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1. Effect of local wall clearance on scrape-off layer electron density profiles in ASDEX Upgrade

Author

B. Tal, E. Wolfrum, M. Bernert, G. Birkenmeier, D. Brida, R. Fischer, G. Grenfell, M. Griener, O. Grover, J. Hobirk, B. Kurzan, T. Lunt, P.A. Schneider, N. Vianello, D. Wendler, the ASDEX Upgrade Team, and the EUROfusion Tokamak Exploitation Team

Subjects
wall clearance, scrape-off layer, recycling, density profiles, plasma edge, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The plasma electron density is measured with multiple diagnostics in the scrape-off layer of the ASDEX Upgrade tokamak. The recorded values are typically in good agreement in the case of exponentially decaying profiles at low densities, but they become inconsistent as soon as a density shoulder is formed, and up to a factor of 3 deviation is experienced at high densities. An idea is put forward; namely, that the local plasma-wall proximity has an influence on the local density and thus the measurement results depend on the local limiter-plasma and limiter-diagnostic distances at the same time. The effect of local wall clearance dependence is demonstrated by creating a plasma having an extremely high scrape-off layer density $\left(n_\mathrm{e} \gt 3\cdot10^{19}\,\textrm{m}^{-3}\right)$ after the H-L back transition and varying the position of the separatrix in different directions. As a possible physical process, neutral recycling at the plasma facing components is identified. Similar behaviour is also observed in the QCE regime, where the appearance of small ELMs barely impacts the scrape-off layer profiles. There are also indications that the local wall clearance does have an impact on the density profile not only in the scrape-off layer, but also in the confined region.

Published
2024
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2. 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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3. Overview of the EUROfusion Tokamak Exploitation programme in support of ITER and DEMO

Author

E. Joffrin, M. Wischmeier, M. Baruzzo, A. Hakola, A. Kappatou, D. Keeling, B. Labit, E. Tsitrone, N. Vianello, the ASDEX Upgrade Team, JET Contributors, the MAST-U Team, the TCV Team, the WEST Team, the EUROfusion Tokamak Exploitation Team:, D. Abate, J. Adamek, M. Agostini, C. Albert, F.C.P. Albert Devasagayam, S. Aleiferis, E. Alessi, J. Alhage, S. Allan, J. Allcock, M. Alonzo, G. Anastasiou, E. Andersson Sunden, C. Angioni, Y. Anquetin, L. Appel, G.M. Apruzzese, M. Ariola, C. Arnas, J.F. Artaud, W. Arter, O. Asztalos, L. Aucone, M.H. Aumeunier, F. Auriemma, J. Ayllon, E. Aymerich, A. Baciero, F. Bagnato, L. Bähner, F. Bairaktaris, P. Balázs, L. Balbinot, I. Balboa, M. Balden, A. Balestri, M. Baquero Ruiz, T. Barberis, C. Barcellona, O. Bardsley, S. Benkadda, T. Bensadon, E. Bernard, M. Bernert, H. Betar, R. Bianchetti Morales, J. Bielecki, R. Bilato, P. Bilkova, W. Bin, G. Birkenmeier, R. Bisson, P. Blanchard, A. Bleasdale, V. Bobkov, A. Boboc, A. Bock, K. Bogar, P. Bohm, T. Bolzonella, F. Bombarda, N. Bonanomi, L. Boncagni, D. Bonfiglio, R. Bonifetto, M. Bonotto, D. Borodin, I. Borodkina, T.O.S.J. Bosman, C. Bourdelle, C. Bowman, S. Brezinsek, D. Brida, F. Brochard, R. Brunet, D. Brunetti, V. Bruno, R. Buchholz, J. Buermans, H. Bufferand, P. Buratti, A. Burckhart, J. Cai, R. Calado, J. Caloud, S. Cancelli, F. Cani, B. Cannas, M. Cappelli, S. Carcangiu, A. Cardinali, S. Carli, D. Carnevale, M. Carole, M. Carpita, D. Carralero, F. Caruggi, I.S. Carvalho, I. Casiraghi, A. Casolari, F.J. Casson, C. Castaldo, A. Cathey, F. Causa, J. Cavalier, M. Cavedon, J. Cazabonne, M. Cecconello, L. Ceelen, A. Celora, J. Cerovsky, C.D. Challis, R. Chandra, A. Chankin, B. Chapman, H. Chen, M. Chernyshova, A.G. Chiariello, P. Chmielewski, A. Chomiczewska, C. Cianfarani, G. Ciraolo, J. Citrin, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, I.H. Coffey, C. Colandrea, L. Colas, S. Conroy, C. Contre, N.J. Conway, L. Cordaro, Y. Corre, D. Costa, S. Costea, D. Coster, X. Courtois, C. Cowley, T. Craciunescu, G. Croci, A.M. Croitoru, K. Crombe, D.J. Cruz Zabala, G. Cseh, T. Czarski, A. Da Ros, A. Dal Molin, M. Dalla Rosa, Y. Damizia, O. D’Arcangelo, P. David, M. De Angeli, E. De la Cal, E. De La Luna, G. De Tommasi, J. Decker, R. Dejarnac, D. Del Sarto, G. Derks, C. Desgranges, P. Devynck, S. Di Genova, L.E. di Grazia, A. Di Siena, M. Dicorato, M. Diez, M. Dimitrova, T. Dittmar, L. Dittrich, J.J. Domínguez Palacios Durán, P. Donnel, D. Douai, S. Dowson, S. Doyle, M. Dreval, P. Drews, L. Dubus, R. Dumont, D. Dunai, M. Dunne, A. Durif, F. Durodie, G. Durr Legoupil Nicoud, B. Duval, R. Dux, T. Eich, A. Ekedahl, S. Elmore, G. Ericsson, J. Eriksson, B. Eriksson, F. Eriksson, S. Ertmer, A. Escarguel, B. Esposito, T. Estrada, E. Fable, M. Faitsch, N. Fakhrayi Mofrad, A. Fanni, T. Farley, M. Farník, N. Fedorczak, F. Felici, X. Feng, J. Ferreira, D. Ferreira, N. Ferron, O. Fevrier, O. Ficker, A.R. Field, A. Figueiredo, N. Fil, D. Fiorucci, M. Firdaouss, R. Fischer, M. Fitzgerald, M. Flebbe, M. Fontana, J. Fontdecaba Climent, A. Frank, E. Fransson, L. Frassinetti, D. Frigione, S. Futatani, R. Futtersack, S. Gabriellini, D. Gadariya, D. Galassi, K. Galazka, J. Galdon, S. Galeani, D. Gallart, A. Gallo, C. Galperti, M. Gambrioli, S. Garavaglia, J. Garcia, M. Garcia Munoz, J. Gardarein, L. Garzotti, J. Gaspar, R. Gatto, P. Gaudio, M. Gelfusa, J. Gerardin, S.N. Gerasimov, R. Gerru Miguelanez, G. Gervasini, Z. Ghani, F.M. Ghezzi, G. Ghillardi, L. Giannone, S. Gibson, L. Gil, A. Gillgren, E. Giovannozzi, C. Giroud, G. Giruzzi, T. Gleiter, M. Gobbin, V. Goloborodko, A. González Ganzábal, T. Goodman, V. Gopakumar, G. Gorini, T. Görler, S. Gorno, G. Granucci, D. Greenhouse, G. Grenfell, M. Griener, W. Gromelski, M. Groth, O. Grover, M. Gruca, A. Gude, C. Guillemaut, R. Guirlet, J. Gunn, T. Gyergyek, L. Hagg, J. Hall, C.J. Ham, M. Hamed, T. Happel, G. Harrer, J. Harrison, D. Harting, N.C. Hawkes, P. Heinrich, S. Henderson, P. Hennequin, R. Henriques, S. Heuraux, J. Hidalgo Salaverri, J. Hillairet, J.C. Hillesheim, A. Hjalmarsson, A. Ho, J. Hobirk, E. Hodille, M. Hölzl, M. Hoppe, J. Horacek, N. Horsten, L. Horvath, M. Houry, K. Hromasova, J. Huang, Z. Huang, A. Huber, E. Huett, P. Huynh, A. Iantchenko, M. Imrisek, P. Innocente, C. Ionita Schrittwieser, H. Isliker, P. Ivanova, I. Ivanova Stanik, M. Jablczynska, S. Jachmich, A.S. Jacobsen, P. Jacquet, A. Jansen van Vuuren, A. Jardin, H. Järleblad, A. Järvinen, F. Jaulmes, T. Jensen, I. Jepu, S. Jessica, T. Johnson, A. Juven, J. Kalis, J. Karhunen, R. Karimov, A.N. Karpushov, S. Kasilov, Y. Kazakov, P.V. Kazantzidis, W. Kernbichler, HT. Kim, D.B. King, V.G. Kiptily, A. Kirjasuo, K.K. Kirov, A. Kirschner, A. Kit, T. Kiviniemi, F. Kjær, E. Klinkby, A. Knieps, U. Knoche, M. Kochan, F. Köchl, G. Kocsis, J.T.W. Koenders, L. Kogan, Y. Kolesnichenko, Y. Kominis, M. Komm, M. Kong, B. Kool, S.B. Korsholm, D. Kos, M. Koubiti, J. Kovacic, Y. Kovtun, E. Kowalska Strzeciwilk, K. Koziol, M. Kozulia, A. Krämer Flecken, A. Kreter, K. Krieger, U. Kruezi, O. Krutkin, O. Kudlacek, U. Kumar, H. Kumpulainen, M.H. Kushoro, R. Kwiatkowski, M. La Matina, M. Lacquaniti, L. Laguardia, P. Lainer, P. Lang, M. Larsen, E. Laszynska, K.D. Lawson, A. Lazaros, E. Lazzaro, M.Y.K. Lee, S. Leerink, M. Lehnen, M. Lennholm, E. Lerche, Y. Liang, A. Lier, J. Likonen, O. Linder, B. Lipschultz, A. Listopad, X. Litaudon, E. Litherland Smith, D. Liuzza, T. Loarer, P.J. Lomas, J. Lombardo, N. Lonigro, R. Lorenzini, C. Lowry, T. Luda di Cortemiglia, A. Ludvig Osipov, T. Lunt, V. Lutsenko, E. Macusova, R. Mäenpää, P. Maget, C.F. Maggi, J. Mailloux, S. Makarov, K. Malinowski, P. Manas, A. Mancini, D. Mancini, P. Mantica, M. Mantsinen, J. Manyer, M. Maraschek, G. Marceca, G. Marcer, C. Marchetto, S. Marchioni, A. Mariani, M. Marin, M. Markl, T. Markovic, D. Marocco, S. Marsden, L. Martellucci, P. Martin, C. Martin, F. Martinelli, L. Martinelli, J.R. Martin Solis, R. Martone, M. Maslov, R. Masocco, M. Mattei, G.F. Matthews, D. Matveev, E. Matveeva, M.L. Mayoral, D. Mazon, S. Mazzi, C. Mazzotta, G. McArdle, R. McDermott, K. McKay, A.G. Meigs, C. Meineri, A. Mele, V. Menkovski, S. Menmuir, A. Merle, H. Meyer, K. Mikszuta Michalik, D. Milanesio, F. Militello, A. Milocco, I.G. Miron, J. Mitchell, R. Mitteau, V. Mitterauer, J. Mlynar, V. Moiseenko, P. Molna, F. Mombelli, C. Monti, A. Montisci, J. Morales, P. Moreau, J.M. Moret, A. Moro, D. Moulton, P. Mulholland, M. Muraglia, A. Murari, A. Muraro, P. Muscente, D. Mykytchuk, F. Nabais, Y. Nakeva, F. Napoli, E. Nardon, M.F. Nave, R.D. Nem, A. Nielsen, S.K. Nielsen, M. Nocente, R. Nouailletas, S. Nowak, H. Nyström, R. Ochoukov, N. Offeddu, S. Olasz, C. Olde, F. Oliva, D. Oliveira, H.J.C. Oliver, P. Ollus, J. Ongena, F.P. Orsitto, N. Osborne, R. Otin, P. Oyola Dominguez, D.I. Palade, S. Palomba, O. Pan, N. Panadero, E. Panontin, A. Papadopoulos, P. Papagiannis, G. Papp, V.V. Parail, C. Pardanaud, J. Parisi, A. Parrott, K. Paschalidis, M. Passoni, F. Pastore, A. Patel, B. Patel, A. Pau, G. Pautasso, R. Pavlichenko, E. Pawelec, B. Pegourie, G. Pelka, E. Peluso, A. Perek, E. Perelli Cippo, C. Perez Von Thun, P. Petersson, G. Petravich, Y. Peysson, V. Piergotti, L. Pigatto, C. Piron, L. Piron, A. Pironti, F. Pisano, U. Plank, B. Ploeckl, V. Plyusnin, A. Podolnik, Y. Poels, G. Pokol, J. Poley, G. Por, M. Poradzinski, F. Porcelli, L. Porte, C. Possieri, A. Poulsen, I. Predebon, G. Pucella, M. Pueschel, P. Puglia, O. Putignano, T. Pütterich, V. Quadri, A. Quercia, M. Rabinski, L. Radovanovic, R. Ragona, H. Raj, M. Rasinski, J. Rasmussen, G. Ratta, S. Ratynskaia, R. Rayaprolu, M. Rebai, A. Redl, D. Rees, D. Refy, M. Reich, H. Reimerdes, B.C.G. Reman, O. Renders, C. Reux, D. Ricci, M. Richou, S. Rienacker, D. Rigamonti, F. Rigollet, F.G. Rimini, D. Ripamonti, N. Rispoli, N. Rivals, J.F. Rivero Rodriguez, C. Roach, G. Rocchi, S. Rode, P. Rodrigues, J. Romazanov, C.F. Romero Madrid, J. Rosato, R. Rossi, G. Rubino, J. Rueda Rueda, J. Ruiz Ruiz, P. Ryan, D. Ryan, S. Saarelma, R. Sabot, M. Salewski, A. Salmi, L. Sanchis, A. Sand, J. Santos, K. Särkimäki, M. Sassano, O. Sauter, G. Schettini, S. Schmuck, P. Schneider, N. Schoonheere, R. Schramm, R. Schrittwieser, C. Schuster, N. Schwarz, F. Sciortino, M. Scotto D’Abusco, S. Scully, A. Selce, L. Senni, M. Senstius, G. Sergienko, S.E. Sharapov, R. Sharma, A. Shaw, U. Sheikh, G. Sias, B. Sieglin, S.A. Silburn, C. Silva, A. Silva, D. Silvagni, B. Simmendefeldt Schmidt, L. Simons, J. Simpson, L. Singh, S. Sipilä, Y. Siusko, S. Smith, A. Snicker, E.R. Solano, V. Solokha, M. Sos, C. Sozzi, F. Spineanu, G. Spizzo, M. Spolaore, L. Spolladore, C. Srinivasan, A. Stagni, Z. Stancar, G. Stankunas, J. Stober, P. Strand, C.I. Stuart, F. Subba, G.Y. Sun, H.J. Sun, W. Suttrop, J. Svoboda, T. Szepesi, G. Szepesi, B. Tal, T. Tala, P. Tamain, G. Tardini, M. Tardocchi, D. Taylor, G. Telesca, A. Tenaglia, A. Terra, D. Terranova, D. Testa, C. Theiler, E. Tholerus, B. Thomas, E. Thoren, A. Thornton, A. Thrysoe, Q. TICHIT, W. Tierens, A. Titarenko, P. Tolias, E. Tomasina, M. Tomes, E. Tonello, A. Tookey, M. Toscano Jiménez, C. Tsironis, C. Tsui, A. Tykhyy, M. Ugoletti, M. Usoltseva, D.F. Valcarcel, A. Valentini, M. Valisa, M. Vallar, M. Valovic, SI. Valvis, M. van Berkel, D. Van Eester, S. Van Mulders, M. van Rossem, R. Vann, B. Vanovac, J. Varela Rodriguez, J. Varje, S. Vartanian, M. Vecsei, L. Velarde Gallardo, M. Veranda, T. Verdier, G. Verdoolaege, K. Verhaegh, L. Vermare, G. Verona Rinati, J. Vicente, E. Viezzer, L. Vignitchouk, F. Villone, B. Vincent, P. Vincenzi, M.O. Vlad, G. Vogel, I. Voitsekhovitch, I. Voldiner, P. Vondracek, N.M.T. VU, T. Vuoriheimo, C. Wade, E. Wang, T. Wauters, M. Weiland, H. Weisen, N. Wendler, D. Weston, A. Widdowson, S. Wiesen, M. Wiesenberger, T. Wijkamp, M. Willensdorfer, T. Wilson, A. Wojenski, C. Wuethrich, I. Wyss, L. Xiang, S. Xu, D. Yadykin, Y. Yakovenko, H. Yang, V. Yanovskiy, R. Yi, B. Zaar, G. Zadvitskiy, L. Zakharov, P. Zanca, D. Zarzoso, Y. Zayachuk, J. Zebrowski, M. Zerbini, P. Zestanakis, C. F. B. Zimmermann, M. Zlobinski, A. Zohar, V.K. Zotta, X. Zou, M. Zuin, M. Zurita, and I. Zychor

