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109 results on '"Höfel, U"'

1. On the role of density fluctuations in the core turbulent transport of Wendelstein 7-X

Author

Carralero, D., Estrada, T., Maragkoudakis, E., Windisch, T., Alonso, J. A., Velasco, J. L., Ford, O., Jakubowski, M., Lazerson, S., Beurskens, M., Bozhenkov, S., Calvo, I., Damm, H., Fuchert, G., García-Regaña, J. M., Höfel, U., Marushchenko, N., Pablant, N., Sánchez, E., Smith, H. M., Pasch, E., and Stange, T.

Subjects
Physics - Plasma Physics
Abstract

A recent characterization of core turbulence carried out with a Doppler reflectometer in the optimized stellarator Wendelstein 7-X (W7-X) found that discharges achieving high ion temperatures at the core featured an ITG-like suppression of density fluctuations driven by a reduction of the gradient ratio $\eta_i = L_n/L_{T_i}$ [D. Carralero et al., Nucl. Fusion, 2021]. In order to confirm the role of ITG turbulence in this process, we set out to establish experimentally the relation between core density fluctuations, turbulent heat flux and global confinement. With this aim, we consider the scenarios found in the previous work and carry out power balance analysis for a number of representative ones, including some featuring high ion temperature. As well, we evaluate the global energy confinement time and discuss it in the context of the ISS04 inter-stellarator scaling. We find that, when turbulence is suppressed as a result of a reduction of $\eta_i$, there is a reduction of ion turbulent transport, and global performance is improved as a result. This is consistent with ITG turbulence limiting the ion temperature at the core of W7-X. In contrast, when turbulence is reduced following a decrease in collisionality, no changes are observed in transport or confinement. This could be explained by ITG modes being combined with TEM turbulence when the later is destabilized at low collisionalities., Comment: Submitted to PPCF, 47th EPS special issue

Published
2021
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2. Bayesian modelling of multiple plasma diagnostics at Wendelstein 7-X

Author

Kwak, Sehyun, Svensson, J., Bozhenkov, S., Mora, H. Trimino, Hoefel, U., Pavone, A., Krychowiak, M., Langenberg, A., Ghim, Y. -c., and Team, W7-X

Subjects
Physics - Plasma Physics
Abstract

Consistent inference of the electron density and temperature has been carried out with multiple heterogeneous plasma diagnostic data sets at Wendelstein 7-X. The predictive models of the interferometer, Thomson scattering and helium beam emission spectroscopy systems have been developed in the Minerva framework and combined to a single joint model. The electron density and temperature profiles are modelled by Gaussian processes with their hyperparameters. The model parameters such as the calibration factor of the Thomson scattering system and the model predictive uncertainties are regarded as additional unknown parameters. The joint posterior probability distribution of the electron density and temperature profiles, hyperparameters of the Gaussian processes and model parameters is explored by Markov chain Monte Carlo algorithms. The posterior samples drawn from the joint posterior distribution are numerically marginalised over the hyperparameters and model parameters to obtain the marginal posterior distributions of the electron density and temperature profiles. The inference of these profiles is performed with different combinations of the interferometer and Thomson scattering data as well as either the empirical electron density and temperature constraints at the limiter/divertor positions introduced by \textit{virtual observations} or the edge density and temperature from the helium beam emission data. Furthermore, the addition of the X-ray imaging crystal spectrometers to the joint model for the ion temperature profiles is demonstrated. All these profiles presented in this work are inferred with the optimal hyperparameters and model parameters by exploring the full joint posterior distribution which intrinsically embodies Bayesian Occam's razor.

Published
2021

3. The impact of heating power on radial heat transport in W7-X

Author

van Milligen, B. Ph., Hoefel, U., Hirsch, M., Carreras, B. A., Hidalgo, C., and Team, the W7-X

Subjects
Physics - Plasma Physics
Abstract

The understanding of the outward radial transport of heat in magnetic confinement fusion devices is a priority for the development of economically viable fusion reactors. Here, we analyze the radial propagation of spontaneously generated electron temperature (T_e) fluctuations measured using the Electron Cyclotron Emission (ECE) diagnostic in Wendelstein 7-X, which disposes of 32 channels, covering a large part of the plasma minor radius. By applying a relatively new statistical analysis technique (the Transfer Entropy), the present work provides, for the first time, a view of the detailed mechanism of electron heat transport in fusion plasmas. It is shown that rational surfaces have a significant impact on radial heat transport and may in fact be essential in setting the global energy confinement. The reported observations provide support for various explanatory concepts suggested in literature: namely, critical gradients, non-locality, and self-organization., Comment: 10 pages, 3 figures

Published
2017
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5. Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

Author

Beidler, C. D., Smith, H. M., Alonso, A., Andreeva, T., Baldzuhn, J., Beurskens, M. N. A., Borchardt, M., Bozhenkov, S. A., Brunner, K. J., Damm, H., Drevlak, M., Ford, O. P., Fuchert, G., Geiger, J., Helander, P., Hergenhahn, U., Hirsch, M., Höfel, U., Kazakov, Ye. O., Kleiber, R., Krychowiak, M., Kwak, S., Langenberg, A., Laqua, H. P., Neuner, U., Pablant, N. A., Pasch, E., Pavone, A., Pedersen, T. S., Rahbarnia, K., Schilling, J., Scott, E. R., Stange, T., Svensson, J., Thomsen, H., Turkin, Y., Warmer, F., Wolf, R. C., and Zhang, D.

Published
2021
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8. Accelerated Bayesian inference of plasma profiles with self-consistent MHD equilibria at W7-X via neural networks

Author

Merlo, A., primary, Pavone, A., additional, Böckenhoff, D., additional, Pasch, E., additional, Fuchert, G., additional, Brunner, K.J., additional, Rahbarnia, K., additional, Schilling, J., additional, Höfel, U., additional, Kwak, S., additional, Svensson, J., additional, Pedersen, T.S., additional, and W7-X team, the, additional

Published
2023
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9. Magnetic configuration effects on the Wendelstein 7-X stellarator

Author

Dinklage, A., Beidler, C. D., Helander, P., Fuchert, G., Maaßberg, H., Rahbarnia, K., Sunn Pedersen, T., Turkin, Y., Wolf, R. C., Alonso, A., Andreeva, T., Blackwell, B., Bozhenkov, S., Buttenschön, B., Czarnecka, A., Effenberg, F., Feng, Y., Geiger, J., Hirsch, M., Höfel, U., Jakubowski, M., Klinger, T., Knauer, J., Kocsis, G., Krämer-Flecken, A., Kubkowska, M., Langenberg, A., Laqua, H. P., Marushchenko, N., Mollén, A., Neuner, U., Niemann, H., Pasch, E., Pablant, N., Rudischhauser, L., Smith, H. M., Schmitz, O., Stange, T., Szepesi, T., Weir, G., Windisch, T., Wurden, G. A., Zhang, D., and and the W7-X Team

Published
2018
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10. Observation of impurity accumulation and its compatibility with high plasma performance in W7-X

Author

Zhang, D, primary, Buttenschön, B, additional, Jablonski, S, additional, Kubkowska, M, additional, Ford, O, additional, Alcusón, J A, additional, Beidler, C D, additional, Burhenn, R, additional, Beurskens, M N A, additional, Langenberg, A, additional, Pablant, N, additional, Reimold, F, additional, Rahbarnia, K, additional, Smith, H M, additional, Wegner, Th, additional, Wurden, G, additional, Bozhenkov, S A, additional, Feng, Y, additional, Brunner, K J, additional, Fuchert, G, additional, Gao, Y, additional, Geiger, J, additional, Giannone, L, additional, Höfel, U, additional, Hirsch, M, additional, Huang, Z, additional, Knauer, J, additional, Kremeyer, T, additional, Krychowiak, M, additional, Kwak, S, additional, Laqua, H P, additional, Laube, R, additional, Neuner, U, additional, Pasch, E, additional, Pavone, A, additional, von Stechow, A, additional, Svensson, J, additional, and Thomsen, H, additional

Published
2023
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11. First feedback-controlled divertor detachment in W7-X: Experience from TDU operation and prospects for operation with actively cooled divertor

Author

Krychowiak, M., primary, König, R., additional, Barbui, T., additional, Brezinsek, S., additional, Brunner, J., additional, Effenberg, F., additional, Endler, M., additional, Feng, Y., additional, Flom, E., additional, Gao, Y., additional, Gradic, D., additional, Hacker, P., additional, Harris, J.H., additional, Hirsch, M., additional, Höfel, U., additional, Jakubowski, M., additional, Kornejew, P., additional, Otte, M., additional, Pandey, A., additional, Pedersen, T.S., additional, Puig, A., additional, Reimold, F., additional, Schmitz, O., additional, Schröder, T., additional, Winters, V., additional, and Zhang, D., additional

Published
2023
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13. ECCD operations in the second experimental campaign at W7-X

Author

Zanini M., Laqua H.P., Stange T., Brandt C., Hirsch M., Höfel U., Marushchenko N., Neuner U., Rahbarnia K., Schilling J., Thomsen H., and Wolf R.C.

Subjects
Physics, QC1-999
Abstract

In the Wendelstein 7-X stellarator, up to 7MW of power are delivered to the plasma by an electron cyclotron resonance heating system consisting of ten 140 GHz gyrotrons [1]. Due to the flexible front steering mirror of each beam line, the power deposition can be varied over the whole plasma radius and is optionally combinable with additional current drive. This flexibility, together with small toroidal currents in the stellarator, makes W7-X a perfect testbed for electron cyclotron current drive (ECCD) experiments, which have been successfully accomplished during the first two experimental campaigns OP1.1 and OP1.2a. Long discharges (lasting up to 30s) have been performed in OP1.2a, thus allowing the study of the current drive time evolution and the possibility to compensate the bootstrap current. ECCD efficiency has been studied using different power deposition profiles combined with a variation of the injection angles in relation to the magnetic field. During ECCD experiments, saw-tooth-like oscillations have been observed. Depending on the driven current density, ECCD can significantly modify the rotational transform (iota) profile, which can locally reach low order rational, thus triggering plasma instabilities. Different current density profiles have been tested, in order to try to understand the main trigger parameter for the instabilities. In particular, effects caused by current density gradient have been investigated producing both co- and counter-current drive at different radial positions: the total current drive is negligible, but a strong current gradient arises by driving currents in opposite directions. In this work an overview of ECCD operations in OP1.2a is given and first results, comparing different diagnostics, are presented. An initial 1-D model, coupled with the ray tracer TRAVIS, is developed, in order to have an estimation of current diffusion times and the radial position where a low order rational crosses the disturbed iota profile.

Published
2019
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14. Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Author

