TY - JOUR
T1 - ELM-induced cold pulse propagation in ASDEX Upgrade
JF - Plasma Physics and Controlled Fusion
Y1 - 2019
A1 - Trier, E.
A1 - Wolfrum, E.
A1 - Willensdorfer, M.
A1 - Yu, Q.
A1 - Hoelzl, M.
A1 - Orain, F.
A1 - Ryter, F.
A1 - Angioni, C.
A1 - Bernert, M.
A1 - Vanovac, B.
A1 - Dunne, M. G.
A1 - Denk, S. S.
A1 - Fuchs, J. C.
A1 - Fischer, R.
A1 - Hennequin, P.
A1 - Kurzan, B.
A1 - Mink, F.
A1 - Mlynek, A.
A1 - Odstrcil, T.
A1 - Schneider, P. A.
A1 - Stroth, U.
A1 - Tardini, G.
A1 - ASDEX Upgrade Team
A1 - EUROfusion MST1 Team
AB - In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.
VL - 61
IS - 4
U1 - FP
U2 - TP
U5 - 0279758ced9029d70a2148b4f3b6cd99
ER -
TY - JOUR
T1 - Analysis of electron cyclotron emission with extended electron cyclotron forward modeling
JF - Plasma Physics and Controlled Fusion
Y1 - 2018
A1 - Denk, S. S.
A1 - Fischer, R.
A1 - Smith, H. M.
A1 - Helander, P.
A1 - Maj, O.
A1 - Poli, E.
A1 - Stober, J.
A1 - Stroth, U.
A1 - Suttrop, W.
A1 - Westerhof, E.
A1 - Willensdorfer, M.
VL - 60
IS - 10
U1 - FP
U2 - IMM
U5 - df59365cf1fee065f44d3cc4dc8ce8d2
ER -
TY - JOUR
T1 - Radiation transport modelling for the interpretation of oblique ECE measurements
JF - EPJ Web of Conferences
Y1 - 2017
A1 - Denk, S. S.
A1 - Fischer, R.
A1 - Maj, O.
A1 - Poli, E.
A1 - Stober, J. K.
A1 - Stroth, U.
A1 - Vanovac, B.
A1 - Suttrop, W.
A1 - Willensdorfer, M.
A1 - ASDEX Upgrade Team
AB - The electron cyclotron emission (ECE) diagnostic provides routinely electron temperature (Te) measurements. At ASDEX Upgrade an electron cyclotron forward model, solving the radiation transport equation for given Te and electron density profile, is used in the framework of integrated data analysis. With this method Te profiles can be obtained from ECE measurements even for plasmas with low optical depth. However, due to the assumption of straight lines of sight and an absorption coefficient in the quasi-perpendicular approximation this forward model is not suitable for the interpretation of measurements by ECE diagnostics with an oblique line of sight. Since radiation transport modelling is required for the interpretation of oblique ECE diagnostics we present in this paper an extended forward model that supports oblique lines of sight. To account for the refraction of the line of sight, ray tracing in the cold plasma approximation was added to the model. Furthermore, an absorption coefficient valid for arbitrary propagation was implemented. Using the revised model it is shown that for the oblique ECE Imaging diagnostic at ASDEX Upgrade there can be a significant difference between the cold resonance position and the point from which most of the observed radiation originates.
VL - 147
U1 - FP
U2 - IMT
U5 - 1251a6e9fed6d8ff8ef5cbbc8558b67d
ER -
TY - JOUR
T1 - Velocimetry analysis of type-I edge localized mode precursors in ASDEX Upgrade
JF - Plasma Physics and Controlled Fusion
Y1 - 2014
A1 - Manz, P.
A1 - Boom, J. E.
A1 - Wolfrum, E.
A1 - Birkenmeier, G.
A1 - Classen, I.G.J.
A1 - Luhmann, N. C., Jr.
A1 - Stroth, U.
AB - When the electron transport barrier remains in its final shape before a type-I edge localized mode (ELM) crash in ASDEX Upgrade, ELM precursors appear as electron temperature fluctuations. In order to relate these precursors to an instability, spatial scales, parity and the cross-phase between electron temperature and radial velocity fluctuations are evaluated by means of velocimetry of measured 2D electron temperature fluctuations. A comprehensive comparison with properties of different instabilities points to microtearing modes. Bispectral analysis indicates a nonlinear coupling of these precursors to a ballooning-type mode prior to the ELM onset.
VL - 56
SN - 0741-3335; 1361-6587
IS - 3
U1 - FP
U2 - PDG
U5 - 1a141e91f9102cfcc78a01ef55826c69
ER -
TY - JOUR
T1 - Direct observations of L-I-H and H-I-L transitions with the X-point reciprocating probe in ASDEX Upgrade
JF - Physics of Plasmas
Y1 - 2014
A1 - Mueller, S. H.
A1 - Conway, G. D.
A1 - Birkenmeier, G.
A1 - Carralero, D.
A1 - Happel, T.
A1 - Herrmann, A.
A1 - Manz, P.
A1 - de Marne, P.
A1 - Mlynek, A.
A1 - H.W. Müller
A1 - Potzel, S.
A1 - Rohde, V.
A1 - Stroth, U.
A1 - Tsalas, M.
A1 - Tynan, G. R.
A1 - Wolfrum, E.
A1 - ASDEX Upgrade Team
AB - A reciprocating Langmuir probe was used to directly measure the behavior of turbulence and flows in the X-point region during transitions between low-(L) and high-confinement (H) mode in ASDEX Upgrade. The probe traverses the divertor horizontally in 140 ms, typically 2-5 cm below the X-point. Toroidal Mach number, density, floating potential (phi(f)), and electron temperature (T-e) are measured. In the regime accessible to the probe (P-inj < 1.5 MW, line-integrated core density <4 x 10(19) m(-2)), the L-H transition features an intermediate phase (I-phase), characterized by limit-cycle oscillations at 0.5-3 kHz [Conway et al., Phys. Rev. Lett. 106, 065001 (2011)]. The probe measurements reveal that this pulsing affects both the density and the toroidal Mach number. It is present in both the low-(LFS) and high-field sides (HFS) of the scrape-off layer, while high-amplitude broadband turbulence usually dominates the private-flux region. Profile comparisons between L-mode and I-phase show lower density in pulsing regions and small shifts in T-e, directed oppositely on LFS and HFS, which are compensated by shifts in phi(f) to yield a surprisingly unchanged plasma potential profile. Directly observed L-I-phase transitions reveal that the onset of the pulsing is preceded by a fast 50% density drop in the HFS X-point region. Back transitions to L-mode occur essentially symmetrically, with the pulsing stopping first, followed by a fast recovery to L-mode density levels in the divertor. (C) 2014 AIP Publishing LLC.
VL - 21
SN - 1070-664X; 1089-7674
IS - 4
U1 - FP
U2 - PDG
U5 - d39b1f03098dac734efb08ae91ea4607
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 - Puschel, M. J.
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 -