Subjects
JET, ASDEX Upgrade, MAST-U, TCV, WEST, Tokamak Exploitation Task Force, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Within the 9th European Framework programme, since 2021 EUROfusion is operating five tokamaks under the auspices of a single Task Force called ‘Tokamak Exploitation’. The goal is to benefit from the complementary capabilities of each machine in a coordinated way and help in developing a scientific output scalable to future largre machines. The programme of this Task Force ensures that ASDEX Upgrade, MAST-U, TCV, WEST and JET (since 2022) work together to achieve the objectives of Missions 1 and 2 of the EUROfusion Roadmap: i) demonstrate plasma scenarios that increase the success margin of ITER and satisfy the requirements of DEMO and, ii) demonstrate an integrated approach that can handle the large power leaving ITER and DEMO plasmas. The Tokamak Exploitation task force has therefore organized experiments on these two missions with the goal to strengthen the physics and operational basis for the ITER baseline scenario and for exploiting the recent plasma exhaust enhancements in all four devices (PEX: Plasma EXhaust) for exploring the solution for handling heat and particle exhaust in ITER and develop the conceptual solutions for DEMO. The ITER Baseline scenario has been developed in a similar way in ASDEX Upgrade, TCV and JET. Key risks for ITER such as disruptions and run-aways have been also investigated in TCV, ASDEX Upgrade and JET. Experiments have explored successfully different divertor configurations (standard, super-X, snowflakes) in MAST-U and TCV and studied tungsten melting in WEST and ASDEX Upgrade. The input from the smaller devices to JET has also been proven successful to set-up novel control schemes on disruption avoidance and detachment.

