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1. Decadal Evolution of Ice‐Ocean Interactions at a Large East Greenland Glacier Resolved at Fjord Scale With Downscaled Ocean Models and Observations

Author

M. Wood, A. Khazendar, I. Fenty, K. Mankoff, A. T. Nguyen, K. Schulz, J. K. Willis, and H. Zhang

Subjects
ice‐ocean interactions, regional ocean modeling, Greenland glaciers, ice sheets, sea level rise, remote sensing, Geophysics. Cosmic physics, QC801-809
Abstract

Abstract In recent decades, the Greenland ice sheet has been losing mass through glacier retreat and ice flow acceleration. This mass loss is linked with variations in submarine melt, yet existing ocean models are either coarse global simulations focused on decadal‐scale variability or fine‐scale simulations for process‐based investigations. Here, we unite these scales with a framework to downscale from a global state estimate (15 km) into a regional model (3 km) that resolves circulation on the continental shelf. We further downscale into a fjord‐scale model (500 m) that resolves circulation inside fjords and quantifies melt. We demonstrate this approach in Scoresby Sund, East Greenland, and find that interannual variations in submarine melt at Daugaard‐Jensen glacier induced by ocean temperature variability are consistent with the decadal changes in glacier ice dynamics. This study provides a framework by which coarse‐resolution models can be refined to quantify glacier submarine melt for future ice sheet projections.

Published
2024
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2. Design and performance of the Hotrod melt-tip ice-drilling system

Author

W. Colgan, C. Shields, P. Talalay, X. Fan, A. P. Lines, J. Elliott, H. Rajaram, K. Mankoff, M. Jensen, M. Backes, Y. Liu, X. Wei, N. B. Karlsson, H. Spanggård, and A. Ø. Pedersen

Subjects
Geophysics. Cosmic physics, QC801-809
Abstract

We introduce the design and performance of an electrothermal ice-drilling system designed to insert a temperature sensor cable into ice. The melt tip is relatively simple and low-cost, designed for a one-way trip to the ice–bed interface. The drilling system consists of a melt tip, umbilical cable, winch, interface, power supply, and support items. The melt tip and the winch are the most novel elements of the drilling system, and we make the hardware and electrical designs of these components available open-access. Tests conducted in a laboratory indicate that the melt tip has an electrical energy to forward melting heat transfer efficiency of ∼35 % with a theoretical maximum penetration rate of ∼12 m h−1at maximum 6.0 kW power. In contrast, ice-sheet testing suggests the melt tip has an analogous heat transfer efficiency of ∼15 % with a theoretical maximum penetration rate of ∼6 m h−1. We expect the efficiency gap between laboratory and field performance to decrease with increasing operator experience. Umbilical freeze-in due to borehole refreezing is the primary depth-limiting factor of the drilling system. Enthalpy-based borehole refreezing assessments predict refreezing below critical umbilical diameter in ∼4 h at −20 ∘C ice temperatures and ∼20 h at −2 ∘C. This corresponds to a theoretical depth limit of up to ∼200 m, depending on firn thickness, ice temperature, and operator experience.

Published
2023
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3. Greenland Geothermal Heat Flow Database and Map (Version 1)

Author

W. Colgan, A. Wansing, K. Mankoff, M. Lösing, J. Hopper, K. Louden, J. Ebbing, F. G. Christiansen, T. Ingeman-Nielsen, L. C. Liljedahl, J. A. MacGregor, Á. Hjartarson, S. Bernstein, N. B. Karlsson, S. Fuchs, J. Hartikainen, J. Liakka, R. S. Fausto, D. Dahl-Jensen, A. Bjørk, J.-O. Naslund, F. Mørk, Y. Martos, N. Balling, T. Funck, K. K. Kjeldsen, D. Petersen, U. Gregersen, G. Dam, T. Nielsen, S. A. Khan, and A. Løkkegaard