Pedersen, Thomas Sunn, Abramovic, I., Agostinetti, P., Torres, M. Agredano, Äkäslompolo, S., Belloso, J. Alcuson, Aleynikov, P., Aleynikova, K., Alhashimi, M., Ali, A., Allen, N., Alonso, A., Anda, G., Andreeva, T., Angioni, C., Arkhipov, A., Arnold, A., Asad, W., Ascasibar, E., Aumeunier, M. H., Avramidis, K., Aymerich, E., Baek, S. G., Bähner, J., Baillod, A., Balden, M., Baldzuhn, J., Ballinger, S., Banduch, M., Bannmann, S., Navarro, A. Bañón, Barbui, T., Beidler, C., Belafdil, C., Bencze, A., Benndorf, A., Beurskens, M., Biedermann, C., Biletskyi, O., Blackwell, B., Blatzheim, M., Bluhm, T., Böckenhoff, D., Bongiovi, G., Borchardt, M., Borodin, D., Boscary, J., Bosch, H., Bosmann, T., Böswirth, B., Böttger, L., Bottino, A., Bozhenkov, S., Brakel, R., Brandt, C., Bräuer, T., Braune, H., Brezinsek, S., Brunner, K., Buller, S., Burhenn, R., Bussiahn, R., Buttenschön, B., Buzás, A., Bykov, V., Calvo, I., Mata, K. Camacho, Caminal, I., Cannas, B., Cappa, A., Carls, A., Carovani, F., Carr, M., Carralero, D., Carvalho, B., Casas, J., Castano-Bardawil, D., Castejon, F., Chaudhary, N., Chelis, I., Chomiczewska, A., Coenen, J. W., Cole, M., Cordella, F., Corre, Y., Crombe, K., Cseh, G., Csillag, B., Damm, H., Day, C., de Baar, M., De la Cal, E., Degenkolbe, S., Demby, A., Denk, S., Dhard, C., Di Siena, A., Dinklage, A., Dittmar, T., Dreval, M., Drevlak, M., Drewelow, P., Drews, P., Dunai, D., Edlund, E., Effenberg, F., Ehrke, G., Endler, M., Ennis, D. A., Escoto, F. J., Estrada, T., Fable, E., Fahrenkamp, N., Fanni, A., Faustin, J., Fellinger, J., Feng, Y., Figacz, W., Flom, E., Ford, O., Fornal, T., Frerichs, H., Freundt, S., Fuchert, G., Fukuyama, M., Füllenbach, F., Gantenbein, G., Gao, Y., Garcia, K., Regaña, J. M.García, García-Cortés, I., Gaspar, J., Gates, D. A., Geiger, J., Geiger, B., Giudicotti, L., González, A., Goriaev, A., Gradic, D., Grahl, M., Graves, J. P., Green, J., Grelier, E., Greuner, H., Groß, S., Grote, H., Groth, M., Gruca, M., Grulke, O., Grün, M., Arnaiz, J. Guerrero, Günter, S., Haak, V., Haas, M., Hacker, P., Hakola, A., Hallenbert, A., Hammond, K., Han, X., Hansen, S. K., Harris, J. H., Hartfuß, H., Hartmann, D., Hathiramani, D., Hatzky, R., Hawke, J., Hegedus, S., Hein, B., Heinemann, B., Helander, P., Henneberg, S., Hergenhahn, U., Hidalgo, C., Hindenlang, F., Hirsch, M., Höfel, U., Hollfeld, K. P., Holtz, A., Hopf, D., Höschen, D., Houry, M., Howard, J., Huang, X., Hubeny, M., Hudson, S., Ida, K., Igitkhanov, Y., Igochine, V., Illy, S., Ionita-Schrittwieser, C., Isobe, M., Jabłczynska, M., Jablonski, S., Jagielski, B., Jakubowski, M., van Vuuren, A. Jansen, Jelonnek, J., Jenko, F., Jensen, T., Jenzsch, H., Junghanns, P., Kaczmarczyk, J., Kallmeyer, J., Kamionka, U., Kandler, M., Kasilov, S., Kazakov, Y., Kennedy, D., Kharwandikar, A., Khokhlov, M., Kiefer, C., Killer, C., Kirschner, A., Kleiber, R., Klinger, T., Klose, S., Knauer, J., Knieps, A., Köchl, F., Kocsis, G., Kolesnichenko, Ya I., Könies, A., König, R., Kontula, J., Kornejew, P., Koschinsky, J., Kozulia, M. M., Krämer-Flecken, A., Krampitz, R., Krause, M., Krawczyk, N., Kremeyer, T., Krier, L., Kriete, D. M., Krychowiak, M., Ksiazek, I., Kubkowska, M., Kuczynski, M., Kühner, G., Kumar, A., Kurki-Suonio, T., Kwak, S., Landreman, M., Lang, P. T., Langenberg, A., Laqua, H., Laube, R., Lazerson, S., Lewerentz, M., Li, C., Liang, Y., Linsmeier, Ch, Lion, J., Litnovsky, A., Liu, S., Lobsien, J., Loizu, J., Lore, J., Lorenz, A., Losada, U., Louche, F., Lunsford, R., Lutsenko, V., Machielsen, M., Mackel, F., Maisano-Brown, J., Maj, O., Makowski, D., Manduchi, G., Maragkoudakis, E., Marchuk, O., Marsen, S., Martines, E., Martinez-Fernandez, J., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., McCarthy, K. J., McCormack, O., McNeely, P., Meister, H., Mendelevitch, B., Mendes, S., Merlo, A., Messian, A., Mielczarek, A., Mishchenko, O., Missal, B., Mitteau, R., Moiseenko, V. E., Mollen, A., Moncada, V., Mönnich, T., Morisaki, T., Moseev, D., Motojima, G., Mulas, S., Mulsow, M., Nagel, M., Naujoks, D., Naulin, V., Neelis, T., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Nicolai, D., Nielsen, S. K., Niemann, H., Nishiza, T., Nishizawa, T., Nührenberg, C., Ochoukov, R., Oelmann, J., Offermanns, G., Ogawa, K., Okamura, S., Ölmanns, J., Ongena, J., Oosterbeek, J., Otte, M., Pablant, N., Alvarez, N. Panadero, Pandey, A., Pasch, E., Pavlichenko, R., Pavone, A., Pawelec, E., Pechstein, G., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plöckl, B., Plunk, G., Pölöskei, P., Pompe, B., Popov, A., Porkolab, M., Proll, J., Pueschel, M. J., Puiatti, M. E., Sitjes, A. Puig, Purps, F., Rahbarnia, K., Rasinski, M., Rasmussen, J., Reiman, A., Reimold, F., Reisner, M., Reiter, D., Richou, M., Riedl, R., Riemann, J., Riße, K., Roberg-Clark, G., Rohde, V., Romazanov, J., Rondeshagen, D., Rong, P., Rudischhauser, L., Rummel, T., Rummel, K., Runov, A., Rust, N., Ryc, L., Salembier, P., Salewski, M., Sanchez, E., Satake, S., Satheeswaran, G., Schacht, J., Scharff, E., Schauer, F., Schilling, J., Schlisio, G., Schmid, K., Schmitt, J., Schmitz, O., Schneider, W., Schneider, M., Schneider, P., Schrittwieser, R., Schröder, T., Schröder, M., Schroeder, R., Schweer, B., Schwörer, D., Scott, E., Shanahan, B., Sias, G., Sichta, P., Singer, M., Sinha, P., Sipliä, S., Slaby, C., Sleczka, M., Smith, H., Smoniewski, J., Sonnendrücker, E., Spolaore, M., Spring, A., Stadler, R., Stanczak, D., Stange, T., Stepanov, I., Stephey, L., Stober, J., Stroth, U., Strumberger, E., Suzuki, C., Suzuki, Y., Svensson, J., Szabolics, T., Szepesi, T., Szücs, M., Tabarés, F. L., Tamura, N., Tancetti, A., Tantos, C., Terry, J., Thienpondt, H., Thomsen, H., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trier, E., Mora, H. Trimino, Tsujimura, T., Turkin, Y., Tykhyi, A., Unterberg, B., van Eeten, P., van Milligen, B. Ph, van Schoor, M., Vano, L., Varoutis, S., Vecsei, M., Vela, L., Velasco, J. L., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vogel, G., Vogt, N., Volkhausen, C., von Stechow, A., Wagner, F., Wang, E., Wang, H., Warmer, F., Wauters, T., Wegener, L., Wegner, T., Weir, G., Wenzel, U., White, A., Wilde, F., Wilms, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, R., Wright, A. M., Wurden, G. A., Xanthopoulos, P., Xu, S., Yamada, H., Yamaguchi, H., Yokoyama, M., Yoshinuma, M., Yu, Q., Zamanov, M., Zanini, M., Zarnstorff, M., Zhang, D., Zhou, S., Zhu, J., Zhu, C., Zilker, M., Zocco, A., Zohm, H., Zoletnik, S., Zsuga, L., Pedersen, Thomas Sunn, Abramovic, I., Agostinetti, P., Torres, M. Agredano, Äkäslompolo, S., Belloso, J. Alcuson, Aleynikov, P., Aleynikova, K., Alhashimi, M., Ali, A., Allen, N., Alonso, A., Anda, G., Andreeva, T., Angioni, C., Arkhipov, A., Arnold, A., Asad, W., Ascasibar, E., Aumeunier, M. H., Avramidis, K., Aymerich, E., Baek, S. G., Bähner, J., Baillod, A., Balden, M., Baldzuhn, J., Ballinger, S., Banduch, M., Bannmann, S., Navarro, A. Bañón, Barbui, T., Beidler, C., Belafdil, C., Bencze, A., Benndorf, A., Beurskens, M., Biedermann, C., Biletskyi, O., Blackwell, B., Blatzheim, M., Bluhm, T., Böckenhoff, D., Bongiovi, G., Borchardt, M., Borodin, D., Boscary, J., Bosch, H., Bosmann, T., Böswirth, B., Böttger, L., Bottino, A., Bozhenkov, S., Brakel, R., Brandt, C., Bräuer, T., Braune, H., Brezinsek, S., Brunner, K., Buller, S., Burhenn, R., Bussiahn, R., Buttenschön, B., Buzás, A., Bykov, V., Calvo, I., Mata, K. Camacho, Caminal, I., Cannas, B., Cappa, A., Carls, A., Carovani, F., Carr, M., Carralero, D., Carvalho, B., Casas, J., Castano-Bardawil, D., Castejon, F., Chaudhary, N., Chelis, I., Chomiczewska, A., Coenen, J. W., Cole, M., Cordella, F., Corre, Y., Crombe, K., Cseh, G., Csillag, B., Damm, H., Day, C., de Baar, M., De la Cal, E., Degenkolbe, S., Demby, A., Denk, S., Dhard, C., Di Siena, A., Dinklage, A., Dittmar, T., Dreval, M., Drevlak, M., Drewelow, P., Drews, P., Dunai, D., Edlund, E., Effenberg, F., Ehrke, G., Endler, M., Ennis, D. A., Escoto, F. J., Estrada, T., Fable, E., Fahrenkamp, N., Fanni, A., Faustin, J., Fellinger, J., Feng, Y., Figacz, W., Flom, E., Ford, O., Fornal, T., Frerichs, H., Freundt, S., Fuchert, G., Fukuyama, M., Füllenbach, F., Gantenbein, G., Gao, Y., Garcia, K., Regaña, J. M.García, García-Cortés, I., Gaspar, J., Gates, D. A., Geiger, J., Geiger, B., Giudicotti, L., González, A., Goriaev, A., Gradic, D., Grahl, M., Graves, J. P., Green, J., Grelier, E., Greuner, H., Groß, S., Grote, H., Groth, M., Gruca, M., Grulke, O., Grün, M., Arnaiz, J. Guerrero, Günter, S., Haak, V., Haas, M., Hacker, P., Hakola, A., Hallenbert, A., Hammond, K., Han, X., Hansen, S. K., Harris, J. H., Hartfuß, H., Hartmann, D., Hathiramani, D., Hatzky, R., Hawke, J., Hegedus, S., Hein, B., Heinemann, B., Helander, P., Henneberg, S., Hergenhahn, U., Hidalgo, C., Hindenlang, F., Hirsch, M., Höfel, U., Hollfeld, K. P., Holtz, A., Hopf, D., Höschen, D., Houry, M., Howard, J., Huang, X., Hubeny, M., Hudson, S., Ida, K., Igitkhanov, Y., Igochine, V., Illy, S., Ionita-Schrittwieser, C., Isobe, M., Jabłczynska, M., Jablonski, S., Jagielski, B., Jakubowski, M., van Vuuren, A. Jansen, Jelonnek, J., Jenko, F., Jensen, T., Jenzsch, H., Junghanns, P., Kaczmarczyk, J., Kallmeyer, J., Kamionka, U., Kandler, M., Kasilov, S., Kazakov, Y., Kennedy, D., Kharwandikar, A., Khokhlov, M., Kiefer, C., Killer, C., Kirschner, A., Kleiber, R., Klinger, T., Klose, S., Knauer, J., Knieps, A., Köchl, F., Kocsis, G., Kolesnichenko, Ya I., Könies, A., König, R., Kontula, J., Kornejew, P., Koschinsky, J., Kozulia, M. M., Krämer-Flecken, A., Krampitz, R., Krause, M., Krawczyk, N., Kremeyer, T., Krier, L., Kriete, D. M., Krychowiak, M., Ksiazek, I., Kubkowska, M., Kuczynski, M., Kühner, G., Kumar, A., Kurki-Suonio, T., Kwak, S., Landreman, M., Lang, P. T., Langenberg, A., Laqua, H., Laube, R., Lazerson, S., Lewerentz, M., Li, C., Liang, Y., Linsmeier, Ch, Lion, J., Litnovsky, A., Liu, S., Lobsien, J., Loizu, J., Lore, J., Lorenz, A., Losada, U., Louche, F., Lunsford, R., Lutsenko, V., Machielsen, M., Mackel, F., Maisano-Brown, J., Maj, O., Makowski, D., Manduchi, G., Maragkoudakis, E., Marchuk, O., Marsen, S., Martines, E., Martinez-Fernandez, J., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., McCarthy, K. J., McCormack, O., McNeely, P., Meister, H., Mendelevitch, B., Mendes, S., Merlo, A., Messian, A., Mielczarek, A., Mishchenko, O., Missal, B., Mitteau, R., Moiseenko, V. E., Mollen, A., Moncada, V., Mönnich, T., Morisaki, T., Moseev, D., Motojima, G., Mulas, S., Mulsow, M., Nagel, M., Naujoks, D., Naulin, V., Neelis, T., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Nicolai, D., Nielsen, S. K., Niemann, H., Nishiza, T., Nishizawa, T., Nührenberg, C., Ochoukov, R., Oelmann, J., Offermanns, G., Ogawa, K., Okamura, S., Ölmanns, J., Ongena, J., Oosterbeek, J., Otte, M., Pablant, N., Alvarez, N. Panadero, Pandey, A., Pasch, E., Pavlichenko, R., Pavone, A., Pawelec, E., Pechstein, G., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plöckl, B., Plunk, G., Pölöskei, P., Pompe, B., Popov, A., Porkolab, M., Proll, J., Pueschel, M. J., Puiatti, M. E., Sitjes, A. Puig, Purps, F., Rahbarnia, K., Rasinski, M., Rasmussen, J., Reiman, A., Reimold, F., Reisner, M., Reiter, D., Richou, M., Riedl, R., Riemann, J., Riße, K., Roberg-Clark, G., Rohde, V., Romazanov, J., Rondeshagen, D., Rong, P., Rudischhauser, L., Rummel, T., Rummel, K., Runov, A., Rust, N., Ryc, L., Salembier, P., Salewski, M., Sanchez, E., Satake, S., Satheeswaran, G., Schacht, J., Scharff, E., Schauer, F., Schilling, J., Schlisio, G., Schmid, K., Schmitt, J., Schmitz, O., Schneider, W., Schneider, M., Schneider, P., Schrittwieser, R., Schröder, T., Schröder, M., Schroeder, R., Schweer, B., Schwörer, D., Scott, E., Shanahan, B., Sias, G., Sichta, P., Singer, M., Sinha, P., Sipliä, S., Slaby, C., Sleczka, M., Smith, H., Smoniewski, J., Sonnendrücker, E., Spolaore, M., Spring, A., Stadler, R., Stanczak, D., Stange, T., Stepanov, I., Stephey, L., Stober, J., Stroth, U., Strumberger, E., Suzuki, C., Suzuki, Y., Svensson, J., Szabolics, T., Szepesi, T., Szücs, M., Tabarés, F. L., Tamura, N., Tancetti, A., Tantos, C., Terry, J., Thienpondt, H., Thomsen, H., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trier, E., Mora, H. Trimino, Tsujimura, T., Turkin, Y., Tykhyi, A., Unterberg, B., van Eeten, P., van Milligen, B. Ph, van Schoor, M., Vano, L., Varoutis, S., Vecsei, M., Vela, L., Velasco, J. L., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vogel, G., Vogt, N., Volkhausen, C., von Stechow, A., Wagner, F., Wang, E., Wang, H., Warmer, F., Wauters, T., Wegener, L., Wegner, T., Weir, G., Wenzel, U., White, A., Wilde, F., Wilms, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, R., Wright, A. M., Wurden, G. A., Xanthopoulos, P., Xu, S., Yamada, H., Yamaguchi, H., Yokoyama, M., Yoshinuma, M., Yu, Q., Zamanov, M., Zanini, M., Zarnstorff, M., Zhang, D., Zhou, S., Zhu, J., Zhu, C., Zilker, M., Zocco, A., Zohm, H., Zoletnik, S., and Zsuga, L.

