chemistry, chemistry.chemical_element, Condensed Matter Physics, Oxygen, chemistry, ASDEX Upgrade, Physics::Plasma Physics, Desorption, Limiting oxygen concentration, Graphite, Atomic physics, Spectroscopy, Carbon
Abstract: The origin of carbon and oxygen impurities observed in the bulk plasma of the ASDEX Upgrade tokamak is investigated by means of particle influx measurements using spectroscopy in the visible spectral range and impurity density measurements using spectroscopy in the soft X ray range. A number of ohmically heated discharges are evaluated and statistically analysed to reduce the influence of the individual experimental scatter. The interpretation of the spectroscopic measurements is supported by mass spectrometry, which allows the partial fluxes of the various molecular species to be resolved. The measured fluxes and concentrations reveal a consistent picture: for low electron densities and impure wall conditions, CO recycling in the main plasma chamber is the dominant source of carbon and oxygen, leading to similar concentrations of these species in the bulk plasma. At higher densities or with freshly boronized walls, the oxygen concentration is significantly reduced to 0.05% of the electron density. The corresponding reduction of carbon saturates at a level of about 0.3%. This behaviour is attributed to chemical erosion due to hydrocarbon formation and desorption with a yield of a few per cent of the hydrogen flux. The resulting carbon ion flux is reduced owing to wall redeposition, but still amounts to about 0.45% of the hydrogen flux. This level imposes severe limitations on the use of graphite in a low temperature, high recycling divertor of a future reactor
Published: 1994

32. Effect of nitrogen seeding on the energy losses and on the time scales of the electron temperature and density collapse of type-I ELMs in JET with the ITER-like wall

Author: T. Eich, Jet-Efda Contributors, D. Dodt, C. Giroud, R. Neu, M.S. Jachmich, G. P. Maddison, C. Perez von Thun, J. Flanagan, M. Kempenaars, C. F. Maggi, B. Sieglin, A. Sirinelli, J. E. Boom, P. J. Lomas, Isabel L. Nunes, Lorenzo Frassinetti, M. N. A. Beurskens, and M.F. Stamp
Subjects: Nuclear and High Energy Physics, Jet (fluid), Materials science, Astrophysics::High Energy Astrophysical Phenomena, Divertor, Magnetic confinement fusion, Collisionality, Condensed Matter Physics, Instability, Computational physics, Pedestal, Physics::Plasma Physics, Electron temperature, High Energy Physics::Experiment, Seeding, Atomic physics
Abstract: The baseline type-I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called the ITER-like wall, JET-ILW).The first JET-ILW results show that the confinement is degraded by 20–30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained to date in JET-ILW baseline plasmas only in the high triangularity shape using N2 seeding.This work compares the energy losses during ELMs and the corresponding time scales of the temperature and density collapse in JET-ILW baseline plasmas with and without N2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, is ~2 ms in the JET-ILW and lower than 1 ms in the JET-C. The energy losses are in the range ΔWELM/Wped ≈ 7–12% in the JET-ILW and ΔWELM/Wped ≈ 10–20% in JET-C, and fit relatively well with earlier multi-machine empirical scalings of ΔWELM/Wped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. Most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale ~8–10 ms (hereafter called slow transport events), that can lead to losses in the range ΔWslow/Wped ≈ 15–22%, slightly larger than the losses in JET-C. The N2 seeding in JET-ILW significantly affects the ELMs. The JET-ILW plasmas with N2 seeding are characterized by ELM energy losses and time scales similar to the JET-C and by the absence of the slow transport events.
Published: 2015