Subjects
Environmental sciences, GE1-350, Geology, QE1-996.5
Abstract

We compile and analyze all available geothermal heat flow measurements collected in and around Greenland into a new database of 419 sites and generate an accompanying spatial map. This database includes 290 sites previously reported by the International Heat Flow Commission (IHFC), for which we now standardize measurement and metadata quality. This database also includes 129 new sites, which have not been previously reported by the IHFC. These new sites consist of 88 offshore measurements and 41 onshore measurements, of which 24 are subglacial. We employ machine learning to synthesize these in situ measurements into a gridded geothermal heat flow model that is consistent across both continental and marine areas in and around Greenland. This model has a native horizontal resolution of 55 km. In comparison to five existing Greenland geothermal heat flow models, our model has the lowest mean geothermal heat flow for Greenland onshore areas. Our modeled heat flow in central North Greenland is highly sensitive to whether the NGRIP (North GReenland Ice core Project) elevated heat flow anomaly is included in the training dataset. Our model's most distinctive spatial feature is pronounced low geothermal heat flow (< 40 mW m−2) across the North Atlantic Craton of southern Greenland. Crucially, our model does not show an area of elevated heat flow that might be interpreted as remnant from the Icelandic plume track. Finally, we discuss the substantial influence of paleoclimatic and other corrections on geothermal heat flow measurements in Greenland. The in situ measurement database and gridded heat flow model, as well as other supporting materials, are freely available from the GEUS Dataverse (https://doi.org/10.22008/FK2/F9P03L; Colgan and Wansing, 2021).

Published
2022
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4. A new compact solid-state neutral particle analyser at ASDEX Upgrade: Setup and physics modeling

Author

S. Martinov, Benedikt Geiger, P. A. Schneider, M. Weiland, F. Ryter, A. Weller, K. Mank, H. Blank, and ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, ASDEX Upgrade, law, Detector, Geiger counter, Plasma, Pitch angle, Neutral particle, Instrumentation, Beam (structure), Spectral line, Computational physics, law.invention
Abstract

At ASDEX Upgrade (AUG), a new compact solid-state detector has been installed to measure the energy spectrum of fast neutrals based on the principle described by Shinohara et al. [Rev. Sci. Instrum. 75, 3640 (2004)]. The diagnostic relies on the usual charge exchange of supra-thermal fast-ions with neutrals in the plasma. Therefore, the measured energy spectra directly correspond to those of confined fast-ions with a pitch angle defined by the line of sight of the detector. Experiments in AUG showed the good signal to noise characteristics of the detector. It is energy calibrated and can measure energies of 40-200 keV with count rates of up to 140 kcps. The detector has an active view on one of the heating beams. The heating beam increases the neutral density locally; thereby, information about the central fast-ion velocity distribution is obtained. The measured fluxes are modeled with a newly developed module for the 3D Monte Carlo code F90FIDASIM [Geiger et al., Plasma Phys. Controlled Fusion 53, 65010 (2011)]. The modeling allows to distinguish between the active (beam) and passive contributions to the signal. Thereby, the birth profile of the measured fast neutrals can be reconstructed. This model reproduces the measured energy spectra with good accuracy when the passive contribution is taken into account.

