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1. Overview of new MAST physics in anticipation of first results from MAST Upgrade

Author

O. Marshall, R. V. Perez, D. Robb, Ben F. McMillan, Michael Barnes, K. J. Gibson, C. Ham, R. J. Akers, J. Lovell, Fabio Riva, L. Piron, J. S. Allcock, Sandra C. Chapman, S.W.A. Irvine, Kurt Flesch, Junchao Huang, I. Klimek, C. D. Challis, S. A. Silburn, A. Kirk, A. Meakins, S. F. Smith, I. Waters, Sean Conroy, G. Naylor, L. Pangione, I. Katramados, Greg Colyer, S. Saarelma, S. Gadgil, Edmund Hood Highcock, Michael Fitzgerald, D. S. Gahle, J. Leland, Paul M. Bryant, S. Hall, Philippa Browning, T. Farley, Saskia Mordijck, L. Appel, T. O'Gorman, Joe Oliver Allen, F. van Wyk, R. O. Dendy, S. S. Henderson, I. T. Chapman, Michael F. J. Fox, H. F. Meyer, Heinke Frerichs, Young-chul Ghim, G. Fishpool, Peter Naylor, Benjamin Daniel Dudson, S. Scannell, R. Stephen, J. Milnes, B. Lloyd, N. Ben Ayed, John Howard, S. Murphy-Sugrue, M. G. O'Mullane, Felix I. Parra, H. R. Wilson, A. W. Morris, S. Gibson, D. A. Ryan, B. Madsen, W. Boeglin, A.J. Thornton, Matthew Carr, K. G. McClements, M. Cox, Ray M. Sharples, S. Allan, K. Mukhi, William Dorland, Oliver Schmitz, G. Cunningham, N. Thomas-Davies, C. Bowman, D. Muir, Colin Roach, O. Myatra, Stanislas Pamela, Mirko Salewski, M. Turnyanskiy, James W. Bradley, Alexander Schekochihin, S. Orchard, Nick Walkden, David Moulton, L. Garzotti, N. J. Conway, R. G. L. Vann, Bruce Lipschultz, M. Price, A. S. Jacobsen, N. Heiberg, G. McArdle, F. Militello, John Omotani, Luke Easy, A. Fil, X. Feng, S. E. Sharapov, L. A. Kogan, Sarah Newton, J. R. Harrison, Bogdan Hnat, A. Sperduti, O. M. Jones, Romualdo Martín, S. Elmore, D. L. Keeling, Matthew Reinke, M. Valovic, Marco Cecconello, A. R. Field, MAST-U Team, and EUROfusion MST1 Team

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Field line, Divertor, MAST, Plasma, Collisionality, Spherical tokamak, Condensed Matter Physics, 01 natural sciences, Resonant magnetic perturbations, 010305 fluids & plasmas, law.invention, Computational physics, Physics::Plasma Physics, law, 0103 physical sciences, 010306 general physics, Neutral particle, Mast upgrade
Abstract

The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ~ 1.3) with similar poloidal cross-section to other medium-size tokamaks. The physics programme concentrates on addressing key physics issues for the operation of ITER, design of DEMO and future spherical tokamaks by utilising high resolution diagnostic measurements closely coupled with theory and modelling to significantly advance our understanding. An empirical scaling of the energy confinement time that favours higher power, lower collisionality devices is consistent with gyrokinetic modelling of electron scale turbulence. Measurements of ion scale turbulence with beam emission spectroscopy and gyrokinetic modelling in up-down symmetric plasmas find that the symmetry of the turbulence is broken by flow shear. Near the non-linear stability threshold, flow shear tilts the density fluctuation correlation function and skews the fluctuation amplitude distribution. Results from fast particle physics studies include the observation that sawteeth are found to redistribute passing and trapped fast particles injected from neutral beam injectors in equal measure, suggesting that resonances between the m = 1 perturbation and the fast ion orbits may be playing a dominant role in the fast ion transport. Measured D–D fusion products from a neutron camera and a charged fusion product detector are 40% lower than predictions from TRANSP/NUBEAM, highlighting possible deficiencies in the guiding centre approximation. Modelling of fast ion losses in the presence of resonant magnetic perturbations (RMPs) can reproduce trends observed in experiments when the plasma response and charge-exchange losses are accounted for. Measurements with a neutral particle analyser during merging-compression start-up indicate the acceleration of ions and electrons. Transport at the plasma edge has been improved through reciprocating probe measurements that have characterised a geodesic acoustic mode at the edge of an ohmic L-mode plasma and particle-in-cell modelling has improved the interpretation of plasma potential estimates from ball-pen probes. The application of RMPs leads to a reduction in particle confinement in L-mode and H-mode and an increase in the core ionization source. The ejection of secondary filaments following type-I ELMs correlates with interactions with surfaces near the X-point. Simulations of the interaction between pairs of filaments in the scrape-off layer suggest this results in modest changes to their velocity, and in most cases can be treated as moving independently. A stochastic model of scrape-off layer profile formation based on the superposition of non-interacting filaments is in good agreement with measured time-average profiles. Transport in the divertor has been improved through fast camera imaging, indicating the presence of a quiescent region devoid of filament near the X-point, extending from the separatrix to ψ n ~ 1.02. Simulations of turbulent transport in the divertor show that the angle between the divertor leg on the curvature vector strongly influences transport into the private flux region via the interchange mechanism. Coherence imaging measurements show counter-streaming flows of impurities due to gas puffing increasing the pressure on field lines where the gas is ionised. MAST Upgrade is based on the original MAST device, with substantially improved capabilities to operate with a Super-X divertor to test extended divertor leg concepts. SOLPS-ITER modelling predicts the detachment threshold will be reduced by more than a factor of 2, in terms of upstream density, in the Super-X compared with a conventional configuration and that the radiation front movement is passively stabilised before it reaches the X-point. 1D fluid modelling reveals the key role of momentum and power loss mechanisms in governing detachment onset and evolution. Analytic modelling indicates that long legs placed at large major radius, or equivalently low at the target compared with the X-point are more amenable to external control. With MAST Upgrade experiments expected in 2019, a thorough characterisation of the sources of the intrinsic error field has been carried out and a mitigation strategy developed.

