Deuterium (D) retention and surface modifications of hot-rolled polycrystalline tungsten (W) exposed to a low-energy ( 40 eV D −1 ), high-flux (2–5 × 10 23 D m −2 s −1 ) D plasma at temperatures of 380 K and 1140 K to fluences up to 1.2 × 10 28 D m −2 have been examined by using nuclear reaction analysis, thermal desorption spectroscopy, and scanning electron microscopy. The samples exposed at 380 K exhibited various types of surface modifications: dome-shaped blister-like structures, stepped flat-topped protrusions, and various types of nanostructures. It was observed that a large fraction of the surface was covered with blisters and protrusions, but their average size and the number density showed almost no fluence dependence. The D depth distributions and total D inventories also barely changed with increasing fluence at 380 K. A substantial amount of D was retained in the subsurface region, and thickness correlated with the depth where the cavities of blisters and protrusions were located. It is therefore suggested that defects appearing during creation of blisters and protrusions govern the D trapping in the investigated fluence range. In addition, a large number of small cracks was observed on the exposed surfaces, which can serve as fast D release channels towards the surface, resulting in a reduction of the effective D influx into the W bulk. On the samples exposed at 1140 K no blisters and protrusions were found. However, wave-like and faceted terrace-like structures were formed instead. The concentrations of trapped D were very low (<10 −5 at. fr.) after the exposure at 1140 K.

VL - 57 UR - http://pubman.mpdl.mpg.de/pubman/item/escidoc:2398377/component/escidoc:2474095/Zibrov_Deuterium.pdf IS - 4 U1 -PSI

U2 -PMI

U5 - eaca8e29ee5c2ec32af62fdee22864c2 ER - TY - JOUR T1 - Plasma–wall interaction studies within the EUROfusion consortium: progress on plasma-facing components development and qualification JF - Nuclear Fusion Y1 - 2017 A1 - Brezinsek, S. A1 - Coenen, J. W. A1 - Schwartz-Selinger, T. A1 - Schmid, K. A1 - Kirschner, A. A1 - Hakola, A. A1 - Tabares, F. L. A1 - van der Meiden, H. J. A1 - Mayoral, M. A1 - Reinhart, M. A1 - Tsitrone, E. A1 - Vernimmen, J. W. M. A1 - Morgan, T. W. A1 - Ahlgren, T. A1 - Aints, M. A1 - Airila, M. A1 - Almaviva, S. A1 - Alves, E. A1 - Angot, T. A1 - Anita, V. A1 - R. Arredondo Parra A1 - Aumayr, F. A1 - Balden, M. A1 - Bauer, J. A1 - Ben Yaala, M. A1 - Berger, B. M. A1 - Bisson, R. A1 - Björkas, C. A1 - Bogdanovic Radovic, I. A1 - Borodin, D. A1 - Bucalossi, J. A1 - Butikova, J. A1 - Butoi, B. A1 - Cadez, I. A1 - Caniello, R. A1 - Caneve, L. A1 - Cartry, G. A1 - Catarino, N. A1 - Čekada, M. A1 - Ciraolo, G. A1 - Ciupinski, L. A1 - Colao, F. A1 - Corre, Y. A1 - Costin, C. A1 - Craciunescu, T. A1 - Cremona, A. A1 - de Angeli, M. A1 - de Castro, A. A1 - Dejarnac, R. A1 - Dellasega, D. A1 - Dinca, P. A1 - Dittmar, T. A1 - Dobrea, C. A1 - Hansen, P. A1 - Drenik, A. A1 - Eich, T. A1 - Elgeti, S. A1 - Falie, D. A1 - Fedorczak, N. A1 - Ferro, Y. A1 - Fornal, T. A1 - Fortuna, E. A1 - Gao, L. A1 - Gasior, P. A1 - Gherendi, M. A1 - Ghezzi, F. A1 - Gosar, Z. A1 - Greuner, H. A1 - Grigore, E. A1 - Grisolia, C. A1 - Groth, M. A1 - Gruca, M. A1 - Grzonka, J. A1 - Gunn, J. P. A1 - Hassouni, K. A1 - Heinola, K. A1 - Höschen, T. A1 - Huber, S. A1 - Jacob, W. A1 - Jepu, I. A1 - Jiang, X. A1 - Jogi, I. A1 - Kaiser, A. A1 - Karhunen, J. A1 - Kelemen, M. A1 - Köppen, M. A1 - Koslowski, H. R. A1 - Kreter, A. A1 - Kubkowska, M. A1 - Laan, M. A1 - Laguardia, L. A1 - Lahtinen, A. A1 - Lasa, A. A1 - Lazic, V. A1 - Lemahieu, N. A1 - Likonen, J. A1 - Linke, J. A1 - Litnovsky, A. A1 - Linsmeier, C. A1 - Loewenhoff, T. A1 - Lungu, C. A1 - Lungu, M. A1 - Maddaluno, G. A1 - Maier, H. A1 - Makkonen, T. A1 - Manhard, A. A1 - Marandet, Y. A1 - Markelj, S. A1 - Marot, L. A1 - Martin, C. A1 - Martin-Rojo, A. B. A1 - Martynova, Y. A1 - Mateus, R. A1 - Matveev, D. A1 - Mayer, M. A1 - Meisl, G. A1 - Mellet, N. A1 - Michau, A. A1 - Miettunen, J. A1 - Möller, S. A1 - Mougenot, J. A1 - Mozetic, M. A1 - Nemanič, V. A1 - Neu, R. A1 - Nordlund, K. A1 - Oberkofler, M. A1 - Oyarzabal, E. A1 - Panjan, M. A1 - Pardanaud, C. A1 - Paris, P. A1 - Passoni, M. A1 - Pegourie, B. A1 - Pelicon, P. A1 - Petersson, P. A1 - Piip, K. A1 - Pintsuk, G. A1 - Pompilian, G. O. A1 - Popa, G. A1 - Porosnicu, C. A1 - Primc, G. A1 - Probst, M. A1 - Räisänen, J. A1 - Rasinski, M. A1 - Ratynskaia, S. A1 - Reiser, D. A1 - Ricci, D. A1 - Richou, M. A1 - Riesch, J. A1 - Riva, G. A1 - Rosinski, M. A1 - Roubin, P. A1 - Rubel, M. A1 - Ruset, C. A1 - Safi, E. A1 - Sergienko, G. A1 - Siketic, Z. A1 - Sima, A. A1 - Spilker, B. A1 - Stadlmayr, R. A1 - Steudel, I. A1 - Ström, P. A1 - Tadic, T. A1 - Tafalla, D. A1 - Tale, I. A1 - Terentyev, D. A1 - Terra, A. A1 - Tiron, V. A1 - Tiseanu, I. A1 - Tolias, P. A1 - Tskhakaya, D. A1 - Uccello, A. A1 - Unterberg, B. A1 - Uytdenhoven, I. A1 - Vassallo, E. A1 - Vavpetic, P. A1 - Veis, P. A1 - Velicu, I. L. A1 - Voitkans, A. A1 - von Toussaint, U. A1 - Weckmann, A. A1 - Wirtz, M. A1 - Zaloznik, A. A1 - Zaplotnik, R. A1 - WP PFC contributors AB - The provision of a particle and power exhaust solution which is compatible with first-wall components and edge-plasma conditions is a key area of present-day fusion research and mandatory for a successful operation of ITER and DEMO. The work package plasma-facing components (WP PFC) within the European fusion programme complements with laboratory experiments, i.e. in linear plasma devices, electron and ion beam loading facilities, the studies performed in toroidally confined magnetic devices, such as JET, ASDEX Upgrade, WEST etc. The connection of both groups is done via common physics and engineering studies, including the qualification and specification of plasma-facing components, and by modelling codes that simulate edge-plasma conditions and the plasma–material interaction as well as the study of fundamental processes. WP PFC addresses these critical points in order to ensure reliable and efficient use of conventional, solid PFCs in ITER (Be and W) and DEMO (W and steel) with respect to heat-load capabilities (transient and steady-state heat and particle loads), lifetime estimates (erosion, material mixing and surface morphology), and safety aspects (fuel retention, fuel removal, material migration and dust formation) particularly for quasi-steady-state conditions. Alternative scenarios and concepts (liquid Sn or Li as PFCs) for DEMO are developed and tested in the event that the conventional solution turns out to not be functional. Here, we present an overview of the activities with an emphasis on a few key results: (i) the observed synergistic effects in particle and heat loading of ITER-grade W with the available set of exposition devices on material properties such as roughness, ductility and microstructure; (ii) the progress in understanding of fuel retention, diffusion and outgassing in different W-based materials, including the impact of damage and impurities like N; and (iii), the preferential sputtering of Fe in EUROFER steel providing an in situ W surface and a potential first-wall solution for DEMO. VL - 57 IS - 11 U1 - PSI U2 - PMI U5 - 4f90e0cf51291a6cb8b6e575c66f5043 ER - TY - JOUR T1 - Effect of the surface temperature on surface morphology, deuterium retention and erosion of EUROFER steel exposed to low-energy, high-flux deuterium plasma JF - Nuclear Materials and Energy Y1 - 2017 A1 - Balden, M. A1 - Elgeti, S. A1 - Zibrov, M. A1 - Bystrov, K. A1 - Morgan, T. W. AB - Samples of EUFROFER, a reduced activation ferritic martensitic steel, were exposed in the linear plasma device Pilot-PSI to a deuterium (D) plasma with incident ion energy of ∼40 eV and incident D flux of 2–6 × 1023 D/m2s to fluences up to 1027 D/m2 at surface temperatures ranging from 400 K to 950 K. The main focus of the study lays on the surface morphology changes dependent on the surface temperature and the surface composition evolution, e.g., the enrichment in tungsten; but also the erosion and the D retention are studied. The created surface morphology varies strongly with surface temperature from needle-like to corral-like structures. The visible lateral length scale of the formed structures is in the range of tens of nanometres to above 1 µm and exhibits two thermal activated regimes below and above ∼770 K with activation energies of 0.2 eV and 1.3 eV, respectively. The lateral variation of the enrichment of heavy elements on the surface is correlated to this surface morphology at least in the high temperature regime, independent of the origin of the enrichment (intrinsic from the sample or deposited by the plasma). Also the erosion exhibits temperature dependence at least above ∼770 K as well as a fluence dependence. The amount of deuterium retained in the top 500 nm is almost independent of the exposure temperature and is of the order of 1018 D/m2, which would correspond to a sub-monolayer D coverage on the surface. The retained D in the volume summing up over the complete samples exceeds the D retained close to the surface by one order of magnitude. VL - 12 U1 - PSI U2 - PMI U5 - 787c5b3cf02a208d32ab996fc57becaa ER - TY - JOUR T1 - Surface morphology and deuterium retention of tungsten after low- and high-flux deuterium plasma exposure JF - Nuclear Fusion Y1 - 2014 A1 - 't Hoen, M. H. J. A1 - Balden, M. A1 - Manhard, A. A1 - Mayer, M. A1 - Elgeti, S. A1 - A. W. Kleyn A1 - Zeijlmans van Emmichoven, P. A. AB -The surface morphology and deuterium retention were investigated of polycrystalline tungsten targets that were exposed to deuterium plasmas at widely varying conditions. By changing only one parameter at a time, the isolated effects of flux, time and pre-damaging on surface modifications and deuterium retention were studied. The sample exposed to low-flux plasma (10 20 m −2 s −1 ) is mostly smooth with only a few areas containing very large blisters(50-500 µ m). The samples exposed to high-flux plasmas (10 24 m −2 s −1 ) show large numbers of smaller blisters(1-10 µ m) and in addition even smaller protrusions (<750 nm). The size of the blisters and their density strongly increase with fluence. Pre-damaging tungsten with MeV ions leads to less blisters but to more protrusions. In addition to these (sub-)micrometer-sized structures, all samples show formation of nanostructures. Comparison of a low-flux and high-flux sample exposed to similar fluence showed that the variation in morphology is dominated by the flux differences. It is shown that the blisters and protrusions originate in inter- and intra-granular cavities, respectively. The depth of the cavities underneath the surface correlates well with the depth distributions of the retained deuterium. Trapping of significant amounts of deuterium therefore seems to take place in and/or close to these cavities and gives rise to an additional peak in the thermal desorption spectrum at 700 K.

VL - 54 IS - 8 U1 -PSI

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U5 - 83f99ef9cf3cb1287671808183e20442 ER - TY - JOUR T1 - Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X JF - Nuclear Fusion Y1 - 2013 A1 - Bosch, H. S. A1 - R C Wolf A1 - Andreeva, T. A1 - Baldzuhn, J. A1 - Birus, D. A1 - Bluhm, T. A1 - Brauer, T. A1 - Braune, H. A1 - Bykov, V. A1 - Cardella, A. A1 - Durodie, F. A1 - Endler, M. A1 - Erckmann, V. A1 - Gantenbein, G. A1 - Hartmann, D. A1 - Hathiramani, D. A1 - Heimann, P. A1 - Heinemann, B. A1 - Hennig, C. A1 - Hirsch, M. A1 - Holtum, D. A1 - Jagielski, J. A1 - Jelonnek, J. A1 - Kasparek, W. A1 - Klinger, T. A1 - Konig, R. A1 - Kornejew, P. A1 - Kroiss, H. A1 - Krom, J. G. A1 - Kuhner, G. A1 - Laqua, H. A1 - Laqua, H. P. A1 - Lechte, C. A1 - Lewerentz, M. A1 - Maier, J. A1 - McNeely, P. A1 - Messiaen, A. A1 - Michel, G. A1 - Ongena, J. A1 - Peacock, A. A1 - Pedersen, T. S. A1 - Riedl, R. A1 - Riemann, H. A1 - Rong, P. A1 - Rust, N. A1 - Schacht, J. A1 - Schauer, F. A1 - Schroeder, R. A1 - Schweer, B. A1 - Spring, A. A1 - Stabler, A. A1 - Thumm, M. A1 - Turkin, Y. A1 - Wegener, L. A1 - Werner, A. A1 - Zhang, D. A1 - Zilker, M. A1 - Akijama, T. A1 - Alzbutas, R. A1 - Ascasibar, E. A1 - Balden, M. A1 - Banduch, M. A1 - Baylard, C. A1 - Behr, W. A1 - Beidler, C. A1 - Benndorf, A. A1 - Bergmann, T. A1 - Biedermann, C. A1 - Bieg, B. A1 - Biel, W. A1 - Borchardt, M. A1 - Borowitz, G. A1 - Borsuk, V. A1 - Bozhenkov, S. A1 - Brakel, R. A1 - Brand, H. A1 - Brown, T. A1 - Brucker, B. A1 - Burhenn, R. A1 - Buscher, K. P. A1 - Caldwell-Nichols, C. A1 - Cappa, A. A1 - Cardella, A. A1 - Carls, A. A1 - Carvalho, P. A1 - Ciupinski, L. A1 - Cole, M. A1 - Collienne, J. A1 - Czarnecka, A. A1 - Czymek, G. A1 - Dammertz, G. A1 - Dhard, C. P. A1 - Davydenko, V. I. A1 - Dinklage, A. A1 - Drevlak, M. A1 - Drotziger, S. A1 - Dudek, A. A1 - Dumortier, P. A1 - Dundulis, G. A1 - von Eeten, P. A1 - Egorov, K. A1 - Estrada, T. A1 - Faugel, H. A1 - Fellinger, J. A1 - Feng, Y. A1 - Fernandes, H. A1 - Fietz, W. H. A1 - Figacz, W. A1 - Fischer, F. A1 - Fontdecaba, J. A1 - Freund, A. A1 - Funaba, T. A1 - Funfgelder, H. A1 - Galkowski, A. A1 - Gates, D. A1 - Giannone, L. A1 - Regana, J. M. G. A1 - Geiger, J. A1 - Geissler, S. A1 - Greuner, H. A1 - Grahl, M. A1 - Gross, S. A1 - Grosman, A. A1 - Grote, H. A1 - Grulke, O. A1 - R. Jaspers A1 - Szabo, V. AB - The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, currently under construction in Greifswald, Germany. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation under plasma conditions relevant for a fusion power plant. Steady-state operation of a fusion device, on the one hand, requires the implementation of special technologies, giving rise to technical challenges during the design, fabrication and assembly of such a device. On the other hand, also the physics development of steady-state operation at high plasma performance poses a challenge and careful preparation. The electron cyclotron resonance heating system, diagnostics, experiment control and data acquisition are prepared for plasma operation lasting 30 min. This requires many new technological approaches for plasma heating and diagnostics as well as new concepts for experiment control and data acquisition. VL - 53 SN - 0029-5515 UR - http://iopscience.iop.org/0029-5515/53/12/126001/ N1 - et al. is: Haas, M. Haiduk, L. Hartfuss, H. J. Harris, J. H. Haus, D. Hein, B. Heitzenroeder, P. Helander, P. Heller, R. Hidalgo, C. Hildebrandt, D. Hohnle, H. Holtz, A. Holzhauer, E. Holzthum, R. Huber, A. Hunger, H. Hurd, F. Ihrke, M. Illy, S. Ivanov, A. Jablonski, S. Jaksic, N. Jakubowski, M. Jensen, H. Jenzsch, H. Kacmarczyk, J. Kaliatk, T. Kallmeyer, J. Kamionka, U. Karaleviciu, R. Kern, S. Keunecke, M. Kleiber, R. Knauer, J. Koch, R. Kocsis, G. Konies, G. Koppen, M. Koslowski, R. Koshurinov, J. Kramer-Flecken, A. Krampitz, R. Kravtsov, Y. Krychowiak, M. Krzesinski, G. Ksiazek, I. Kubkowska, F. Kus, A. Langish, S. Laube, R. Laux, M. Lazerson, S. Lennartz, M. Li, C. Lietzow, R. Lohs, A. Lorenz, A. Louche, F. Lubyako, L. Lumsdaine, A. Lyssoivan, A. Maassberg, H. Marek, P. Martens, C. Marushchenko, N. Mayer, M. Mendelevitch, B. Mertens, P. Mikkelsen, D. Mishchenko, A. Missal, B. Mizuuchi, T. Modrow, H. Monnich, T. Morizaki, T. Murakami, S. Musielok, F. Nagel, M. Naujoks, D. Neilson, H. Neubauer, O. Neuner, U. Nocentini, R. Noterdaeme, J. M. Nuhrenberg, C. Obermayer, S. Offermanns, G. Oosterbeek, H. Otte, M. Panin, A. Pap, M. Paquay, S. Pasch, E. Peng, X. Petrov, S. Pilopp, D. Pirsch, H. Plaum, B. Pompon, F. Povilaitis, M. Preinhaelter, J. Prinz, O. Purps, F. Rajna, T. Recesi, S. Reiman, A. Reiter, D. Remmel, J. Renard, S. Rhode, V. Riemann, J. Rimkevicius, S. Risse, K. Rodatos, A. Rodin, I. Rome, M. Roscher, H. J. Rummel, K. Rummel, T. Runov, A. Ryc, L. Sachtleben, J. Samartsev, A. Sanchez, M. Sano, F. Scarabosio, A. Schmid, M. M. Schmitz, H. Schmitz, O. Schneider, M. Schneider, W. Scheibl, L. Scholz, M. Schroder, G. Schroder, M. Schruff, J. Schumacher, H. Shikhovtsev, I. V. Shoji, M. Siegl, G. Skodzik, J. Smirnow, M. Speth, E. Spong, D. A. Stadler, R. Sulek, Z. Szabolics, T. Szetefi, T. Szokefalvi-Nagy, Z. Tereshchenko, A. Thomsen, H. Thumm, M. Timmermann, D. Tittes, H. Toi, K. Tournianski, M. von Toussaint, U. Tretter, J. Tulipan, S. Turba, P. Uhlemann, R. Urban, J. Urbonavicius, E. Urlings, P. Valet, S. Van Eester, D. Van Schoor, M. Vervier, M. Viebke, H. Vilbrandt, R. Vrancken, M. Wauters, T. Weissgerber, M. Weiss, E. Weller, A. Wendorf, J. Wenzel, U. Windisch, T. Winkler, E. Winkler, M. Wolowski, J. Wolters, J. Wrochna, G. Xanthopoulos, P. Yamada, H. Yokoyama, M. Zacharias, D. Zajac, J. Zangl, G. Zarnstorff, M. Zeplien, H. Zoletnik, S. Zuin, M. U1 - FP U2 - TP U5 - 9ec4f6d15344384bf80d916052633c5f ER - TY - JOUR T1 - Overview of ASDEX Upgrade results JF - Nuclear Fusion Y1 - 2013 A1 - Stroth, U. A1 - Adamek, J. A1 - Aho-Mantila, L. A1 - Akaslompolo, S. A1 - Amdor, C. A1 - Angioni, C. A1 - Balden, M. A1 - Bardin, S. A1 - L. Barrera Orte A1 - Behler, K. A1 - Belonohy, E. A1 - Bergmann, A. A1 - Bernert, M. A1 - Bilato, R. A1 - Birkenmeier, G. A1 - Bobkov, V. A1 - Boom, J. A1 - Bottereau, C. A1 - Bottino, A. A1 - Braun, F. A1 - Brezinsek, S. A1 - Brochard, T. A1 - M. Brüdgam A1 - Buhler, A. A1 - Burckhart, A. A1 - Casson, F. J. A1 - Chankin, A. A1 - Chapman, I. A1 - Clairet, F. A1 - Classen, I.G.J. A1 - Coenen, J. W. A1 - Conway, G. D. A1 - Coster, D. P. A1 - Curran, D. A1 - da Silva, F. A1 - P. de Marné A1 - D'Inca, R. A1 - Douai, D. A1 - Drube, R. A1 - Dunne, M. A1 - Dux, R. A1 - Eich, T. A1 - Eixenberger, H. A1 - Endstrasser, N. A1 - Engelhardt, K. A1 - Esposito, B. A1 - Fable, E. A1 - Fischer, R. A1 - H. Fünfgelder A1 - Fuchs, J. C. A1 - K. Gál A1 - M. García Muñoz A1 - Geiger, B. A1 - Giannone, L. A1 - T. Görler A1 - da Graca, S. A1 - Greuner, H. A1 - Gruber, O. A1 - Gude, A. A1 - Guimarais, L. A1 - S. Günter A1 - Haas, G. A1 - Hakola, A. H. A1 - Hangan, D. A1 - Happel, T. A1 - T. Härtl A1 - Hauff, T. A1 - Heinemann, B. A1 - Herrmann, A. A1 - Hobirk, J. A1 - H. Höhnle A1 - M. Hölzl A1 - Hopf, C. A1 - Houben, A. A1 - Igochine, V. A1 - Ionita, C. A1 - Janzer, A. A1 - Jenko, F. A1 - Kantor, M. A1 - C.-P. Käsemann A1 - Kallenbach, A. A1 - S. Kálvin A1 - Kantor, M. A1 - Kappatou, A. A1 - Kardaun, O. A1 - Kasparek, W. A1 - Kaufmann, M. A1 - Kirk, A. A1 - H.-J. Klingshirn A1 - Kocan, M. A1 - Kocsis, G. A1 - Konz, C. A1 - Koslowski, R. A1 - Krieger, K. A1 - Kubic, M. A1 - Kurki-Suonio, T. A1 - Kurzan, B. A1 - Lackner, K. A1 - Lang, P. T. A1 - Lauber, P. A1 - Laux, M. A1 - Lazaros, A. A1 - Leipold, F. A1 - Leuterer, F. A1 - Lindig, S. A1 - Lisgo, S. A1 - Lohs, A. A1 - Lunt, T. A1 - Maier, H. A1 - Makkonen, T. A1 - Mank, K. A1 - M.-E. Manso A1 - Maraschek, M. A1 - Mayer, M. A1 - McCarthy, P. J. A1 - McDermott, R. A1 - Mehlmann, F. A1 - Meister, H. A1 - Menchero, L. A1 - Meo, F. A1 - Merkel, P. A1 - Merkel, R. A1 - Mertens, V. A1 - Merz, F. A1 - Mlynek, A. A1 - Monaco, F. A1 - Müller, S. A1 - H.W. Müller A1 - M. Münich A1 - Neu, G. A1 - Neu, R. A1 - Neuwirth, D. A1 - Nocente, M. A1 - Nold, B. A1 - Noterdaeme, J. M. A1 - Pautasso, G. A1 - Pereverzev, G. A1 - B. Plöckl A1 - Podoba, Y. A1 - Pompon, F. A1 - Poli, E. A1 - Polozhiy, K. A1 - Potzel, S. A1 - M. J. Pueschel A1 - Putterich, T. A1 - Rathgeber, S. K. A1 - Raupp, G. A1 - Reich, M. A1 - Reimold, F. A1 - Ribeiro, T. A1 - Riedl, R. A1 - Rohde, V. A1 - G. J. van Rooij A1 - Roth, J. A1 - Rott, M. A1 - Ryter, F. A1 - Salewski, M. A1 - Santos, J. A1 - Sauter, P. A1 - Scarabosio, A. A1 - Schall, G. A1 - Schmid, K. A1 - Schneider, P. A. A1 - Schneider, W. A1 - Schrittwieser, R. A1 - Schubert, M. A1 - Schweinzer, J. A1 - Scott, B. A1 - Sempf, M. A1 - Sertoli, M. A1 - Siccinio, M. A1 - Sieglin, B. A1 - Sigalov, A. A1 - Silva, A. A1 - Sommer, F. A1 - A. Stäbler A1 - Stober, J. A1 - Streibl, B. A1 - Strumberger, E. A1 - Sugiyama, K. A1 - Suttrop, W. A1 - Tala, T. A1 - Tardini, G. A1 - Teschke, M. A1 - Tichmann, C. A1 - Told, D. A1 - Treutterer, W. A1 - Tsalas, M. A1 - VanZeeland, M. A. A1 - Varela, P. A1 - Veres, G. A1 - Vicente, J. A1 - Vianello, N. A1 - Vierle, T. A1 - Viezzer, E. A1 - Viola, B. A1 - Vorpahl, C. A1 - Wachowski, M. A1 - Wagner, D. A1 - Wauters, T. A1 - Weller, A. A1 - Wenninger, R. A1 - Wieland, B. A1 - Willensdorfer, M. A1 - Wischmeier, M. A1 - Wolfrum, E. A1 - E. Würsching A1 - Yu, Q. A1 - Zammuto, I. A1 - Zasche, D. A1 - Zehetbauer, T. A1 - Zhang, Y. A1 - Zilker, M. A1 - Zohm, H. AB - The medium size divertor tokamak ASDEX Upgrade (major and minor radii 1.65 m and 0.5 m, respectively, magnetic-field strength 2.5 T) possesses flexible shaping and versatile heating and current drive systems. Recently the technical capabilities were extended by increasing the electron cyclotron resonance heating (ECRH) power, by installing 2 × 8 internal magnetic perturbation coils, and by improving the ion cyclotron range of frequency compatibility with the tungsten wall. With the perturbation coils, reliable suppression of large type-I edge localized modes (ELMs) could be demonstrated in a wide operational window, which opens up above a critical plasma pedestal density. The pellet fuelling efficiency was observed to increase which gives access to H-mode discharges with peaked density profiles at line densities clearly exceeding the empirical Greenwald limit. Owing to the increased ECRH power of 4 MW, H-mode discharges could be studied in regimes with dominant electron heating and low plasma rotation velocities, i.e. under conditions particularly relevant for ITER. The ion-pressure gradient and the neoclassical radial electric field