Published
2015

5. Overview of ASDEX Upgrade results

Author

A. Kallenbach, J. Adamek, L. Aho-Mantila, S. Äkäslompolo, C. Angioni, C.V. Atanasiu, M. Balden, K. Behler, E. Belonohy, A. Bergmann, M. Bernert, R. Bilato, V. Bobkov, J. Boom, A. Bottino, F. Braun, M. Brüdgam, A. Buhler, A. Burckhart, A. Chankin, I.G.J. Classen, G.D. Conway, D.P. Coster, P. de Marné, R. D'Inca, R. Drube, R. Dux, T. Eich, N. Endstrasser, K. Engelhardt, B. Esposito, E. Fable, H.-U. Fahrbach, L. Fattorini, R. Fischer, A. Flaws, H. Fünfgelder, J.C. Fuchs, K. Gál, M. García Muñoz, B. Geiger, M. Gemisic Adamov, L. Giannone, C. Giroud, T. Görler, S. da Graca, H. Greuner, O. Gruber, A. Gude, S. Günter, G. Haas, A.H. Hakola, D. Hangan, T. Happel, T. Hauff, B. Heinemann, A. Herrmann, N. Hicks, J. Hobirk, H. Höhnle, M. Hölzl, C. Hopf, L. Horton, M. Huart, V. Igochine, C. Ionita, A. Janzer, F. Jenko, C.-P. Käsemann, S. Kálvin, O. Kardaun, M. Kaufmann, A. Kirk, H.-J. Klingshirn, M. Kocan, G. Kocsis, H. Kollotzek, C. Konz, R. Koslowski, K. Krieger, T. Kurki-Suonio, B. Kurzan, K. Lackner, P.T. Lang, P. Lauber, M. Laux, F. Leipold, F. Leuterer, A. Lohs, N.C. Luhmann, T. Lunt, A. Lyssoivan, H. Maier, C. Maggi, K. Mank, M.-E. Manso, M. Maraschek, P. Martin, M. Mayer, P.J. McCarthy, R. McDermott, H. Meister, L. Menchero, F. Meo, P. Merkel, R. Merkel, V. Mertens, F. Merz, A. Mlynek, F. Monaco, H.W. Müller, M. Münich, H. Murmann, G. Neu, R. Neu, B. Nold, J.-M. Noterdaeme, H.K. Park, G. Pautasso, G. Pereverzev, Y. Podoba, F. Pompon, E. Poli, K. Polochiy, S. Potzel, M. Prechtl, M.J. Püschel, T. Pütterich, S.K. Rathgeber, G. Raupp, M. Reich, B. Reiter, T. Ribeiro, R. Riedl, V. Rohde, J. Roth, M. Rott, F. Ryter, W. Sandmann, J. Santos, K. Sassenberg, P. Sauter, A. Scarabosio, G. Schall, K. Schmid, P.A. Schneider, W. Schneider, G. Schramm, R. Schrittwieser, J. Schweinzer, B. Scott, M. Sempf, F. Serra, M. Sertoli, M. Siccinio, A. Sigalov, A. Silva, A.C.C. Sips, F. Sommer, A. Stäbler, J. Stober, B. Streibl, E. Strumberger, K. Sugiyama, W. Suttrop, T. Szepesi, G. Tardini, C. Tichmann, D. Told, W. Treutterer, L. Urso, P. Varela, J. Vincente, N. Vianello, T. Vierle, E. Viezzer, C. Vorpahl, D. Wagner, A. Weller, R. Wenninger, B. Wieland, C. Wigger, M. Willensdorfer, M. Wischmeier, E. Wolfrum, E. Würsching, D. Yadikin, Q. Yu, I. Zammuto, D. Zasche, T. Zehetbauer, Y. Zhang, M. Zilker, H. Zohm, and Science and Technology of Nuclear Fusion

Subjects
PHYSICS, Nuclear and High Energy Physics, 0103 physical sciences, TOKAMAK, 010306 general physics, Condensed Matter Physics, 7. Clean energy, 01 natural sciences, 010305 fluids & plasmas, REFLECTOMETRY
Abstract

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 × 1020 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 × 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 Alfvén eigenmodes have been investigated by time-resolved energy and pitch angle measurements. This allowed the separation of the convective and diffusive loss mechanisms.