Published
2024
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4. 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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5. 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. Chira, P. Chmielewski, A. Chomiczewska, L. Chone, J. Cieslik, G. Ciraolo, D. Ciric, J. Citrin, Ł. Ciupinski, R. Clarkson, M. Cleverly, P. Coates, V. Coccorese, R. Coelho, J.W. Coenen, I.H. Coffey, A. Colangeli, L. Colas, J. Collins, S. Conroy, C. Contré, N.J. Conway, D. Coombs, P. Cooper, S. Cooper, L. Cordaro, C. Corradino, Y. Corre, G. Corrigan, D. Coster, T. Craciunescu, S. Cramp, D. Craven, R. Craven, G. Croci, D. Croft, K. Crombé, T. Cronin, N. Cruz, A. Cufar, A. Cullen, A. Dal Molin, S. Dalley, P. David, A. Davies, J. Davies, S. Davies, G. Davis, K. Dawson, S. Dawson, I. Day, G. De Tommasi, J. Deane, M. Dearing, M. De Bock, J. Decker, R. Dejarnac, E. Delabie, E. de la Cal, E. de la Luna, D. Del Sarto, A. Dempsey, W. Deng, A. Dennett, G.L. Derks, G. De Temmerman, F. Devasagayam, P. de Vries, P. Devynck, A. di Siena, D. Dickinson, T. Dickson, M. Diez, P. Dinca, T. Dittmar, L. Dittrich, J. Dobrashian, T. Dochnal, A.J.H. Donné, W. Dorland, S. Dorling, S. Dormido-Canto, R. Dotse, D. Douai, S. Dowson, R. Doyle, M. Dreval, P. Drews, G. Drummond, Ph. Duckworth, H.G. Dudding, R. Dumont, P. Dumortier, D. Dunai, T. Dunatov, M. Dunne, I. Ďuran, F. Durodié, R. Dux, T. Eade, E. Eardley, J. Edwards, T. Eich, A. Eksaeva, H. El-Haroun, R.D. Ellis, G. Ellwood, C. Elsmore, S. Emery, G. Ericsson, B. Eriksson, F. Eriksson, J. Eriksson, L.G. Eriksson, S. Ertmer, G. Evans, S. Evans, E. Fable, D. Fagan, M. Faitsch, D. Fajardo Jimenez, M. Falessi, A. Fanni, T. Farmer, I. Farquhar, B. Faugeras, S. Fazinić, N. Fedorczak, K. Felker, R. Felton, H. Fernandes, D.R. Ferreira, J. Ferreira, G. Ferrò, J. Fessey, O. Février, O. Ficker, A.R. Field, A. Figueiredo, J. Figueiredo, A. Fil, N. Fil, P. Finburg, U. Fischer, G. Fishpool, L. Fittill, M. Fitzgerald, D. Flammini, J. Flanagan, S. Foley, N. Fonnesu, M. Fontana, J.M. Fontdecaba, L. Fortuna, E. Fortuna-Zalesna, M. Fortune, C. Fowler, P. Fox, O. Franklin, E. Fransson, L. Frassinetti, R. Fresa, D. Frigione, T. Fülöp, M. Furseman, S. Gabriellini, D. Gadariya, S. Gadgil, K. Gál, S. Galeani, A. Galkowski, D. Gallart, M. Gambrioli, T. Gans, J. Garcia, M. García-Muñoz, L. Garzotti, J. Gaspar, R. Gatto, P. Gaudio, D. Gear, T. Gebhart, S. Gee, M. Gelfusa, R. George, S.N. Gerasimov, R. Gerru, G. Gervasini, M. Gethins, Z. Ghani, M. Gherendi, P.-I. Gherghina, F. Ghezzi, L. Giacomelli, C. Gibson, L. Gil, M.R. Gilbert, A. Gillgren, E. Giovannozzi, C. Giroud, G. Giruzzi, J. Goff, V. Goloborodko, R. Gomes, J.-F. Gomez, B. Gonçalves, M. Goniche, J. Gonzalez-Martin, A. Goodyear, S. Gore, G. Gorini, T. Görler, N. Gotts, E. Gow, J.P. Graves, J. Green, H. Greuner, E. Grigore, F. Griph, W. Gromelski, M. Groth, C. Grove, R. Grove, N. Gupta, S. Hacquin, L. Hägg, A. Hakola, M. Halitovs, J. Hall, C.J. Ham, M. Hamed, M.R. Hardman, Y. Haresawa, G. Harrer, J.R. Harrison, D. Harting, D.R. Hatch, T. Haupt, J. Hawes, N.C. Hawkes, J. Hawkins, S. Hazael, J. Hearmon, P. Heesterman, P. Heinrich, M. Held, W. Helou, O. Hemming, S.S. Henderson, R. Henriques, R.B. Henriques, D. Hepple, J. Herfindal, G. Hermon, J.C. Hillesheim, K. Hizanidis, A. Hjalmarsson, A. Ho, J. Hobirk, O. Hoenen, C. Hogben, A. Hollingsworth, S. Hollis, E. Hollmann, M. Hölzl, M. Hook, M. Hoppe, J. Horáček, N. Horsten, A. Horton, L.D. Horton, L. Horvath, S. Hotchin, Z. Hu, Z. Huang, E. Hubenov, A. Huber, V. Huber, T. Huddleston, G.T.A. Huijsmans, Y. Husain, P. Huynh, A. Hynes, D. Iglesias, M.V. Iliasova, M. Imríšek, J. Ingleby, P. Innocente, V. Ioannou-Sougleridis, N. Isernia, I. Ivanova-Stanik, E. Ivings, S. Jachmich, T. Jackson, A.S. Jacobsen, P. Jacquet, H. Järleblad, A. Järvinen, F. Jaulmes, N. Jayasekera, F. Jenko, I. Jepu, E. Joffrin, T. Johnson, J. Johnston, C. Jones, E. Jones, G. Jones, L. Jones, T.T.C. Jones, A. Joyce, M. Juvonen, A. Kallenbach, P. Kalnina, D. Kalupin, P. Kanth, A. Kantor, A. Kappatou, O. Kardaun, J. Karhunen, E. Karsakos, Ye.O. Kazakov, V. Kazantzidis, D.L. Keeling, W. Kelly, M. Kempenaars, D. Kennedy, K. Khan, E. Khilkevich, C. Kiefer, H.-T. Kim, J. Kim, S.H. Kim, D.B. King, D.J. Kinna, V.G. Kiptily, A. Kirjasuo, K.K. Kirov, A. Kirschner, T. Kiviniemi, G. Kizane, C. Klepper, A. Klix, G. Kneale, M. Knight, P. Knight, R. Knights, S. Knipe, U. Knoche, M. Knolker, M. Kocan, F. Köchl, G. Kocsis, J.T.W. Koenders, Y. Kolesnichenko, Y. Kominis, M. Kong, B. Kool, V. Korovin, S.B. Korsholm, B. Kos, D. Kos, M. Koubiti, Y. Kovtun, E. Kowalska-Strzęciwilk, K. Koziol, Y. Krasikov, A. Krasilnikov, V. Krasilnikov, M. Kresina, A. Kreter, K. Krieger, A. Krivska, U. Kruezi, I. Książek, H. Kumpulainen, B. Kurzan, S. Kwak, O.J. Kwon, B. Labit, M. Lacquaniti, A. Lagoyannis, L. Laguardia, A. Laing, V. Laksharam, N. Lam, H.T. Lambertz, B. Lane, M. Langley, E. Lascas Neto, E. Łaszyńska, K.D. Lawson, A. Lazaros, E. Lazzaro, G. Learoyd, C. Lee, K. Lee, S. Leerink, T. Leeson, X. Lefebvre, H.J. Leggate, J. Lehmann, M. Lehnen, D. Leichtle, F. Leipold, I. Lengar, M. Lennholm, E. Leon Gutierrez, L.A. Leppin, E. Lerche, A. Lescinskis, S. Lesnoj, L. Lewin, J. Lewis, J. Likonen, Ch. Linsmeier, X. Litaudon, E. Litherland-Smith, F. Liu, T. Loarer, A. Loarte, R. Lobel, B. Lomanowski, P.J. Lomas, J. Lombardo, R. Lorenzini, S. Loreti, V.P. Loschiavo, M. Loughlin, T. Lowe, C. Lowry, T. Luce, R. Lucock, T. Luda Di Cortemiglia, M. Lungaroni, C.P. Lungu, T. Lunt, V. Lutsenko, B. Lyons, J. Macdonald, E. Macusova, R. Mäenpää, H. Maier, J. Mailloux, S. Makarov, P. Manas, A. Manning, P. Mantica, M.J. Mantsinen, J. Manyer, A. Manzanares, Ph. Maquet, M. Maraschek, G. Marceca, G. Marcer, C. Marchetto, O. Marchuk, A. Mariani, G. Mariano, M. Marin, A. Marin Roldan, M. Marinelli, T. Markovič, L. Marot, C. Marren, S. Marsden, S. Marsen, J. Marsh, R. Marshall, L. Martellucci, A.J. Martin, C. Martin, R. Martone, S. Maruyama, M. Maslov, M. Mattei, G.F. Matthews, D. Matveev, E. Matveeva, A. Mauriya, F. Maviglia, M. Mayer, M.-L. Mayoral, S. Mazzi, C. Mazzotta, R. McAdams, P.J. McCarthy, P. McCullen, R. McDermott, D.C. McDonald, D. McGuckin, V. McKay, L. McNamee, A. McShee, D. Mederick, M. Medland, S. Medley, K. Meghani, A.G. Meigs, S. Meitner, S. Menmuir, K. Mergia, S. Mianowski, P. Middleton, J. Mietelski, K. Mikszuta-Michalik, D. Milanesio, E. Milani, E. Militello-Asp, F. Militello, J. Milnes, A. Milocco, S. Minucci, I. Miron, J. Mitchell, J. Mlynář, V. Moiseenko, P. Monaghan, I. Monakhov, A. Montisci, S. Moon, R. Mooney, S. Moradi, R.B. Morales, L. Morgan, F. Moro, J. Morris, T. Mrowetz, L. Msero, S. Munot, A. Muñoz-Perez, M. Muraglia, A. Murari, A. Muraro, B. N’Konga, Y.S. Na, F. Nabais, R. Naish, F. Napoli, E. Nardon, V. Naulin, M.F.F. Nave, R. Neu, S. Ng, M. Nicassio, D. Nicolai, A.H. Nielsen, S.K. Nielsen, D. Nina, C. Noble, C.R. Nobs, M. Nocente, H. Nordman, S. Nowak, H. Nyström, J. O’Callaghan, M. O’Mullane, C. O’Neill, C. Olde, H.J.C. Oliver, R. Olney, J. Ongena, G.P. Orsitto, A. Osipov, R. Otin, N. Pace, L.W. Packer, E. Pajuste, D. Palade, J. Palgrave, O. Pan, N. Panadero, T. Pandya, E. Panontin, A. 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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6. An extensive analysis of SOL properties in high-δ plasmas in ASDEX Upgrade