Published
2019
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2. NBI fast ion confinement in the helical core of MAST hybrid-like plasmas

Author

M. Turnyanskiy, W. A. Cooper, David Pfefferlé, C. Misev, S. Sangaroon, I. T. Chapman, and Jonathan Graves

Subjects
Physics, Nuclear and High Energy Physics, education.field_of_study, Population, Rotational symmetry, fast ion redistribution, Plasma, Condensed Matter Physics, Ion, Amplitude, Physics::Plasma Physics, Ionization, current drive, hybrid scenario, Pinch, Magnetohydrodynamic drive, Atomic physics, education, internal kink mode
Abstract

Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled using the guiding-centre approximation in the internal kinked magnetic topology. General coordinate guiding-centre equations are extended for this purpose. It is found that the kinked core spirals around the position of strongest ionization, which remains geometrically centred, so that a large fraction of the population is deposited in the high shear external region where the plasma is almost axisymmetric. Those particles ionized in the low shear region exhibit exotic drift motion due to the strongly non-axisymmetric equilibrium, periodically passing near the magnetic axis and then reflected by the boundary of the kinked equilibrium, which in this respect acts as a confining pinch. Broad agreement is found against experimental measurement of fast ion particle confinement degradation as the MAST LLM amplitude varies.

Published
2014
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3. Overview of physics results from MAST towards ITER/DEMO and the MAST Upgrade

Author

Erwin Verwichte, K. Imada, R. Zagórski, J. R. Robinson, A. Kirk, M. Kocan, M. Romanelli, I. T. Chapman, Simon Freethy, G. Fishpool, Ian Abel, E. Havlickova, N. J. Conway, S. Zoletnik, V. A. Rozhansky, Young-chul Ghim, D. F. Howell, Michael Barnes, S. Saarelma, M. Cox, A. W. Morris, K. J. Gibson, G. McArdle, R. Scannell, A. Sykes, Daniel Dunai, E. G. Kaveeva, Bogdan Hnat, M. Price, B. Lloyd, R. J. Akers, Felix I. Parra, Alexander Schekochihin, P. Denner, C. D. Challis, D Temple, T. C. Hender, L. Garzotti, O. M. Jones, A. Allan, M. D. Driscoll, P. Cahyna, A. Darke, N. C. Hawkes, S. Sangaroon, H. R. Wilson, Steven Cowley, Romualdo Martín, S. Elmore, J. Horacek, Michael Lehnen, G. Naylor, Edmund Highcock, R. G. L. Vann, Y. Dnestrovsky, N. Ben Ayed, R. O. Dendy, A. V. Danilov, Wojciech Fundamenski, H. Leggate, P. Molchanov, K. G. McClements, T. O'Gorman, I. Wodniak, P. Voskoboynikov, A. N. Saveliev, J. Seidl, David Taylor, S. E. Sharapov, N. C. Barratt, H. F. Meyer, G. P. Maddison, D. Higgins, Greg Colyer, S. Warder, A. Patel, M. Turnyanskiy, D. Ciric, Eric Nardon, A.J. Thornton, C. M. Roach, J. R. Harrison, Ben F. McMillan, S. Lisgo, Vladimir Shevchenko, G. De Temmerman, Mikhail Gryaznevich, Patrick Tamain, L. Appel, Volker Naulin, Benjamin Daniel Dudson, Otto Asunta, S. Shibaev, P. Dura, D. Stork, Clive Michael, M. De Bock, A. Y. Dnestrovsky, Greg J. Tallents, John Canik, Saskia Mordijck, Yunfeng Liang, Fulvio Militello, G. Cunningham, Yueqiang Liu, Anders Nielsen, G.M. Voss, Thomas Morgan, Matthew Lilley, S. D. Pinches, J. Storrs, J. Mailloux, D. L. Keeling, Matthew Hole, B. J. Crowley, M. Valovic, Marco Cecconello, P. Hill, R. J. Lake, A. R. Field, N. Thomas-Davies, D. Muir, S. Allan, Stanislas Pamela, David Dickinson, James W. Bradley, M. R. Dunstan, William Heidbrink, M.R. O'Brien, MAST Team, NBI Team, and Science and Technology of Nuclear Fusion