Published
2011
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6. Addendum to papers from Axially Symmetric Divertor Experiment (ASDEX) Upgrade Team, published in Review of Scientific Instruments

Author

T. Eich, D. Yadikin, P. de Marne, Piero Martin, C. Tichmann, T. Lunt, K. Behler, A. Kammel, E. Strumberger, G. Tardini, K.H. Behringer, G. D. Conway, Bill Scott, F. Monaco, M. Rott, Manfred Zilker, A. Stäbler, K. Krieger, Taina Kurki-Suonio, G. Haas, G. Koscis, B. Streibl, R. Merkel, M. Mantsinen, L. Urso, B. Langer, A. Gude, A. Kirk, J. Stober, H. Doerk-Bendig, T. Hauff, M. Gemisic Adamov, G. Schall, H. Zohm, H.-J. Klingshirn, Karl Schmid, J. M. Santos, Emanuele Poli, K. McCormick, J. Neuhauser, A. Kagarmanov, J. Hobirk, D. Wagner, D. Zasche, Fernando Meo, A. Herrmann, Michael Kaufmann, W. Suttrop, E. Würsching, M. Reich, C. Angioni, G. Pautasso, N. Hicks, G. Antar, C. Wigger, B. Kurzan, H. Meister, Wolf-Dieter Schneider, V. Rohde, C. Vorpahl, Martin Laux, A. Lohs, Jari Likonen, M. Sertoli, D. P. Coster, P. Varela, O. J. W. F. Kardaun, J. Schweinzer, A. Lyssoivan, C. Konz, M. Püschel, M. Manso, L. Fattorini, S. Kálvin, K. Gal, H. Greuner, S. da Graca, Analiza M. Silva, Marco Brambilla, E. Wolfrum, K. Sassenberg, R. Bilato, M. Huart, R. Fischer, M. Münich, K. Mank, V. Mertens, H. Kollotzek, P. Merkel, L. Giannone, H. D. Murmann, N. Hammer, M. Sempf, M. Hölzl, M. Maraschek, Peter Lang, B. Reiter, Sibylle Günter, J. Roth, Lin Liu, H.-U. Fahrbach, Bernd Heinemann, P. Sauter, W. Treutterer, C. V. Atanasiu, I. Classen, U. Seidel, G. V. Pereverzev, Roman Schrittwieser, O. Gruber, R. Riedl, Cary Forest, Patrick J. McCarthy, A. Bergmann, Julia Fuchs, Philipp Lauber, V. Igochine, J. Adamek, F. Ryter, S. Potzel, Tobias Görler, M. Janzer, H. W. Müller, M. Brüdgam, F. Merz, E. Speth, A. Mlynek, M. Garcia-Munoz, F. Serra, E. Vainonen-Ahlgren, M. Balden, J.-M. Noterdaeme, M. Kick, H. F. Meyer, N. Endstrasser, A. V. Chankin, Gerhard Raupp, Mattia Siccinio, Frank Jenko, K.-H. Steuer, Alberto Bottino, K. Engelhardt, T. Pütterich, Q. Yu, R. Drube, R. Dux, A. Sigalov, K. Lackner, Christian Hopf, W. Sandmann, A. Scarabosio, A. Buhler, A. Kallenbach, Thomas Zehetbauer, T. Ribeiro, R. Neu, R. M. McDermott, M. Mayer, R. D’Inca, D. Holtum, F. Braun, G. Neu, B. Nold, J. E. Boom, D. Dodt, R. Stadler, S. Gori, V. Bobkov, M. Wischmeier, F. Leuterer, Peter Schneider, and W. Becker

Subjects
Scientific instrument, Physics, ASDEX Upgrade, Divertor, Nuclear engineering, Addendum, Axial symmetry, Instrumentation, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract

This addendum applies to papers authored by contributors from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade Team published in Review of Scientific Instruments. This addendum provides the full list of ASDEX Upgrade Team contributors and their affiliations.