Abstract

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ion-temperature-gradient turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases.

Published
2022

15. Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Author

Sunn Pedersen, Thomas, primary, Abramovic, I., additional, Agostinetti, P., additional, Agredano Torres, M., additional, Äkäslompolo, S., additional, Alcuson Belloso, J., additional, Aleynikov, P., additional, Aleynikova, K., additional, Alhashimi, M., additional, Ali, A., additional, Allen, N., additional, Alonso, A., additional, Anda, G., additional, Andreeva, T., additional, Angioni, C., additional, Arkhipov, A., additional, Arnold, A., additional, Asad, W., additional, Ascasibar, E., additional, Aumeunier, M.-H., additional, Avramidis, K., additional, Aymerich, E., additional, Baek, S.-G., additional, Bähner, J., additional, Baillod, A., additional, Balden, M., additional, Baldzuhn, J., additional, Ballinger, S., additional, Banduch, M., additional, Bannmann, S., additional, Banon Navarro, A., additional, Bañón Navarro, A., additional, Barbui, T., additional, Beidler, C., additional, Belafdil, C., additional, Bencze, A., additional, Benndorf, A., additional, Beurskens, M., additional, Biedermann, C., additional, Biletskyi, O., additional, Blackwell, B., additional, Blatzheim, M., additional, Bluhm, T., additional, Böckenhoff, D., additional, Bongiovi, G., additional, Borchardt, M., additional, Borodin, D., additional, Boscary, J., additional, Bosch, H., additional, Bosmann, T., additional, Böswirth, B., additional, Böttger, L., additional, Bottino, A., additional, Bozhenkov, S., additional, Brakel, R., additional, Brandt, C., additional, Bräuer, T., additional, Braune, H., additional, Brezinsek, S., additional, Brunner, K., additional, Buller, S., additional, Burhenn, R., additional, Bussiahn, R., additional, Buttenschön, B., additional, Buzás, A., additional, Bykov, V., additional, Calvo, I., additional, Camacho Mata, K., additional, Caminal, I., additional, Cannas, B., additional, Cappa, A., additional, Carls, A., additional, Carovani, F., additional, Carr, M., additional, Carralero, D., additional, Carvalho, B., additional, Casas, J., additional, Castano-Bardawil, D., additional, Castejon, F., additional, Chaudhary, N., additional, Chelis, I., additional, Chomiczewska, A., additional, Coenen, J.W., additional, Cole, M., additional, Cordella, F., additional, Corre, Y., additional, Crombe, K., additional, Cseh, G., additional, Csillag, B., additional, Damm, H., additional, Day, C., additional, de Baar, M., additional, De la Cal, E., additional, Degenkolbe, S., additional, Demby, A., additional, Denk, S., additional, Dhard, C., additional, Di Siena, A., additional, Dinklage, A., additional, Dittmar, T., additional, Dreval, M., additional, Drevlak, M., additional, Drewelow, P., additional, Drews, P., additional, Dunai, D., additional, Edlund, E., additional, Effenberg, F., additional, Ehrke, G., additional, Endler, M., additional, Ennis, D.A., additional, Escoto, F.J., additional, Estrada, T., additional, Fable, E., additional, Fahrenkamp, N., additional, Fanni, A., additional, Faustin, J., additional, Fellinger, J., additional, Feng, Y., additional, Figacz, W., additional, Flom, E., additional, Ford, O., additional, Fornal, T., additional, Frerichs, H., additional, Freundt, S., additional, Fuchert, G., additional, Fukuyama, M., additional, Füllenbach, F., additional, Gantenbein, G., additional, Gao, Y., additional, Garcia, K., additional, García Regaña, J.M., additional, García-Cortés, I., additional, Gaspar, J., additional, Gates, D.A., additional, Geiger, J., additional, Geiger, B., additional, Giudicotti, L., additional, González, A., additional, Goriaev, A., additional, Gradic, D., additional, Grahl, M., additional, Graves, J.P., additional, Green, J., additional, Grelier, E., additional, Greuner, H., additional, Groß, S., additional, Grote, H., additional, Groth, M., additional, Gruca, M., additional, Grulke, O., additional, Grün, M., additional, Guerrero Arnaiz, J., additional, Günter, S., additional, Haak, V., additional, Haas, M., additional, Hacker, P., additional, Hakola, A., additional, Hallenbert, A., additional, Hammond, K., additional, Han, X., additional, Hansen, S.K., additional, Harris, J.H., additional, Hartfuß, H., additional, Hartmann, D., additional, Hathiramani, D., additional, Hatzky, R., additional, Hawke, J., additional, Hegedus, S., additional, Hein, B., additional, Heinemann, B., additional, Helander, P., additional, Henneberg, S., additional, Hergenhahn, U., additional, Hidalgo, C., additional, Hindenlang, F., additional, Hirsch, M., additional, Höfel, U., additional, Hollfeld, K.P., additional, Holtz, A., additional, Hopf, D., additional, Höschen, D., additional, Houry, M., additional, Howard, J., additional, Huang, X., additional, Hubeny, M., additional, Hudson, S., additional, Ida, K., additional, Igitkhanov, Y., additional, Igochine, V., additional, Illy, S., additional, Ionita-Schrittwieser, C., additional, Isobe, M., additional, Jabłczyńska, M., additional, Jablonski, S., additional, Jagielski, B., additional, Jakubowski, M., additional, Jansen van Vuuren, A., additional, Jelonnek, J., additional, Jenko, F., additional, Jensen, T., additional, Jenzsch, H., additional, Junghanns, P., additional, Kaczmarczyk, J., additional, Kallmeyer, J., additional, Kamionka, U., additional, Kandler, M., additional, Kasilov, S., additional, Kazakov, Y., additional, Kennedy, D., additional, Kharwandikar, A., additional, Khokhlov, M., additional, Kiefer, C., additional, Killer, C., additional, Kirschner, A., additional, Kleiber, R., additional, Klinger, T., additional, Klose, S., additional, Knauer, J., additional, Knieps, A., additional, Köchl, F., additional, Kocsis, G., additional, Kolesnichenko, Ya.I., additional, Könies, A., additional, König, R., additional, Kontula, J., additional, Kornejew, P., additional, Koschinsky, J., additional, Kozulia, M.M., additional, Krämer-Flecken, A., additional, Krampitz, R., additional, Krause, M., additional, Krawczyk, N., additional, Kremeyer, T., additional, Krier, L., additional, Kriete, D.M., additional, Krychowiak, M., additional, Ksiazek, I., additional, Kubkowska, M., additional, Kuczynski, M., additional, Kühner, G., additional, Kumar, A., additional, Kurki-Suonio, T., additional, Kwak, S., additional, Landreman, M., additional, Lang, P.T., additional, Langenberg, A., additional, Laqua, H.P., additional, Laqua, H., additional, Laube, R., additional, Lazerson, S., additional, Lewerentz, M., additional, Li, C., additional, Liang, Y., additional, Linsmeier, Ch., additional, Lion, J., additional, Litnovsky, A., additional, Liu, S., additional, Lobsien, J., additional, Loizu, J., additional, Lore, J., additional, Lorenz, A., additional, Losada, U., additional, Louche, F., additional, Lunsford, R., additional, Lutsenko, V., additional, Machielsen, M., additional, Mackel, F., additional, Maisano-Brown, J., additional, Maj, O., additional, Makowski, D., additional, Manduchi, G., additional, Maragkoudakis, E., additional, Marchuk, O., additional, Marsen, S., additional, Martines, E., additional, Martinez-Fernandez, J., additional, Marushchenko, M., additional, Masuzaki, S., additional, Maurer, D., additional, Mayer, M., additional, McCarthy, K.J., additional, Mccormack, O., additional, McNeely, P., additional, Meister, H., additional, Mendelevitch, B., additional, Mendes, S., additional, Merlo, A., additional, Messian, A., additional, Mielczarek, A., additional, Mishchenko, O., additional, Missal, B., additional, Mitteau, R., additional, Moiseenko, V.E., additional, Mollen, A., additional, Moncada, V., additional, Mönnich, T., additional, Morisaki, T., additional, Moseev, D., additional, Motojima, G., additional, Mulas, S., additional, Mulsow, M., additional, Nagel, M., additional, Naujoks, D., additional, Naulin, V., additional, Neelis, T., additional, Neilson, H., additional, Neu, R., additional, Neubauer, O., additional, Neuner, U., additional, Nicolai, D., additional, Nielsen, S.K., additional, Niemann, H., additional, Nishiza, T., additional, Nishizawa, T., additional, Nührenberg, C., additional, Ochoukov, R., additional, Oelmann, J., additional, Offermanns, G., additional, Ogawa, K., additional, Okamura, S., additional, Ölmanns, J., additional, Ongena, J., additional, Oosterbeek, J., additional, Otte, M., additional, Pablant, N., additional, Panadero Alvarez, N., additional, Pandey, A., additional, Pasch, E., additional, Pavlichenko, R., additional, Pavone, A., additional, Pawelec, E., additional, Pechstein, G., additional, Pelka, G., additional, Perseo, V., additional, Peterson, B., additional, Pilopp, D., additional, Pingel, S., additional, Pisano, F., additional, Plöckl, B., additional, Plunk, G., additional, Pölöskei, P., additional, Pompe, B., additional, Popov, A., additional, Porkolab, M., additional, Proll, J., additional, Pueschel, M.J., additional, Puiatti, M.-E., additional, Puig Sitjes, A., additional, Purps, F., additional, Rahbarnia, K., additional, Rasiński, M., additional, Rasmussen, J., additional, Reiman, A., additional, Reimold, F., additional, Reisner, M., additional, Reiter, D., additional, Richou, M., additional, Riedl, R., additional, Riemann, J., additional, Riße, K., additional, Roberg-Clark, G., additional, Rohde, V., additional, Romazanov, J., additional, Rondeshagen, D., additional, Rong, P., additional, Rudischhauser, L., additional, Rummel, T., additional, Rummel, K., additional, Runov, A., additional, Rust, N., additional, Ryc, L., additional, Salembier, P., additional, Salewski, M., additional, Sanchez, E., additional, Satake, S., additional, Satheeswaran, G., additional, Schacht, J., additional, Scharff, E., additional, Schauer, F., additional, Schilling, J., additional, Schlisio, G., additional, Schmid, K., additional, Schmitt, J., additional, Schmitz, O., additional, Schneider, W., additional, Schneider, M., additional, Schneider, P., additional, Schrittwieser, R., additional, Schröder, T., additional, Schröder, M., additional, Schroeder, R., additional, Schweer, B., additional, Schwörer, D., additional, Scott, E., additional, Shanahan, B., additional, Sias, G., additional, Sichta, P., additional, Singer, M., additional, Sinha, P., additional, Sipliä, S., additional, Slaby, C., additional, Sleczka, M., additional, Smith, H., additional, Smoniewski, J., additional, Sonnendrücker, E., additional, Spolaore, M., additional, Spring, A., additional, Stadler, R., additional, Stańczak, D., additional, Stange, T., additional, Stepanov, I., additional, Stephey, L., additional, Stober, J., additional, Stroth, U., additional, Strumberger, E., additional, Suzuki, C., additional, Suzuki, Y., additional, Svensson, J., additional, Szabolics, T., additional, Szepesi, T., additional, Szücs, M., additional, Tabarés, F.L., additional, Tamura, N., additional, Tancetti, A., additional, Tantos, C., additional, Terry, J., additional, Thienpondt, H., additional, Thomsen, H., additional, Thumm, M., additional, Travere, J.M., additional, Traverso, P., additional, Tretter, J., additional, Trier, E., additional, Trimino Mora, H., additional, Tsujimura, T., additional, Turkin, Y., additional, Tykhyi, A., additional, Unterberg, B., additional, van Eeten, P., additional, van Milligen, B.Ph., additional, van Schoor, M., additional, Vano, L., additional, Varoutis, S., additional, Vecsei, M., additional, Vela, L., additional, Velasco, J.L., additional, Vervier, M., additional, Vianello, N., additional, Viebke, H., additional, Vilbrandt, R., additional, Vogel, G., additional, Vogt, N., additional, Volkhausen, C., additional, von Stechow, A., additional, Wagner, F., additional, Wang, E., additional, Wang, H., additional, Warmer, F., additional, Wauters, T., additional, Wegener, L., additional, Wegner, T., additional, Weir, G., additional, Wenzel, U., additional, White, A., additional, Wilde, F., additional, Wilms, F., additional, Windisch, T., additional, Winkler, M., additional, Winter, A., additional, Winters, V., additional, Wolf, R., additional, Wright, A.M., additional, Wurden, G.A., additional, Xanthopoulos, P., additional, Xu, S., additional, Yamada, H., additional, Yamaguchi, H., additional, Yokoyama, M., additional, Yoshinuma, M., additional, Yu, Q., additional, Zamanov, M., additional, Zanini, M., additional, Zarnstorff, M., additional, Zhang, D., additional, Zhou, S., additional, Zhu, J., additional, Zhu, C., additional, Zilker, M., additional, Zocco, A., additional, Zohm, H., additional, Zoletnik, S., additional, and Zsuga, L., additional

Published
2022
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16. Confinement degradation and plasma loss induced by strong sawtooth crashes at W7-X

Author

W7-X Team, Zanini, M., Buttenschön, B., Laqua, H. P., Thomsen, H., Stange, T., Brandt, C., Braune, H., Brunner, K. J., Dinklage, A., Gao, Y., Hirsch, M., Höfel, U., Knauer, J., Marsen, S., Marushchenko, N., Pavone, A., Rahbarnia, K., Schilling, J., Turkin, Y., Wolf, R. C., Zocco, A., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Technology, Nuclear and High Energy Physics, Materials science, Plasma, Sawtooth wave, Condensed Matter Physics, 01 natural sciences, Molecular physics, 010305 fluids & plasmas, 0103 physical sciences, ddc:530, 010306 general physics, ddc:600, Degradation (telecommunications)
Abstract

Sawtooth-like crashes were observed during electron cyclotron current drive experiments for strikeline controls at the optimised superconducting stellarator Wendelstein 7-X (W7-X). The majority of the crashes did not have a relevant impact on plasma performance. However, a limited number of events, characterised by a large plasma volume affected by the instability, have been related to a strong deterioration performance and even to the premature termination of the plasma. The hot plasma core expelled during these sawtooth crashes can reach the plasma edge, where plasma surface interaction can occur and impurities can be released. The x-ray tomography shows a strong radiation increase starting from the edge and moving towards the inner plasma regions. This results in the cooling down and shrinking of the plasma, which eventually leads to a poor coupling of the ECRH to the electrons, that can in turn result in a plasma loss. A relation between the size and amplitude of the sawtooth crashes and the impurity increase is reported.