Author

A. Redl, T. Eich, N. Vianello, J. Adamek, M. Bernert, G. Birkenmeier, D. Brida, P. David, M. Faitsch, R. Fischer, G. Grenfell, R. Ochoukov, V. Rohde, B. Tal, M. Dreval, the ASDEX Upgrade Team, and the EUROfusion Tokamak Exploitation Team

Subjects
ASDEX Upgrade, power exhaust, QCE regime, filamentary transport, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

A set of dedicated H-mode discharges with constant heating power combining Neutral Beam Injection and Electron Cyclotron Resonance Heating have been executed at the ASDEX Upgrade tokamak using a high triangularity magnetic geometry in order to investigate the impact of filamentary transport to divertor and non-divertor components. The evolution of upstream scrape-off layer (SOL) profiles have been correlated with dedicated separatrix quantities, mostly with the turbulence control parameter $\alpha_{\mathrm{t}}$ (Eich and Manz 2021 Nucl. Fusion 61 086016) describing the turbulence level at the separatrix. With increasing $\alpha_{\mathrm{t}}$ , a broadening of the upstream density profiles in the near-SOL together with the formation of a density shoulder in the far-SOL have been observed. This phenomenon is associated with an enhanced filamentary transport dominating the radial turbulent transport in the far-SOL and confirmed by means of the cooling water calorimetry on non-divertor components. The probe measurements conducted with the ball-pen probe-head mounted on the midplane manipulator and a retarding-field analyzer close to the limiter surface indicate that the key mechanism increasing the radial filamentary transport to the first wall is an increase of the particle flux $\Gamma_\mathrm{r,fil}$ , caused primarily by the packing fraction $f_\mathrm{PF, fil}$ and the filament density $n_\mathrm{e,fil}$ . At the same time, the electron temperature $T_\mathrm{e}$ and ion temperature $T_\mathrm{i}$ measured close to the limiter surface show only small variations above $\alpha_\mathrm{t}$ > 0.5. Both the filamentary heat flux and the gross erosion derived from the first wall probe measurements reach a magnitude that should be considered in the design of future fusion reactors.

Published
2024
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7. L-H transition studies in tritium and deuterium–tritium campaigns at JET with Be wall and W divertor

Author

E.R. Solano, G. Birkenmeier, C. Silva, E. Delabie, J.C. Hillesheim, A. Baciero, I. Balboa, M. Baruzzo, A. Boboc, M. Brix, J. Bernardo, C. Bourdelle, I.S. Carvalho, P. Carvalho, C.D. Challis, M. Chernyshova, A. Chomiczewska, R. Coelho, I. Coffey, T. Craciunescu, E. de la Cal, E. de la Luna, R. Dumont, P. Dumortier, M. Fontana, J.M. Fontdecaba, L. Frassinetti, D. Gallart, J. Garcia, C. Giroud, W. Gromelski, R.B. Henriques, J. Hall, A. Ho, L.D. Horton, L. Horvath, P. Jacquet, I. Jepu, E. Joffrin, A. Kappatou, D.L. Keeling, D.B. King, V.G. Kiptily, K.K. Kirov, D. Kos, E. Kowalska-Strzęciwilk, M. Lennholm, E. Lerche, E. Litherland-Smith, A. Loarte, B. Lomanowski, P.J. Lomas, C.F. Maggi, J. Mailloux, M.J. Mantsinen, M. Maslov, A.G. Meigs, I. Monakhov, R.B. Morales, A.H. Nielsen, D. Nina, C. Noble, E. Pawelec, M. Poradzinski, G. Pucella, P. Puglia, D. Réfy, J. Juul Rasmussen, E. Righi, F.G. Rimini, T. Robinson, M. Sertoli, S.A. Silburn, G. Sips, P. Sirén, Ž. Štancar, H.J. Sun, G. Szepesi, D. Taylor, E. Tholerus, B. Thomas, G. Verdoolaege, P. Vincenzi, B. Viola, N. Vianello, T. Wilson, and JET Contributors

Subjects
L-H transition, power threshold, tokamaks, Tritium, DT, JET-ILW, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The recent deuterium–tritium campaign in JET-ILW (DTE2) has provided a unique opportunity to study the isotope dependence of the L-H power threshold in an ITER-like wall environment (Be wall and W divertor). Here we present results from dedicated L-H transition experiments at JET-ILW, documenting the power threshold in tritium and deuterium–tritium plasmas, comparing them with the matching deuterium and hydrogen datasets. From earlier experiments in JET-ILW it is known that as plasma isotopic composition changes from deuterium, through varying deuterium/hydrogen concentrations, to pure hydrogen, the value of the line averaged density at which the threshold is minimum, ${\bar n_{{\text{e}},{\text{min}}}}$ , increases, leading us to expect that ${\bar n_{{\text{e}},{\text{min}}}}$ (T) < ${\bar n_{{\text{e}},{\text{min}}}}$ (DT) < ${\bar n_{{\text{e}},{\text{min}}}}$ (D) < ${\bar n_{{\text{e}},{\text{min}}}}$ (H). The new power threshold data confirms these expectations in most cases, with the corresponding ordering of the minimum power thresholds. We present a comparison of this data to power threshold scalings, used for extrapolation to future devices such as ITER and DEMO.

Published
2023
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8. Experimental characterization of the quasi-coherent mode in EDA H-Mode and QCE scenarios at ASDEX Upgrade

Author

J. Kalis, G. Birkenmeier, P. Manz, T. Eich, M. Griener, R. Goti, M. Cavedon, L. Gil, M. Faitsch, L. Radovanovic, D. Wendler, E. Wolfrum, U. Stroth, the ASDEX Upgrade Team, and the EUROfusion MST1 Team

Subjects
fusion, plasma edge, plasma modes, EDA H-mode, quasi-continuous exhaust, quasi-coherent mode, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

The quasi-coherent mode (QCM), appearing in enhanced D $_{\alpha}$ high confinement mode (EDA H-mode) and quasi-continuous exhaust (QCE) plasmas has been analysed in detail at ASDEX Upgrade via thermal helium beam spectroscopy under various discharge parameters. In both scenarios the QCM appears to be localized close to the separatrix and to propagate in ion diamagnetic direction in the plasma frame. The poloidal wavenumber of the QCM is about $0.025 \lt k_{\theta}\rho_\mathrm{s} \lt 0.075$ and the radial wavenumber is $k_{\mathrm{r}}\approx {0}~\textrm{cm}^{-1}$ . It was found that the plasmas are generally below the ideal MHD limit at the separatrix. All the properties are consistent with ideal, resistive or kinetic ballooning modes. Simultaneous to the appearance of the QCM, higher harmonic modes can be observed in EDA H-modes, which are exclusively visible in magnetic pick-up coils and have toroidal mode numbers of up to n = 10. By performing a bicoherence analysis it was found that the higher harmonic modes and the QCM are coupling, but are disjoint phenomena. Qualitatively, the bandwidth of the QCM serves as a promising distinctive feature between QCE plasmas and EDA H-modes.

Published
2023
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9. Experimentally corroborated model of pressure relaxation limit cycle oscillations in the vicinity of the transition to high confinement in tokamaks

Author

O. Grover, P. Manz, A.Y. Yashin, D.I. Réfy, J. Seidl, N. Vianello, G. Birkenmeier, E.R. Solano, M. Sos, P. Bohm, P. Bilkova, M. Hron, R. Panek, the ASDEX Upgrade Team, the COMPASS Team, the Globus-M Team, and JET Contributors

Subjects
tokamak, limit cycle oscillations, turbulence, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

An analytical formula systematically predicts the observed frequency of pressure relaxation limit cycle oscillations in the vicinity of the transition to high confinement in four tokamaks (JET, ASDEX Upgrade, COMPASS, Globus-M). The experimental dataset spans the widest available range of frequencies, machine sizes and plasma ion species. The machine size dependence is explained by the connection length scale of plasma flows parallel to the magnetic field. The model also explains the observed up-down poloidal current asymmetry and the impact of the plasma ion species mass and charge.

