A large scale program to develop a conceptual design for a demonstration fusion power plant (DEMO) has been initiated in Europe. Central elements are the baseline design points, which are developed by system codes. The assessment of the credibility of these design points is often hampered by missing information. The main physics and technology content of the central European system codes have been published (Kovari et al 2014 Fusion Eng. Des . 89 3054–69, 2016 Fusion Eng. Des . 104 9–20, Reux et al 2015 Nucl. Fusion 55 073011). In addition, this publication discusses key input parameters for the pulsed and conservative design option...).

VL - 57 UR - http://www.euro-fusionscipub.org/wp-content/uploads/WPPMIPR16_16121_submitted.pdf IS - 1 U1 -FP

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U3 - FP120 U5 - 6b859a47ed93fe9914481453756cfbce ER - TY - JOUR T1 - Tearing mode formation induced by internal crash events at different β N JF - Nuclear Fusion Y1 - 2017 A1 - Igochine, V. A1 - Classen, I. A1 - Dunne, M. A1 - Gude, A. A1 - Gunter, S. A1 - Lackner, K. A1 - McDermott, R. M. A1 - Sertoli, M. A1 - Vezinet, D.. A1 - Willensdorfer, M. A1 - Yu, Q. A1 - Zohm, H. A1 - ASDEX Upgrade Team AB -Tearing mode formation after internal crash events like sawteeth or fishbones is one of the most important MHD processes that results in a big island structure and associated confinement degradation. The process implies magnetic reconnection at the rational surface, which has been investigated in great detail in the ASDEX Upgrade tokamak. Using direct local measurements, it is found that the crash leads to the formation of an ideal kink mode with large saturated amplitude at the resonant surface immediately after the sawtooth crash. This kink mode transforms into a tearing mode on a much longer timescale than the crash itself. The ideal kink mode, formed at the resonant surface after the crash, provides the driving force for the magnetic reconnection. The conversion of the ideal kink mode into a tearing mode after the internal crash is similar for various values of plasma rotation and normalized pressure.

VL - 57 UR - http://pubman.mpdl.mpg.de/pubman/item/escidoc:2398199:6/component/escidoc:2401513/Igochine_Tearing.pdf IS - 3 U1 -FP

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U5 - c6df82450ccb1327528ac6de28bc9dfe ER - TY - JOUR T1 - MHD limits and plasma response in high-beta hybrid operations in ASDEX Upgrade JF - Nuclear Fusion Y1 - 2017 A1 - Igochine, V. A1 - Piovesan, P. A1 - Classen, I. G. J. A1 - Dunne, M. A1 - Gude, A. A1 - Lauber, P. A1 - Liu, Y. A1 - Maraschek, M. A1 - Marrelli, L. A1 - McDermott, R. A1 - Reich, M. A1 - Ryan, D. A1 - Schneller, M. A1 - Strumberger, E. A1 - Suttrop, W. A1 - Tardini, G. A1 - Zohm, H. A1 - ASDEX Upgrade Team A1 - EUROfusion MST1 Team VL - 57 UR - http://www.euro-fusionscipub.org/wp-content/uploads/eurofusion/WPMST1PR16_16800_submitted.pdf IS - 11 U1 -FP