Published
2010
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7. Plasma wall interaction and its implication in an all tungsten divertor tokamak

Author

Emanuele Poli, Y. R. Martin, L. Fattorini, Fernando Meo, M. Sertoli, G. Tardini, M. Garcia Munoz, T T Ribeiro, Qiang Yu, E. Vainonen-Ahlgren, Laure Vermare, G. Haas, K. Lackner, W. Sandmann, O. J. W. F. Kardaun, M. Rott, R. Merkel, K.-H. Steuer, Piero Martin, A. Kallenbach, P. de Marne, K. Gál, Alberto Bottino, N. Hicks, M. Gemisic-Adamov, Michael Kaufmann, Bruce D. Scott, A. Gude, J. Stober, H. Zohm, V. Mertens, H. D. Murmann, C. V. Atanasiu, K.H. Behringer, D. Wagner, V. Igochine, J.-M. Noterdaeme, Th. Pütterich, K. Sassenberg, A. Flaws, M. Püschel, F. Serra, G. Neu, H. Kollotzek, A. Bergmann, R. Pugno, H. W. Müller, W. Schustereder, K. McCormick, H. Meister, H. Greuner, R. Bilato, M. Huart, Wolf-Dieter Schneider, A. Lohs, R. Schrittwieser, W. Becker, F. Ryter, F. Merz, V. Bobkov, H. F. Meyer, M. Mlynek, Julia Fuchs, M. Mayer, C. F. Maggi, D. Holtum, F. Braun, Peter Lang, J. Hobirk, Taina Kurki-Suonio, A. C. C. Sips, S. da Graca, W. Suttrop, M. Balden, Marco Brambilla, T. Eich, H. Maier, J. M. Santos, M. Wischmeier, C. Tröster, Garrard Conway, E. Würsching, B. Nold, T. Bertoncelli, B. Reiter, M. Zilker, Ana Elisa Bauer de Camargo Silva, Ch. Hopf, C. Angioni, Sibylle Günter, A. Stäbler, R. Riedl, E. Speth, G. Kocsis, Thomas Zehetbauer, Philipp Lauber, S. Kálvin, J. Schirmer, G. V. Pereverzev, K. Engelhardt, C. Tichmann, E. Wolfrum, P. Varela, A. Manini, Patrick J. McCarthy, J. Harhausen, J. Roth, S. Gori, H.-U. Fahrbach, A. Scarabosio, Bernd Heinemann, L. D. Horton, M. E. Manso, Lin Liu, A. Schmid, P. Merkel, Rudolf Neu, D. Yadikin, L. Giannone, C. Konz, M. Maraschek, F. Monaco, E. Strumberger, R. Fischer, J. Fink, K. Mank, S. Dietrich, G. Pautasso, R. Drube, R. Dux, V. Rohde, A. Sigalov, A. Buhler, Martin Laux, Jari Likonen, D. P. Coster, J. Schweinzer, L. Urso, G. Schall, D. Zasche, Ursel Fantz, G. Schramm, A. V. Chankin, K. Behler, Gerhard Raupp, K. Krieger, O. Gruber, K. Dimova, S. Schweizer, J. Neuhauser, A. Herrmann, M. Reich, B. Kurzan, P. Franzen, U. Seidel, M. Kick, and W. Treutterer

Subjects
Tokamak, Materials science, Divertor, Facing Components, Transport, chemistry.chemical_element, Flux, Plasma, Effective radiated power, Tungsten, Condensed Matter Physics, law.invention, Nuclear Energy and Engineering, Alcator C-Mod, chemistry, ASDEX Upgrade, Erosion, law, Iter-Like Wall, Atomic physics, Asdex Upgrade Divertor, Operation
Abstract

ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors close to one was achieved. After the initial conditioning phase, oxygen concentrations similar to that in previous campaigns with boronizations could be achieved. Despite the removal of all macroscopic carbon sources, no strong change in C influxes and C content could be observed so far. The W concentrations are similar to the ones measured previously in discharges with old boronization and only partial coverage of the surfaces with W. Concomitantly it is found that although the W erosion flux in the divertor is larger than the W sources in the main chamber in most of the scenarios, it plays only a minor role for the W content in the main plasma. For large antenna distances and strong gas puffing, ICRH power coupling could be optimized to reduce the W influxes. This allowed a similar increase of stored energy as yielded with comparable beam power. However, a strong increase of radiated power and a loss of H-Mode was observed for conditions with high temperature edge plasma close to the antennas. The use of ECRH allowed keeping the central peaking of the W concentration low and even phases of improved H-modes have already been achieved.