Published
2021

17. Author Correction: Magnetic configuration effects on the Wendelstein 7-X stellarator

Author

Dinklage, A., Beidler, C. D., Helander, P., Fuchert, G., Maaßberg, H., Rahbarnia, K., Sunn Pedersen, T., Turkin, Y., Wolf, R. C., Alonso, A., Andreeva, T., Blackwell, B., Bozhenkov, S., Buttenschön, B., Czarnecka, A., Effenberg, F., Feng, Y., Geiger, J., Hirsch, M., Höfel, U., Jakubowski, M., Klinger, T., Knauer, J., Kocsis, G., Krämer-Flecken, A., Kubkowska, M., Langenberg, A., Laqua, H. P., Marushchenko, N., Mollén, A., Neuner, U., Niemann, H., Pasch, E., Pablant, N., Rudischhauser, L., Smith, H. M., Schmitz, O., Stange, T., Szepesi, T., Weir, G., Windisch, T., Wurden, G. A., Zhang, D., and and the W7-X Team

Published
2018
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18. Publisher Correction: Magnetic configuration effects on the Wendelstein 7-X stellarator

Author

Dinklage, A., Beidler, C. D., Helander, P., Fuchert, G., Maaßberg, H., Rahbarnia, K., Sunn Pedersen, T., Turkin, Y., Wolf, R. C., Alonso, A., Andreeva, T., Blackwell, B., Bozhenkov, S., Buttenschön, B., Czarnecka, A., Effenberg, F., Feng, Y., Geiger, J., Hirsch, M., Höfel, U., Jakubowski, M., Klinger, T., Knauer, J., Kocsis, G., Krämer-Flecken, A., Kubkowska, M., Langenberg, A., Laqua, H. P., Marushchenko, N., Mollén, A., Neuner, U., Niemann, H., Pasch, E., Pablant, N., Rudischhauser, L., Smith, H. M., Schmitz, O., Stange, T., Szepesi, T., Weir, G., Windisch, T., Wurden, G. A., Zhang, D., and and the W7-X Team

Published
2018
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20. Plasma radiation behavior approaching high-radiation scenarios in W7-X

Author

W7-X Team, Zhang, D., Burhenn, R., Feng, Y., König, R., Buttenschön, B., Beidler, C. D., Hacker, P., Reimold, F., Thomsen, H., Laube, R., Klinger, T., Giannone, L., Penzel, F., Pavone, A., Krychowiak, M., Beurskens, M., Bozhenkov, S., Brunner, J. K., Effenberg, F., Fuchert, G., Gao, Y., Geiger, J., Hirsch, M., Höfel, U., Jakubowski, M., Knauer, J., Kwak, S., Laqua, H. P., Niemann, H., Otte, M., Pedersen, T. Sunn, Pasch, E., Pablant, N., Rahbarnia, K., Svensson, J., Blackwell, B., Drews, P., Endler, M., Rudischhauser, L., Wang, E., Weir, G., Winters, V., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Nuclear and High Energy Physics, Technology, business.industry, High radiation, Plasma radiation, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Optics, 0103 physical sciences, ddc:620, 010306 general physics, business, ddc:600
Abstract

The W7-X stellarator has so far performed experiments under both limiter and divertor conditions. The plasma is mostly generated by ECR-heating with powers up to 6.5 MW, and the plasma density is usually limited by the radiation losses from low-Z impurities (such as carbon and oxygen) released mainly from the graphite targets. The present work first summarizes the radiation loss fractions f rad achieved in quasi-stationary hydrogen plasmas in both operational phases, and then shows how impurity radiation behaves differently with the two different boundary conditions as the plasma density increases. The divertor operation is emphasized and some beneficial effects (with respect to impurity radiation) are highlighted: (1) intensive radiation is located at the edge (r/a > 0.8) even at high radiation loss fractions, (2) the plasma remains stable up to f rad approaching unity, (3) the reduction in the stored energy is about 10% for high f rad scenarios. Moreover, effects of wall boronisation on impurity radiation profiles are also presented.

Published
2021
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21. Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X

Author

W7-X Team, Weir, G. M., Xanthopoulos, P., Hirsch, M., Höfel, U., Stange, T., Pablant, N., Grulke, O., Äkäslompolo, S., Alcusón, J., Bozhenkov, S., Beurskens, M., Dinklage, A., Fuchert, G., Geiger, J., Landreman, M., Langenberg, A., Lazerson, S., Marushchenko, N., Pasch, E., Schilling, J., Scott, E. R., Turkin, Y., Klinger, T., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Nuclear and High Energy Physics, Technology, Heat pulse, Electron, Collisionality, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, Atomic physics, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract

The optimized stellarator Wendelstein 7-X (W7-X) is designed to have an approximately quasi-isodynamic magnetic configuration with reduced neoclassical transport in comparison to a classical stellarator, and turbulent transport is expected to be a significant source of anomalous heat transport across the plasma minor radius. The ion temperature gradient driven mode and the trapped electron mode (TEM) are thought to be responsible for the ion-scale turbulence in W7-X plasmas with volume averaged pressure below 1%. In this work, the electron temperature gradient driven turbulence is shown to be a good candidate for the explanation of the observed electron heat flux, in the inner plasma region where the density gradient is weak (in the outer region, a relatively stronger density gradient would drive additional TEM turbulence). The experimental electron heat transport measured during electron cyclotron resonant heating power and plasma density scans is compared to neoclassical predictions, and the stiffness in the electron heat transport measured during transient transport experiments is presented in three common magnetic configurations of W7-X. In low-⟨β⟩ plasma discharges, the stiffness in the electron heat flux, quantified by the ratio of the heat pulse to power balance diffusivity, χ e H P / χ e P B , is measured to be less than 2, and trend downwards with increasing collisionality.

Published
2021
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22. Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X

Author

Weir, G.M., Xanthopoulos, P., Hirsch, M., Höfel, U., Stange, T., Pablant, N., Grulke, O., Äkäslompolo, S., Alcusón, J., Bozhenkov, S., Beurskens, M., Dinklage, A., Fuchert, G., Geiger, J., Landreman, M., Langenberg, A., Lazerson, S., Marushchenko, N., Pasch, E., Schilling, J., Scott, E.R., Turkin, Y., Klinger, T., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, and Weggen, Jörg

Published
2021
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23. ECCD-induced sawtooth crashes at W7-X

Author

W7-X Team, Zanini, M., Laqua, H. P., Thomsen, H., Stange, T., Brandt, C., Braune, H., Brunner, K. J., Fuchert, G., Hirsch, M., Knauer, J., Höfel, U., Marsen, S., Pasch, E., Rahbarnia, K., Schilling, J., Turkin, Y., Wolf, R. C., Zocco, A., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Technology, Nuclear and High Energy Physics, Tokamak, Toroid, Divertor, Sawtooth wave, Condensed Matter Physics, 01 natural sciences, Instability, 010305 fluids & plasmas, law.invention, Computational physics, Amplitude, law, Physics::Plasma Physics, 0103 physical sciences, 11. Sustainability, Electron temperature, ddc:530, 010306 general physics, ddc:600, Stellarator
Abstract

The optimised superconducting stellarator W7-X generates its rotational transform by means of external coils, therefore no toroidal current is necessary for plasma confinement. Electron cyclotron current drive experiments were conducted for strikeline control and safe divertor operation. During current drive experiments periodic and repetitive crashes of the central electron temperature, similar to sawtooth crashes in tokamaks, were detected. Measurements from soft x-ray tomography and electron cyclotron emission show that the crashes are preceded by weak oscillating precursors and a displacement of the plasma core, consistent with a (m, n) = (1, 1) mode. The displacement occurs within 100 μ s , followed by expulsion and redistribution of the core into the external part of the plasma. Two types of crashes, with different frequencies and amplitudes are detected in the experimental program. For these non-stationary parameters a strong dependence on the toroidal current is found. A 1-D heuristic model for current diffusion is proposed as a first step to explain the characteristic crash time. Initial results show that the modelled current diffusion timescale is consistent with the initial crash frequency and that the toroidal current rise shifts the position where the instability is triggered, resulting in larger crash amplitudes.

Published
2020

24. Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase

Author

Massachusetts Institute of Technology. Department of Physics, Wolf, R. C., Alonso, A., Äkäslompolo, S., Baldzuhn, J., Beurskens, M., Beidler, C. D., Biedermann, C., Bosch, H.-S., Bozhenkov, S., Brakel, R., Braune, H., Brezinsek, S., Brunner, K.-J., Damm, H., Dinklage, A., Drewelow, P., Effenberg, F., Feng, Y., Ford, O., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Harder, N., Hartmann, D., Helander, P., Heinemann, B., Hirsch, M., Höfel, U., Hopf, C., Ida, K., Isobe, M., Jakubowski, M. W., Kazakov, Y. O., Killer, C., Klinger, T., Knauer, J., König, R., Krychowiak, M., Langenberg, A., Laqua, H. P., Lazerson, S., McNeely, P., Marsen, S., Marushchenko, N., Nocentini, R., Ogawa, K., Orozco, G., Osakabe, M., Otte, M., Pablant, N., Pasch, E., Pavone, A., Porkolab, Miklos, Puig Sitjes, A., Rahbarnia, K., Riedl, R., Rust, N., Scott, E., Schilling, J., Schroeder, R., Stange, T., von Stechow, A., Strumberger, E., Sunn Pedersen, T., Svensson, J., Thomson, H., Turkin, Y., Vano, L., Wauters, T., Wurden, G., Yoshinuma, M., Zanini, M., Zhang, D., Massachusetts Institute of Technology. Department of Physics, Wolf, R. C., Alonso, A., Äkäslompolo, S., Baldzuhn, J., Beurskens, M., Beidler, C. D., Biedermann, C., Bosch, H.-S., Bozhenkov, S., Brakel, R., Braune, H., Brezinsek, S., Brunner, K.-J., Damm, H., Dinklage, A., Drewelow, P., Effenberg, F., Feng, Y., Ford, O., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Harder, N., Hartmann, D., Helander, P., Heinemann, B., Hirsch, M., Höfel, U., Hopf, C., Ida, K., Isobe, M., Jakubowski, M. W., Kazakov, Y. O., Killer, C., Klinger, T., Knauer, J., König, R., Krychowiak, M., Langenberg, A., Laqua, H. P., Lazerson, S., McNeely, P., Marsen, S., Marushchenko, N., Nocentini, R., Ogawa, K., Orozco, G., Osakabe, M., Otte, M., Pablant, N., Pasch, E., Pavone, A., Porkolab, Miklos, Puig Sitjes, A., Rahbarnia, K., Riedl, R., Rust, N., Scott, E., Schilling, J., Schroeder, R., Stange, T., von Stechow, A., Strumberger, E., Sunn Pedersen, T., Svensson, J., Thomson, H., Turkin, Y., Vano, L., Wauters, T., Wurden, G., Yoshinuma, M., Zanini, M., and Zhang, D.