Subjects
Physics, Nuclear and High Energy Physics, Mega Ampere Spherical Tokamak, Heat flux, Physics::Plasma Physics, Turbulence, Divertor, Magnetic confinement fusion, Spherical tokamak, Condensed Matter Physics, Neutral beam injection, Resonant magnetic perturbations, Computational physics
Abstract

New diagnostic, modelling and plant capability on the Mega Ampère Spherical Tokamak (MAST) have delivered important results in key areas for ITER/DEMO and the upcoming MAST Upgrade, a step towards future ST devices on the path to fusion currently under procurement. Micro-stability analysis of the pedestal highlights the potential roles of micro-tearing modes and kinetic ballooning modes for the pedestal formation. Mitigation of edge localized modes (ELM) using resonant magnetic perturbation has been demonstrated for toroidal mode numbers n = 3, 4, 6 with an ELM frequency increase by up to a factor of 9, compatible with pellet fuelling. The peak heat flux of mitigated and natural ELMs follows the same linear trend with ELM energy loss and the first ELM-resolved Ti measurements in the divertor region are shown. Measurements of flow shear and turbulence dynamics during L-H transitions show filaments erupting from the plasma edge whilst the full flow shear is still present. Off-axis neutral beam injection helps to strongly reduce the redistribution of fast-ions due to fishbone modes when compared to on-axis injection. Low-k ion-scale turbulence has been measured in L-mode and compared to global gyro-kinetic simulations. A statistical analysis of principal turbulence time scales shows them to be of comparable magnitude and reasonably correlated with turbulence decorrelation time. Te inside the island of a neoclassical tearing mode allow the analysis of the island evolution without assuming specific models for the heat flux. Other results include the discrepancy of the current profile evolution during the current ramp-up with solutions of the poloidal field diffusion equation, studies of the anomalous Doppler resonance compressional Alfvén eigenmodes, disruption mitigation studies and modelling of the new divertor design for MAST Upgrade. The novel 3D electron Bernstein synthetic imaging shows promising first data sensitive to the edge current profile and flows. © 2013 IAEA, Vienna.

Published
2013
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4. Observation of fast ion behaviour with a neutron emission profile monitor in MAST

Author

I. Wodniak, R. Akers, Göran Ericsson, Marco Cecconello, Sean Conroy, M. Turnyanskiy, and S. Sangaroon

Subjects
Physics, Nuclear and High Energy Physics, Neutron emission, Astrophysics::High Energy Astrophysical Phenomena, Sawtooth wave, Spherical tokamak, Condensed Matter Physics, Collimated light, Ion, Physics::Plasma Physics, Emissivity, Neutron, Atomic physics, Magnetohydrodynamics, Astrophysics::Galaxy Astrophysics
Abstract

Preliminary measurements of neutron emissivity at the Mega Amp Spherical Tokamak (MAST) along collimated lines-of-sight show a clear correlation between the neutron emissivity temporal and spatial evolution and the evolution of different MHD instabilities. In particular, the variations in neutron emissivity during sawtooth oscillations are compared with changes in the classical fast ion slowing-down time, while fast ion losses are observed in bursts during fishbones or as a continuous process during long-lived modes.

Published
2012
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5. Scaling of H-mode energy confinement withIpandBTin the MAST spherical tokamak

Author

A. Patel, M. Turnyanskiy, G. Cunningham, M. Valovič, R. J. Akers, L. Garzotti, D. Muir, David Taylor, B. Lloyd, and M. J. Walsh

Subjects
Physics, Nuclear and High Energy Physics, Tokamak, Toroid, Magnetic confinement fusion, Plasma, Spherical tokamak, Condensed Matter Physics, Thermal diffusivity, law.invention, Magnetic field, Physics::Plasma Physics, law, Physics::Space Physics, Atomic physics, Scaling
Abstract

The dependences of energy confinement on plasma current and toroidal magnetic field have been investigated in the MAST spherical tokamak in H-mode plasmas. Multivariate fits show that the dependence of energy confinement time on plasma current Ip is weaker than linear while the dependence on toroidal magnetic field BT is stronger than linear, in contrast to conventional energy confinement scalings. These Ip and BT dependences have also been confirmed by single parameter scans. Transport analysis indicates that the strong BT scaling of energy confinement could possibly be explained by weaker q and stronger ν* dependence of heat diffusivity in comparison with conventional tokamaks.