Published
2023
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10. Turbulence characterization during the suppression of edge-localized modes by magnetic perturbations on ASDEX Upgrade

Author

N. Leuthold, W. Suttrop, M. Willensdorfer, G. Birkenmeier, D. Brida, M. Cavedon, M. Dunne, G.D. Conway, R. Fischer, L. Gil, T. Happel, P. Hennequin, A. Kappatou, A. Kirk, P. Manz, R.M. McDermott, J. Vicente, H. Zohm, the ASDEX Upgrade Team, and the EUROfusion MST1 Team

Subjects
edge-localized-mode, resonant magnetic perturbation, density pump-out, turbulent particle transport, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

We study localized edge turbulence in the ASDEX Upgrade tokamak that appears if resonant magnetic perturbations (RMP) are applied to suppress edge localized modes (ELMs) in the high confinement mode. The concomitant density fluctuations are detected by microwave reflectometry at the outboard midplane. Two modes can be distinguished, (a) a broadband fluctuation below a threshold of the RMP field amplitude, and (b) a narrow-band quasi-coherent mode (QCM) above the threshold. The broadband fluctuation is toroidally spread out but disappears at the toroidal position of maximum E × B shear in the gradient region. Temporal and spatial correlation along field lines of the midplane density fluctuation and the divertor particle flux suggests that this mode is producing significant particle transport across the gradient region and into the divertor, hence contributing to the plasma density reduction that is often observed when applying RMP fields (the so-called ‘pump-out’ effect). The QCM is also toroidally localized, its radial extent grows with increasing RMP field amplitude, and leads to further increased divertor particle flux compared to the broadband mode. Our observations suggest that both modes not only play an important role in keeping the plasma density stationary in the absence of ELMs but also to reduce the plasma pressure such that the plasma edge becomes stable against ELMs.

Published
2023
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11. Effect of the divertor configuration on the JET edge radial electric field

Author

C. Silva, E.R. Solano, J.C. Hillesheim, E. Delabie, G. Birkenmeier, L. Gil, C. Giroud, R.B. Morales, D. Nina, and JET Contributors

Subjects
Nuclear and High Energy Physics, Condensed Matter Physics, Paper, radial electric field, divertor configuration, L-H power threshold, flow shear, Doppler backscattering, JET, ddc
Abstract

The role of the divertor configuration and divertor plasma physics on the L–H transition is poorly understood, leading to large uncertainties in predicting the L–H power threshold in future devices. This contribution reports on edge perpendicular plasma flow measurements by Doppler backscattering in JET L–H transition experiments with the outer divertor strike-point at different positions: horizontal target (HT), vertical target (VT), and in the corner configuration (between the HT and VTs). The edge perpendicular flow was found to be significantly affected by changes in the divertor configuration in the region inside the separatrix. Our results do not show evidence for the existence of a critical edge flow shear needed to achieve H-mode for different divertor configurations, with a larger shear observed for the VT configuration. No significant change in the shear flow and in the density fluctuation level is measured preceding the L–H transition in the region just inside the separatrix. The dynamics of the L–H transitions are also influenced by the divertor configuration with divertor oscillations (DOs) observed only in the HT configuration. Interestingly, DOs are associated with marked changes in the edge perpendicular flow around the separatrix.

Published
2022

12. Experimental investigation of beam-ion losses induced by magnetic perturbations using the light ion beam probe technique in the ASDEX Upgrade tokamak

Author

J. Galdon-Quiroga, L. Sanchis-Sanchez, X. Chen, G. Birkenmeier, K. Gage, P. Cano-Megias, J. Gonzalez-Martin, W.W. Heidbrink, O. Putignano, D. Ryan, G. Suarez Lopez, B. Tal, M.A. VanZeeland, E. Viezzer, M. Willensdorfer, null the ASDEX Upgrade Team, null the EUROfusion MST1 Team, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team

Subjects
Nuclear and High Energy Physics, Condensed Matter Physics
Abstract

The impact of externally applied magnetic perturbations (MPs) on fast-ion losses has been investigated by means of the light ion beam probe (LIBP) technique in the ASDEX Upgrade tokamak. The LIBP technique allows to experimentally infer the fast-ion orbit displacement induced by MPs via first-orbit losses using scintillator based fast-ion loss detector (FILD) measurements. The fast-ion orbit displacement against different applied MP spectra has been studied. These shots were conducted in ELM mitigated H-mode plasmas. A rigid rotation of the MP coils was applied with a frequency of 1 Hz, with an n = 2 configuration and changing the differential phase between the upper and lower set of coils (ΔΦul) on a shot-to-shot basis. Beam sources Q7 (tangential) and Q8 (radial) were used to probe different fast-ion orbits with FILD1. The measured fast-ion orbit displacement ranges from 3 to 20 mm approximately, and no qualitative difference is observed between ions from beam sources Q7 and Q8. The minimum is found for a ΔΦul ∼ 50°, which is shifted with respect to the minimum of the plasma boundary displacement, found at ΔΦul ∼ 0°. A first attempt to validate the orbit following code ASCOT—including the plasma response calculated with the MARS-F code—against these experimental measurements is performed. While the dependence of the first-orbit fast-ion displacement with ΔΦul does not match the experimental measurements, these simulations do capture other features such as the order of magnitude of the orbit displacement and the importance of the toroidal spectrum of the applied perturbation.

Published
2022

13. The upgraded ASDEX Upgrade contribution to the ITPA confinement database: description and analysis

Author

F. Ryter, C. Angioni, G. Tardini, G. Birkenmeier, P. David, M. Dunne, R. Fischer, T. Pütterich, J. Schweinzer, J. Stober, The ASDEX Upgrade Team, The EUROfusion MST1 Team, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team

Subjects
Nuclear and High Energy Physics, Materials science, ASDEX Upgrade, Nuclear engineering, 0103 physical sciences, ITPA, 010306 general physics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas
Abstract

The ITPA multi-machine confinement database has been recently extended, in particular to account for the effect of the metallic plasma facing components installed in the ASDEX Upgrade and JET tokamaks during the last decade. Confinement data from the ASDEX Upgrade tokamak have been contributed to the ITPA confinement database since 1994. The present version, which includes data from 1994 to 2017, is described and discussed in this article. The aim of this work is to document the database before it is made public and report on the main results on the confinement properties reflected in this database. Through the transition from carbon to metallic wall, the operation at low density originally accessible with the carbon wall, has been strongly limited by the occurrence of tungsten accumulation. However, at medium and high densities, the confinement properties with the carbon and metallic walls are rather similar. The database analysis yields in both cases a rather strong plasma current dependence and a clearly negative magnetic field dependence. The density dependence is negligible, while the well-known positive impact of triangularity appears very clearly. These dependences are partly at variance with the widely-used IPB98(y,2) confinement scaling, but in agreement with the analysis of the upgraded ITPA multi-machine and JET databases. The confinement degradation observed at high density with strong gas puffing can be clearly attributed to the density profile in the outer plasma region, as reported in previous studies.

Published
2021
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14. The power threshold of H-mode access in mixed hydrogen–tritium and pure tritium plasmas at JET with ITER-like wall

Author

G. Birkenmeier, E.R. Solano, E. Lerche, D. Taylor, D. Gallart, M.J. Mantsinen, E. Delabie, I.S. Carvalho, P. Carvalho, E. Pawelec, J.C. Hillesheim, F. Parra Diaz, C. Silva, S. Aleiferis, J. Bernardo, A. Boboc, D. Douai, E. Litherland-Smith, R. Henriques, K.K. Kirov, C.F. Maggi, J. Mailloux, M. Maslov, F.G. Rimini, S.A. Silburn, P. Sirén, H. Weisen, JET Contributors, and Barcelona Supercomputing Center

Subjects
Nuclear and High Energy Physics, Física::Física de fluids [Àrees temàtiques de la UPC], Isòtops, L–H transition, Tritium plasmas, Paper, magnetic confinement fusion, fusion plasmas, L-H transition, JET tokamak, tritium plasmas, Tritium, Condensed Matter Physics, jet tokamak, ddc, Physics::Plasma Physics, Fusion plasmas, Physics::Space Physics, Magnetic confinement fusion, Physics::Accelerator Physics, Tokamaks, l-h transition
Abstract

The heating power to access the high confinement mode (H-mode), PLH, scales approximately inversely with the isotope mass of the main ion plasma species as found in (protonic) hydrogen, deuterium and tritium plasmas in many fusion facilities over the last decades. In first dedicated L–H transition experiments at the Joint European Torus (JET) tokamak facility with the ITER-like wall (ILW), the power threshold, PLH, was studied systematically in plasmas of pure tritium and hydrogen–tritium mixtures at a magnetic field of 1.8 T and a plasma current of 1.7 MA in order to assess whether this scaling still holds in a metallic wall device. The measured power thresholds, PLH, in Ohmically heated tritium plasmas agree well with the expected isotope scaling for metallic walls and the lowest power threshold was found in Ohmic phases at low density. The measured power thresholds in ion cyclotron heated plasmas of pure tritium or hydrogen–tritium mixtures are significantly higher than the expected isotope mass scaling due to higher radiation levels. However, when the radiated power is taken into account, the ion cyclotron heated plasmas exhibit similar power thresholds as a neutral beam heated plasma, and are close to the scaling. The tritium plasmas in this study tended to higher electron heating fractions and, when heated with ion cyclotron waves, to relatively higher radiation fractions compared to other isotopes potentially impeding access to sustained H-modes. The authors thank P.A. Schneider, F. Ryter, A. Nielsen, and A. Kappatou for fruitful discussions and for help with data analysis tools. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom Research and Training Programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. G. Birkenmeier received funding from the Helmholtz Association under Grant No. VH-NG-1350. Peer Reviewed "Article signat per 27 autors/es: G. Birkenmeier, E.R. Solano, E. Lerche, D. Taylor, D. Gallart, M.J. Mantsinen, E. Delabie, I.S. Carvalho, P. Carvalho, E. Pawelec, J.C. Hillesheim, F. Parra Diaz, C. Silva, S. Aleiferis, J. Bernardo, A. Boboc, D. Douai, E. Litherland-Smith, R. Henriques, K.K. Kirov, C.F. Maggi, J. Mailloux, M. Maslov, F.G. Rimini, S.A. Silburn, P. Sirén, H. Weisen and JET Contributors"

Published
2022

15. Self-sustained divertor oscillations in ASDEX Upgrade

Author

M. Griener, M. Bernert, W. Zhang, T. Happel, P. Heinrich, U. Stroth, G. Haas, F. Reimold, M. Cavedon, P. Manz, P. David, M. Wischmeier, U. Plank, G. Birkenmeier, D. Brida, Heinrich, P, Manz, P, Bernert, M, Birkenmeier, G, Brida, D, Cavedon, M, David, P, Griener, M, Haas, G, Happel, T, Plank, U, Reimold, F, Stroth, U, Wischmeier, M, Zhang, W, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Nuclear engineering, Divertor, scrape-off layer, divertor oscillation, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, ASDEX Upgrade, law, detachment, neutral flux through PFR, 0103 physical sciences, divertor, magnetically confined plasma, 010306 general physics, tokamak
Abstract

Alternating radiation phenomena between the inner and outer divertor regions in the sub kHz range are investigated in the tokamak ASDEX Upgrade. While the inner divertor oscillates between the onset and fluctuating state of detachment, the outer divertor oscillates between conditions where it can maintain high recycling conditions or not. The detachment state of the inner divertor determines the magnitude of the neutral flux through the private flux region, thus sets the recycling conditions at the outer divertor. In return these recycling conditions determine the particle content in the divertor, hence the detachment state at the inner divertor.

