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Overview of ASDEX upgrade results

(2013) NUCLEAR FUSION. 53(10).
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Abstract
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 x 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.
Keywords
ITER, PHYSICS, INSTABILITIES

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Chicago
Stroth, U, J Adamek, L Aho-Mantila, S Akaslompolo, C Amdor, C Angioni, M Balden, et al. 2013. “Overview of ASDEX Upgrade Results.” Nuclear Fusion 53 (10).
APA
Stroth, U., Adamek, J., Aho-Mantila, L., Akaslompolo, S., Amdor, C., Angioni, C., Balden, M., et al. (2013). Overview of ASDEX upgrade results. NUCLEAR FUSION, 53(10).
Vancouver
1.
Stroth U, Adamek J, Aho-Mantila L, Akaslompolo S, Amdor C, Angioni C, et al. Overview of ASDEX upgrade results. NUCLEAR FUSION. BRISTOL: IOP PUBLISHING LTD; 2013;53(10).
MLA
Stroth, U, J Adamek, L Aho-Mantila, et al. “Overview of ASDEX Upgrade Results.” NUCLEAR FUSION 53.10 (2013): n. pag. Print.
@article{7148639,
  abstract     = {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 x 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.},
  articleno    = {104003},
  author       = {Stroth, U and Adamek, J and Aho-Mantila, L and Akaslompolo, S and Amdor, C and Angioni, C and Balden, M and Bardin, S and Orte, LB and Behler, K and Belonohy, E and Bergmann, A and Bernert, M and Bilato, R and Birkenmeier, G and Bobkov, V and Boom, J and Bottereau, C and Bottino, A and Braun, F and Brezinsek, S and Brochard, T and Brudgam, M and Buhler, A and Burckhart, A and Casson, FJ and Chankin, A and Chapman, I and Clairet, F and Classen, IGJ and Coenen, JW and Conway, GD and Coster, DP and Curran, D and da Silva, F and de Marne, P and D'Inca, R and Douai, D and Drube, R and Dunne, M and Dux, R and Eich, T and Eixenberger, H and Endstrasser, N and Engelhardt, K and Esposito, B and Fable, E and Fischer, R and Funfgelder, H and Fuchs, JC and Gal, K and Munoz, MG and Geiger, B and Giannone, L and Gorler, T and da Graca, S and Greuner, H and Gruber, O and Gude, A and Guimarais, L and Gunter, S and Haas, G and Hakola, AH and Hangan, D and Happel, T and Hartl, T and Hauff, T and Heinemann, B and Herrmann, A and Hobirk, J and Hohnle, H and Holzl, M and Hopf, C and Houben, A and Igochine, V and Ionita, C and Janzer, A and Jenko, F and Kantor, M and Kasemann, CP and Kallenbach, A and Kalvin, S and Kantor, M and Kappatou, A and Kardaun, O and Kasparek, W and Kaufmann, M and Kirk, A and Klingshirn, HJ and Kocan, M and Kocsis, G and Konz, C and Koslowski, R and Krieger, K and Kubic, M and Kurki-Suonio, T and Kurzan, B and Lackner, K and Lang, PT and Lauber, P and Laux, M and Lazaros, A and Leipold, F and Leuterer, F and Lindig, S and Lisgo, S and Lohs, A and Lunt, T and Maier, H and Makkonen, T and Mank, K and Manso, ME and Maraschek, M and Mayer, M and McCarthy, PJ and McDermott, R and Mehlmann, F and Meister, H and Menchero, L and Meo, F and Merkel, P and Merkel, R and Mertens, V and Merz, F and Mlynek, A and Monaco, F and Muller, S and Muller, HW and Munich, M and Neu, G and Neu, R and Neuwirth, D and Nocente, M and Nold, B and Noterdaeme, Jean-Marie and Pautasso, G and Pereverzev, G and Plockl, B and Podoba, Y and Pompon, F and Poli, E and Polozhiy, K and Potzel, S and Puschel, MJ and Putterich, T and Rathgeber, SK and Raupp, G and Reich, M and Reimold, F and Ribeiro, T and Riedl, R and Rohde, V and Rooij, GV and Roth, J and Rott, M and Ryter, F and Salewski, M and Santos, J and Sauter, P and Scarabosio, A and Schall, G and Schmid, K and Schneider, PA and Schneider, W and Schrittwieser, R and Schubert, M and Schweinzer, J and Scott, B and Sempf, M and Sertoli, M and Siccinio, M and Sieglin, B and Sigalov, A and Silva, A and Sommer, F and Stabler, A and Stober, J and Streibl, B and Strumberger, E and Sugiyama, K and Suttrop, W and Tala, T and Tardini, G and Teschke, M and Tichmann, C and Told, D and Treutterer, W and Tsalas, M and Van Zeeland, MA and Varela, P and Veres, G and Vicente, J and Vianello, N and Vierle, T and Viezzer, E and Viola, B and Vorpahl, C and Wachowski, M and Wagner, D and Wauters, T and Weller, A and Wenninger, R and Wieland, B and Willensdorfer, M and Wischmeier, M and Wolfrum, E and Wursching, E and Yu, Q and Zammuto, I and Zasche, D and Zehetbauer, T and Zhang, Y and Zilker, M and Zohm, H},
  issn         = {0029-5515},
  journal      = {NUCLEAR FUSION},
  language     = {eng},
  number       = {10},
  pages        = {9},
  publisher    = {IOP PUBLISHING LTD},
  title        = {Overview of ASDEX upgrade results},
  url          = {http://dx.doi.org/10.1088/0029-5515/53/10/104003},
  volume       = {53},
  year         = {2013},
}

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