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164 results on '"J.L. Terry"'

151. Impurity sources during lower hybrid heating on Alcator

Author

S. Texter, J. E. Rice, A.S. Wan, H.L. Manning, Yuichi Takase, S. F. Knowlton, E.S. Marmar, Bruce Lipschultz, Brian LaBombard, Miklos Porkolab, and J.L. Terry

Subjects
Nuclear and High Energy Physics, Tokamak, Materials science, Silicon, chemistry.chemical_element, Plasma, Condensed Matter Physics, Lower hybrid oscillation, law.invention, Heat flux, chemistry, law, Sputtering, Impurity, Limiter, Atomic physics
Abstract

Impurity source mechanisms which appear during the heating of the Alcator C tokamak by injection of lower hybrid frequency waves are described. Silicon is a dominant impurity in these experiments where SiC was the limiter surface material. At low values of injected power, the silicon source rate is dominated by physical sputtering. As the amount of injected power is raised, evaporation caused by the tail electron heat flux to the limiter becomes the primary source for impurities entering the plasma. Measurements of silicon line emission from the plasma as well as other central and edge parameters are presented as functions of injected radiofrequency power.

Published
1986

152. Transport analysis of injected impurities in currentless Heliotron E plasmas

Author

T. Mizuuchi, S. Sudo, Hiroshi Kaneko, John Rice, Osamu Motojima, Hiroyuki Okada, Y. Takeiri, Masahide Sato, T. Mutoh, Tokuhiro Obiki, Katsumi Kondo, Hideki Zushi, Earl Marmar, A. Iiyoshi, Sakae Besshou, Fumimichi Sano, J.L. Terry, and Koji Uo

Subjects
Nuclear and High Energy Physics, Electron density, Materials science, Plasma, Electron, Fusion power, Condensed Matter Physics, law.invention, Ion, Physics::Plasma Physics, law, Impurity, Diffusion (business), Atomic physics, Stellarator
Abstract

Impurity transport in currentless Heliotron E plasmas is examined. The main aim of the experiment is to clarify the density dependence of impurity transport both in electron cyclotron heated (ECH) and neutral beam injected (NBI) plasmas. In experiments with a stationary electron density, the confinement time of impurities is determined as a function of the line averaged electron density. The inherent difference between ECH and NBI plasmas, observed in an earlier measurement, seems to have been masked by the operating conditions. From a direct comparison between NBI plasmas and simultaneous ECH and NBI heated plasmas of the same density, a pumping-out effect of impurities by the ECH pulse is established. From numerical analyses, the unexpected discrepancy between observed and calculated VUV spectral data can be explained by a charge exchange process. The observed impurity transport is found to be well described by a model which incorporates the effects of radial diffusion and inward convection. The inward flow does not seem to be due to the plasma potential because the flow is also observed in ECH plasmas where the heating power is expected to contribute to a reversed potential. The flow velocity is of the order of the classical friction between background ions and seems to play only a minor role in various aspects of impurity transport in NBI plasmas, such as impurity accumulation. The variety in impurity transport in Heliotron E plasmas is best understood by changes in the diffusion coefficient.

Published
1987

153. Observations of Centrally Peaked Impurity Profiles Following Pellet Injection in the Alcator-CTokamak

Author

J. E. Hopf, J.L. Terry, R. D. Petrasso, J. Parker, Martin Greenwald, D.J. Sigmar, and K.W. Wenzel

Subjects
Tokamak, Materials science, Hydrogen, General Physics and Astronomy, chemistry.chemical_element, Plasma, Thermal diffusivity, Spectral line, law.invention, chemistry, law, Impurity, Electrical resistivity and conductivity, Atomic physics, Carbon
Abstract

Highly peaked carbon and molybdenum profiles occured after hydrogen pellet injection. 40 ms after injection, carbon was well fit by (T-italic/sub e-italic//T/sub e/(0))/sup =/ for r-italicapprox.

Published
1986

154. The molybdenum spectrum emitted by a tokamak plasma in the 300–500 Å range

Author

J. E. Rice, H. W. Moos, Anand K. Bhatia, Michael Finkenthal, R. E. Bell, Earl Marmar, and J.L. Terry

Subjects
Physics, Range (particle radiation), Tokamak, General Physics and Astronomy, chemistry.chemical_element, Plasma, Computer Science::Digital Libraries, law.invention, chemistry, Physics::Plasma Physics, Molybdenum, law, Ionization, Astrophysics::Solar and Stellar Astrophysics, Physics::Atomic Physics, Atomic physics, Quadrupole magnet, Line (formation)
Abstract

Lines belonging to ionization states ranging from Mo VI to Mo XIV have been observed in the Alcator A tokamak plasma. New lines of Mo XIII, among them a forbidden magnetic quadrupole line, have been identified and classified.