Published
2020

16. Connecting the global H-mode power threshold to the local radial electric field at ASDEX Upgrade

Author

T. Happel, G. Birkenmeier, R. Dux, E. Viezzer, M. Cavedon, Th. Pütterich, E. Wolfrum, M. Willensdorfer, Pascale Hennequin, U. Stroth, F. Ryter, U. Plank, Max-Planck-Institut für Plasmaphysik [Garching] (IPP), Laboratoire de Physique des Plasmas (LPP), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École polytechnique (X)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, EUROfusion Consortium, Cavedon, M, Birkenmeier, G, Putterich, T, Ryter, F, Viezzer, E, Wolfrum, E, Dux, R, Happel, T, Hennequin, P, Plank, U, Stroth, U, Willensdorfer, M, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Nuclear and High Energy Physics, Tokamak, radial electric field, Electron, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, ASDEX Upgrade, [PHYS.PHYS.PHYS-PLASM-PH]Physics [physics]/Physics [physics]/Plasma Physics [physics.plasm-ph], law, Electric field, 0103 physical sciences, power threshold, 010306 general physics, Spectroscopy, tokamak, Scaling, ComputingMilieux_MISCELLANEOUS, Physics, Plasma, Condensed Matter Physics, L-H transition, Deuterium, Atomic physics
Abstract

The relation between the macroscopic input power required at ASDEX Upgrade to access the H-mode Pthr and the microscopic E x B shear has been investigated via fast charge-exchange recombination spectroscopy (CXRS) measurements at various toroidal magnetic fields, different electron densities, and in both hydrogen and deuterium plasmas. For the H-mode onset, a threshold in the v E x B minimum, an approximation of the E x B shear, has been found. This identifies v E x B and not Er as the important player for the L-H transition. A database of measurements including CXRS, Doppler reflectometry measurements and comparison to neoclassical approximations shows a threshold v E x B of (6.7 ± 1.0) km/s ranging over a factor of three in Pthr. Using these findings, a simple derivation of the Pthr scaling is proposed giving a physics interpretation of the Bt, density and surface dependence of Pthr. EUROfusion Consortium Grant Agreement No. 633053

Published
2020

17. Plasma shaping and its impact on the pedestal of ASDEX Upgrade: edge stability and inter-ELM dynamics at varied triangularity

Author

Florian Laggner, M. G. Dunne, Friedrich Aumayr, M. Cavedon, E. Wolfrum, R. Fischer, G. Birkenmeier, M. Willensdorfer, EUROfusion MST1 Team, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, Asdex Upgrade Team, T, Laggner, F, Wolfrum, E, Cavedon, M, Dunne, M, Birkenmeier, G, Fischer, R, Willensdorfer, M, and Aumayr, F

Subjects
Nuclear and High Energy Physics, Electron density, Materials science, Phase (waves), Plasma, Condensed Matter Physics, 01 natural sciences, edge localised mode, 010305 fluids & plasmas, H-mode, ELM behaviour, Pedestal, ASDEX Upgrade, Plasma shaping, 0103 physical sciences, Electron temperature, Atomic physics, Magnetohydrodynamics, plasma shaping, 010306 general physics, tokamak
Abstract

The plasma shape, in particular the triangularity (δ), impacts on the pedestal stability. A scan of δ including a variation of heating power (P heat) and gas puff was performed to study the behaviour of edge localised modes (ELMs) and the pre-ELM pedestal stability for different plasma shapes. Generally, at higher δ the pedestal top electron density (n e) is enhanced and the ELM repetition frequency (f ELM) is reduced. For all δ, the pedestal top n e is already fully established to its pre-ELM value during the initial recovery phase of the n e pedestal, which takes place immediately after the ELM crash. The lowering of the f ELM with increasing δ is related to longer pedestal recovery phases, especially the last pre-ELM phase with clamped pedestal gradients (after the recovery phases of the n e and electron temperature (T e) pedestal) is extended. In all investigated discharge intervals, the pre-ELM pedestal profiles are in agreement with peeling-ballooning (PB) theory. Over the investigated range of δ, two well-separated f ELM bands are observed in several discharge intervals. Their occurrence is linked to the inter-ELM pedestal stability. In both kinds of ELM cycles the pedestal evolves similarly, however, the 'fast' ELM cycle occurs before the global plasma stored energy (W MHD) increases, which then provides a stabilising effect on the pedestal, extending the inter-ELM period in the case of the 'slow' ELM cycle. At the end of a 'fast' ELM cycle the n e profile is radially shifted inwards relative to the n e profile at the end of a 'slow' ELM cycle, leading to a reduced pressure gradient. The appearance of two f ELM bands suggests that the pedestal becomes more likely PB unstable in certain phases of the inter-ELM evolution. Such a behaviour is possible because the evolution of the global plasma is not rigidly coupled to the evolution of the pedestal structure on the timescales of an ELM cycle.

Published
2018
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18. Impact of lithium pellets on plasma performance in the ASDEX Upgrade all-metal-wall tokamak

Author

M. Bernert, T. Pütterich, G. Birkenmeier, Rudolf Neu, R. Fischer, R. Arredondo Parra, V. Nikolaeva, Benedikt Geiger, Ahmed Diallo, E. Wolfrum, S. Potzel, R. M. McDermott, Antti Hakola, E. Fable, Tamás Szepesi, R. Maingi, Peter Lang, B. Sieglin, A. Kappatou, D.K. Mansfield, Florian Laggner, M. Oberkofler, Mike Dunne, Bernhard Ploeckl, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Nuclear and High Energy Physics, Materials science, Tokamak, ELMs, Pellets, chemistry.chemical_element, Radiation, Tungsten, 01 natural sciences, 010305 fluids & plasmas, law.invention, Metal, ASDEX Upgrade, law, 0103 physical sciences, Pellet, 010306 general physics, Plasma, Condensed Matter Physics, plasma facing components, tokamak ASDEX upgrade, Li pellets, chemistry, visual_art, confinement, visual_art.visual_art_medium, Atomic physics
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%.

Published
2017
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19. Interplay between turbulence, neoclassical and zonal flows during the transition from low to high confinement mode at ASDEX Upgrade

Author

Ulrich Stroth, G. Birkenmeier, E. Viezzer, P. Manz, T. Happel, F. Ryter, M. Cavedon, Florian Laggner, Th. Pütterich, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, Cavedon, M, Putterich, T, Viezzer, E, Birkenmeier, G, Happel, T, Laggner, F, Manz, P, Ryter, F, and Stroth, U

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Turbulence, L-H transition, neoclassical flow, turbulence flow interaction, Phase (waves), Mechanics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Flow reduction, Physics::Fluid Dynamics, High-confinement mode, ASDEX Upgrade, law, Limit cycle, 0103 physical sciences, Relaxation (physics), Statistical physics, 010306 general physics
Abstract

The spatio-temporal interplay between turbulence, mean and zonal flows has been investigated at the L–H and H–L transitions in the edge region of the ASDEX Upgrade tokamak. Close to both transitions, an intermediate phase (I-phase) characterized by ‘limit cycle like oscillations’ (LCOs) is observed in which periodic bursts of turbulence correlate with E × B flow reduction and relaxation of gradients. During the I-phase, the E × B velocity is dominated by the mean flows indicating that turbulence driven flows are small. Periodic dithers between L-mode and the phases with LCOs are also observed just before the H-mode onset where the edge density and temperature profile gradients evolve on similar timescale as the flows. Thus connection between mean and E × B flows holds during the all evolution from L-mode to H-mode demonstrating the fundamental role of the neoclassical flows in the L–H transition physics.

Published
2016

20. Investigations on the edge kinetic data in regimes with type-I and mitigated ELMs at ASDEX Upgrade

Author

S. K. Rathgeber, L. Barrera, W. Suttrop, R. Fischer, G. Birkenmeier, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Nuclear and High Energy Physics, Electron density, Materials science, Computer Science::Neural and Evolutionary Computation, Electron, Edge (geometry), Atmospheric temperature range, Condensed Matter Physics, Kinetic energy, Pedestal, ASDEX Upgrade, Physics::Plasma Physics, Atomic physics, Pressure gradient
Abstract

The behaviour of profiles and gradients of electron density, temperature and pressure at the edge of ASDEX Upgrade was studied in regimes with type-I and small edge localized modes (ELMs) of discharges with and without applied magnetic perturbations (MPs). Estimation of the edge kinetic parameters was performed by means of integrated data analysis for joint reconstruction of electron density and temperature profiles via combination of data from different diagnostics. The MP fields for ELM mitigation were produced by 16 in-vessel coils allowing to execute this survey with large variations in poloidal spectrum and resonant component of the error field. With several dedicated discharges the effect of MPs on the edge kinetic data and ELMs was determined in dependence of heating power, gas puff and MP-coil configuration. Small ELMs are dominant—with and without MPs—in regimes with reduced pedestal top electron temperatures and flattened edge electron pressure gradients compared to type-I ELM phases. Furthermore, application of MPs opens an additional small ELM regime in the high temperature range at reduced electron pressure gradient.