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U5 - 5511418de1f750db2e2d76e753b969b6 ER - TY - JOUR T1 - Field-Line Localized Destabilization of Ballooning Modes in Three-Dimensional Tokamaks JF - Physical Review Letters Y1 - 2017 A1 - Willensdorfer, M. A1 - Cote, T. B. A1 - Hegna, C. A1 - Suttrop, W. A1 - Zohm, H. A1 - Dunne, M. A1 - Strumberger, E. A1 - Birkenmeier, G. A1 - Denk, S. S. A1 - Vanovac, B. A1 - Mink, F. A1 - Luhmann, N. C. A1 - ASDEX Upgrade Team AB - Field-line localized ballooning modes have been observed at the edge of high confinement mode plasmas in ASDEX Upgrade with rotating 3D perturbations induced by an externally applied n = 2 error field and during a moderate level of edge localized mode mitigation. The observed ballooning modes are localized to the field lines which experience one of the two zero crossings of the radial flux surface displacement during one rotation period. The localization of the ballooning modes agrees very well with the localization of the largest growth rates from infinite-n ideal ballooning stability calculations using a realistic 3D ideal magnetohydrodynamic equilibrium. This analysis predicts a lower stability with respect to the axisymmetric case. The primary mechanism for the local lower stability is the 3D distortion of the local magnetic shear PB - American Physical Society VL - 119 IS - 8 U1 - FP U2 - PEPD U5 - 1d6ed9bafa05f7cdb28d82d1f88a7a70 ER - TY - JOUR T1 - Plasma response measurements of external magnetic perturbations using electron cyclotron emission and comparisons to 3D ideal MHD equilibrium JF - Plasma Physics and Controlled Fusion Y1 - 2016 A1 - Willensdorfer, M. A1 - Denk, S. S. A1 - Strumberger, E. A1 - Suttrop, W. A1 - Vanovac, B. A1 - Brida, D. A1 - Cavedon, M. A1 - Classen, I. A1 - Dunne, M. A1 - Fietz, S. A1 - Fischer, R. A1 - Kirk, A. A1 - Laggner, F. M. A1 - Liu, Y. Q. A1 - Odstrcil, T. A1 - Ryan, D. A. A1 - Viezzer, E. A1 - Zohm, H. A1 - Luhmann, I. C. A1 - ASDEX Upgrade Team A1 - EUROfusion MST1 Team AB -The plasma response from an external n = 2 magnetic perturbation field in ASDEX Upgrade has been measured using mainly electron cyclotron emission (ECE) diagnostics and a rigid rotating field. To interpret ECE and ECE-imaging (ECE-I) measurements accurately, forward modeling of the radiation transport has been combined with ray tracing. The measured data is compared to synthetic ECE data generated from a 3D ideal magnetohydrodynamics (MHD) equilibrium calculated by VMEC. The measured amplitudes of the helical displacement around the outboard midplane are in reasonable agreement with the one from the synthetic VMEC diagnostics. Both exceed the predictions from the vacuum field calculations and indicate the presence of a kink response at the edge, which amplifies the perturbation. VMEC and MARS-F have been used to calculate the properties of this kink mode. The poloidal mode structure of the magnetic perturbation of this kink mode at the edge peaks at poloidal mode numbers larger than the resonant components vertical bar m vertical bar > vertical bar nq vertical bar, whereas the poloidal mode structure of its displacement is almost resonant vertical bar m vertical bar approximate to vertical bar nq vertical bar. This is expected from ideal MHD in the proximity of rational surfaces. The displacement measured by ECE-I confirms this resonant response.