Published
2009
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6. Study of the fast ion confinement and current profile control on MAST

Author

S. D. Pinches, Clive Michael, D. L. Keeling, M. Turnyanskiy, G. Cunningham, N. J. Conway, R. J. Akers, and H. F. Meyer

Subjects
Nuclear and High Energy Physics, Materials science, Magnetic confinement fusion, Plasma, Fusion power, Condensed Matter Physics, Instability, Neutral beam injection, Ion, symbols.namesake, Stark effect, symbols, Atomic physics, Electric current
Abstract

One of the main operational aims of the MAST experiment (Darke et al 1994 Proc. 18th Symp. on Fusion Technology (Karlsruhe, Germany, 1994) p 799) and the proposed MAST upgrade is to investigate possible mechanisms to control the q-profile and drive off-axis current. Experiments were carried out to determine the extent to which the q-profile may be modified using two different approaches, transient and steady-state. Transient effects during the plasma current ramp-up phase were investigated with the aim of developing a start-up regime that can later be used as a target plasma for non-inductive current drive or to access advanced modes of operation such as the hybrid or improved H-mode. The most significant effect in this case was observed when early neutral beam injection (NBI) was applied to the fast current ramp-rate start-up plasmas causing reversed magnetic shear and the plasma current to 'pile-up' off-axis.In steady-state experiments, in which off-axis NBI was studied, results indicate that broadening the fast ion deposition profile by off-axis neutral beam (NB) injection helps to avoid harmful plasma instabilities and significantly extends the operational window of MAST. Long pulse (>0.65 s) H-mode plasmas were achieved with plasma duration limited only by present machine and NBI engineering limits. In order to match the experimentally observed neutron rate and stored energy a low level of anomalous fast ion diffuse ion (Db ~ 0.5 m2 s−1) is required. The introduction of the fast ion diffusion broadens the neutral beam current drive profile and degrades the relative contribution of NB driven current from ~40% to ~30%. To obtain direct measurements of the current profile, a multi-chord motional stark effect diagnostic has been commissioned on MAST and is currently delivering first results in order to confirm the off-axis location of the NB driven current.

Published
2009
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7. TRANSP modelling of total and local neutron emission on MAST

Author

R. J. Akers, Göran Ericsson, I. Klimek, A. Meakins, O. M. Jones, Ivan Lupelli, D. L. Keeling, M. Gorelenkova, Marco Cecconello, and M. Turnyanskiy

Subjects
Physics, Nuclear and High Energy Physics, Neutron count, Neutron emission, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, Plasma, Condensed Matter Physics, Collimated light, Nuclear physics, Mast (sailing), Physics::Plasma Physics, Neutron flux, Physics::Space Physics, Nuclear Experiment
Abstract

The results of TRANSP simulations of neutron count rate profiles measured by a collimated neutron flux monitor-neutron camera (NC)-for different plasma scenarios on MAST are reported. In addition, ...

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8. Major results from the first plasma campaign of the Wendelstein 7-X stellarator