Published
2021

25. Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X

Author

Weir, G.M., primary, Xanthopoulos, P., additional, Hirsch, M., additional, Höfel, U., additional, Stange, T., additional, Pablant, N., additional, Grulke, O., additional, Äkäslompolo, S., additional, Alcusón, J., additional, Bozhenkov, S., additional, Beurskens, M., additional, Dinklage, A., additional, Fuchert, G., additional, Geiger, J., additional, Landreman, M., additional, Langenberg, A., additional, Lazerson, S., additional, Marushchenko, N., additional, Pasch, E., additional, Schilling, J., additional, Scott, E.R., additional, Turkin, Y., additional, and Klinger, T., additional

Published
2021
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27. ECCD-induced sawtooth crashes at W7-X

Author

Zanini, M., primary, Laqua, H.P., additional, Thomsen, H., additional, Stange, T., additional, Brandt, C., additional, Braune, H., additional, Brunner, K.J., additional, Fuchert, G., additional, Hirsch, M., additional, Knauer, J., additional, Höfel, U., additional, Marsen, S., additional, Pasch, E., additional, Rahbarnia, K., additional, Schilling, J., additional, Turkin, Y., additional, Wolf, R.C., additional, and Zocco, A., additional

Published
2020
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28. Enhanced energy confinement after series of pellets in Wendelstein 7-X

Author

Baldzuhn, J, primary, Damm, H, additional, Beidler, C D, additional, McCarthy, K, additional, Panadero, N, additional, Biedermann, C, additional, Bozhenkov, S A, additional, Dinklage, A, additional, Brunner, K J, additional, Fuchert, G, additional, Kazakov, Y, additional, Beurskens, M, additional, Dibon, M, additional, Geiger, J, additional, Grulke, O, additional, Höfel, U, additional, Klinger, T, additional, Köchl, F, additional, Knauer, J, additional, Kocsis, G, additional, Kornejew, P, additional, Lang, P T, additional, Langenberg, A, additional, Laqua, H, additional, Pablant, N A, additional, Pasch, E, additional, Pedersen, T S, additional, Ploeckl, B, additional, Rahbarnia, K, additional, Schlisio, G, additional, Scott, E R, additional, Stange, T, additional, Von Stechow, A, additional, Szepesi, T, additional, Turkin, Y, additional, Wagner, F, additional, Winters, V, additional, Wurden, G, additional, and Zhang, D., additional

Published
2020
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29. Numerical modeling of the electron temperature crashes observed in Wendelstein 7-X stellarator experiments

Author

W7-X Team, Yu, Q., Strumberger, E., Igochine, V., Lackner, K., Laqua, H. P., Zanini, M., Braune, H., Hirsch, M., Höfel, U., Marsen, S., Stange, T., Wolf, R. C., Günter, S., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Nuclear and High Energy Physics, Technology, Safety factor, Q value, Cyclotron, Electron, Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Computational physics, law, 0103 physical sciences, Electron temperature, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract

Numerical calculations based on nonlinear two-fluid equations have been carried out to understand the sawtooth-like crashes of electron temperature observed in Wendelstein 7-X stellarator experiments with electron cyclotron current drive (ECCD). The application of ECCD leads to non-monotonic radial profiles of the safety factor q with two q = 1 surfaces in the plasma core region. Using input parameters similar to the experiment, numerical calculations show two types of crashes of the central electron temperature depending on the growth of the internal kink mode coupled to double tearing modes. When the distance between two equilibrium q = 1 surfaces is sufficiently large, the internal kink mode leads to a fast radial displacement of the hot core from the center to the region of the q = 1 surfaces. In agreement with experimental observation, this causes a full crash of central electron temperature in about 20–30 microseconds. When the distance between the two q = 1 surfaces is not large enough, partial crashes of the central electron temperature are found. During these crashes the hot core only temporally moves outwards. Then it moves back, because the double tearing mode perturbation leads to an increase of the minimum q value about one.

Published
2020

30. Investigation of mode activity in NBI-heated experiments of Wendelstein 7-X

Author

W7-X Team, Slaby, C., Äkäslompolo, S., Borchardt, M., Geiger, J., Kleiber, R., Könies, A., Bozhenkov, S., Brandt, C., Dinklage, A., Dreval, M., Ford, O., Fuchert, G., Hartmann, D., Hirsch, M., Höfel, U., Huang, Z., McNeely, P., Pablant, N., Rahbarnia, K., Rust, N., Schilling, J., Stechow, A. von, Thomsen, H., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, Department of Applied Physics, Aalto-yliopisto, Aalto University, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Nuclear and High Energy Physics, Technology, Continuous spectrum, Plasma, Condensed Matter Physics, 01 natural sciences, Neutral beam injection, 010305 fluids & plasmas, law.invention, Computational physics, Alfvén wave, Distribution function, Physics::Plasma Physics, law, Electric field, 0103 physical sciences, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract

openaire: EC/H2020/633053/EU//EUROfusion The 2018 operation phase (OP 1.2b) of the stellarator Wendelstein 7-X (W7-X) included, for the first time, neutral beam injection (NBI) to heat the plasma. Since the injection geometry at W7-X is not parallel, this generates both passing and trapped fast particles. During longer phases of NBI injection, with the primary purpose to study the heating efficiency of this system, Alfven eigenmodes (AEs) were observed by a number of diagnostics, including the phase contrast imaging (PCI) system, the magnetic pick-up coils (Mirnov coils), and the soft x-ray multi-camera tomography system (XMCTS). Alfven eigenmodes are of great interest for future fusion reactors as it has been shown that the resonant interaction of fast ions with self-excited AEs can lead to enhanced transport of fast ions and potentially to energy losses. This is especially true for so-called gap-modes, Alfven eigenmodes with frequencies in gaps of the continuous spectrum, since they lack continuum damping. These modes are commonly known to be excited by fast ions, but other destabilizing mechanisms, e.g. the electron-pressure gradient are also possible. In this article we present a first analysis of the experimentally observed frequencies from the theoretical side. The calculation of shear Alfven wave continua for selected cases and the assignment of observed frequencies to the gaps of the continuous spectra are presented. Using the ideal-MHD code CKA (Konies A. 200710th IAEA TM on Energetic Particles in Magnetic Confinement System), we find gap modes that match the experimental measurements in terms of the observed frequencies. We emphasize the crucial roles played by the coupling of sound and Alfven waves as well as of the Doppler shift arising as a consequence of the radial electric field in W7-X. We employ the perturbative gyrokinetic code CKA-EUTERPE (Feh ' er 2013 Simulation of the interaction between Alfv ' en waves and fast particles), using a slowing-down distribution function for the fast ions as calculated by the Monte-Carlo particle following code ASCOT (Hirvijokiet al2014Comput. Phys. Commun.185 1310-21) to assess the fast-ion drive. We find that the fast-ion drive is insufficient to overcome the background-plasma damping. The fact that unstable modes were observed experimentally may point to problems with the modelling or indicate the existence of other destabilizing mechanisms, e.g. associated with the electron-pressure gradient (Windischet al2017Plasma Phys. Control. Fusion59 105002) that sensitively depend on the profiles of the background plasma.

Published
2020

31. The Langmuir probe system in the Wendelstein 7-X test divertor

Author

W7-X Team, Rudischhauser, L., Endler, M., Höfel, U., Hammond, K. C., Kallmeyer, J. P., Blackwell, B. D., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
010302 applied physics, Physics, Technology, Plasma parameters, Divertor, Phase (waves), Mechanics, Bayesian inference, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, symbols.namesake, 0103 physical sciences, Range (statistics), symbols, Langmuir probe, Wendelstein 7-X, ddc:600, Instrumentation
Abstract

The design and evaluation of the Langmuir probe system used in the first divertor operation phase of Wendelstein 7-X is described. The probes are integrated into the target plates and have individually facetted surfaces to keep the angle of incidence of the magnetic field within an appropriate range for different magnetic configurations. Multiple models for the derivation of plasma parameters from current–voltage characteristics are introduced. These are analyzed with regard to their assumptions and limitations, generalized, and adapted to our use case. A detailed comparison is made to determine the most suitable model. It is found that the choice of model has a large impact, for example, resulting in a change in the inferred temperatures of up to a factor two. This evaluation is implemented in a Bayesian modeling framework and automated to allow for joint analysis with other diagnostics and a replacement of ad hoc assumptions. We rigorously treat parameter uncertainties, revealing strong correlations between them. General and flexible model formulations permit an expansion to additional effects.

Published
2020

32. Enhanced energy confinement after series of pellets in Wendelstein 7-X

Author

W7-X Team, Baldzuhn, J., Damm, H., Beidler, C. D., McCarthy, K., Panadero, N., Biedermann, C., Bozhenkov, S. A., Dinklage, A., Brunner, K. J., Fuchert, G., Kazakov, Y., Beurskens, M., Dibon, M., Geiger, J., Grulke, O., Höfel, U., Klinger, T., Köchl, F., Knauer, J., Kocsis, G., Kornejew, P., Lang, P. T., Langenberg, A., Laqua, H., Pablant, N. A., Pasch, E., Pedersen, T. S., Ploeckl, B., Rahbarnia, K., Schlisio, G., Scott, E. R., Stange, T., Von Stechow, A., Szepesi, T., Turkin, Y., Wagner, F., Winters, V., Wurden, G., Zhang, D., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Technology, Materials science, Series (mathematics), Pellets, Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Nuclear Energy and Engineering, Impurity, 0103 physical sciences, Wendelstein 7-X, Atomic physics, 010306 general physics, ddc:600, Energy (signal processing)
Abstract

A series of ice pellets was injected into the advanced stellarator Wendelstein 7-X (W7-X). Although the pellets were small and slow, deep and efficient particle fueling could be observed experimentally. The most striking feature appearing after the injection of the pellets, however, was a transient increase in the energy confinement time. This transient phase resembled in several aspects modes of enhanced confinement after gas-puff or pellet injection, as observed in other fusion experiments. All experimental attempts, to prolong this phase, failed. In this paper, discharges are described that show the enhanced energy confinement, and some conditions are summarized which seem to be essential in order to generate it. The focus here is on deep particle fueling by pellets, and shaping of the density profiles during and after the series of pellets. During this time, neutral gas particle re-fueling at the plasma edge is reduced, while density profile peaking and low impurity radiation losses are present.

Published
2020

33. Enhanced energy confinement after series of pellets in Wendelstein 7-X

Author

Baldzuhn, J, Damm, H, Beidler, C D, McCarthy, K, Panadero, N, Biedermann, C, Bozhenkov, S A, Dinklage, A, Brunner, K J, Fuchert, G, Kazakov, Y, Beurskens, M, Dibon, M, Geiger, J, Grulke, O, Höfel, U, Klinger, T, Köchl, F, Knauer, J, Kocsis, G, Kornejew, P, Lang, P T, Langenberg, A, Laqua, H, Pablant, N A, Pasch, E, Pedersen, T S, Ploeckl, B, Rahbarnia, K, Schlisio, G, Scott, E R, Stange, T, Von Stechow, A, Szepesi, T, Turkin, Y, Wagner, F, Winters, V, Wurden, G, Zhang, D., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, and Weggen, Jörg

Published
2020
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34. High density and high performance operation with pellet injection in W7-X

Author

Bozhenkov, S., Kazakov, Y., Baldzuhn, J., Laqua, H., Alonso, J., Beurskens, M., Brandt, C., Brunner, K., Damm, H., Fuchert, G., Hirsch, M., Höfel, U., Jakubowski, M., Knauer, J., Kocsis, G., König, R., Langenberg, A., Lazerson, S., Marushchenko, N., McCarthy, K., Pasch, E., Pablant, N., Panadero Alvarez, N., Rahbarnia, K., Schmitt, J., Thomsen, H., Turkin, Y., Warmer, F., Wurden, G., Zhang, D., Pedersen, T., Wolf, R., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2019

35. Investigations of the role of neoclassical transport in ion-root plasmas on W7-X

Author

Pablant, N., Langenberg, A., Alonso, A., Baldzuhn, J., Beidler, C., Böttger, L., Bozhenkov, S., Burhenn, R., Brunner, K., Dinklage, A., Fuchert, G., Ford, O., Gates, D., Geiger, J., Grulke, O., Hirsch, M., Höfel, U., Huang, Z., Kazakov, Y., Knauer, J., Krychowiak, M., Kring, J., Laqua, H., Landreman, M., Lazerson, S., Maaßberg, H., Marchuck, O., Mollen, A., Pasch, E., Pavone, A., Porkolab, M., Satake, S., Schröder, T., Smith, H., Svensson, J., Traverso, P., Turkin, Y., Velasco, J., Stechow, A., Warmer, F., Weir, G., Wolf, R., Zhang, D., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2019

36. The effects of magnetic topology on the SOL island structure and turbulence transport in the first divertor plasma operation of W7-X

Author

Liu, S., Liang, Y., Drews, P., Killer, C., Knieps, A., Xu, G., Wang, H., Wu, X., Han, X., Höschen, D., Krämer-Flecken, A., Nicolai, D., Satheeswaran, G., Alonso, A., Cai, J., Charl, A., Cosfeld, J., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Henkel, M., Hirsch, M., Höfel, U., Jakubowski, M., König, R., Neubauer, O., Pasch, E., Rahbarnia, K., Rack, M., Sandri, N., Sereda, S., Schweer, B., Wang, E., Wei, Y., Weir, G., Windisch, T., Xu, S., Gao, X., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2019

37. Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements

Author

Langenberg, A., Warmer, F., Fuchert, G., Marchuk, O., Dinklage, A., Wegner, Th., Alonso, J. A., Bozhenkov, S., Brunner, K. J., Burhenn, R., Buttenschön, B., Drews, P., Geiger, B., Grulke, O., Hirsch, M., Höfel, U., Hollfeld, K. P., Killer, C., Knauer, J., Krings, T., Kunkel, F., Neuner, U., Offermanns, G., Pablant, N. A., Pasch, E., Rahbarnia, K., Satheeswaran, G., Schilling, J., Schweer, B., Thomsen, H., Traverso, P., Wolf, R. C., Baumann, Klaus, Dammertz, G., Fietz, W. H., Gantenbein, Gerd, Huber, Martina, Hunger, Hermann, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Losert, M., Meier, A., Mellein, Daniel, Papenfuß, Daniel, Samartsev, Andrey, Scherer, Theo, Schlaich, A., Spiess, W., Thumm, Manfred, Wadle, Simone, and Weggen, Jörg

Subjects
Technology, ddc:600
Published
2019
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38. Pellet fueling experiments in Wendelstein 7-X

Author

W7-X Team, Baldzuhn, J., Damm, H., Beidler, C. D., McCarthy, K., Panadero, N., Biedermann, C., Bozhenkov, S. A., Brunner, K. J., Fuchert, G., Kazakov, Y., Beurskens, M., Dibon, M., Geiger, J., Grulke, O., Höfel, U., Klinger, T., Köchl, F., Knauer, J., Kocsis, G., Kornejew, P., Lang, P. T., Langenberg, A., Laqua, H., Pablant, N. A., Pasch, E., Pedersen, T. S., Ploeckl, B., Rahbarnia, K., Schlisio, G., Scott, E. R., Stange, T., Stechow, A. von, Szepesi, T., Turkin, Y., Wagner, F., Winters, V., Wurden, G., Zhang, D., Gantenbein, Gerd, Huber, Martina, Hunger, Hermann, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Losert, M., Meier, A., Mellein, Daniel, Papenfuß, Daniel, Samartsev, Andrey, Scherer, Theo, Schlaich, A., Spiess, W., Thumm, Manfred, Wadle, Simone, and Weggen, Jörg