VL - 58 SN - 0741-3335 UR - https://arxiv.org/abs/1603.09150 IS - 11 U1 -FP

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U3 - FP120 U5 - a1e652bc93cbf7fd81c614e73a717c8b ER - TY - JOUR T1 - Influence of externally applied magnetic perturbations on neoclassical tearing modes at ASDEX Upgrade JF - Nuclear Fusion Y1 - 2015 A1 - Fietz, S. A1 - Bergmann, A. A1 - Classen, I. A1 - Maraschek, M. A1 - M. García-Muñoz A1 - Suttrop, W. A1 - Zohm, H. A1 - ASDEX Upgrade Team AB - The influence of externally applied magnetic perturbations (MPs) on neoclassical tearing modes (NTM) and the plasma rotation in general is investigated at the ASDEX Upgrade tokamak (AUG). The low n resonant components of the applied field exert local torques and influence the stability of NTMs. The non-resonant components of the error field do not influence MHD modes directly but slow down the plasma rotation globally due to a neoclassical toroidal viscous torque (NTV). Both components slow down the plasma rotation, which in consequence increases the probability for the appearance of locked modes. To investigate the impact of externally applied MPs on already existing modes and the influence on the rotation profile, experimental observations are compared to modelling results. The model used here solves a coupled equation system that includes the Rutherford equation and the equation of motion, taking into account the resonant effects and the resistive wall. It is shown that the NTV torque can be neglected in this modelling. To match the experimental frequency evolution of the mode the MP field strength at the resonant surface has to be increased compared to the vacuum approximation. This leads to an overestimation of the stabilizing effect on the NTMs. The reconstruction of the entire rotation profile via the equation of motion including radial dependencies, confirms that the NTV is negligibly small and that small resonant torques at different resonant surfaces have the same effect as one large one. This modelling suggests that in the experiment resonant torques at different surfaces are acting and slowing down the plasma rotation requiring a smaller torque at the specific resonant surface of the NTM. This additionally removes the overestimated influence on the island stability, whereas the braking of the island's rotation is caused by the sum of all torques. Consequently, to describe the effect of MPs on the evolution of one island, all other islands and the corresponding torques must also be taken into account. VL - 55 IS - 1 U1 - FP U2 - PDG U5 - d7ef3c45d2c39d6b80277fd1403be7f0 ER - TY - JOUR T1 - Recent ASDEX Upgrade research in support of ITER and DEMO JF - Nuclear Fusion Y1 - 2015 A1 - Zohm, H. A1 - ASDEX Upgrade Team A1 - EUROfusion MST1 Team A1 - M.R. de Baar VL - 55 IS - 10 U1 - FP U2 - TP U5 - c97b7c936d1f1c6026f3145209635617 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 - Preliminary design of the ITER ECH Upper Launcher JF - Fusion Engineering and Design Y1 - 2013 A1 - Strauss, D. A1 - Aiello, G. A1 - Chavan, R. A1 - Cirant, S. A1 - de M. Baar A1 - Farina, D. A1 - Gantenbein, G. A1 - Goodman, T. P. A1 - Henderson, M. A. A1 - Kasparek, W. A1 - Kleefeldt, K. A1 - Landis, J. D. A1 - Meier, A. A1 - Moro, A. A1 - Platania, P. A1 - Plaum, B. A1 - Poli, E. A1 - Ramponi, G. A1 - Ronden, D. A1 - Saibene, G. A1 - Sanchez, F. A1 - Sauter, O. A1 - Scherer, T. A1 - Schreck, S. A1 - Serikov, A. A1 - Sozzi, C. A1 - Spaeh, P. A1 - Vaccaro, A. A1 - Zohm, H. KW - Diamond windows KW - Electron cyclotron heating KW - ITER KW - mm-Wave optics KW - Prototyping KW - Testing AB - Abstract The design of the ITER electron cyclotron launchers recently reached the preliminary design level - the last major milestone before design finalization. The ITER ECH system contains 24 installed gyrotrons providing a maximum ECH injected power of 20 MW through transmission lines towards the tokamak. There are two EC launcher types both using a front steering mirror; one equatorial launcher (EL) for plasma heating and four upper launchers (UL) for plasma mode stabilization (neoclassical tearing modes and the sawtooth instability). A wide steering angle range of the ULs allows focusing of the beam on magnetic islands which are expected on the rational magnetic flux surfaces q = 1 (sawtooth instability), q = 3/2 and q = 2 (NTMs). In this paper the preliminary design of the ITER ECH UL is presented, including the optical system and the structural components. Highlights of the design include the torus CVD-diamond windows, the frictionless, front steering mechanism and the plasma facing blanket shield module (BSM). Numerical simulations as well as prototype tests are used to verify the design. VL - 88 UR - http://www.sciencedirect.com/science/article/pii/S0920379613003347 U1 - FP U2 - TP U5 - 7d23bc282d1dfc079da6ee58f8bd69fb ER - TY - JOUR T1 - Solitary magnetic perturbations at the ELM onset JF - Nuclear Fusion Y1 - 2012 A1 - Wenninger, R. P. A1 - Zohm, H. A1 - Boom, J. E. A1 - Burckhart, A. A1 - M.G. Dunne A1 - Dux, R. A1 - Eich, T. A1 - Fischer, R. A1 - Fuchs, C. A1 - M. García-Muñoz A1 - Igochine, V. A1 - M. Hölzl A1 - Luhmann N.C. Jr A1 - Lunt, T. A1 - Maraschek, M. A1 - H.W. Müller A1 - Park, H. K. A1 - Schneider, P. A. A1 - Sommer, F. A1 - Suttrop, W. A1 - Viezzer, E. A1 - ASDEX Upgrade Team AB - Tokamak H-mode plasmas frequently exhibit edge-localized modes (ELMs). ELMs allow maintaining sufficient plasma purity and thus enable stationary H-mode. On the other hand in a future device ELMs may cause divertor power flux densities far in excess of tolerable material limits. The size of the energy loss per ELM is determined by saturation effects in the non-linear phase of the ELM, which at present is hardly understood. ASDEX Upgrade is now equipped with a set of fast sampling diagnostics, which is well suited to investigate the chain of events around the ELM crash with appropriate temporal resolution(⩽10 µ s). Solitary magnetic perturbations (SMPs) are identified as dominant features in the radial magnetic fluctuations below 100 kHz. They are typically observed close(±100 µ s) to the onset of pedestal erosion. SMPs are field aligned structures rotating in the electron diamagnetic drift direction with perpendicular velocities of about 10 km s −1 . A comparison of perpendicular velocities suggests that the perturbation evoking SMPs is located at or inside the separatrix. Analysis of very pronounced examples showed that the number of peaks per toroidal turn is 1 or 2, which is clearly lower than the corresponding numbers in linear stability calculations. In combination with strong peaking of the magnetic signals this results in a solitary appearance resembling modes like palm tree modes, edge snakes or outer modes. This behaviour has been quantified as solitariness and correlated with main plasma parameters. SMPs may be considered as a signature of the non-linear ELM phase originating at the separatrix or further inside. Thus they provide a handle to investigate the transition from linear to non-linear ELM phase. By comparison with data from gas puff imaging processes in the non-linear phase at or inside the separatrix and in the scrape-off layer (SOL) can be correlated. A connection between the passing of an SMP and the onset of radial filament propagation has been found. Eventually the findings related to SMPs may contribute to a future quantitative understanding of the non-linear ELM evolution. VL - 52 UR - http://stacks.iop.org/0029-5515/52/i=11/a=114025 U1 - FP U2 - PDG U5 - ba5199e39ab958efb141bf5c030b4118 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 - Overview of the ITER EC H&CD system and its capabilities JF - Fusion Engineering and Design Y1 - 2011 A1 - Omori, T. A1 - Henderson, M. A. A1 - Albajar, F. A1 - Alberti, S. A1 - Baruah, U. A1 - Bigelow, T. S. A1 - Becket, B. A1 - Bertizzolo, R. A1 - Bonicelli, T. A1 - Brusch, A. A1 - Caughman, J. B. A1 - Chavan, R. A1 - Cirant, S. A1 - Collazos, A. A1 - Cox, D. A1 - Darbos, C. A1 - M.R. de Baar A1 - Denisov, G. A1 - Farina, D. A1 - Gandini, F. A1 - Gassmann, T. A1 - Goodman, T. P. A1 - Heidinger, R. A1 - Hogge, J. P. A1 - Illy, S. A1 - Jean, O. A1 - Jin, J. A1 - Kajiwara, K. A1 - Kasparek, W. A1 - Kasugai, A. A1 - Kern, S. A1 - Kobayashi, N. A1 - Kumric, H. A1 - Landis, J. D. A1 - Moro, A. A1 - Nazare, C. A1 - Oda, Y. A1 - Pagonakis, I. A1 - Piosczyk, B. A1 - Platania, P. A1 - Plaum, B. A1 - Poli, E. A1 - Porte, L. A1 - Purohit, D. A1 - Ramponi, G. A1 - Rao, S. L. A1 - Rasmussen, D. A. A1 - Ronden, D. M. S. A1 - Rzesnicki, T. A1 - Saibene, G. A1 - Sakamoto, K. A1 - Sanchez, F. A1 - Scherer, T. A1 - Shapiro, M. A. A1 - Sozzi, C. A1 - Spaeh, P. A1 - Strauss, D. A1 - Sauter, O. A1 - Takahashi, K. A1 - Temkin, R. J. A1 - Thumm, M. A1 - Tran, M. Q. A1 - Udintsev, V.S. A1 - Zohm, H. KW - DESIGN KW - Electron Cyclotron KW - gyrotron KW - ITER KW - launcher KW - MHD stabilization AB -The Electron Cyclotron (EC) system for the ITER tokamak is designed to inject >= 20 MW RF power into the plasma for Heating and Current Drive (H&CD) applications. The EC system consists of up to 26 gyrotrons (between 1 and 2 MW each), the associated power supplies, 24 transmission lines and 5 launchers. The EC system has a diverse range of applications including central heating and current drive, current profile tailoring and control of plasma magneto-hydrodynamic (MUD) instabilities such as the sawtooth and neoclassical tearing modes (NTMs). This diverse range of applications requires the launchers to be capable of depositing the EC power across nearly the entire plasma cross section. This is achieved by two types of antennas: an equatorial port launcher (capable of injecting up to 20 MW from the plasma axis to mid-radius) and four upper port launchers providing access from inside of mid radius to near the plasma edge. The equatorial launcher design is optimized for central heating, current drive and profile tailoring, while the upper launcher should provide a very focused and peaked current density profile to control the plasma instabilities. The overall EC system has been modified during the past 3 years taking into account the issues identified in the ITER design review from 2007 and 2008 as well as integrating new technologies. This paper will review the principal objectives of the EC system, modifications made during the past 2 years and how the design is compliant with the principal objectives. (C) 2011 ITER Organization. Published by Elsevier B.V. All rights reserved.