emerge as key parameters for the transition. Using the total simultaneously available heating power of 23 MW, high performance discharges have been carried out where feed-back controlled radiative cooling in the core and the divertor allowed the divertor peak power loads to be maintained below 5 MW m −2 . Under attached divertor conditions, a multi-device scaling expression for the power-decay length was obtained which is independent of major radius and decreases with magnetic field resulting in a decay length of 1 mm for ITER. At higher densities and under partially detached conditions, however, a broadening of the decay length is observed. In discharges with density ramps up to the density limit, the divertor plasma shows a complex behaviour with a localized high-density region in the inner divertor before the outer divertor detaches. Turbulent transport is studied in the core and the scrape-off layer (SOL). Discharges over a wide parameter range exhibit a close link between core momentum and density transport. Consistent with gyro-kinetic calculations, the density gradient at half plasma radius determines the momentum transport through residual stress and thus the central toroidal rotation. In the SOL a close comparison of probe data with a gyro-fluid code showed excellent agreement and points to the dominance of drift waves. Intermittent structures from ELMs and from turbulence are shown to have high ion temperatures even at large distances outside the separatrix. VL - 53 UR - http://hdl.handle.net/11858/00-001M-0000-0026-E166-7 IS - 10 U1 - FP U2 - PDG U5 - 0b5b08fdc590c85cc01e6d1db1958848 ER - TY - JOUR T1 - Overview on plasma operation with a full tungsten wall in ASDEX Upgrade JF - Journal of Nuclear Materials Y1 - 2013 A1 - Neu, R. A1 - Kallenbach, A. A1 - Balden, M. A1 - Bobkov, V. A1 - Coenen, J. W. A1 - Drube, R. A1 - Dux, R. A1 - Greuner, H. A1 - Herrmann, A. A1 - Hobirk, J. A1 - H. Höhnle A1 - Krieger, K. A1 - M. Kočan A1 - Lang, P. A1 - Lunt, T. A1 - Maier, H. A1 - Mayer, M. A1 - H.W. Müller A1 - Potzel, S. A1 - Putterich, T. A1 - Rapp, J. A1 - Rohde, V. A1 - Ryter, F. A1 - Schneider, P. A. A1 - Schweinzer, J. A1 - Sertoli, M. A1 - Stober, J. A1 - Suttrop, W. A1 - Sugiyama, K. A1 - G. J. van Rooij A1 - Wischmeier, M. AB - Abstract Operation with all tungsten plasma facing components has become routine in ASDEX Upgrade. The conditioning of the device is strongly simplified and short glow discharges are used only on a daily basis. The long term fuel retention was reduced by more than a factor of 5 as demonstrated in gas balance as well as in post mortem analyses. Injecting nitrogen for radiative cooling, discharges with additional heating power up to 23 MW have been achieved, providing good confinement (H98y2=1), divertor power loads around 5 MW m−2 and divertor temperatures below 10 eV. ELM mitigation by pellet ELM pacemaking or magnetic perturbation coils reduces the deposited energy during ELMs, but also keeps the W density at the pedestal low. As a recipe to keep the central W concentration sufficiently low, central (wave) heating is well established and low density H-Modes could be re-established with the newly available ECRH power of up to 4 MW. The ICRH induced W sources could be strongly reduced by applying boron coatings to the poloidal guard limiters. VL - 438, Supplement UR - http://www.sciencedirect.com/science/article/pii/S0022311513000147 N1 -The formation of metallic nanostructures by exposure of molybdenum and tungsten surfaces to high fluxes of low energy helium ions is studied as a function of the ion energy, plasma exposure time, and surface temperature. Helium plasma exposure leads to the formation of nanoscopic filaments on the surface of both metals. The size of the helium-induced nanostructure increases with increasing surface temperature while the thickness of the modified layer increases with time. In addition, the growth rate of the nanostructured layer also depends on the surface temperature. The size of the nanostructure appears linked with the size of the near-surface voids induced by the low energy ions. The results presented here thus demonstrate that surface processing by low-energy helium ions provides an efficient route for the formation of porous metallic nanostructures. (C) 2012 American Vacuum Society.