33. Collection strategy, inner morphology, and size distribution of dust particles in ASDEX Upgrade

Author: N. Endstrasser, M. Balden, Paul W. Humrickhouse, S. Elgeti, Marcin Rasinski, U. von Toussaint, V. Rohde, R. Neu, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Electric arc, Core (optical fiber), Nuclear and High Energy Physics, Materials science, Volume (thermodynamics), ASDEX Upgrade, Scanning electron microscope, Particle, Nanotechnology, Plasma, Composite material, Condensed Matter Physics, Porosity
Abstract: The dust collection and analysis strategy in ASDEX Upgrade (AUG) is described. During five consecutive operation campaigns (2007–2011), Si collectors were installed, which were supported by filtered vacuum sampling and collection with adhesive tapes in 2009. The outer and inner morphology (e.g. shape) and elemental composition of the collected particles were analysed by scanning electron microscopy. The majority of the ∼50 000 analysed particles on the Si collectors of campaign 2009 contain tungsten—the plasma-facing material in AUG—and show basically two different types of outer appearance: spheroids and irregularly shaped particles. By far most of the W-dominated spheroids consist of a solid W core, i.e. solidified W droplets. A part of these particles is coated with a low-Z material; a process that seems to happen presumably in the far scrape-off layer plasma. In addition, some conglomerates of B, C and W appear as spherical particles after their contact with plasma. By far most of the particles classified as B-, C- and W-dominated irregularly shaped particles consist of the same conglomerate with varying fraction of embedded W in the B–C matrix and some porosity, which can exceed 50%. The fragile structures of many conglomerates confirm the absence of intensive plasma contact. Both the ablation and mobilization of conglomerate material and the production of W droplets are proposed to be triggered by arcing. The size distribution of each dust particle class is best described by a log-normal distribution allowing an extrapolation of the dust volume and surface area. The maximum in this distribution is observed above the resolution limit of 0.28 µm only for the W-dominated spheroids, at around 1 µm. The amount of W-containing dust is extrapolated to be less than 300 mg on the horizontal areas of AUG.
Published: 2014

34. Compatibility of ITER scenarios with full tungsten wall in ASDEX Upgrade

Author: Th. Pütterich, R. Dux, O. Gruber, A. Herrmann, T. Eich, C. F. Maggi, R. Neu, A. C. C. Sips, J. Stober, Julia Fuchs, A. Kallenbach, and J. Schweinzer
Subjects: Nuclear and High Energy Physics, Toroid, Materials science, Divertor, chemistry.chemical_element, Plasma, Tungsten, Effective radiated power, Condensed Matter Physics, chemistry, ASDEX Upgrade, Sputtering, Limiter, Atomic physics
Abstract: The transition of ASDEX Upgrade (AUG) from a graphite device to a full tungsten device is demonstrated with a reduction by an order of magnitude in both the carbon deposition and deuterium retention. The tungsten source is dominated by sputtering from intrinsic light impurities, and the tungsten influxes from the outboard limiters are the main source for the plasma. In H-mode discharges, central heating (neutral beams, ECRH) is used to increase turbulent outward transport avoiding tungsten accumulation. ICRH can only be used after boronization as its application otherwise results in large W influxes due to light impurities accelerated by electrical fields at the ICRH antennas. ELMs are important in reducing the inward transport of tungsten in the H-mode edge barrier and are controlled by gas puffing. Even without boronization, stationary, ITER baseline H-modes (confinement enhancement factor from ITER 98(y, 2) scaling H 98 ∼ 1, normalized beta βN ∼ 2), with W concentrations below 3 × 10−5 were routinely achieved up to 1.2 MA plasma current. The compatibility of high performance improved H-modes with unboronized W wall was demonstrated, achieving H 98 = 1.1 and βN up to 2.6 at modest triangularities δ ⩽ 0.3 as required for advanced scenarios in ITER. With boronization the light impurities and the radiated power fraction especially in the divertor were reduced and the divertor plasma was actively cooled by N2 seeding. N2 seeding does not only protect the divertor tiles but also considerably improves the performance of improved H-mode discharges. The energy confinement increased to H 98-factors of 1.25 (βN ∼ 2.7) and thereby exceeded the best values in a carbon-dominated AUG machine under similar conditions. Recent investigations show that this improvement is due to higher temperatures rather than to peaking of the electron density profile. Further ITER discharge scenario tests include the demonstration of ECRF assisted low voltage plasma start-up and current rise to q 95 = 3 at toroidal electric fields below 0.3 V m−1, to achieve a ITER compatible range of plasma internal inductance of 0.71–0.97. The results reported here strongly support tungsten as a first wall material solution.
Published: 2009

35. Studies of the Quiescent H-mode regime in ASDEX Upgrade and JET.

Author: W. Suttrop, V. Hynönen, T. Kurki-Suonio, P.T. Lang, M. Maraschek, R. Neu, A. Stäbler, G.D. Conway, S. Hacquin, M. Kempenaars, P.J. Lomas, M.F.F. Nave, R.A. Pitts, K.-D. Zastrow, and the ASDEX Upgrade team and contributors to the JET-EFDA workprogramme
Published: 2005

36. Active conditioning of ASDEX Upgrade tungsten plasma-facing components and discharge enhancement through boron and boron nitride particulate injection.