Published
2007
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8. Overview of ASDEX Upgrade results

Author

H. Zohm 1), C. Angioni 1), R. Arslanbekov 1), C. Atanasiu 2), G. Becker 1), W. Becker 1), K. Behler 1), K. Behringer 1), A. Bergmann 1), R. Bilato 1), V. Bobkov 1), D. Bolshukhin 1), T. Bolzonella 3), K. Borrass 1), M. Brambilla 1), F. Braun 1), A. Buhler 1), A. Carlson 1), G.D. Conway 1), D. P. Coster 1), R, Drube 1), R. Dux 1), S. Egorov 4), T. Eich 1), K. Engelhardt 1), H.-U. Fahrbach 1), U. Fantz 5), H. Faugel 1), K.H. Finken 6), M. Foley 7), P. Franzen 1), J. C. Fuchs 1), J. Gafert 1), K.B. Fournier 8), G. Gantenbein 9), O. Gehre 1), A. Geier 1), J. Gernhardt 1), T. Goodman 10), O. Gruber 1), A. Gude 1), S. G¨unter 1), G. Haas 1), D. Hartmann 1), B. Heger 5), B. Heinemann 1), A. Herrmann 1), J. Hobirk 1), F. Hofmeister 1), H. Hohen¨ocker 1), L. D. Horton 1), V. Igochine 1), A. Jacchia 11), M. Jakobi 1), F. Jenko 1), A. Kallenbach 1), O. Kardaun 1), M. Kaufmann 1), A. Keller 1), A. Kendl 1), J.-W. Kim 1), K. Kirov 1), R. Kochergov 1), H. Kollotzek 1), W. Kraus 1), K. Krieger 1), T. Kurki-Suonio 12) B. Kurzan 1), P. T. Lang 1), C. Lasnier, P. Lauber 1), M. Laux 1), A.W. Leonard 13), F. Leuterer 1), A. Lohs 1), A. Lorenz 1), R. Lorenzini 3), C. Maggi 1), H. Maier 1), K. Mank 1), M.-E. Manso 14), P. Mantica 12), M. Maraschek 1), E. Martines 3), K.-F. Mast 1), P. McCarthy 7), D. Meisel 1), H. Meister 1), F. Meo 1), P. Merkel 1), R. Merkel 1), D. Merkl 1), V. Mertens 1), F. Monaco 1), A.M¨uck 1), H.W.M¨uller 1), M.M¨unich 1), H.Murmann 1), Y.-S. Na 1), G. Neu 1), R. Neu 1), J. Neuhauser 1), F. Nguyen 15), D. Nishijima 1), Y. Nishimura 1), J.-M. Noterdaeme 1), I. Nunes 14), G. Pautasso 1), A. G. Peeters 1), G. Pereverzev 1), S. D. Pinches 1), E. Poli 1), M. Proschek 16), R. Pugno 1), E. Quigley 7), G. Raupp 1), M. Reich 1), T. Ribeiro 14), R. Riedl 1), V. Rohde 1), J. Roth 1), F. Ryter 1), S. Saarelma 12), W. Sandmann 1), A. Savtchkov 6), O. Sauter 10), S. Schade 1), H.-B. Schilling 1), W. Schneider 1), G. Schramm 1), E. Schwarz 1), J. Schweinzer 1), S. Schweizer 1), B. D. Scott 1), U. Seidel 1), F. Serra 14), S. Sesnic 1), C. Sihler 1), A. Silva 14), A. C. C. Sips 1), E. Speth 1), A. St¨abler 1), K.-H. Steuer 1), J. Stober 1), B. Streibl 1), E. Strumberger 1), W. Suttrop 1), A. Tabasso 1), A. Tanga 1), G. Tardini 1), C. Tichmann 1), W. Treutterer 1), M. Troppmann 1), H. Urano 1), P. Varela 14), O. Vollmer 1), D. Wagner 1), U. Wenzel 1), F. Wesner 1), E. Westerhof 17), R. Wolf 1), E. Wolfrum 1), E. W¨ursching 1), S.-W. Yoon 1), Q. Yu 1), D. Zasche 1), T. Zehetbauer 1), and H.-P. Zehrfeld 1)