VL - 30 SN - 0734-2101 U1 -PSI

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U5 - b374bafe384141c27f7d25ba6fa74a18 ER - TY - JOUR T1 - Overview of ASDEX Upgrade results JF - Nuclear Fusion Y1 - 2011 A1 - Kallenbach, A. A1 - Adamek, J. A1 - Aho-Mantila, L. A1 - Akaslompolo, S. A1 - Angioni, C. A1 - Atanasiu, C. V. A1 - Balden, M. A1 - Behler, K. A1 - Belonohy, E. A1 - Bergmann, A. A1 - Bernert, M. A1 - Bilato, R. A1 - Bobkov, V. A1 - Boom, J. A1 - Bottino, A. A1 - Braun, F. A1 - Brudgam, M. A1 - Buhler, A. A1 - Burckhart, A. A1 - Chankin, A. A1 - Classen, I.G.J. A1 - Conway, G. D. A1 - Coster, D. P. A1 - de Marne, P. A1 - D'Inca, R. A1 - Drube, R. A1 - Dux, R. A1 - Eich, T. A1 - Endstrasser, N. A1 - Engelhardt, K. A1 - Esposito, B. A1 - Fable, E. A1 - Fahrbach, H. U. A1 - Fattorini, L. A1 - Fischer, R. A1 - Flaws, A. A1 - Funfgelder, H. A1 - Fuchs, J. C. A1 - Gal, K. A1 - Munoz, M. G. A1 - Geiger, B. A1 - Adamov, M. G. A1 - Giannone, L. A1 - Giroud, C. A1 - Gorler, T. A1 - da Graca, S. A1 - Greuner, H. A1 - Gruber, O. A1 - Gude, A. A1 - Gunter, S. A1 - Haas, G. A1 - Hakola, A. H. A1 - Hangan, D. A1 - Happel, T. A1 - Hauff, T. A1 - Heinemann, B. A1 - Herrmann, A. A1 - Hicks, N. A1 - Hobirk, J. A1 - Hohnle, H. A1 - Holzl, M. A1 - Hopf, C. A1 - Horton, L. A1 - Huart, M. A1 - Igochine, V. A1 - Ionita, C. A1 - Janzer, A. A1 - Jenko, F. A1 - Kasemann, C. P. A1 - Kalvin, S. A1 - Kardaun, O. A1 - Kaufmann, M. A1 - Kirk, A. A1 - Klingshirn, H. J. A1 - Kocan, M. A1 - Kocsis, G. A1 - Kollotzek, H. A1 - Konz, C. A1 - Koslowski, R. A1 - Krieger, K. A1 - Kurki-Suonio, T. A1 - Kurzan, B. A1 - Lackner, K. A1 - Lang, P. T. A1 - Lauber, P. A1 - Laux, M. A1 - Leipold, F. A1 - Leuterer, F. A1 - Lohs, A. A1 - N C Luhmann Jr. A1 - Lunt, T. A1 - Lyssoivan, A. A1 - Maier, H. A1 - Maggi, C. A1 - Mank, K. A1 - Manso, M. E. A1 - Maraschek, M. A1 - Martin, P. A1 - Mayer, M. A1 - McCarthy, P. J. A1 - McDermott, R. A1 - Meister, H. A1 - Menchero, L. A1 - Meo, F. A1 - Merkel, P. A1 - Merkel, R. A1 - Mertens, V. A1 - Merz, F. A1 - Mlynek, A. A1 - Monaco, F. A1 - Muller, H. W. A1 - Munich, M. A1 - Murmann, H. A1 - Neu, G. A1 - Neu, R. A1 - Nold, B. A1 - Noterdaeme, J. M. A1 - Park, H. K. A1 - Pautasso, G. A1 - Pereverzev, G. A1 - Podoba, Y. A1 - Pompon, F. A1 - Poli, E. A1 - Polochiy, K. A1 - Potzel, S. A1 - Prechtl, M. A1 - M. J. Pueschel A1 - Putterich, T. A1 - Rathgeber, S. K. A1 - Raupp, G. A1 - Reich, M. A1 - Reiter, B. A1 - Ribeiro, T. A1 - Riedl, R. A1 - Rohde, V. A1 - Roth, J. A1 - Rott, M. A1 - Ryter, F. A1 - Sandmann, W. A1 - Santos, J. A1 - Sassenberg, K. A1 - Sauter, P. A1 - Scarabosio, A. A1 - Schall, G. A1 - Schmid, K. A1 - Schneider, P. A. A1 - Schneider, W. A1 - Schramm, G. A1 - Schrittwieser, R. A1 - Schweinzer, J. A1 - Scott, B. A1 - Sempf, M. A1 - Serra, F. A1 - Sertoli, M. A1 - Siccinio, M. A1 - Sigalov, A. A1 - Silva, A. A1 - Sips, A.C.C. A1 - Sommer, F. A1 - Stabler, A. A1 - Stober, J. A1 - Streibl, B. A1 - Strumberger, E. A1 - Sugiyama, K. A1 - Suttrop, W. A1 - Szepesi, T. A1 - Tardini, G. A1 - Tichmann, C. A1 - Told, D. A1 - Treutterer, W. A1 - Urso, L. A1 - Varela, P. A1 - Vincente, J. A1 - Vianello, N. A1 - Vierle, T. A1 - Viezzer, E. A1 - Vorpahl, C. A1 - Wagner, D. A1 - Weller, A. A1 - Wenninger, R. A1 - Wieland, B. A1 - Wigger, C. A1 - Willensdorfer, M. A1 - Wischmeier, M. A1 - Wolfrum, E. A1 - Wursching, E. A1 - Yadikin, D. A1 - Yu, Q. A1 - Zammuto, I. A1 - Zasche, D. A1 - Zehetbauer, T. A1 - Zhang, Y. A1 - Zilker, M. A1 - Zohm, H. KW - PHYSICS KW - REFLECTOMETRY KW - TOKAMAK AB - The ASDEX Upgrade programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. After the finalization of the tungsten coating of the plasma facing components, the re-availability of all flywheel-generators allowed high-power operation with up to 20 MW heating power at I(p) up to 1.2 MA. Implementation of alternative ECRH schemes (140 GHz O2- and X3-mode) facilitated central heating above n(e) = 1.2 x 10(20) m(-3) and low q(95) operation at B(t) = 1.8 T. Central O2-mode heating was successfully used in high P/R discharges with 20 MW total heating