Author: R. Lunsford, V. Rohde, A. Bortolon, R. Dux, A. Herrmann, A. Kallenbach, R.M. McDermott, P. David, A. Drenik, F. Laggner, R. Maingi, D. K. Mansfield, A. Nagy, R. Neu, E. Wolfrum, and team, the ASDEX Upgrade
Subjects: BORON nitride, TUNGSTEN alloys, BORON, TUNGSTEN, OPTICAL spectroscopy, GREAT powers (International relations)
Abstract: The injection of boron (B) and boron nitride (BN) powders into ASDEX Upgrade H-mode discharges have demonstrated effective control of tungsten influx in low density/collisionality operational regimes, similar to conventional boronization methods. Sub-mm powder particles are gravitationally accelerated into the upper edge of a lower single null H-mode plasma with a boundary shape roughly conforming to the shape of the poloidal midplane limiters. Visible spectroscopy measurements at one of the outer limiter showed increases in both B and N signal levels, as well as elevated B levels in the divertor, and an increase in total radiated power by greater than a factor of two during BN injection. Globally the BN injection improved energy confinement by 10%–20%, associated with improvements in pedestal performance similar to gaseous N injection. Following conditioning discharges with B powder injection, three low gas-fueling discharges with magnetic perturbations for ELM suppression were successfully conducted. These first results suggest that the application of B containing powders can be used to both improve plasma performance in real-time, and to improve overall wall conditions for subsequent discharges. [ABSTRACT FROM AUTHOR]
Published: 2019
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37. Fracture behavior of random distributed short tungsten fiber-reinforced tungsten composites.

Author: Y. Mao, J.W. Coenen, J. Riesch, S. Sistla, J. Almanstötter, J. Reiser, A. Terra, C. Chen, Y. Wu, L. Raumann, T. Höschen, H. Gietl, R. Neu, Ch. Linsmeier, and C. Broeckmann
Subjects: TUNGSTEN alloys, FIBROUS composites, TUNGSTEN, FUSION reactors, FRACTURE toughness, BEND testing
Abstract: In future fusion reactors, tungsten is considered as the main candidate material for plasma-facing components. However, the intrinsic brittleness of tungsten is of great concern during operation. To overcome this drawback, tungsten fiber-reinforced tungsten composites (Wf/W) are being developed relying on extrinsic toughening principles. Tungsten (W) fibers with extremely high tensile strength and ductility are used to reinforce a tungsten matrix. In this work, field assisted sintering technology (FAST) is used to produce Wf/W material. Mechanical characterizations including Charpy impact and 3-point bending tests are performed. Based on the 3-point bending test results, the Wf/W materials can facilitate a promising pseudo-ductile behavior even at room temperature, similar to fiber reinforced ceramic composites. Fracture energy density and fracture toughness together with the crack-resistance curves (R-curves) are measured. Compared to conventional pure tungsten, Wf/W shows significant improvement in fracture toughness. [ABSTRACT FROM AUTHOR]
Published: 2019
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38. Determination of the tolerable impurity concentrations in a fusion reactor using a consistent set of cooling factors.