Author

H. Maaßberg, M. Grahl, V. Moncada, Marek Scholz, Naoki Tamura, H. Neilson, R. Koziol, M. Krychowiak, A. Lücke, T. Estrada, R. Munk, M. Marushchenko, K. Toi, Heinrich P. Laqua, S. Paqay, Olaf Grulke, K. Baumann, A. Czermak, Ivan Calvo, Yasuhiro Suzuki, P.J. Heitzenroeder, H. Hölbe, G. Offermanns, Gintautas Dundulis, U. Stridde, H. Hunger, S. Valet, P. Denner, N. Krawczyk, O. Mishchenko, Andrey Samartsev, Mantas Povilaitis, Andrea Pavone, H. Schumacher, P. Aleynikov, H. P. Laqua, U. Wenzel, M. Sibilia, J. Ongena, Kian Rahbarnia, A. Galkowski, T.A. Scherer, C. Slaby, J. Nührenberg, H.-J. Roscher, Martin Köppen, L.-G. Böttger, A. Czarnecka, R. Krampitz, M. Zilker, T. Kremeyer, J. Wendorf, V. Bykov, A. Goriaev, Josef Preinhaelter, A. Alonso, Peter Titus, G. Czymek, Andreas Langenberg, Matteo Zuin, A. Gogoleva, F. Musielok, A. Zeitler, Andreas Schlaich, P. Xanthopoulos, Victoria Winters, M. Losert, D. A. Hartmann, Roberto Guglielmo Citarella, L. Pacios Rodriguez, Boyd Blackwell, E. Blanco, Hans-Stephan Bosch, R. König, R. Stadler, J. Mittelstaedt, Ch. Linsmeier, U. Höfel, N. Panadero Alvarez, E. Pasch, Francesco Cordella, M. Knaup, Fabian Wilde, M. C. Zarnstorff, B. Mendelevitch, Toru Ii Tsujimura, T. Szabolics, Hayato Tsuchiya, J.C. Schmitt, Tadas Kaliatka, Sadayoshi Murakami, Samuel Lazerson, W. Spiess, J. M. García Regaña, P. Junghans, María Sánchez, A. Grosman, I. Yamada, K. P. Hollfeld, K. Aleynikova, Gábor Náfrádi, T. Krings, Daniel Papenfuß, José Luis Velasco, P. Drewelow, N. A. Pablant, S. Renard, Alessandro Zocco, F. Wagner, D. Böckenhoff, S. Ryosuke, Michael Kramer, A. Vorkörper, M. Turnyanskiy, R. Riedl, W. Figacz, H. Trimino Mora, A. da Silva, D. Gradic, M. Keunecke, A. Pieper, M. Houry, S. Pingel, K. H. Schlüter, J. Loizu Cisquella, L. Carraro, S. Schmuck, M. Banduch, Sehyun Kwak, T. Ilkei, X. Huang, Stefan Illy, N. Fahrenkamp, I. Vakulchyk, G. Kocsis, Ph. Mertens, T. Morizaki, K. Czerski, F. V. Chernyshev, Bernd Heinemann, L. Lewerentz, B.J. Peterson, Francisco Castejón, Olaf Neubauer, D. Zhang, Torsten Bluhm, F. Köchl, C.P. von Thun, Michael Cole, Fabio Pisano, R. Brakel, Peter Traverso, G. Orozco, Wolf-Dieter Schneider, A. A. Ivanov, S. Sipliä, V. Szabó, D. Pilopp, A. Cappa, G. Anda, H. Braune, A. Krämer-Flecken, R. Sakamoto, A. Charl, Hiroshi Kasahara, Massimiliano Romé, J.-H. Feist, Mark Cianciosa, M. Führer, G. Schlisio, Taina Kurki-Suonio, F. Purps, H. Esteban, A. H. Reiman, J. Krom, C. D. Beidler, D. Loesser, H. M. Smith, Nengchao Wang, Axel Könies, Oliver Schmitz, T. Bräuer, M. Hirsch, Gabriel G. Plunk, Felix Warmer, R. Karalevicius, Riccardo Nocentini, J.L. Terry, John Jelonnek, Arnold Lumsdaine, L. Ryć, M. N. A. Beurskens, H. Jenzsch, Z. Sulek, Donald A. Spong, A. Khilchenko, P. Marek, R. Schroeder, T. Schröder, B. Standley, Manfred Thumm, B. Brünner, T. Fornal, Benedikt Geiger, H. Frerichs, R. Kleiber, T. Funaba, Andreas Meier, S. Degenkolbe, P. Rong, Dag Hathiramani, Matthias F. Schneider, Simppa Äkäslompolo, M. R. Stoneking, A. Dudek, Jiawu Zhu, X. Han, T. Windisch, Y. Wei, Detlev Reiter, J. Tretter, N. Rust, J. P. Kallmeyer, J. Baldzuhn, P. Bolgert, Dirk Timmermann, Shinsuke Satake, Luis Vela Vela, Yu. Turkin, Z. Szökefalvi-Nagy, Sigitas Rimkevicius, Naoki Kenmochi, Ulrich Neuner, M. Garcia-Munoz, V. Perseo, Matthias Otte, A. Puig Sitjes, Tamás Szepesi, A. da Molin, Alexis Terra, C. Guerard, J.M. Hernández Sánchez, A. Rodatos, J. Assmann, D. Höschen, Albert Mollén, A. Hölting, Tom Wauters, Adnan Ali, Ewa Pawelec, W. Kasparek, Ryo Yasuhara, D. Kinna, P. Sinha, B. Wiegel, Horacio Fernandes, M. E. Puiatti, S. Récsei, E. Ascasíbar, J.-M. Travere, C. Hidalgo, Joris Fellinger, H. Schmitz, Suguru Masuzaki, Katsumi Ida, G. Pelka, Jim-Felix Lobsien, S. Wolf, Jörg Schacht, J. Koshurinov, Han Zhang, P. Kornejew, J M Fontdecaba, T. Ngo, E. Wang, B. Hein, Gerd Gantenbein, Michael Drevlak, M. Vervier, J. W. Oosterbeek, H. Röhlinger, J. P. Knauer, B. Schweer, Jakub Urban, David Maurer, I. Ksiazek, David Gates, S. C. Liu, S. Massidda, F. Remppel, A.H. Wright, G. Satheeswaran, Monika Kubkowska, K. Rummel, Kai Jakob Brunner, Torsten Stange, J. Riemann, Thomas Klinger, S. Obermayer, H. Brand, Christine Hennig, A. Werner, N. Gierse, S. A. Henneberg, R. Vilbrandt, J. Wolowski, T. Sunn Pedersen, M. Dostal, G. A. Wurden, I. Abramovic, Carsten Lechte, R. Lang, S. A. Bozhenkov, G. Ehrke, K. J. McCarthy, Egidijus Urbonavicius, M. Schröder, S. Jablonski, Martina Huber, M. Nagel, Yunfeng Liang, O. P. Ford, Barbara Cannas, T. Mizuuchi, Anatoly Panin, Jan Skodzik, V. V. Lutsenko, R. Koslowski, R. Laube, Jonathan T. Green, B. Unterberg, Jeremy Lore, Laurie Stephey, J. H. E. Proll, M. Czerwinski, Venanzio Giannella, Jörg Weggen, S. Marsen, Clifford M Surko, Grzegorz Gawlik, B. Roth, D. Birus, Ch. Brandt, M. Mardenfeld, K. Riße, Y. Feng, Alexandra M. Freund, M. Vergote, S. Wadle, H. Thomsen, Wilfried Behr, A. Runov, L. Wegener, Burkhard Plaum, J. Svensson, Dmitry Moseev, Łukasz Ciupiński, G. M. Weir, E. Winkler, W. Pan, E. Erckmann, D. Mellein, B. Shanahan, Th. Kobarg, Marek Barlak, John Howard, Günter Dammertz, M. Endler, D.P. Dhard, N. Vianello, L. V. Lubyako, R. Burhenn, J. Thomas, N. Panadero, M. Gruca, T. Mönnich, J. Majano-Brown, Wolfgang Biel, S. Tulipán, J. H. Harris, C. Nührenberg, A. Carls, H. Viebke, Walter H. Fietz, L. Haiduk, S. Brezinsek, Heinz Grote, S. Langish, V. Huber, Jacek Jagielski, David Ennis, P. Kraszewsk, J. Kacmarczyk, Kunihiro Ogawa, U. Kamionka, O. Bertuch, F. Durodié, B. Missal, A. de la Peña, Robertas Alzbutas, Anett Spring, Yu Gao, Matt Landreman, Dirk Naujoks, Florian Effenberg, P. McNeely, Ya. I. Kolesnichenko, B. Gonçalves, B. van Millingen, M. Blatzheim, X. Peng, F. Harberts, M. W. Jakubowski, F. Köster, Gábor Cseh, Ph. Drews, Christoph Biedermann, G. Claps, L. Rudischhauser, Bernardo B. Carvalho, M. Yokoyama, Seung Gyou Baek, Felix Schauer, V. Borsuk, Th. Rummel, J. Boscary, Fumimichi Sano, J. R. Danielson, M. Rack, G. Fuchert, H.