Subjects
Technology, ddc:600
Published
2019

39. Pellet fueling experiments in Wendelstein 7-X

Author

Baldzuhn, J, primary, Damm, H, additional, Beidler, C D, additional, McCarthy, K, additional, Panadero, N, additional, Biedermann, C, additional, Bozhenkov, S A, additional, Brunner, K J, additional, Fuchert, G, additional, Kazakov, Y, additional, Beurskens, M, additional, Dibon, M, additional, Geiger, J, additional, Grulke, O, additional, Höfel, U, additional, Klinger, T, additional, Köchl, F, additional, Knauer, J, additional, Kocsis, G, additional, Kornejew, P, additional, Lang, P T, additional, Langenberg, A, additional, Laqua, H, additional, Pablant, N A, additional, Pasch, E, additional, Pedersen, T S, additional, Ploeckl, B, additional, Rahbarnia, K, additional, Schlisio, G, additional, Scott, E R, additional, Stange, T, additional, von Stechow, A, additional, Szepesi, T, additional, Turkin, Y, additional, Wagner, F, additional, Winters, V, additional, Wurden, G, additional, and Zhang, D, additional

Published
2019
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40. First Observation of a Stable Highly Dissipative Divertor Plasma Regime on the Wendelstein 7-X Stellarator

Author

Zhang, D., primary, König, R., additional, Feng, Y., additional, Burhenn, R., additional, Brezinsek, S., additional, Jakubowski, M., additional, Buttenschön, B., additional, Niemann, H., additional, Pavone, A., additional, Krychowiak, M., additional, Kwak, S., additional, Svensson, J., additional, Gao, Y., additional, Pedersen, T. S., additional, Alonso, A., additional, Baldzuhn, J., additional, Beidler, C. D., additional, Biedermann, C., additional, Bozhenkov, S., additional, Brunner, K. J., additional, Damm, H., additional, Hirsch, M., additional, Giannone, L., additional, Drewelow, P., additional, Effenberg, F., additional, Fuchert, G., additional, Hammond, K. C., additional, Höfel, U., additional, Killer, C., additional, Knauer, J., additional, Laqua, H. P., additional, Laube, R., additional, Pablant, N., additional, Pasch, E., additional, Penzel, F., additional, Rahbarnia, K., additional, Reimold, F., additional, Thomsen, H., additional, Winters, V., additional, Wagner, F., additional, and Klinger, T., additional

Published
2019
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41. Overview of first Wendelstein 7-X high-performance operation

Author

Klinger, T., primary, Andreeva, T., additional, Bozhenkov, S., additional, Brandt, C., additional, Burhenn, R., additional, Buttenschön, B., additional, Fuchert, G., additional, Geiger, B., additional, Grulke, O., additional, Laqua, H.P., additional, Pablant, N., additional, Rahbarnia, K., additional, Stange, T., additional, von Stechow, A., additional, Tamura, N., additional, Thomsen, H., additional, Turkin, Y., additional, Wegner, T., additional, Abramovic, I., additional, Äkäslompolo, S., additional, Alcuson, J., additional, Aleynikov, P., additional, Aleynikova, K., additional, Ali, A., additional, Alonso, A., additional, Anda, G., additional, Ascasibar, E., additional, Bähner, J.P., additional, Baek, S.G., additional, Balden, M., additional, Baldzuhn, J., additional, Banduch, M., additional, Barbui, T., additional, Behr, W., additional, Beidler, C., additional, Benndorf, A., additional, Biedermann, C., additional, Biel, W., additional, Blackwell, B., additional, Blanco, E., additional, Blatzheim, M., additional, Ballinger, S., additional, Bluhm, T., additional, Böckenhoff, D., additional, Böswirth, B., additional, Böttger, L.-G., additional, Borchardt, M., additional, Borsuk, V., additional, Boscary, J., additional, Bosch, H.-S., additional, Beurskens, M., additional, Brakel, R., additional, Brand, H., additional, Bräuer, T., additional, Braune, H., additional, Brezinsek, S., additional, Brunner, K.-J., additional, Bussiahn, R., additional, Bykov, V., additional, Cai, J., additional, Calvo, I., additional, Cannas, B., additional, Cappa, A., additional, Carls, A., additional, Carralero, D., additional, Carraro, L., additional, Carvalho, B., additional, Castejon, F., additional, Charl, A., additional, Chaudhary, N., additional, Chauvin, D., additional, Chernyshev, F., additional, Cianciosa, M., additional, Citarella, R., additional, Claps, G., additional, Coenen, J., additional, Cole, M., additional, Cole, M.J., additional, Cordella, F., additional, Cseh, G., additional, Czarnecka, A., additional, Czerski, K., additional, Czerwinski, M., additional, Czymek, G., additional, da Molin, A., additional, da Silva, A., additional, Damm, H., additional, de la Pena, A., additional, Degenkolbe, S., additional, Dhard, C.P., additional, Dibon, M., additional, Dinklage, A., additional, Dittmar, T., additional, Drevlak, M., additional, Drewelow, P., additional, Drews, P., additional, Durodie, F., additional, Edlund, E., additional, van Eeten, P., additional, Effenberg, F., additional, Ehrke, G., additional, Elgeti, S., additional, Endler, M., additional, Ennis, D., additional, Esteban, H., additional, Estrada, T., additional, Fellinger, J., additional, Feng, Y., additional, Flom, E., additional, Fernandes, H., additional, Fietz, W.H., additional, Figacz, W., additional, Fontdecaba, J., additional, Ford, O., additional, Fornal, T., additional, Frerichs, H., additional, Freund, A., additional, Funaba, T., additional, Galkowski, A., additional, Gantenbein, G., additional, Gao, Y., additional, García Regaña, J., additional, Gates, D., additional, Geiger, J., additional, Giannella, V., additional, Gogoleva, A., additional, Goncalves, B., additional, Goriaev, A., additional, Gradic, D., additional, Grahl, M., additional, Green, J., additional, Greuner, H., additional, Grosman, A., additional, Grote, H., additional, Gruca, M., additional, Guerard, C., additional, Hacker, P., additional, Han, X., additional, Harris, J.H., additional, Hartmann, D., additional, Hathiramani, D., additional, Hein, B., additional, Heinemann, B., additional, Helander, P., additional, Henneberg, S., additional, Henkel, M., additional, Hernandez Sanchez, J., additional, Hidalgo, C., additional, Hirsch, M., additional, Hollfeld, K.P., additional, Höfel, U., additional, Hölting, A., additional, Höschen, D., additional, Houry, M., additional, Howard, J., additional, Huang, X., additional, Huang, Z., additional, Hubeny, M., additional, Huber, M., additional, Hunger, H., additional, Ida, K., additional, Ilkei, T., additional, Illy, S., additional, Israeli, B., additional, Jablonski, S., additional, Jakubowski, M., additional, Jelonnek, J., additional, Jenzsch, H., additional, Jesche, T., additional, Jia, M., additional, Junghanns, P., additional, Kacmarczyk, J., additional, Kallmeyer, J.-P., additional, Kamionka, U., additional, Kasahara, H., additional, Kasparek, W., additional, Kazakov, Y.O., additional, Kenmochi, N., additional, Killer, C., additional, Kirschner, A., additional, Kleiber, R., additional, Knauer, J., additional, Knaup, M., additional, Knieps, A., additional, Kobarg, T., additional, Kocsis, G., additional, Köchl, F., additional, Kolesnichenko, Y., additional, Könies, A., additional, König, R., additional, Kornejew, P., additional, Koschinsky, J.-P., additional, Köster, F., additional, Krämer, M., additional, Krampitz, R., additional, Krämer-Flecken, A., additional, Krawczyk, N., additional, Kremeyer, T., additional, Krom, J., additional, Krychowiak, M., additional, Ksiazek, I., additional, Kubkowska, M., additional, Kühner, G., additional, Kurki-Suonio, T., additional, Kurz, P.A., additional, Kwak, S., additional, Landreman, M., additional, Lang, P., additional, Lang, R., additional, Langenberg, A., additional, Langish, S., additional, Laqua, H., additional, Laube, R., additional, Lazerson, S., additional, Lechte, C., additional, Lennartz, M., additional, Leonhardt, W., additional, Li, C., additional, Li, Y., additional, Liang, Y., additional, Linsmeier, C., additional, Liu, S., additional, Lobsien, J.-F., additional, Loesser, D., additional, Loizu Cisquella, J., additional, Lore, J., additional, Lorenz, A., additional, Losert, M., additional, Lücke, A., additional, Lumsdaine, A., additional, Lutsenko, V., additional, Maaßberg, H., additional, Marchuk, O., additional, Matthew, J.H., additional, Marsen, S., additional, Marushchenko, M., additional, Masuzaki, S., additional, Maurer, D., additional, Mayer, M., additional, McCarthy, K., additional, McNeely, P., additional, Meier, A., additional, Mellein, D., additional, Mendelevitch, B., additional, Mertens, P., additional, Mikkelsen, D., additional, Mishchenko, A., additional, Missal, B., additional, Mittelstaedt, J., additional, Mizuuchi, T., additional, Mollen, A., additional, Moncada, V., additional, Mönnich, T., additional, Morisaki, T., additional, Moseev, D., additional, Murakami, S., additional, Náfrádi, G., additional, Nagel, M., additional, Naujoks, D., additional, Neilson, H., additional, Neu, R., additional, Neubauer, O., additional, Neuner, U., additional, Ngo, T., additional, Nicolai, D., additional, Nielsen, S.K., additional, Niemann, H., additional, Nishizawa, T., additional, Nocentini, R., additional, Nührenberg, C., additional, Nührenberg, J., additional, Obermayer, S., additional, Offermanns, G., additional, Ogawa, K., additional, Ölmanns, J., additional, Ongena, J., additional, Oosterbeek, J.W., additional, Orozco, G., additional, Otte, M., additional, Pacios Rodriguez, L., additional, Panadero, N., additional, Panadero Alvarez, N., additional, Papenfuß, D., additional, Paqay, S., additional, Pasch, E., additional, Pavone, A., additional, Pawelec, E., additional, Pedersen, T.S., additional, Pelka, G., additional, Perseo, V., additional, Peterson, B., additional, Pilopp, D., additional, Pingel, S., additional, Pisano, F., additional, Plaum, B., additional, Plunk, G., additional, Pölöskei, P., additional, Porkolab, M., additional, Proll, J., additional, Puiatti, M.-E., additional, Puig Sitjes, A., additional, Purps, F., additional, Rack, M., additional, Récsei, S., additional, Reiman, A., additional, Reimold, F., additional, Reiter, D., additional, Remppel, F., additional, Renard, S., additional, Riedl, R., additional, Riemann, J., additional, Risse, K., additional, Rohde, V., additional, Röhlinger, H., additional, Romé, M., additional, Rondeshagen, D., additional, Rong, P., additional, Roth, B., additional, Rudischhauser, L., additional, Rummel, K., additional, Rummel, T., additional, Runov, A., additional, Rust, N., additional, Ryc, L., additional, Ryosuke, S., additional, Sakamoto, R., additional, Salewski, M., additional, Samartsev, A., additional, Sanchez, E., additional, Sano, F., additional, Satake, S., additional, Schacht, J., additional, Satheeswaran, G., additional, Schauer, F., additional, Scherer, T., additional, Schilling, J., additional, Schlaich, A., additional, Schlisio, G., additional, Schluck, F., additional, Schlüter, K.-H., additional, Schmitt, J., additional, Schmitz, H., additional, Schmitz, O., additional, Schmuck, S., additional, Schneider, M., additional, Schneider, W., additional, Scholz, P., additional, Schrittwieser, R., additional, Schröder, M., additional, Schröder, T., additional, Schroeder, R., additional, Schumacher, H., additional, Schweer, B., additional, Scott, E., additional, Sereda, S., additional, Shanahan, B., additional, Sibilia, M., additional, Sinha, P., additional, Sipliä, S., additional, Slaby, C., additional, Sleczka, M., additional, Smith, H., additional, Spiess, W., additional, Spong, D.A., additional, Spring, A., additional, Stadler, R., additional, Stejner, M., additional, Stephey, L., additional, Stridde, U., additional, Suzuki, C., additional, Svensson, J., additional, Szabó, V., additional, Szabolics, T., additional, Szepesi, T., additional, Szökefalvi-Nagy, Z., additional, Tancetti, A., additional, Terry, J., additional, Thomas, J., additional, Thumm, M., additional, Travere, J.M., additional, Traverso, P., additional, Tretter, J., additional, Trimino Mora, H., additional, Tsuchiya, H., additional, Tsujimura, T., additional, Tulipán, S., additional, Unterberg, B., additional, Vakulchyk, I., additional, Valet, S., additional, Vano, L., additional, van Milligen, B., additional, van Vuuren, A.J., additional, Vela, L., additional, Velasco, J.-L., additional, Vergote, M., additional, Vervier, M., additional, Vianello, N., additional, Viebke, H., additional, Vilbrandt, R., additional, Vorköper, A., additional, Wadle, S., additional, Wagner, F., additional, Wang, E., additional, Wang, N., additional, Wang, Z., additional, Warmer, F., additional, Wauters, T., additional, Wegener, L., additional, Weggen, J., additional, Wei, Y., additional, Weir, G., additional, Wendorf, J., additional, Wenzel, U., additional, Werner, A., additional, White, A., additional, Wiegel, B., additional, Wilde, F., additional, Windisch, T., additional, Winkler, M., additional, Winter, A., additional, Winters, V., additional, Wolf, S., additional, Wolf, R.C., additional, Wright, A., additional, Wurden, G., additional, Xanthopoulos, P., additional, Yamada, H., additional, Yamada, I., additional, Yasuhara, R., additional, Yokoyama, M., additional, Zanini, M., additional, Zarnstorff, M., additional, Zeitler, A., additional, Zhang, D., additional, Zhang, H., additional, Zhu, J., additional, Zilker, M., additional, Zocco, A., additional, Zoletnik, S., additional, and Zuin, M., additional