Author: T. Pütterich, E. Fable, R. Dux, M. O’Mullane, R. Neu, and M. Siccinio
Subjects: FUSION reactors, INDUSTRIAL contamination, NUCLEAR reactor design & construction, NUCLEAR charge, SOFT X rays, PLASMA pressure
Abstract: In the present work, the tolerable impurity level and composition for a reactor plasma using several sets of model assumptions are evaluated. Special care was taken to evaluate a comprehensive and consistent set of atomic data for 35 different elements, such that the impurity level for various elements may be studied as a function of their nuclear charge. The data set may not only be useful for the presented work or for system codes which design fusion reactors, but also for interpretation of bolometric measurements. Additionally, the predictions of the spectral distribution of the radiated power is of high quality such that soft x-ray broadband measurements may be interpreted. In the present work the data is used for predicting the radiated power in a reactor plasma, using a 0D, several variants of a 0.5D model and a realistic 1D ASTRA modelling of a DEMO plasma, i.e. the EU DEMO1 2015 design. The maximal or appropriate impurity content of a reactor plasma for all models can be determined, such that the predictions from a simplistic 0D model can be compared to less simplistic models and a proper reactor simulation. These comparisons suggest that with the simplistic models the impurity content may be estimated within a factor of about 1.5, independent of the realization of the reactor plasma. At the same time this study underlines the sensitivity of the reactor performance on the impurity mixture and especially of the He content of the plasma. Additionally, an extended 0.5D model is presented which is able to predict variations of the fusion yield Q and the He concentration, when both is known for a reference scenario. These predictions prove to be of high accuracy when compared to the 1D ASTRA modelling and thus, allow the net impact of an increased dilution and a simlutaneous temperature rise at constant plasma pressure to be evaluated. Furthermore, the parameter space is scanned with more than 105 model reactor plasmas demonstrating that the use of a low-Z impurity diminishes the possibility of an economical feasible reactor plasma. The main results of the parameter scan are made available via scaling formulae. [ABSTRACT FROM AUTHOR]
Published: 2019
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39. Evolution of nitrogen concentration and ammonia production in N2-seeded H-mode discharges at ASDEX Upgrade.

Author: A. Drenik, L. Laguardia, R. McDermott, G. Meisl, R. Neu, M. Oberkofler, E. Pawelec, R.A. Pitts, S. Potzel, T. Pütterich, T. Reichbauer, V. Rohde, M. Seibt, G. De Temmerman, R. Zaplotnik, team, the ASDEX-Upgrade, and team, the EUROfusion MST1
Subjects: AMMONIA, NITROGEN
Abstract: Ammonia formation was studied in a series of dedicated nitrogen seeded H-mode discharges at ASDEX Upgrade. The evolution of ammonia formation was investigated with a reference phase before the seeding, and a long, stable flat-top nitrogen-seeded phase. It was monitored with divertor spectroscopy and analysis of the exhaust gas. The amount of the detected ammonia increased continuously over the course of five discharges with the same nitrogen seeding rate. The same trend was observed in the nitrogen density in the core plasma, as measured by charge exchange recombination spectroscopy and other signals, linked to the effects of nitrogen seeding. The results show that the rate of ammonia formation exhibited the same trend as the nitrogen density in the plasma. This density, in turn, was strongly influenced by the nitrogen wall inventory. The spatial distribution of the detected ammonia suggests that a significant contribution to the net ammonia formation is made in plasma-shaded areas, through surface reactions of neutral species. [ABSTRACT FROM AUTHOR]
Published: 2019
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40. Interaction of metal dust adhered on castellated substrates with the ELMy H-mode plasmas of ASDEX-Upgrade.

Author: S. Ratynskaia, P. Tolias, M. De Angeli, V. Rohde, A. Herrmann, D. Ripamonti, G. Riva, E. Thorén, L. Vignitchouk, B. Sieglin, K. Krieger, R. Neu, Team, The ASDEX-Upgrade, and Team, The EUROfusion MST1
Subjects: METAL dusting (Corrosion), CASTELLATED beams, H-mode plasma confinement, HEAT resistant alloys, FUSION reactor divertors, BERYLLIUM, HEAT transfer
Abstract: Castellated substrates with adhered micron dust have been exposed in the outer ASDEX-Upgrade divertor to ELMy H-mode discharges. Beryllium proxy (chromium, copper) and refractory metal (tungsten, molybdenum) dust has been deposited on the plasma-facing and plasma-shadowed sides of the monoblocks as well as the bottom of the gaps. Interaction with time-averaged transient heat loads up to 5 MW m−2 led to dust remobilization, clustering, melting and wetting-induced coagulation. The amount of dust released in the vessel has been quantified and remobilized dust trajectories inferred. Gaps can efficiently trap locally adhered dust, but dust detaching from adjacent monoblocks does not preferentially move inside the gaps implying that they do not constitute a dust accumulation site. Heat transfer simulations of melting events are also reported taking into account heat constriction due to the finite contact area and the presence of surface roughness. [ABSTRACT FROM AUTHOR]
Published: 2018
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41. Fracture behavior of random distributed short tungsten fiber-reinforced tungsten composites