-J. Hartfuß, W. Leonhardt, Georg Kühner, D. R. Mikkelsen, M. Borchardt, A. Benndorf, P. Scholz, R. C. Wolf, I.V. Shikhovtsev, Holger Niemann, Andreas Zimbal, J. Geiger, T. Barbui, M. Lennartz, A. Lorenz, Andreas Dinklage, G. Krzesiński, J. Zajac, B. Israeli, R. Schrittwieser, M.J. Cole, S. Zoletnik, O. Marchuk, Per Helander, B. Buttenschön, P. van Eeten, Tamara Andreeva, Hiroshi Yamada, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Max-Planck-Institut fur Plasmaphysik Teilinstitut Greifswald, Wendelsteinstr. 1, 17491 Greifswald, Germany, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), KFKI Research Institute for Particle and Nuclear Physics (KFKI-RMKI), Forschungszentrum Julich GmbH, Institut fur Energie- und Klimaforschung---Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), Wilhelm-Johnen-Strase, 52428 Julich, Germany, University of Maryland, Princeton, Laboratory for Plasma Physics of the Ecole Royale Militaire/Koninklijke Militaire School (LPP-ERM/KMS), Avenue de la Renaissance 30, 1000 Bruxelles, Belgien, Los Alamos National Laboratory (LANL), Institute of Physics, Massachusetts Institute of Technology, Cambridge, University of Wisconsin-Madison, National Centre for Nuclear Research (NCBJ), Institut für Experimentelle Kernphysik, Universität Karlsruhe (IEKP), Geoscience Australia, Max Planck Institut für Plasma Physik and Excellence Cluster, Eindhoven University of Technology, Università degli Studi di Cagliari = University of Cagliari (UniCa), Consorzio Interuniversitario per la Fisica Spaziale (CIFS), Instituto Superior Técnico, Universidade de Lisboa (IST), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Computer Science and Mathematics Division, Oak Ridge National Laboratory, Università di Milano, Warsaw University of Technology, ENEA-Frascati, IPPLM Institute of Plasma Physics and Laser Microfusion, 23 Hery Str., 01-497 Warsaw, Poland, Institute of Nuclear Physics PAN, University of Szczecin, 70-453, aleja Papieza Jana Pawla II 22A, Szczecin, Poland, Milano, University of California [San Diego] (UC San Diego), University of California (UC), International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Brandenburg University of Technology Cottbus-Senftenberg, Universitatsplatz 1, 01968 Senftenberg, Germany, National Institute for Fusion Science (NIFS), 322-6 Oroshicho, Toki, Gifu Prefecture 509-5202, Japan, Universidad Carlos III de Madrid (UC3M), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Budker Institute of Nuclear Physics (BINP), 11, akademika Lavrentieva prospect, Novosibirsk, 630090, Russian Federation, Institut für Raumfahrtsysteme, Universität Stuttgart (IRS), Fraunhofer-Institut fur Schicht- und Oberflachentechnik IST, Bienroder Weg 54 E, 38108 Braunschweig, Germany, Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften (IWF), Kiev Institute for Nuclear Research, A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP), Institut für Optik und Atomare Physik, Technische Universität Berlin, University of Opole, plac Kopernika 11a, 45-001 Opole, Poland, School of Electrical Engineering, Aalto University, Physikalisch-Technische Bundesanstalt (PTB), Kyoto University, Institute of Plasma Physics, Chinese Academy of Sciences, 350 Shushanhu Rd., Hefei, Anhui 230031, People's Republic of China, Institute of Plasma Physics of the Czech Academy of Science, Za Slovankou 1782/3, 182 00 Prague 8---Liben, Czechia, Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche (IFP-CNR), Fraunhofer-Institut fur Werkzeugmaschinen und Umformtechnik IWU, Reichenhainer Strase 88, 09126 Chemnitz, Germany, Universität Rostock, Wayne State University, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro, 7, 00185 Roma, Italy, Max Planck Institute for Plasma Physics, CIEMAT, Wigner Research Centre for Physics, Jülich Research Centre, University of Maryland, College Park, Princeton University, Royal Military Academy, Los Alamos National Laboratory, Lithuanian Energy Institute, Massachusetts Institute of Technology, Narodowe Centrum Badań Jadrowych, Karlsruhe Institute of Technology, Australian National University, University of Cagliari, National Research Council of Italy, Instituto Superior Tecnico Lisboa, Ioffe Institute, Oak Ridge National Laboratory, University of Salerno, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, Soltan Institute for Nuclear Studies, The Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences, University of Szczecin, University of Milan - Bicocca, University of California San Diego, Auburn University, Brandenburg University of Technology, National Institute for Fusion Science, Universidad Carlos III de Madrid, CEA, Culham Centre for Fusion Energy, RAS - Budker Institute of Nuclear Physics, University of Stuttgart, Fraunhofer Institute for Surface Engineering and Thin Films, Austrian Academy of Sciences, NASU - Institute of Nuclear Research, RAS - Institute of Applied Physics, Technical University of Berlin, University of Opole, Department of Applied Physics, Physikalisch-Technische Bundesanstalt, CAS - Institute of Plasma Physics, Czech Academy of Sciences, Istituto di Fisica Del Plasma Piero Caldirola, Fraunhofer Institute for Machine Tools and Forming Technology, University of Rostock, Lawrence University, Aalto-yliopisto, Aalto University, Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, Claps, G., and Cordella, F