Published
2014

21. Stationary ELM-free H-mode in ASDEX Upgrade.

Author

L. Gil, C. Silva, T. Happel, G. Birkenmeier, G.D. Conway, L. Guimarais, A. Kallenbach, T. Pütterich, J. Santos, P.A. Schneider, M. Schubert, E. Seliunin, A. Silva, J. Stober, U. Stroth, E. Trier, E. Wolfrum, ASDEX, and EUROfusion

Subjects
CYCLOTRON resonance, FUSION reactor divertors
Abstract

A stationary H-mode without edge localized modes (ELMs) has been recently achieved in the ASDEX Upgrade tokamak by applying central electron cyclotron resonance heating above the L-H power threshold with adequate fueling. It is naturally obtained in favorable ∇B configuration and has several features which are desirable for future reactors, such as dominant electron heating, low input torque, possibility of access at low input power, good energy confinement (), high density (), and no impurity accumulation despite the absence of ELMs. This regime is similar to the EDA H-mode and always features an edge electromagnetic quasi-coherent mode which seems to be responsible for enhanced transport losses, as its appearance and disappearance are correlated with changes in edge and divertor parameters. [ABSTRACT FROM AUTHOR]

Published
2020
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22. Identity of the JET M-mode and the ASDEX Upgrade I-phase phenomena.

Author

D.I. Réfy, E.R. Solano, N. Vianello, S. Zoletnik, D. Dunai, B. Tál, M. Brix, R. Gomes, G. Birkenmeier, E. Wolfrum, F. Laggner, M. Griener, O. Asztalos, E. Delabie, team, ASDEX Upgrade, Contributors, JET, and MST1, EUROfusion

Subjects
FREQUENCIES of oscillating systems, EMISSION spectroscopy, ELECTRON temperature, PLASMA boundary layers, PLASMA density, ELECTRON density
Abstract

An H-mode plasma state free of edge-localized mode (ELM), close to the L-H transition with clear density and temperature pedestal has been observed both at the Joint European Torus (JET) and at the ASDEX Upgrade (AUG) tokamaks usually identified by a low frequency (LFO, 1–2 kHz), m  =  1, n  =  0 oscillation of the magnetics and the modulation of pedestal profiles. The regime at JET is referred to as M-mode while at AUG as intermediate phase or I-phase. This contribution aims at a comparative analysis of these phenomena in terms of the density and temperature pedestal properties, the magnetic oscillations and symmetries. Lithium beam emission spectroscopy (Li-BES) and reflectometer measurements at JET and AUG show that the M-mode and the I-phase modulates the plasma edge density. A high frequency oscillation of the magnetics and the density at the pedestal is also associated with both the M-mode and the I-phase, and its power is modulated with the LFO frequency. The power modulation happens simultaneously in every Mirnov coil signal where it can be detected. The bursts of the magnetic signals and the density at the pedestal region are followed by the flattening of the density profile, and by a radially outward propagating density pulse in the scrape-off layer (SOL). The analysis of the helium line ratio spectroscopy (He-BES) signals at AUG revealed that the electron temperature is modulated in phase with the density, thus the I-phase modulates the pressure profile gradient. This analysis gave opportunity to compare Li-BES and He-BES density profiles at different locations suggesting a toroidal and poloidal symmetry of the density modulation. The presented results indicate that the regimes, the AUG I-phase and the JET M-mode, exhibit similar characteristics, which leads to the conclusion that the regimes are likely the same. [ABSTRACT FROM AUTHOR]

Published
2020
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23. On the role of filaments in perpendicular heat transport at the scrape-off layer.

Author

D. Carralero, S. Artene, M. Bernert, G. Birkenmeier, M. Faitsch, P. Manz, P. De Marne, U. Stroth, M. Wischmeier, E. Wolfrum, Team, The Asdex Upgrade, and Team, The Euro-Fusion Mst1

Subjects
FIBERS, TOKAMAKS, HEAT flux, PLASMA boundary layers, ADVECTION
Abstract

In this work we carry out quantitative measurements of particle and heat transport associated to SOL filaments in a tokamak, and relate density shoulder formation to the advection of energy in the far SOL. For the first time, this attempt includes direct measurements of ion and electron temperatures for background and filaments. With this aim, we combine data from a number of equivalent L-mode discharges from the ASDEX Upgrade tokamak in which different probe heads were installed on the midplane manipulator. This approach is validated by a comparison with independent diagnostics. Results indicate an increase of heat transport associated to filaments after the shoulder formation. Several centimeters into the SOL, filaments are still found to carry a substantial fraction (up to one fifth) of the power ejected at the separatrix. [ABSTRACT FROM AUTHOR]

Published
2018
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24. Plasma shaping and its impact on the pedestal of ASDEX Upgrade: edge stability and inter-ELM dynamics at varied triangularity.

Author

F.M. Laggner, E. Wolfrum, M. Cavedon, M.G. Dunne, G. Birkenmeier, R. Fischer, M. Willensdorfer, F. Aumayr, Team, The EUROfusion MST1, and Team, The ASDEX Upgrade

Subjects
HEATING, LOCALIZED modes, ELECTRON density, SOBOLEV gradients, TIMESCALE number
Abstract

The plasma shape, in particular the triangularity (δ), impacts on the pedestal stability. A scan of δ including a variation of heating power (Pheat) and gas puff was performed to study the behaviour of edge localised modes (ELMs) and the pre-ELM pedestal stability for different plasma shapes. Generally, at higher δ the pedestal top electron density (ne) is enhanced and the ELM repetition frequency (fELM) is reduced. For all δ, the pedestal top ne is already fully established to its pre-ELM value during the initial recovery phase of the ne pedestal, which takes place immediately after the ELM crash. The lowering of the fELM with increasing δ is related to longer pedestal recovery phases, especially the last pre-ELM phase with clamped pedestal gradients (after the recovery phases of the ne and electron temperature (Te) pedestal) is extended. In all investigated discharge intervals, the pre-ELM pedestal profiles are in agreement with peeling–ballooning (PB) theory. Over the investigated range of δ, two well-separated fELM bands are observed in several discharge intervals. Their occurrence is linked to the inter-ELM pedestal stability. In both kinds of ELM cycles the pedestal evolves similarly, however, the ‘fast’ ELM cycle occurs before the global plasma stored energy (WMHD) increases, which then provides a stabilising effect on the pedestal, extending the inter-ELM period in the case of the ‘slow’ ELM cycle. At the end of a ‘fast’ ELM cycle the ne profile is radially shifted inwards relative to the ne profile at the end of a ‘slow’ ELM cycle, leading to a reduced pressure gradient. The appearance of two fELM bands suggests that the pedestal becomes more likely PB unstable in certain phases of the inter-ELM evolution. Such a behaviour is possible because the evolution of the global plasma is not rigidly coupled to the evolution of the pedestal structure on the timescales of an ELM cycle. [ABSTRACT FROM AUTHOR]

Published
2018
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25. Stationary ELM-free H-mode in ASDEX Upgrade

Author

A. Silva, E. Seliunin, M. Schubert, Carlos A. Silva, Asdex, L. Gil, T. Happel, Ulrich Stroth, J. Stober, J. M. Santos, Th. Pütterich, G. Birkenmeier, L. Guimarais, G. D. Conway, EUROfusion, E. Trier, E. Wolfrum, P. A. Schneider, and A. Kallenbach

Subjects
Nuclear physics, Physics, Nuclear and High Energy Physics, Pedestal, ASDEX Upgrade, 0103 physical sciences, Mode (statistics), 010306 general physics, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas
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26. Three dimensional boundary displacement due to stable ideal kink modes excited by external n = 2 magnetic perturbations.

Author

M. Willensdorfer, E. Strumberger, W. Suttrop, M. Dunne, R. Fischer, G. Birkenmeier, D. Brida, M. Cavedon, S.S. Denk, V. Igochine, L. Giannone, A. Kirk, J. Kirschner, A. Medvedeva, T. Odstrčil, D.A. Ryan, Team, The ASDEX Upgrade, and Team, The EUROfusion MST1

Subjects
KINK instability, MAGNETIC fields, MAGNETOHYDRODYNAMICS, ELECTRICAL conductors, PLASMA devices
Abstract

In low-collisionality scenarios exhibiting mitigation of edge localized mode (ELMs), stable ideal kink modes at the edge are excited by externally applied magnetic perturbation (MP)-fields. In ASDEX Upgrade these modes can cause three-dimensional (3D) boundary displacements up to the centimeter range. These displacements have been measured using toroidally localized high resolution diagnostics and rigidly rotating MP-fields with various applied poloidal mode spectra. These measurements are compared to non-linear 3D ideal magnetohydrodynamics (MHD) equilibria calculated by VMEC. Comprehensive comparisons have been conducted, which consider for instance plasma movements due to the position control system, attenuation due to internal conductors and changes in the edge pressure profiles. VMEC accurately reproduces the amplitude of the displacement and its dependencies on the applied poloidal mode spectra. Quantitative agreement is found around the low field side (LFS) midplane. The response at the plasma top is qualitatively compared. The measured and predicted displacements at the plasma top maximize when the applied spectra is optimized for ELM-mitigation. The predictions from the vacuum modeling generally fails to describe the displacement at the LFS midplane as well as at the plasma top. When the applied mode spectra is set to maximize the displacement, VMEC and the measurements clearly surpass the predictions from the vacuum modeling by a factor of four. Minor disagreements between VMEC and the measurements are discussed. This study underlines the importance of the stable ideal kink modes at the edge for the 3D boundary displacement in scenarios relevant for ELM-mitigation. [ABSTRACT FROM AUTHOR]

Published
2017
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27. Turbulence characteristics of the I-mode confinement regime in ASDEX Upgrade.