Author: Ch. Linsmeier, Till Höschen, Yucheng Wu, Christoph Broeckmann, Alexis Terra, J. Almanstötter, H. Gietl, L. Raumann, S. Sistla, R. Neu, C. Chen, Yiran Mao, J. W. Coenen, J. Reiser, and Johann Riesch
Subjects: Nuclear and High Energy Physics, Materials science, Composite number, chemistry.chemical_element, 02 engineering and technology, Tungsten, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, chemistry, 0103 physical sciences, Fracture (geology), Fiber, Composite material, ddc:620, 0210 nano-technology
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42. DEMO divertor limitations during and in between ELMs

Author: G. Strohmayer, M. Wischmeier, A. Loarte, A. Kallenbach, Ronald Wenninger, D. C. McDonald, R. Neu, B. Sieglin, T. Eich, P. A. Schneider, Th. Pütterich, G. Federici, M. Bernert, C.G. Lowry, E. Fable, and F. Reimold
Subjects: Physics, Nuclear and High Energy Physics, Energy loss, Divertor, Nuclear engineering, Condensed Matter Physics, 7. Clean energy, Energy density, Maximum size, Boundary value problem, Atomic physics, Overheating (electricity), Order of magnitude, Power density
Abstract: Operation of DEMO in comparison to ITER will be significantly more demanding, as various additional limitations of physical and technical nature have to be respected. In particular a set of extremely restrictive boundary conditions on divertor operation during and in between ELMs will have to be respected. It is of high importance to describe these limitations in order to consider them as early as possible in the ongoing development of the DEMO concept design. This paper extrapolates the existing physics basis on power and particle exhaust to DEMO.In phases between ELMs or with mitigated ELMs surface overheating and W sputtering pose challenging boundary conditions. For attached divertor conditions at 90% total radiation fraction a peak power density of about 15 MW m−2 convected or radiated to the outer divertor is estimated. As this clearly exceeds the tolerable limit, some degree of divertor detachment is regarded as essential for the operation of DEMO. A loss of detachment with a peak power density of more than 30 MW m−2 cannot be tolerated for more than a second before the divertor would suffer from a destructive event. The combination of the limitations on the peak power flux density and W sputtering rate necessitates divertor temperatures less than 4 eV.For uncontrolled ELMs sizes in the order of 100 MJ are estimated. Results on ELM broadening from JET suggest that in DEMO an energy density limit of 0.5 MJ m−2 per ELM is exceeded by a factor of about 8 for a large range of relative ELM sizes. This highlights the necessity of a reactor-relevant ELM control technique for DEMO, which is capable of reducing the maximum size of the energy loss per ELM to the divertor by more than an order of magnitude without a strong reduction of confinement.
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43. Evolution of nitrogen concentration and ammonia production in N 2 -seeded H-mode discharges at ASDEX Upgrade

Author: S. Potzel, G. De Temmerman, R. M. McDermott, Aleksander Drenik, M. Seibt, M. Oberkofler, Rok Zaplotnik, T. Reichbauer, L. Laguardia, Ewa Pawelec, Th. Pütterich, R.A. Pitts, V. Rohde, R. Neu, Gerd Meisl, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team
Subjects: Nuclear and High Energy Physics, ammonia, ASDEX Upgrade, mass spectrometry, nitrogen seeding, plasma-surface interaction, residual gas analysis, Divertor, Analytical chemistry, Exhaust gas, chemistry.chemical_element, Condensed Matter Physics, 01 natural sciences, Nitrogen, 010305 fluids & plasmas, Ammonia production, Ammonia, chemistry.chemical_compound, chemistry, 0103 physical sciences, Seeding, 010306 general physics, Spectroscopy
Abstract: Ammonia formation was studied in a series of dedicated nitrogen seeded H-mode discharges at ASDEX Upgrade. The evolution of ammonia formation was investigated with a reference phase before the seeding, and a long, stable flat-top nitrogen-seeded phase. It was monitored with divertor spectroscopy and analysis of the exhaust gas. The amount of the detected ammonia increased continuously over the course of five discharges with the same nitrogen seeding rate. The same trend was observed in the nitrogen density in the core plasma, as measured by charge exchange recombination spectroscopy and other signals, linked to the effects of nitrogen seeding. The results show that the rate of ammonia formation exhibited the same trend as the nitrogen density in the plasma. This density, in turn, was strongly influenced by the nitrogen wall inventory. The spatial distribution of the detected ammonia suggests that a significant contribution to the net ammonia formation is made in plasma-shaded areas, through surface reactions of neutral species.
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44. Numerical analyses of baseline JT-60SA design concepts with the COREDIV code.