Subjects
Magnetic confinement, Nuclear and High Energy Physics, Technology and Engineering, Plasma heating, Cyclotron resonance, CONFINEMENT, 01 natural sciences, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, PHYSICS, Nuclear physics, stellarator, current drive, magnetic confinement, plasma heating, Condensed Matter Physics, law, 0103 physical sciences, ddc:530, 010306 general physics, tellarator, Stellarator, Physics, Magnetic confinement fusion, Plasma, 530 Physik, TRANSPORT, Current drive, Electron temperature, Plasma diagnostics, Atomic physics, Wendelstein 7-X, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 1019 m−3 , central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre. EURATOM 633053

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9. Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design

Author

O. M. Jones, J. Milnes, M. Turnyanskiy, I. Klimek, K. G. McClements, M. Cecconello, N. C. Hawkes, D. L. Keeling, C. D. Challis, T R Barrett, A. Meakins, and Mast Team

Subjects
Physics, Nuclear and High Energy Physics, education.field_of_study, Tokamak, Population, FOS: Physical sciences, Plasma, Condensed Matter Physics, Physics - Plasma Physics, law.invention, Ion, Plasma Physics (physics.plasm-ph), Amplitude, Distribution function, Physics::Plasma Physics, law, Physics::Space Physics, Redistribution (chemistry), Magnetohydrodynamics, Atomic physics, education
Abstract