Published
1981

155. Multichannel light detector system for visible continuum measurements on Alcator C

Author

J.L. Terry, E.S. Marmar, and M. Foord

Subjects
Physics, Brightness, Tokamak, business.industry, Continuum (design consultancy), Detector, Electromagnetic radiation, Particle detector, law.invention, Wavelength, Optics, law, Electron temperature, business, Instrumentation
Abstract

A spatially resolving visible light detector system has been constructed and used to measure continuum radiation in the wavelength region near 5360 A on the Alcator C tokamak. The instrument measures the line integral brightnesses from 20 chords through the plasma. For high‐electron temperature regimes and relatively line‐free wavelength regions, Zeff(r, t) is inferred from Abel inverted brightness profiles. During the steady‐state portion of the discharge, Zeff(r) is usually found to be constant within 10% out to r/a = 0.75.

Published
1982

156. Precision measurements of the wavelengths of emission lines of Na-like and Mg-like Kr in alcator C

Author

J.L. Terry, K. Kondo, J. E. Rice, and Earl Marmar

Subjects
Physics, Tokamak, business.industry, Detector, General Physics and Astronomy, Plasma, law.invention, Ion, Wavelength, Optics, Physics::Plasma Physics, law, Emission spectrum, Atomic physics, business, Spectrograph
Abstract

The wavelengths of lines from Mg- and Na-like Kr ions were precisely determined by puffing Kr gas into Alcator C tokamak plasmas and observing with a time-resolving spectrograph equipped with a multi-element spectral detector.

Published
1986

157. Ion Bernstein wave heating experiments on Alcator C

Author

J.L. Terry, Yuichi Takase, J. D. Moody, S.M. Wolfe, C.L. Fiore, F. S. McDermott, and Miklos Porkolab

Subjects
Physics, Tokamak, Hydrogen, Analytical chemistry, chemistry.chemical_element, Plasma, Charged particle, law.invention, Ion, Deuterium, chemistry, law, Impurity, Atomic physics, Ohmic contact
Abstract

ICRF ion Bernstein wave heating has been studied on the Alcator C tokamak in both the hydrogen 3/2 (B=7.6T) and deuterium 5/2(B=9.3T, ω=3ωcD at the plasma edge, x/a≂0.87) subharmonic regimes. Rf power of up to 180 kW at 183.6 MHz was coupled into the plasma for up to 150 ms using a toroidal current loop with a loading resistance between 1 and 2Ω. Ion heating effieciencies, neΔTi/Prf, of up to 5.5 eV m−3/kW at B=9.3T and 2.5 eV m−3/kW at B=7.6T at ne(Oh)=0.8×1020 m−3 were observed. A two temperature minority (deuterium) (TD

Published
1987

158. Energy confinement of lower-hybrid-current-driven tokamak plasmas

Author

S. F. Knowlton, S. Texter, F. S. McDermott, Miklos Porkolab, J.L. Terry, C.L. Fiore, P.T. Bonoli, S. McCool, and Yuichi Takase

Subjects
Nuclear physics, Physics, Tokamak, law, General Physics and Astronomy, Plasma, Atomic physics, Lower hybrid oscillation, law.invention
Abstract

L'energie stockee dans la queue d'electrons porteuse de courant peut etre une large fraction de l'energie cinetique totale dans un plasma induit par courant RF, alors que l'energie residant dans le plasma est comparable a celle d'une decharge ohmique similaire. Aux densites n e ≤3×10 13 cm −3 , le temps de confinement global du plasma RF est semblable a celui d'un plasma ohmique, mais se degrade par rapport a son contre-partie ohlique aux densites ou puissances plus elevees

Published
1986

159. LOWER HYBRID HEATING EXPERIMENTS ON THE ALCATOR-C AND THE VERSATOR-II TOKAMAKS

Author

M. Porkolab, J.J. Schuss, Y. Takase, S. Texter, C.L. Fiore, R. Gandy, M.J. Greenwald, D.A. Gwinn, B. Lipschultz, E.S. Marmar, D.S. Pappas, R.R. Parker, J.E. Rice, J.L. Terry, S.M. Wolfe, S.F. Knowlton, K.I. Chen, S.C. Luckhardt, M.J. Mayberry, P.I. Bonoli, B. Coppi, and R. Englade

Subjects
Waveguide (electromagnetism), Tokamak, Hydrogen, Chemistry, RF power amplifier, Analytical chemistry, chemistry.chemical_element, Plasma, Lower hybrid oscillation, law.invention, Ion, law, Atomic physics, Microwave
Abstract

We report on initial results from lower hybrid wave heating experiments carried out on the MIT Alcator C and Versator II tokamaks. In the Alcator C experiments a 4 waveguide array, with internally brazed ceramic windows has been used to inject 160 kW of microwave power at 4.6 GHz into the plasma with n O ≤ 1 × 10 15 cm −3 , and B O ≤ 12 T. An RF power density of 8 kW/cm 2 has been transmitted into the plasma without RF breakdown. RF coupling studies show optimal coupling (R ≤ 10%) when the local density at the waveguide mouth is 25–50 times overdense. Initial heating experiments show an ion tail formation in hydrogen discharge peaking at a density of at B = 8.9 T, and bulk ion heating at a density of at B ≃ 11 T. Evidence of RF current enhancement has been observed at a density of n ≃ 3 × 10 13 cm −3 .