Author: R. Zagórski, K. Gałązka, I. Ivanova-Stanik, W. Stępniewski, L. Garzotti, G. Giruzzi, R. Neu, and M. Romanelli
Subjects: NUMERICAL analysis, NUCLEAR fusion, FUSION reactor divertors, DENSITY, SIMULATION methods & models
Abstract: JT-60SA reference design scenarios at high (#3) and low (#2) density have been analyzed with the help of the self-consistent COREDIV code. Simulations results for a standard C wall and full W wall have been compared in terms of the influence of impurities, both intrinsic (C, W) and seeded (N, Ar, Ne, Kr), on the radiation losses and plasma parameters. For scenario #3 in a C environment, the regime of detachment on divertor plates can be achieved with N or Ne seeding, whereas for the low density and high power scenario (#2), the C and seeding impurity radiation does not effectively reduce power to the targets. In this case, only an increase of either average density or edge density together with Kr seeding might help to develop conditions with strong radiation losses and semi-detached conditions in the divertor. The calculations show that, in the case of a W divertor, the power load to the plate is mitigated by seeding and the central plasma dilution is smaller compared to the C divertor. For the high density case (#3) with Ne seeding, operation in full detachment mode is predicted. Ar seems to be an optimal choice for the low-density high-power scenario #2, showing a wide operating window, whereas Ne leads to high plasma dilution at high seeding levels albeit not achieving semi-detached conditions in the divertor. [ABSTRACT FROM AUTHOR]
Published: 2017
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45. Video analysis of dust events in full-tungsten ASDEX Upgrade.

Author: F. Brochard, A. Shalpegin, S. Bardin, T. Lunt, V. Rohde, J.L. Briançon, G. Pautasso, C. Vorpahl, R. Neu, and Team, The ASDEX Upgrade
Subjects: DUSTY plasmas, TOKAMAKS, TUNGSTEN, PHYSICS experiments, ALGORITHMS, PLASMA flow
Abstract: Fast video data recorded during seven consecutive operation campaigns (2008–2012) in full-tungsten ASDEX Upgrade have been analyzed with an algorithm developed to automatically detect and track dust particles. A total of 2425 discharges have been analyzed, corresponding to 12 204 s of plasma operation. The analysis aimed at precisely identifying and sorting the discharge conditions responsible of the dust generation or remobilization. Dust rates are found to be significantly lower than in tokamaks with carbon PFCs. Significant dust events occur mostly during off-normal plasma phases such as disruptions and particularly those preceded by vertical displacement events (VDEs). Dust rates are also increased but to a lower extent during type-I ELMy H-modes. The influences of disruption energy, heating scenario, vessel venting and vessel vibrations are also presented. [ABSTRACT FROM AUTHOR]
Published: 2017
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46. Impact of lithium pellets on plasma performance in the ASDEX Upgrade all-metal-wall tokamak.