The phenomenon of redistribution of neutral beam fast-ions due to MHD activity in plasma has been observed on many tokamaks and more recently has been a focus of research on MAST (Turnyanskiy M. et al, 2011 Nucl. Fusion 53 053016). n=1 fishbone modes are observed to cause a large decrease in the neutron emission rate corresponding to a significant perturbation of the fast-ion population in the plasma. Theoretical work on fishbone modes states that the fast-ion distribution itself acts as the source of free energy driving the modes that cause the redistribution. Therefore a series of experiments have been carried out on MAST to investigate a range of plasma density levels at two neutral beam power levels to determine the region within this parameter space in which MHD activity and consequent fast-ion redistribution is suppressed. Analysis of these experiments shows complete suppression of MHD activity at high density with increasing activity and fast-ion redistribution at lower densities and higher NB power accompanied by strong evidence for localisation of the redistribution effect to a specific region in the plasma core. The results also indicate correlations between the form of the modelled fast-ion distribution function, the amplitude and growth rate of the fishbone modes, and the magnitude of the redistribution effect. The same analysis has been carried out on models of MAST-Upgrade baseline plasma scenarios to determine whether significant fast-ion redistribution is likely to occur in that device. A simple change to the neutral-beam injector geometry is proposed which is shown to have a significant mitigating effect in terms of the fishbone mode drive and is therefore expected to allow effective plasma heating and current drive over a wider range of plasma conditions in MAST-Upgrade., Comment: 26 pages, 7 figures. This is an author-created, un-copyedited version of an article submitted for publication in Nuclear Fusion. IOP Publishing Ltd and IAEA are not responsible for any errors or omissions in this version of the manuscript or any version derived from it

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10. TRANSP modelling of total and local neutron emission on MAST.

Author

I. Klimek, D. Keeling, A. Meakins, M. Cecconello, G. Ericsson, O. Jones, M. Gorelenkova, R. Akers, I. Lupelli, Team, the MAST, and M. Turnyanskiy

Subjects
TOKAMAKS, NEUTRON emission, SIMULATION methods & models, DEUTERIUM ions, NUCLEAR fusion, PLASMA beam injection heating
Abstract

The results of TRANSP simulations of neutron count rate profiles measured by a collimated neutron flux monitor–neutron camera (NC)—for different plasma scenarios on MAST are reported. In addition, the effect of various plasma parameters on neutron emission is studied by means of TRANSP simulation. The fast ion redistribution and losses due to fishbone modes, which belong to a wider category of energetic particle modes, are observed by the NC and modelled in TRANSP. [ABSTRACT FROM AUTHOR]

Published
2015
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11. Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design.

Author

D.L. Keeling, T.R. Barrett, M. Cecconello, C.D. Challis, N. Hawkes, O.M. Jones, I. Klimek, K.G. McClements, A. Meakins, J. Milnes, M. Turnyanskiy, and Team, the MAST

Subjects
MAGNETOHYDRODYNAMICS, PLASMA instabilities, NEUTRAL beams, FAST ions, PLASMA stability
Abstract

The phenomenon of the redistribution of neutral beam fast ions due to magnetohydrodynamic (MHD) activity in plasma has been observed on many tokamaks and more recently has been a focus of research on MAST (Turnyanskiy et al 2013 Nucl. Fusion53 053016). n = 1 fishbone modes are observed to cause a large decrease in the neutron emission rate indicating the existence of a significant perturbation of the fast-ion population in the plasma. Theoretical work on fishbone modes states that the fast-ion distribution itself acts as the source of free energy driving the modes that cause the redistribution. Therefore a series of experiments have been carried out on MAST to investigate a range of plasma densities at two neutral-beam power levels to determine the region within this parameter space in which fishbone activity and consequent fast-ion redistribution is suppressed. Analysis of these experiments shows complete suppression of fishbone activity at high densities with increasing activity and fast-ion redistribution at lower densities and higher neutral-beam power, accompanied by strong evidence that the redistribution effect primarily affects a specific region in the plasma core with a weaker effect over a wider region of the plasma. The results also indicate the existence of correlations between gradients in the modelled fast-ion distribution function, the amplitude and growth rate of the fishbone modes, and the magnitude of the redistribution effect. The same analysis has been carried out on models of MAST-Upgrade baseline plasma scenarios to determine whether significant fast-ion redistribution due to fishbone modes is likely to occur in that device. A simple change to the neutral-beam injector geometry is proposed which is shown to have a significant mitigating effect in terms of the fishbone mode drive and is therefore expected to allow effective plasma heating and current drive over a wider range of plasma conditions in MAST-Upgrade. [ABSTRACT FROM AUTHOR]

Published
2015
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