Published
2019
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43. Overview of first Wendelstein 7-X high-performance operation

Author

Klinger, T., Andreeva, T., Bozhenkov, S., Brandt, C., Burhenn, R., Buttenschön, B., Fuchert, G., Geiger, B., Grulke, O., Laqua, H.P., Pablant, N., Rahbarnia, K., Stange, T., von Stechow, A., Tamura, N., Thomsen, H., Turkin, Y., Wegner, T., Abramovic, I., Äkäslompolo, S., Alcuson, J., Aleynikov, P., Aleynikova, K., Ali, A., Alonso, A., Anda, G., Ascasibar, E., Bähner, J.P., Baek, S.G., Balden, M., Baldzuhn, J., Banduch, M., Barbui, T., Behr, W., Beidler, C., Benndorf, A., Biedermann, C., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., Böckenhoff, D., Böswirth, B., Böttger, L.-G., Borchardt, M., Borsuk, V., Boscary, J., Bosch, H.-S., Beurskens, M., Brakel, R., Brand, H., Bräuer, T., Braune, H., Brezinsek, S., Brunner, K.-J., Bussiahn, R., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., Carralero, D., Carraro, L., Carvalho, B., Castejon, F., Charl, A., Chaudhary, N., Chauvin, D., Chernyshev, F., Cianciosa, M., Citarella, R., Claps, G., Coenen, J., Cole, M., Cole, M.J., Cordella, F., Cseh, G., Czarnecka, A., Czerski, K., Czerwinski, M., Czymek, G., da Molin, A., da Silva, A., Damm, H., de la Pena, A., Degenkolbe, S., Dhard, C.P., Dibon, M., Dinklage, A., Dittmar, T., Drevlak, M., Drewelow, P., Drews, P., Durodie, F., Edlund, E., van Eeten, P., Effenberg, F., Ehrke, G., Elgeti, S., Endler, M., Ennis, D., Esteban, H., Estrada, T., Fellinger, J., Feng, Y., Flom, E., Fernandes, H., Fietz, W.H., Figacz, W., Fontdecaba, J., Ford, O., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Gao, Y., García Regaña, J., Gates, D., Geiger, J., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Guerard, C., Hacker, P., Han, X., Harris, J.H., Hartmann, D., Hathiramani, D., Hein, B., Heinemann, B., Helander, P., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hirsch, M., Hollfeld, K.P., Höfel, U., Hölting, A., Höschen, D., Houry, M., Howard, J., Huang, X., Huang, Z., Hubeny, M., Huber, M., Hunger, H., Ida, K., Ilkei, T., Illy, S., Israeli, B., Jablonski, S., Jakubowski, M., Jelonnek, J., Jenzsch, H., Jesche, T., Jia, M., Junghanns, P., Kacmarczyk, J., Kallmeyer, J.-P., Kamionka, U., Kasahara, H., Kasparek, W., Kazakov, Y.O., Kenmochi, N., Killer, C., Kirschner, A., Kleiber, R., Knauer, J., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., Köchl, F., Kolesnichenko, Y., Könies, A., König, R., Kornejew, P., Koschinsky, J.-P., Köster, F., Krämer, M., Krampitz, R., Krämer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Krychowiak, M., Ksiazek, I., Kubkowska, M., Kühner, G., Kurki-Suonio, T., Kurz, P.A., Kwak, S., Landreman, M., Lang, P., Lang, R., Langenberg, A., Langish, S., Laqua, H., Laube, R., Lazerson, S., Lechte, C., Lennartz, M., Leonhardt, W., Li, C., Li, Y., Liang, Y., Linsmeier, C., Liu, S., Lobsien, J.-F., Loesser, D., Loizu Cisquella, J., Lore, J., Lorenz, A., Losert, M., Lücke, A., Lumsdaine, A., Lutsenko, V., Maaßberg, H., Marchuk, O., Matthew, J.H., Marsen, S., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., McCarthy, K., McNeely, P., Meier, A., Mellein, D., Mendelevitch, B., Mertens, P., Mikkelsen, D., Mishchenko, A., Missal, B., Mittelstaedt, J., Mizuuchi, T., Mollen, A., Moncada, V., Mönnich, T., Morisaki, T., Moseev, D., Murakami, S., Náfrádi, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Ngo, T., Nicolai, D., Nielsen, S.K., Niemann, H., Nishizawa, T., Nocentini, R., Nührenberg, C., Nührenberg, J., Obermayer, S., Offermanns, G., Ogawa, K., Ölmanns, J., Ongena, J., Oosterbeek, J.W., Orozco, G., Otte, M., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfuß, D., Paqay, S., Pasch, E., Pavone, A., Pawelec, E., Pedersen, T.S., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., Pölöskei, P., Porkolab, M., Proll, J., Puiatti, M.-E., Puig Sitjes, A., Purps, F., Rack, M., Récsei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riedl, R., Riemann, J., Risse, K., Rohde, V., Röhlinger, H., Romé, M., Rondeshagen, D., Rong, P., Roth, B., Rudischhauser, L., Rummel, K., Rummel, T., Runov, A., Rust, N., Ryc, L., Ryosuke, S., Sakamoto, R., Salewski, M., Samartsev, A., Sanchez, E., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schilling, J., Schlaich, A., Schlisio, G., Schluck, F., Schlüter, K.-H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schröder, M., Schröder, T., Schroeder, R., Schumacher, H., Schweer, B., Scott, E., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Sipliä, S., Slaby, C., Sleczka, M., Smith, H., Spiess, W., Spong, D.A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Svensson, J., Szabó, V., Szabolics, T., Szepesi, T., Szökefalvi-Nagy, Z., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J.M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulipán, S., Unterberg, B., Vakulchyk, I., Valet, S., Vano, L., van Milligen, B., van Vuuren, A.J., Vela, L., Velasco, J.-L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vorköper, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Warmer, F., Wauters, T., Wegener, L., Weggen, J., Wei, Y., Weir, G., Wendorf, J., Wenzel, U., Werner, A., White, A., Wiegel, B., Wilde, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, S., Wolf, R.C., Wright, A., Wurden, G., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zanini, M., Zarnstorff, M., Zeitler, A., Zhang, D., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., Zuin, M., Klinger, T., Andreeva, T., Bozhenkov, S., Brandt, C., Burhenn, R., Buttenschön, B., Fuchert, G., Geiger, B., Grulke, O., Laqua, H.P., Pablant, N., Rahbarnia, K., Stange, T., von Stechow, A., Tamura, N., Thomsen, H., Turkin, Y., Wegner, T., Abramovic, I., Äkäslompolo, S., Alcuson, J., Aleynikov, P., Aleynikova, K., Ali, A., Alonso, A., Anda, G., Ascasibar, E., Bähner, J.P., Baek, S.G., Balden, M., Baldzuhn, J., Banduch, M., Barbui, T., Behr, W., Beidler, C., Benndorf, A., Biedermann, C., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., Böckenhoff, D., Böswirth, B., Böttger, L.-G., Borchardt, M., Borsuk, V., Boscary, J., Bosch, H.-S., Beurskens, M., Brakel, R., Brand, H., Bräuer, T., Braune, H., Brezinsek, S., Brunner, K.-J., Bussiahn, R., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., Carralero, D., Carraro, L., Carvalho, B., Castejon, F., Charl, A., Chaudhary, N., Chauvin, D., Chernyshev, F., Cianciosa, M., Citarella, R., Claps, G., Coenen, J., Cole, M., Cole, M.J., Cordella, F., Cseh, G., Czarnecka, A., Czerski, K., Czerwinski, M., Czymek, G., da Molin, A., da Silva, A., Damm, H., de la Pena, A., Degenkolbe, S., Dhard, C.P., Dibon, M., Dinklage, A., Dittmar, T., Drevlak, M., Drewelow, P., Drews, P., Durodie, F., Edlund, E., van Eeten, P., Effenberg, F., Ehrke, G., Elgeti, S., Endler, M., Ennis, D., Esteban, H., Estrada, T., Fellinger, J., Feng, Y., Flom, E., Fernandes, H., Fietz, W.H., Figacz, W., Fontdecaba, J., Ford, O., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Gao, Y., García Regaña, J., Gates, D., Geiger, J., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Guerard, C., Hacker, P., Han, X., Harris, J.H., Hartmann, D., Hathiramani, D., Hein, B., Heinemann, B., Helander, P., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hirsch, M., Hollfeld, K.P., Höfel, U., Hölting, A., Höschen, D., Houry, M., Howard, J., Huang, X., Huang, Z., Hubeny, M., Huber, M., Hunger, H., Ida, K., Ilkei, T., Illy, S., Israeli, B., Jablonski, S., Jakubowski, M., Jelonnek, J., Jenzsch, H., Jesche, T., Jia, M., Junghanns, P., Kacmarczyk, J., Kallmeyer, J.-P., Kamionka, U., Kasahara, H., Kasparek, W., Kazakov, Y.O., Kenmochi, N., Killer, C., Kirschner, A., Kleiber, R., Knauer, J., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., Köchl, F., Kolesnichenko, Y., Könies, A., König, R., Kornejew, P., Koschinsky, J.-P., Köster, F., Krämer, M., Krampitz, R., Krämer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Krychowiak, M., Ksiazek, I., Kubkowska, M., Kühner, G., Kurki-Suonio, T., Kurz, P.A., Kwak, S., Landreman, M., Lang, P., Lang, R., Langenberg, A., Langish, S., Laqua, H., Laube, R., Lazerson, S., Lechte, C., Lennartz, M., Leonhardt, W., Li, C., Li, Y., Liang, Y., Linsmeier, C., Liu, S., Lobsien, J.-F., Loesser, D., Loizu Cisquella, J., Lore, J., Lorenz, A., Losert, M., Lücke, A., Lumsdaine, A., Lutsenko, V., Maaßberg, H., Marchuk, O., Matthew, J.H., Marsen, S., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., McCarthy, K., McNeely, P., Meier, A., Mellein, D., Mendelevitch, B., Mertens, P., Mikkelsen, D., Mishchenko, A., Missal, B., Mittelstaedt, J., Mizuuchi, T., Mollen, A., Moncada, V., Mönnich, T., Morisaki, T., Moseev, D., Murakami, S., Náfrádi, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Ngo, T., Nicolai, D., Nielsen, S.K., Niemann, H., Nishizawa, T., Nocentini, R., Nührenberg, C., Nührenberg, J., Obermayer, S., Offermanns, G., Ogawa, K., Ölmanns, J., Ongena, J., Oosterbeek, J.W., Orozco, G., Otte, M., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfuß, D., Paqay, S., Pasch, E., Pavone, A., Pawelec, E., Pedersen, T.S., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., Pölöskei, P., Porkolab, M., Proll, J., Puiatti, M.-E., Puig Sitjes, A., Purps, F., Rack, M., Récsei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riedl, R., Riemann, J., Risse, K., Rohde, V., Röhlinger, H., Romé, M., Rondeshagen, D., Rong, P., Roth, B., Rudischhauser, L., Rummel, K., Rummel, T., Runov, A., Rust, N., Ryc, L., Ryosuke, S., Sakamoto, R., Salewski, M., Samartsev, A., Sanchez, E., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schilling, J., Schlaich, A., Schlisio, G., Schluck, F., Schlüter, K.-H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schröder, M., Schröder, T., Schroeder, R., Schumacher, H., Schweer, B., Scott, E., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Sipliä, S., Slaby, C., Sleczka, M., Smith, H., Spiess, W., Spong, D.A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Svensson, J., Szabó, V., Szabolics, T., Szepesi, T., Szökefalvi-Nagy, Z., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J.M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulipán, S., Unterberg, B., Vakulchyk, I., Valet, S., Vano, L., van Milligen, B., van Vuuren, A.J., Vela, L., Velasco, J.-L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vorköper, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Warmer, F., Wauters, T., Wegener, L., Weggen, J., Wei, Y., Weir, G., Wendorf, J., Wenzel, U., Werner, A., White, A., Wiegel, B., Wilde, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, S., Wolf, R.C., Wright, A., Wurden, G., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zanini, M., Zarnstorff, M., Zeitler, A., Zhang, D., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., and Zuin, M.