Author: P.T. Lang, R. Maingi, D.K. Mansfield, R.M. McDermott, R. Neu, E. Wolfrum, R. Arredondo Parra, M. Bernert, G. Birkenmeier, A. Diallo, M. Dunne, E. Fable, R. Fischer, B. Geiger, A. Hakola, V. Nikolaeva, A. Kappatou, F. Laggner, M. Oberkofler, and B. Ploeckl
Subjects: LITHIUM, PLASMA gases, TOKAMAKS, TUNGSTEN, FUSION reactors
Abstract: The impact of lithium (Li) on plasma performance was investigated at the ASDEX Upgrade tokamak, which features a full tungsten wall. Li pellets containing 1.6 × 1020 Li atoms were launched with a speed of 600 m s−1 to achieve deep penetration into the plasma and minimize the impact on the first wall. Homogeneous transient Li concentrations in the plasma of up to 15% were established. The Li sustainment time in the plasma decreased with an increasing heating power from 150 to 40 ms. Due to the pellet rate being restricted to 2 Hz, no Li pile-up could take place. No significant positive impact on plasma properties, as reported from other tokamak devices, could be found; the Li pellets rather caused a small reduction in plasma energy, mainly due to enhanced radiation. Due to pellet injection, a short-lived Li layer was formed on the plasma-facing components, which lasted a few discharges and led to moderately beneficial effects during plasma start-up. Most pellets were found to trigger type-I ELMs, either by their direct local perturbation or indirectly by the altered edge conditions; however, reliability was less than 100%. [ABSTRACT FROM AUTHOR]
Published: 2017
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47. First results with 3-strap ICRF antennas in ASDEX Upgrade.

Author: V. Bobkov, F. Braun, R. Dux, A. Herrmann, H. Faugel, H. Fünfgelder, A. Kallenbach, R. Neu, J.-M. Noterdaeme, R. Ochoukov, Th. Pütterich, A. Tuccilo, O. Tudisco, Y. Wang, Q. Yang, and team, ASDEX Upgrade
Subjects: ANTENNAS (Electronics), FUSION reactor divertors, TOKAMAKS, TUNGSTEN, LIMITER circuits, BORON
Abstract: The 3-strap antennas in ASDEX Upgrade allow ICRF operation with low tungsten (W) content in the confined plasma with W-coated antenna limiters. With the 3-strap antenna configuration, the local W impurity source at the antenna is drastically reduced and the core W concentration is similar to that of the boron coated 2-strap antenna at a given ICRF power. Operation of the 3-strap antennas with the power ratio between the central and the outer straps of and is adopted to minimize the ICRF-specific W release. [ABSTRACT FROM AUTHOR]
Published: 2016
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48. Effect of nitrogen seeding on the energy losses and on the time scales of the electron temperature and density collapse of type-I ELMs in JET with the ITER-like wall.

Author: L. Frassinetti, C. Perez von Thun, Contributors, JET-EFDA, D. Dodt, J.E. Boom, T. Eich, M.N.A. Beurskens, A. Sirinelli, J. Flanagan, M.S. Jachmich, P. Lomas, B. Sieglin, R. Neu, C. Giroud, C. Maggi, M. Kempenaars, G. Maddison, M. Stamp, and I. Nunes
Subjects: PARTICLE range (Nuclear physics), LOCALIZED modes, ELECTRON temperature measurement
Abstract: The baseline type-I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called the ITER-like wall, JET-ILW).The first JET-ILW results show that the confinement is degraded by 20–30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained to date in JET-ILW baseline plasmas only in the high triangularity shape using N2 seeding.This work compares the energy losses during ELMs and the corresponding time scales of the temperature and density collapse in JET-ILW baseline plasmas with and without N2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, is ∼2 ms in the JET-ILW and lower than 1 ms in the JET-C. The energy losses are in the range ΔWELM/Wped ≈ 7–12% in the JET-ILW and ΔWELM/Wped ≈ 10–20% in JET-C, and fit relatively well with earlier multi-machine empirical scalings of ΔWELM/Wped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. Most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale ∼8–10 ms (hereafter called slow transport events), that can lead to losses in the range ΔWslow/Wped ≈ 15–22%, slightly larger than the losses in JET-C. The N2 seeding in JET-ILW significantly affects the ELMs. The JET-ILW plasmas with N2 seeding are characterized by ELM energy losses and time scales similar to the JET-C and by the absence of the slow transport events. [ABSTRACT FROM AUTHOR]
Published: 2015
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49. The H-mode pedestal structure and its role on confinement in JET with a carbon and metal wall.