Subjects
___
Abstract

Recent results from ASDEX Upgrade are presented. An improved understanding of energy and particle transport emerges in terms of a 'critical gradient' model for the temperature gradients. Coupling this to particle diffusion explains most of the observed behaviour of the density profiles, in particular the finding that strong central heating reduces the tendency for density profile peaking. Internal transport barriers with Te and Ti in excess of 20 keV (but not simultaneously) have been achieved. By shaping the plasma, a regime with small type II ELMs has been established. Here, the maximum power deposited on the target plates was greatly reduced at constant average power. Also, an increase of the ELM frequency by injection of shallow pellets was demonstrated. ELMfree operation is possible in the QH-mode regime previously found in DIII-D which has also been established on ASDEX Upgrade. Regarding stability, a regime with benign NTMs was found. During ECCD stabilisation of NTMs, bN could be increased well above the usual onset level without a reappearance of the NTM. ECRH and ECCD have also been used to control the sawtooth repetition frequency at a moderate fraction of the total heating power. The inner wall of the ASDEX Upgrade vessel has increasingly been covered with tungsten without detrimental effects on plasma performance. Regarding scenario integration, a scenario with a large fraction of noninductively driven current ( 50%), but without internal tranport barrier has been established. It combines improved confinement (tE=tITER98 1:2) and stability (bN 3:5) at high Greenwald fraction (ne=nGW 0:85) in steady state and with type II ELMy edge

Published
2003

10. The subgingival microbiomes in periodontitis and health of individuals with rheumatoid arthritis and at risk of developing rheumatoid arthritis

Author

Z. Cheng, T. Do, K. Mankia, J.L. Meade, L. Hunt, J. Nam, A. Tugnait, A. Speirs, V. Clerehugh, P. Emery, and D. Devine

Subjects
Infectious and parasitic diseases, RC109-216, Microbiology, QR1-502
Abstract

Serum anti-citrullinated protein antibodies (ACPAs), present in 70% of people with rheumatoid arthritis (RA), can be detected ≤10years before the onset of clinical disease. RA and periodontitis are epidemiologically associated and we have reported a high incidence of periodontitis in people who are ACPA+ and at risk of RA. Periodontal bacteria may contribute by multiple routes to the generation of RA-autoantibodies. This study aims to characterise the subgingival microbiomes from periodontitis and health in individuals with/without RA and at risk of RA. Forty-five ACPA+ no RA (RA-at-risk; RAR), 31 healthy controls (HC) and 30 ACPA+ RA patients (RA) underwent a periodontal examination. DNA from subgingival plaque from healthy and deep pocket sites were paired-end sequenced using the Illumina HiSeq3000 and data analysed using MG-RAST + DESeq. Metagenomes in RA samples had high proportions of Actinobacteria; RAR microbiomes contained higher proportions of Bacteroidetes than HC. The relative abundance of P. gingivalis was high in periodontitis and RAR; Aggregatibacter actinomycetemcomitans was detected with similar frequency in each group. Other bacteria implicated in periodontitis and/or autoantibody generation (Filifactor alocis, Prevotella spp, Leptotrichia spp.) were detected. Analyses are on-going to elucidate the diversity and functional potential of the subgingival microbiome associated with RA.