Author

P. Manz, T. Happel, F. Ryter, M. Bernert, G. Birkenmeier, G.D. Conway, M. Dunne, L. Guimarais, P. Hennequin, A. Hetzenecker, C. Honoré, P. Lauber, M. Maraschek, V.E. Nikolaeva, D. Prisiazhniuk, U. Stroth, E. Viezzer, and Team2, The ASDEX Upgrade

Subjects
TURBULENCE, PLASMA confinement, GEODESIC flows, PERTURBATION theory, WAVELETS (Mathematics)
Abstract

Besides strong geodesic acoustic mode (GAM) activity, turbulence in the I-mode confinement regime of ASDEX Upgrade exhibits two prominent features, the weakly coherent mode (WCM) and strongly intermittent solitary density perturbations. The nonlinear interaction between these structures is studied in detail by means of a conditional averaged wavelet-bicoherence analysis. The wavelet analysis reveals that these density perturbations are at the WCM frequency. The GAM is coupled to all frequency scales of the velocity fluctuations via a modulational instability. The WCM shows coupling to higher frequencies prior to the bursts, indicating a process resembling wave-steepening. A possible mechanism for the generation of such solitary density perturbations by a Korteweg–de Vries-like nonlinearity is discussed. [ABSTRACT FROM AUTHOR]

Published
2017
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28. Recent progress towards a quantitative description of filamentary SOL transport.

Author

D. Carralero, M. Siccinio, M. Komm, S.A. Artene, F.A. D’Isa, J. Adamek, L. Aho-Mantila, G. Birkenmeier, M. Brix, G. Fuchert, M. Groth, T. Lunt, P. Manz, J. Madsen, S. Marsen, H.W. Müller, U. Stroth, H.J. Sun, N. Vianello, and M. Wischmeier

Subjects
PLASMA boundary layers, TOKAMAKS, NUCLEAR physics, SIMULATION methods & models, STATISTICAL correlation
Abstract

A summary of recent results on filamentary transport, mostly obtained with the ASDEX-Upgrade tokamak (AUG), is presented and discussed in an attempt to produce a coherent picture of scrape-off layer (SOL) filamentary transport. A clear correlation is found between L-mode density shoulder formation in the outer midplane and a transition between the sheath-limited and the inertial filamentary regimes. Divertor collisionality is found to be the parameter triggering the transition. A clear reduction of the ion temperature takes place in the far SOL after the transition, both for the background and the filaments. This coincides with a strong variation of the ion temperature distribution, which deviates from Gaussianity and becomes dominated by a strong peak below 5 eV. The filament transition mechanism triggered by a critical value of collisionality seems to be generally applicable to inter-ELM H-mode plasmas, although a secondary threshold related to deuterium fueling is observed. EMC3-EIRENE simulations of neutral dynamics show that an ionization front near the main chamber wall is formed after the shoulder formation. Finally, a clear increase of SOL opacity to neutrals is observed, associated with the shoulder formation. A common SOL transport framework is proposed to account for all these results, and their potential implications for future generation devices are discussed. [ABSTRACT FROM AUTHOR]

Published
2017
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29. Interplay between turbulence, neoclassical and zonal flows during the transition from low to high confinement mode at ASDEX Upgrade.

Author

M. Cavedon, T. Pütterich, E. Viezzer, G. Birkenmeier, T. Happel, F. M. Laggner, P. Manz, F. Ryter, U. Stroth, and Team, The ASDEX Upgrade

Subjects
TURBULENCE, TOKAMAKS, TEMPERATURE effect, OSCILLATIONS, PLASMA confinement
Abstract

The spatio-temporal interplay between turbulence, mean and zonal flows has been investigated at the L–H and H–L transitions in the edge region of the ASDEX Upgrade tokamak. Close to both transitions, an intermediate phase (I-phase) characterized by ‘limit cycle like oscillations’ (LCOs) is observed in which periodic bursts of turbulence correlate with flow reduction and relaxation of gradients. During the I-phase, the velocity is dominated by the mean flows indicating that turbulence driven flows are small. Periodic dithers between L-mode and the phases with LCOs are also observed just before the H-mode onset where the edge density and temperature profile gradients evolve on similar timescale as the flows. Thus connection between mean and flows holds during the all evolution from L-mode to H-mode demonstrating the fundamental role of the neoclassical flows in the L–H transition physics. [ABSTRACT FROM AUTHOR]

Published
2017
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30. 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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31. Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions.

Author

G. Birkenmeier, M. Cavedon, G.D. Conway, P. Manz, U. Stroth, R. Fischer, G. Fuchert, T. Happel, F.M. Laggner, M. Maraschek, A. Medvedeva, V. Nikolaeva, D. Prisiazhniuk, T. Pütterich, F. Ryter, L.M. Shao, M. Willensdorfer, E. Wolfrum, H. Zohm, and Team, the ASDEX Upgrade

Subjects
*OSCILLATIONS, *PLASMA gases, *FUSION reactor divertors, *TOKAMAKS, *MAGNETIC fields, *PLASMA currents
Abstract

Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as . [ABSTRACT FROM AUTHOR]

Published
2016
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32. Geodesic oscillations and the weakly coherent mode in the I-mode of ASDEX Upgrade.

Author

P. Manz, P. Lauber, V.E. Nikolaeva, T. Happel, F. Ryter, G. Birkenmeier, A. Bogomolov, G.D. Conway, M.E. Manso, M. Maraschek, D. Prisiazhniuk, and E. Viezzer

Subjects
GEODESICS, OSCILLATIONS, TURBULENCE, ENERGY transfer, FLUCTUATIONS (Physics)
Abstract

Density fluctuations in I-mode discharges in ASDEX Upgrade are studied. The I-mode specific weakly coherent mode (WCM) appears at the transition from the L to I-mode. The WCM but also the turbulence in general are strongly modulated by a low frequency mode which can be related to the geodesic acoustic mode (GAM). The GAM induces an energy transfer away from the central WCM frequency, indicating an underlying instability responsible for the WCM. During the I-mode magnetic fluctuations close to the WCM frequency are intensified, which can be assigned to the geodesic Alfvénic oscillation. The geodesic Alfvénic oscillation is already present in the L-mode, and does not follow changes of frequency of the WCM, therefore it is not responsible for the WCM. [ABSTRACT FROM AUTHOR]

Published
2015
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33. Filament transport, warm ions and erosion in ASDEX Upgrade L-modes.

Author

G. Birkenmeier, P. Manz, D. Carralero, F.M. Laggner, G. Fuchert, K. Krieger, H. Maier, F. Reimold, K. Schmid, R. Dux, T. Pütterich, M. Willensdorfer, E. Wolfrum, and Team, The ASDEX Upgrade

Subjects
*TOKAMAKS, *FIBERS, *PLASMA boundary layers, *EMISSION spectroscopy, *ION temperature, *NUCLEAR fusion
Abstract

The dynamics of blob filaments are investigated in the scrape-off layer of ASDEX Upgrade by means of lithium beam emission spectroscopy. A comparison of the measurements in L-mode with a recently developed analytical blob model based on a drift-interchange-Alfvén fluid model indicates an influence of a finite ion temperature on the blob dynamics which has typically been neglected in other blob models. The blob dynamics agree well with the sheath-connected regime at lower plasma densities, and inertial effects play only a minor role. At higher densities, a transition into another regime with large blob amplitudes and increased transport is found. This points to a prominent role of blob transport at higher Greenwald fractions. On the basis of the measured blob properties, the erosion on plasma facing components is estimated. For pure deuterium plasmas, the high ion temperatures of blobs lead to a dominant erosion induced by blobs. However, if an impurity concentration of 1% is taken into account, the blob-induced erosion plays a minor role and background plasma parameters determine the total gross erosion. [ABSTRACT FROM AUTHOR]

Published
2015
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34. An experimental investigation of the high density transition of the scrape-off layer transport in ASDEX Upgrade.

Author

D. Carralero, G. Birkenmeier, H.W. Müller, P. Manz, P. deMarne, S.H. Müller, F. Reimold, U. Stroth, M. Wischmeier, E. Wolfrum, and Team, The ASDEX Upgrade

Subjects
*PLASMA boundary layers, *FUSION reactor divertors, *LANGMUIR probes, *L-mode plasma confinement, *PLASMA instabilities
Abstract

A multidiagnostic approach, utilizing Langmuir probes in the midplane, X-point and divertor walls, along with lithium beam and infrared measurements is employed to evaluate the evolution of the scrape-off layer (SOL) of ASDEX Upgrade across the L-mode density transition leading to the formation of a density shoulder. The flattening of the SOL density profiles is linked to a regime change of filaments, which become faster and larger, and to a similar flattening of the q∥ profile. This transition is related to the beginning of outer divertor detachment and leads to the onset of a velocity shear layer in the SOL. Experimental measurements are in good agreement with several filament models which describe the process as a transition from conduction to convection-dominated SOL perpendicular transport caused by an increase of parallel collisionality. These results could be of great relevance since both ITER and DEMO will feature detached divertors and densities largely over the transition values, and might therefore exhibit convective transport levels different to those observed typically in present-day devices. [ABSTRACT FROM AUTHOR]

Published
2014
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