Author: M.J. Leyland, M.N.A. Beurskens, L. Frassinetti, C. Giroud, S. Saarelma, P.B. Snyder, J. Flanagan, S. Jachmich, M. Kempenaars, P. Lomas, G. Maddison, R. Neu, I. Nunes, and K.J. Gibson
Subjects: THOMSON scattering, H-mode plasma confinement, PARTICLES (Nuclear physics), PLASMA stability, PLASMA physics
Abstract: We present the pedestal structure, as determined from the high-resolution Thomson scattering measurements, for a database of low and high triangularity (δ ≈ 0.22–0.39) 2.5 MA, type I ELMy H-mode JET plasmas after the installation of the new ITER-like wall (JET-ILW). The database explores the effect of increasing deuterium fuelling and nitrogen seeding with a view to explain the observed changes in performance (edge and global). The low triangularity JET-ILW plasmas show no significant change in performance and pedestal structure with increasing gas dosing. These results are in good agreement with EPED1 predictions. At high triangularity, for pure deuterium fuelled JET-ILW plasmas, there is a 20–30% reduction in global performance and pressure pedestal height in comparison to JET-C plasmas. This reduction in performance is primarily due to a degradation of the temperature pedestal height. The global performance and pressure pedestal height of JET-ILW plasmas can be partially recovered to that of JET-C plasmas with additional nitrogen seeding (Giroud et al 2013 Nucl. Fusion53 113025). This observed improvement in performance is predominately due to a significant increase in density pedestal height as well as a small increase in the temperature pedestal height. A key result with increasing deuterium fuelling for JET-ILW plasmas is there is no improvement in pressure pedestal height however the pedestal still widens which is inconsistent with the scaling. Furthermore, a key result with increasing nitrogen seeding is the pressure pedestal widening is due to an increase in the temperature pedestal width whilst the density pedestal shows no clear trend. The comparison of EPED1 predictions with the measurements at high triangularity is complex as, for example, for pure deuterium fuelled plasmas there is very good agreement for the pedestal height but not the width. In addition, current EPED1 runs under-predict the pedestal height and width at high nitrogen seeding for JET-ILW plasmas however further work is required to determine the significance of these deviations. Understanding these deviations is essential as provides an insight to the physical mechanisms governing the pedestal structure and edge performance. [ABSTRACT FROM AUTHOR]
Published: 2015
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50. DEMO divertor limitations during and in between ELMs.

Author: R.P. Wenninger, M. Bernert, T. Eich, E. Fable, G. Federici, A. Kallenbach, A. Loarte, C. Lowry, D. McDonald, R. Neu, T. Pütterich, P. Schneider, B. Sieglin, G. Strohmayer, F. Reimold, and M. Wischmeier
Subjects: LONG distance telephone service, SPIRAL antennas, FLUCTUATIONS (Physics), TOKAMAKS -- Design & construction, BOUNDARY value problems
Abstract: Operation of DEMO in comparison to ITER will be significantly more demanding, as various additional limitations of physical and technical nature have to be respected. In particular a set of extremely restrictive boundary conditions on divertor operation during and in between ELMs will have to be respected. It is of high importance to describe these limitations in order to consider them as early as possible in the ongoing development of the DEMO concept design. This paper extrapolates the existing physics basis on power and particle exhaust to DEMO.In phases between ELMs or with mitigated ELMs surface overheating and W sputtering pose challenging boundary conditions. For attached divertor conditions at 90% total radiation fraction a peak power density of about 15 MW m−2 convected or radiated to the outer divertor is estimated. As this clearly exceeds the tolerable limit, some degree of divertor detachment is regarded as essential for the operation of DEMO. A loss of detachment with a peak power density of more than 30 MW m−2 cannot be tolerated for more than a second before the divertor would suffer from a destructive event. The combination of the limitations on the peak power flux density and W sputtering rate necessitates divertor temperatures less than 4 eV.For uncontrolled ELMs sizes in the order of 100 MJ are estimated. Results on ELM broadening from JET suggest that in DEMO an energy density limit of 0.5 MJ m−2 per ELM is exceeded by a factor of about 8 for a large range of relative ELM sizes. This highlights the necessity of a reactor-relevant ELM control technique for DEMO, which is capable of reducing the maximum size of the energy loss per ELM to the divertor by more than an order of magnitude without a strong reduction of confinement. [ABSTRACT FROM AUTHOR]
Published: 2014
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