Abstract

The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

Published
2019

44. Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies:Paper

Author

Wolf, R C, Bozhenkov, S, Dinklage, A, Fuchert, G, Kazakov, Y O, Laqua, H P, Marsen, S, Marushchenko, N B, Stange, T, Zanini, M, Abramovic, I, Alonso, A, Baldzuhn, J, Beurskens, M, Beidler, C D, Braune, H, Brunner, K J, Chaudhary, N, Damm, H, Drewelow, P, Gantenbein, G, Gao, Yu, Geiger, J, Hirsch, M, Höfel, U, Jakubowski, M, Jelonnek, J, Jensen, T, Kasparek, W, Knauer, J, Korsholm, Søren Bang, Langenberg, A, Lechte, C, Leipold, F., Mora, H Trimino, Neuner, U, Nielsen, S. K., Moseev, D, Oosterbeek, H, Pablant, N, Pasch, E, Plaum, B, Pedersen, T Sunn, Sitjes, A Puig, Rahbarnia, K, Rasmussen, J., Salewski, M., Schilling, J, Scott, E, Stejner, M., Thomsen, H, Thumm, M, Turkin, Y, Wilde, F, Wolf, R C, Bozhenkov, S, Dinklage, A, Fuchert, G, Kazakov, Y O, Laqua, H P, Marsen, S, Marushchenko, N B, Stange, T, Zanini, M, Abramovic, I, Alonso, A, Baldzuhn, J, Beurskens, M, Beidler, C D, Braune, H, Brunner, K J, Chaudhary, N, Damm, H, Drewelow, P, Gantenbein, G, Gao, Yu, Geiger, J, Hirsch, M, Höfel, U, Jakubowski, M, Jelonnek, J, Jensen, T, Kasparek, W, Knauer, J, Korsholm, Søren Bang, Langenberg, A, Lechte, C, Leipold, F., Mora, H Trimino, Neuner, U, Nielsen, S. K., Moseev, D, Oosterbeek, H, Pablant, N, Pasch, E, Plaum, B, Pedersen, T Sunn, Sitjes, A Puig, Rahbarnia, K, Rasmussen, J., Salewski, M., Schilling, J, Scott, E, Stejner, M., Thomsen, H, Thumm, M, Turkin, Y, and Wilde, F

Abstract

For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equipped with a steady-state capable ECRH system, operating at 140 GHz, which corresponds to the 2nd cyclotron harmonic of the electrons at a magnetic field of 2.5 T. Ten gyrotrons are operational and already delivered 7 MW to W7-X plasmas. Combined with pellet injection, the highest triple product (0.68 × 1020 keV m−3 s), observed up to now in stellarators, was achieved (Sunn Pedersen et al 2018 Plasma Phys. Control. Fusion 61 014035). For the first time, W7-X plasmas were sustained by 2nd harmonic O-mode heating, approaching the collisionality regime for which W7-X was optimized. Power deposition scans did not show any indication of electron temperature profile resilience. In low-density, low-power plasmas a compensation of the bootstrap current with electron-cyclotron current drive (ECCD) was demonstrated. Sufficiently strong ECCD close to the plasma centre produced periodic internal plasma-crash events, which coincide with the appearance of low order rationals of the rotational transform.

Published
2019

45. Bayesian inference of spatially resolved Zeff profiles from line integrated bremsstrahlung spectra.

Author

Kwak, Sehyun, Hergenhahn, U., Höfel, U., Krychowiak, M., Pavone, A., Svensson, J., Ford, O., König, R., Bozhenkov, S., Fuchert, G., Pasch, E., Brunner, K. J., Knauer, J., Kornejew, P., Trimiño Mora, Humberto, and Pedersen, T. S.

Subjects
BREMSSTRAHLUNG, NUCLEAR fusion, GAUSSIAN processes, ELECTRON density, THOMSON scattering, CARTESIAN coordinates
Abstract

In nuclear fusion research, the effective ion charge Zeff, which characterizes the overall content of impurities, can be experimentally derived from the plasma electron–ion bremsstrahlung, given the electron density ne and temperature Te. At Wendelstein 7-X, a multichannel near-infrared spectrometer is installed to collect the plasma bremsstrahlung along 27 lines of sight covering more than half the plasma cross section, which provides information on Zeff over the entire plasma radius. To infer spatially resolved Zeff profiles, a Bayesian model is developed in the Minerva framework. Zeff, ne, and Te profiles are modeled as Gaussian processes, whose smoothness is determined by hyperparameters. These profiles are transformed to fields in Cartesian coordinates, given the poloidal magnetic flux surfaces calculated by the variational moments equilibrium code. Given all these physical quantities, the model predicts line-of-sight integrals of near-infrared bremsstrahlung spectra. The model includes the predictive (forward) models of the interferometer, Thomson scattering system, and visible and near-infrared spectrometers. Given the observations of all these diagnostics, the posterior probability distribution of Zeff profiles is calculated and shown as an inference solution. The smoothness (gradient) of the profiles is optimally chosen by Bayesian Occam's razor. Furthermore, wall reflections can significantly pollute the measurements of the plasma bremsstrahlung, which leads to over-estimation of Zeff values in the edge region. In the first results presented in this work, this problem does not appear, and the posterior samples of Zeff profiles are overall plausible and consistent with Zeff values inferred, given the data from the single-channel visible spectrometer. [ABSTRACT FROM AUTHOR]

Published
2021
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46. Measurements of the parameter dependencies of the bootstrap current in the W7-X stellarator.

Author

Neuner, U., Rahbarnia, K., Beidler, C.D., Dinklage, A., Turkin, Y., Stange, T., Andreeva, T., Schilling, J., Thomsen, H., Beurskens, M., Bozhenkov, S., Brunner, K.J., Damm, H., Fuchert, G., Geiger, J., Hergenhahn, U., Höfel, U., Knauer, J., Krychowiak, M., and Kwak, S.

Subjects
STELLARATORS, PLASMA density, MAGNETIC traps, ABSOLUTE value, TOROIDAL plasma
Abstract

Intrinsic, diffusion-driven toroidal (bootstrap) currents between −7 and 17 kA were measured in the optimised stellarator Wendelstein 7-X (W7-X) for several magnetic configurations at line-integrated plasma densities between 2 × 1019 and 1.6 × 1020 m−2 and heating powers between 0.5 and 6 MW. The sign of the bootstrap current changes with field reversal, and its magnitude decreases with the mirror term and the rotational transform of the magnetic configuration as well as the line-integrated plasma density, and increases with the heating power. Both the absolute values and the dependencies agree with neoclassical calculations within their respective uncertainties, confirming the neoclassical optimisation of W7-X for small bootstrap currents. [ABSTRACT FROM AUTHOR]

Published
2021
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47. Flux surface identification by spatio-temporal coupling with partial mutual information analysis of electron cyclotron emission data.

Author

Arnaiz, J F Guerrero, Dinklage, A, Pompe, B, Geiger, J, Hirsch, M, Höfel, U, Marushchenko, N, Turkin, Y, and Wolf, R C

Subjects
ELECTRON emission, CYCLOTRON resonance, BLOOD volume, EQUILIBRIUM testing, FLUX (Energy)
Abstract

Fluctuations of electron cyclotron emission (ECE) signals are analyzed for differently heated Wendelstein 7-X plasmas. The fluctuations appear to travel predominantly on flux surfaces and are used as 'tracers' in multivariate time series. Different statistical techniques are assessed to reveal the coupling and information entropy-based coupling analysis are conducted. All these techniques provide evidence that the fluctuation analysis allows one to check the consistency of magneto-hydrodynamic (MHD) equilibrium calculations. Expanding the suite of techniques applied in fusion data analysis, partial mutual information (PMI) analysis is introduced. PMI generalizes traditional partial correlation (Frenzel and Pompe Phys. Rev. Lett. 99 204101) and also Schreiber's transfer entropy (Schreiber 2000 Phys. Rev. Lett. 85 461). The main additional capability of PMI is to allow one to discount for specific spurious data. Since PMI analysis allows one to study the effect of common drivers, the influence of the electron cyclotron resonance heating on the mutual dependencies of simultaneous ECE measurements was assessed. Additionally, MHD mode activity was found to be coupled in a limited volume in the plasma core for different plasmas. The study reveals an experimental test for equilibrium calculations and ECE radiation transport. [ABSTRACT FROM AUTHOR]

Published
2021
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48. Investigation of mode activity in NBI-heated experiments of Wendelstein 7-X.

Author

Slaby, C., Äkäslompolo, S., Borchardt, M., Geiger, J., Kleiber, R., Könies, A., Bozhenkov, S., Brandt, C., Dinklage, A., Dreval, M., Ford, O., Fuchert, G., Hartmann, D., Hirsch, M., Höfel, U., Huang, Z., McNeely, P., Pablant, N., Rahbarnia, K., and Rust, N.

Subjects
PLASMA turbulence, DOPPLER effect, FAST ions, MAGNETIC confinement, PLASMA Alfven waves, MAGNETIC particles
Abstract

The 2018 operation phase (OP 1.2b) of the stellarator Wendelstein 7-X (W7-X) included, for the first time, neutral beam injection (NBI) to heat the plasma. Since the injection geometry at W7-X is not parallel, this generates both passing and trapped fast particles. During longer phases of NBI injection, with the primary purpose to study the heating efficiency of this system, Alfvén eigenmodes (AEs) were observed by a number of diagnostics, including the phase contrast imaging (PCI) system, the magnetic pick-up coils (Mirnov coils), and the soft x-ray multi-camera tomography system (XMCTS). Alfvén eigenmodes are of great interest for future fusion reactors as it has been shown that the resonant interaction of fast ions with self-excited AEs can lead to enhanced transport of fast ions and potentially to energy losses. This is especially true for so-called gap-modes, Alfvén eigenmodes with frequencies in gaps of the continuous spectrum, since they lack continuum damping. These modes are commonly known to be excited by fast ions, but other destabilizing mechanisms, e.g. the electron-pressure gradient are also possible. In this article we present a first analysis of the experimentally observed frequencies from the theoretical side. The calculation of shear Alfvén wave continua for selected cases and the assignment of observed frequencies to the gaps of the continuous spectra are presented. Using the ideal-MHD code CKA (Könies A. 2007 10th IAEA TM on Energetic Particles in Magnetic Confinement System), we find gap modes that match the experimental measurements in terms of the observed frequencies. We emphasize the crucial roles played by the coupling of sound and Alfvén waves as well as of the Doppler shift arising as a consequence of the radial electric field in W7-X. We employ the perturbative gyrokinetic code CKA-EUTERPE (Feh´er 2013 Simulation of the interaction between Alfv´en waves and fast particles), using a slowing-down distribution function for the fast ions as calculated by the Monte-Carlo particle following code ASCOT (Hirvijoki et al 2014 Comput. Phys. Commun. 185 1310–21) to assess the fast-ion drive. We find that the fast-ion drive is insufficient to overcome the background-plasma damping. The fact that unstable modes were observed experimentally may point to problems with the modelling or indicate the existence of other destabilizing mechanisms, e.g. associated with the electron-pressure gradient (Windisch et al 2017 Plasma Phys. Control. Fusion 59 105002) that sensitively depend on the profiles of the background plasma. [ABSTRACT FROM AUTHOR]

Published
2020
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49. Impact of boronizations on impurity sources and performance in Wendelstein 7-X.

Author

Sereda, S., Brezinsek, S., Wang, E., Barbui, T., Brakel, R., Buttenschön, B., Goriaev, A., Hergenhahn, U., Höfel, U., Jakubowski, M., Knieps, A., König, R., Krychowiak, M., Kwak, S., Liang, Y., Naujoks, D., Pavone, A., Rasinski, M., Rudischhauser, L., and Ślęczka, M.

Subjects
HYDROGEN plasmas, ELECTRON density, BORON, HYDROGEN as fuel, MOLECULAR spectra, HYDROGEN, OXYGEN
Abstract

The low-Z oxygen and carbon were the main plasma impurities in the Wendelstein 7-X (W7-X) stellarator in the last experimental campaign with the passively cooled graphite divertor. To tackle this issue boronization (Winter et al 1989 J. Nucl. Mater. 162–4 712–23) was applied, which has led to one of the main achievements of the campaign: plasma operation at high core densities of more than 1020 m−3 in hydrogen fueled plasmas due to the reduced radiation-induced density limit. In total three boronizations were applied. After the first boronization the oxygen to hydrogen flux ratio (normalized influx of oxygen) at the divertor substantially decreased by a factor of 10 and the carbon to hydrogen flux ratio (normalized influx of carbon) decreased by a factor of 4 as obtained from spectroscopy. In the same time, boron emission appeared in the spectra. Between the boronizations oxygen and carbon normalized influxes increased but never reached the pre-boronization values. With each subsequent boronization O level decreased even more, reaching the lowest values after the third boronization which were more than a factor of 100 lower than before the first boronization. Such a decrease in low-Z impurity concentration significantly extended the operation window of W7-X in terms of line-integrated electron density (from 4ċ1019 m−2 to more than 1ċ1020 m−2) and diamagnetic energy (from 330 kJ up to 510 kJ). Zeff decreased from 4.5 down to values close to 1.2 as obtained from bremsstrahlung measurements. The above mentioned values are given for the two reference discharges before and after boronization. [ABSTRACT FROM AUTHOR]

Published
2020
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50. Numerical modeling of the electron temperature crashes observed in Wendelstein 7-X stellarator experiments.

Author

Yu, Q., Strumberger, E., Igochine, V., Lackner, K., Laqua, H.P., Zanini, M., Braune, H., Hirsch, M., Höfel, U., Marsen, S., Stange, T., Wolf, R.C., Günter, S., and 7-X, Wendelstein

Subjects
NUMERICAL calculations, SAFETY factor in engineering, NONLINEAR equations, CYCLOTRONS, ELECTRON temperature
Abstract

Numerical calculations based on nonlinear two-fluid equations have been carried out to understand the sawtooth-like crashes of electron temperature observed in Wendelstein 7-X stellarator experiments with electron cyclotron current drive (ECCD). The application of ECCD leads to non-monotonic radial profiles of the safety factor q with two q = 1 surfaces in the plasma core region. Using input parameters similar to the experiment, numerical calculations show two types of crashes of the central electron temperature depending on the growth of the internal kink mode coupled to double tearing modes. When the distance between two equilibrium q = 1 surfaces is sufficiently large, the internal kink mode leads to a fast radial displacement of the hot core from the center to the region of the q = 1 surfaces. In agreement with experimental observation, this causes a full crash of central electron temperature in about 20–30 microseconds. When the distance between the two q = 1 surfaces is not large enough, partial crashes of the central electron temperature are found. During these crashes the hot core only temporally moves outwards. Then it moves back, because the double tearing mode perturbation leads to an increase of the minimum q value about one. [ABSTRACT FROM AUTHOR]

Published
2020
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