Published
2017
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11. Assimilation of impurities during massive gas injection in ASDEX Upgrade.

Author

G. Pautasso, A. Mlynek, M. Bernert, K. Mank, A. Herrmann, R. Dux, H.W. Müller, A. Scarabosio, M. Sertoli, and Team, the ASDEX Upgrade

Subjects
GAS injection, TOKAMAKS, VALVES, PLASMA gases, NEON, COLLISIONS (Nuclear physics), RADIATION
Abstract

Experiments of disruption mitigation with massive gas injection are conducted in ASDEX Upgrade with fast valves located close to the plasma. The valves and the dedicated experiment are described in this paper. The dependence of the fuelling efficiency on plasma and gas parameters is documented and discussed. Several sources of uncertainties affecting its evaluation and physical interpretation have been addressed. An actual fuelling efficiency of 40% has been reached for neon injection with valves close to the plasma and for gas quantities relevant for the thermal and current quench mitigation of ITER. Refuelling the plasma after thermal quench is shown to be feasible; this result opens the possibility of raising the density in a runaway beam and therefore of increasing the collisional drag on and the radiative energy losses of the fast electrons. [ABSTRACT FROM AUTHOR]

Published
2015
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12. Spring-driven high speed valve for massive gas injection in tokamaks.

Author

Dibon M, Mank K, Pautasso G, Griener M, Herrmann A, Mertens V, Neu R, Ploeckl B, and Rohde V

Abstract

A new high speed gas valve was developed for disruption mitigation studies in the tokamak ASDEX Upgrade. The valve was designed to operate inside the vacuum vessel to reduce the time of flight of the injected gas and to prevent dispersion of the gas cloud before the gas reaches the plasma. A spring-driven mechanism was chosen for the valve as it is robust against the high magnetic fields and electromagnetic disturbances inside the vessel. The internal gas reservoir (128 cm 3 ) of the valve, which holds the mitigation gas, is opened within 1.5 ms, and the maximal stroke between the valve plate and nozzle (diameter 13 mm) is 4.5 mm. This allows a peak flow rate of 72 kPam 3 /s after 1 ms which was determined both analytically and numerically. The highest gas velocity (approximately 560 m/s) is reached 0.6 ms after the valve is opened. The gas cloud expands in a pear shape with an opening angle of 49°.

Published
2017
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13. A new compact solid-state neutral particle analyser at ASDEX Upgrade: Setup and physics modeling.

Author

Schneider PA, Blank H, Geiger B, Mank K, Martinov S, Ryter F, Weiland M, and Weller A

Abstract

At ASDEX Upgrade (AUG), a new compact solid-state detector has been installed to measure the energy spectrum of fast neutrals based on the principle described by Shinohara et al. [Rev. Sci. Instrum. 75, 3640 (2004)]. The diagnostic relies on the usual charge exchange of supra-thermal fast-ions with neutrals in the plasma. Therefore, the measured energy spectra directly correspond to those of confined fast-ions with a pitch angle defined by the line of sight of the detector. Experiments in AUG showed the good signal to noise characteristics of the detector. It is energy calibrated and can measure energies of 40-200 keV with count rates of up to 140 kcps. The detector has an active view on one of the heating beams. The heating beam increases the neutral density locally; thereby, information about the central fast-ion velocity distribution is obtained. The measured fluxes are modeled with a newly developed module for the 3D Monte Carlo code F90FIDASIM [Geiger et al., Plasma Phys. Controlled Fusion 53, 65010 (2011)]. The modeling allows to distinguish between the active (beam) and passive contributions to the signal. Thereby, the birth profile of the measured fast neutrals can be reconstructed. This model reproduces the measured energy spectra with good accuracy when the passive contribution is taken into account.

Published
2015
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