power and divertor load control with nitrogen seeding. Improved energy confinement is obtained with nitrogen seeding both for type-I and type-III ELMy conditions. The main contributor is increased plasma temperature, no significant changes in the density profile have been observed. This behaviour may be explained by higher pedestal temperatures caused by ion dilution in combination with a pressure limited pedestal and hollow nitrogen profiles. Core particle transport simulations with gyrokinetic calculations have been benchmarked by dedicated discharges using variations of the ECRH deposition location. The reaction of normalized electron density gradients to variations of temperature gradients and the T(e)/T(i) ratio could be well reproduced. Doppler reflectometry studies at the L-H transition allowed the disentanglement of the interplay between the oscillatory geodesic acoustic modes, turbulent fluctuations and the mean equilibrium E x B flow in the edge negative E(r) well region just inside the separatrix. Improved pedestal diagnostics revealed also a refined picture of the pedestal transport in the fully developed H-mode type-I ELM cycle. Impurity ion transport turned out to be neoclassical in between ELMs. Electron and energy transport remain anomalous, but exhibit different recovery time scales after an ELM. After recovery of the pre-ELM profiles, strong fluctuations develop in the gradients of n(e) and T(e). The occurrence of the next ELM cannot be explained by the local current diffusion time scale, since this turns out to be too short. Fast ion losses induced by shear Alfven eigenmodes have been investigated by time-resolved energy and pitch angle measurements. This allowed the separation of the convective and diffusive loss mechanisms. VL - 51 SN - 0029-5515 IS - 9 N1 - ISI Document Delivery No.: 818DPTimes Cited: 1Cited Reference Count: 45SI U1 - FP U2 - PDG U5 - a193177a90d5b600862ca1e40bcc67af ER - TY - JOUR T1 - Plasma surface interactions in impurity seeded plasmas JF - Journal of Nuclear Materials Y1 - 2011 A1 - Kallenbach, A. A1 - Balden, M. A1 - Dux, R. A1 - Eich, T. A1 - Giroud, C. A1 - Huber, A. A1 - G. P. Maddison A1 - Mayer, M. A1 - McCormick, K. A1 - Neu, R. A1 - Petrie, T. W. A1 - Putterich, T. A1 - Rapp, J. A1 - Reinke, M. L. A1 - Schmid, K. A1 - Schweinzer, J. A1 - Wolfe, S. KW - ASDEX UPGRADE KW - BOUNDARY KW - divertor KW - EDGE PROPERTIES KW - H-MODE DISCHARGES KW - HEAT LOAD KW - HIGH-DENSITY KW - IMPROVED CONFINEMENT KW - JET KW - TOKAMAK AB -With tokamak devices developing towards higher heating powers, and carbon plasma facing components being increasingly replaced by high-Z materials like tungsten, impurity seeding for radiative power dissipation gains more importance. This review summarizes the core and divertor radiative characteristics of potential seeding species, namely noble gases and nitrogen. Due to its radiative capability below 10 eV, nitrogen turns out to be a suitable replacement for carbon as a divertor radiator. For typical plasma parameters and high radiation levels, it becomes the most important eroding species for high-Z plasma facing components. Nitrogen exhibits pronounced storage in near-surface tungsten layers in an about 1:1 W/N atomic ratio, which may effect W sputtering. While the inter-ELM erosion of tungsten can be almost completely eliminated by electron temperature reduction, type-I ELMs remain an effective sputtering source. Since a large ELM cannot be significantly ameliorated by radiation, impurity seeding has to be integrated with a benign ELM scenario, like the type-III ELMy H-mode or active ELM control by pellets or resonant magnetic perturbations. (C) 2010 Elsevier B.V. All rights reserved.

VL - 415 SN - 0022-3115 IS - 1, Suppl. N1 - ISI Document Delivery No.: 862XTTimes Cited: 3Cited Reference Count: 4819th International Conference on Plasma-Surface Interactions in Controlled Fusion Devices (PSI)MAY 24-28, 2010San Diego, CALawrence Livermore Natl LabS U1 -PSI

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U5 - 6643b17b2ab92eef6511ae0a8d4e6815 ER -