VL - 86 SN - 0920-3796 IS - 6-8 N1 - ISI Document Delivery No.: 853KZTimes Cited: 1Cited Reference Count: 2526th Symposium on Fusion Technology (SOFT)SEP 27-OCT 01, 2010Porto, PORTUGALInst Plasmas Fusao Nucl (IPFN), Commiss European Union, Inst Soldadura Qualidade (ISQ), Fundacao Ciencia Tecnologia (FCT), Univ Tecnica Lisboa (UTL), TAP, Andante U1 -FP

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U5 - c370f03eff7f1a27a15a35be0d59bc06 ER - TY - JOUR T1 - ELM pacing investigations at JET with the new pellet launcher JF - Nuclear Fusion Y1 - 2011 A1 - Lang, P. T. A1 - Alonso, A. A1 - Alper, B. A1 - Belonohy, E. A1 - Boboc, A. A1 - Devaux, S. A1 - Eich, T. A1 - Frigione, D. A1 - Gal, K. A1 - Garzotti, L. A1 - Geraud, A. A1 - Kocsis, G. A1 - Kochl, F. A1 - Lackner, K. A1 - Loarte, A. A1 - Lomas, P. J. A1 - Maraschek, M. A1 - Muller, H. W. A1 - Neu, R. A1 - Neuhauser, J. A1 - Petravich, G. A1 - Saibene, G. A1 - Schweinzer, J. A1 - Thomsen, H. A1 - Tsalas, M. A1 - Wenninger, R. A1 - Zohm, H. KW - ASDEX UPGRADE KW - ENERGY KW - INJECTION KW - ITER KW - LOSSES KW - MODE AB -A new pellet injection system was installed at JET designed for both fuelling and ELM pacing. The purpose of the pacing section was to validate pellet ELM pacing as a suitable tool for ELM mitigation in ITER. Pellet pacing was confirmed at the large size scale of JET. The dynamics of triggered ELMs was investigated with respect to their spontaneous counterparts. Triggered ELMs show features also typical for spontaneous ELMs in several operational regimes. Since none of these regimes was unsettled by the pellets this is a strong hint for compatibility with other plasma control tools. Observations and modelling results indicate the ELM triggering occurs by the evolution of the pellet ablation plasmoid into the first ELM filament followed by a poloidal spread of the instability. An ELM obviously can be forced by a pellet due to the strong local perturbation imposed already under unusual onset conditions but then evolves like any ELM typical for the corresponding plasma regime. For tool optimization the pellet mass and hence the convective confinement losses imposed have to be minimized. In our experiments, a lower mass threshold was observed for the first time. It has been found that to reliably trigger an ELM the pellet needs to be sufficiently large (and fast) to penetrate close to the pedestal top. Recent investigations are clear steps forward to validate the pellet pacing approach for ITER.

VL - 51 SN - 0029-5515 IS - 3 N1 - ISI Document Delivery No.: 729AETimes Cited: 4Cited Reference Count: 38 U1 -FP

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U5 - 506bca96c5637433dac75b877a0bcc14 ER - TY - JOUR T1 - Structure and dynamics of sawteeth crashes in ASDEX Upgrade JF - Physics of Plasmas Y1 - 2010 A1 - Igochine, V. A1 - Boom, J. A1 - Classen, I. A1 - Dumbrajs, O. A1 - Gunter, S. A1 - Lackner, K. A1 - Pereverzev, G. A1 - Zohm, H. KW - PLASMA KW - RECONNECTION KW - TOKAMAK AB - The crash phase of the sawteeth in ASDEX Upgrade tokamak [Herrmann et al., Fusion Sci. Technol. 44(3), 569 (2003)] is investigated in detail in this paper by means of soft x-ray (SXR) and electron cyclotron emission (ECE) diagnostics. Analysis of precursor and postcursor (1,1) modes shows that the crash does not affect the position of the resonant surface q=1. Our experimental results suggest that sawtooth crash models should contain two ingredients to be consistent with experimental observations: (1) the (1,1) mode structure should survive the crash and (2) the flux changes should be small to preserve the position of the q=1 surface close to its original location. Detailed structure of the reconnection point was investigated with ECE imaging diagnostic. It is shown that reconnection starts locally. The expelled core is hot which is consistent with SXR tomography results. The observed results can be explained in the framework of a stochastic model. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3529363] VL - 17 SN - 1070-664X UR -