Published
1982

160. Fluctuating zonal flows in the I-mode regime in Alcator C-Mod

Author

Istvan Cziegler, Randy Michael Churchill, Bruce Lipschultz, M. Xu, Patrick Diamond, J. M. Sierchio, P. Manz, George Tynan, Nicolas Fedorczak, J.L. Terry, A.E. Hubbard, and Christian Theiler

Subjects
Physics, Fusion, Work (thermodynamics), Tokamak, Turbulence, Plasma, Condensed Matter Physics, law.invention, Computational physics, Thermal transport, law, Physics::Plasma Physics, Plasma diagnostics, Zero frequency, Atomic physics
Abstract

Velocity fields and density fluctuations of edge turbulence are studied in I-mode [F. Ryter et al., Plasma Phys. Controlled Fusion 40, 725 (1998)] plasmas of the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] tokamak, which are characterized by a strong thermal transport barrier in the edge while providing little or no barrier to the transport of both bulk and impurity particles. Although previous work showed no clear geodesic-acoustic modes (GAM) on C-Mod, using a newly implemented, gas-puff-imaging based time-delay-estimate velocity inference algorithm, GAM are now shown to be ubiquitous in all I-mode discharges examined to date, with the time histories of the GAM and the I-mode specific [D. Whyte et al., Nucl. Fusion 50, 105005 (2010)] Weakly Coherent Mode (WCM, f = 100–300 kHz, Df/f approx. 0.5; and k_theta approx. 1.3 cm-1) closely following each other through the entire duration of the regime. Thus, the I-mode presents an example of a plasma state in which zero frequency zonal flows and GAM continuously coexist. Using two-field (density-velocity and radial-poloidal velocity) bispectral methods, the GAM are shown to be coupled to the WCM and to be responsible for its broad frequency structure. The effective nonlinear growth rate of the GAM is estimated, and its comparison to the collisional damping rate seems to suggest a new view on I-mode threshold physics.

162. Using x‐ray arrays to measure impurity transport in the Alcator‐C tokamak

Author

N. Kerr Del Grande, N. Loter, J. E. Hopf, J.L. Terry, F. H. Séguin, and R. D. Petrasso

Subjects
Physics, Tokamak, Impurity, law, Temporal resolution, Ionization, Plasma diagnostics, Plasma, Atomic physics, Spectroscopy, Instrumentation, law.invention, Ion
Abstract

Using three different x‐ray arrays simultaneously, we have made measurements of the transport of aluminum (Z=13) or silicon (Z=14) injected into MIT’s Alcator tokamak plasma. Each array has ∼2 cm spatial and 15 μs temporal resolution. Since Alcator core temperatures are typically between 1 and 2 keV, fully stripped, H‐ and He‐like ions are the only ionization states of the injected impurity with significant populations for r/a≲0.7. The spectral responses of the arrays have been tailored so that each array has a markedly different response to the x radiations from these three ionization states. Through the use of two of these arrays, time‐resolved density profiles of fully stripped and total injected impurities, and studies of their transport, have been previously reported. Current work and description of the analysis method will be presented.

Published
1985

163. Observations of centrally peaked impurity profiles following pellet injection in the Alcator‐C tokamak

Author

D.J. Sigmar, Martin Greenwald, K.W. Wenzel, J. E. Hopf, J.L. Terry, and R. D. Petrasso

Subjects
Tokamak, Materials science, Thermodynamic equilibrium, chemistry.chemical_element, Sawtooth wave, law.invention, chemistry, Impurity, Molybdenum, law, Electrical resistivity and conductivity, Pellet, Atomic physics, Instrumentation, Carbon
Abstract

Differently filtered x‐ray arrays have been used to instantaneously measure central carbon and molybdenum profiles, Alcator’s dominant light and heavy impurities, following pellet injection. Approximately 40 ms after the pellet, the width of the carbon profile was close to the neoclassical prediction of a source‐free equilibrium state. (Carbon is a plateau impurity.) The experimental molybdenum profile, which is more uncertain, was between a factor of 1.3 and 3.0 that of the asymptotic prediction of neoclassical theory. Carbon, the dominant nonhydrogenic contributor to Zeff, was found to dramatically affect sawtooth dynamics by altering the central resistivity. Specifically, following injection of the pellet the carbon profile became progressively more peaked, the effect of which was to lengthen the sawtooth period. Approximately 40 ms after the pellet, an internal disruption occurred which reduced on‐axis carbon and molybdenum by a factor of 3. (In comparison, the corresponding temperature drop was only ...

Published
1986

164. 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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