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51. 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

52. 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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53. 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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61. Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas

Author

W7-X Team, Beurskens, M. N. A., Bozhenkov, S. A., Ford, O., Xanthopoulos, P., Zocco, A., Turkin, Y., Alonso, A., Beidler, C., Calvo, I., Carralero, D., Estrada, T., Fuchert, G., Grulke, O., Hirsch, M., Ida, K., Jakubowski, M., Killer, C., Krychowiak, M., Kwak, S., Lazerson, S., Langenberg, A., Lunsford, R., Pablant, N., Pasch, E., Pavone, A., Reimold, F., Romba, Th., Stechow, A. von, Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, D., Wolf, R. C., 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

Subjects
Technology, ddc:600
Published
2021

62. Publisher Correction: 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., H��fel, 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., Zhang, D., Abramovic, I., ��k��slompolo, S., Alcus��n, J., Aleynikov, P., Aleynikova, K., Ali, A., Anda, G., Ascasibar, E., B��hner, J. P., Baek, S. G., Balden, M., Banduch, M., Barbui, T., Behr, W., Benndorf, A., Biedermann, C., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., B��ckenhoff, D., B��swirth, B., B��ttger, L.-G., Borsuk, V., Boscary, J., Bosch, H.-S., Brakel, R., Brand, H., Brandt, C., Br��uer, T., Braune, H., Brezinsek, S., Brunner, K.-J., Burhenn, R., Bussiahn, R., Buttensch��n, B., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., 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., De La Pena, A., Degenkolbe, S., Dhard, C. P., Dibon, M., Dinklage, A., Dittmar, T., Drewelow, P., Drews, P., Durodie, F., Edlund, E., 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., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Gao, Y., Garc��a Rega��a, J., Gates, D., Geiger, B., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Grulke, O., Guerard, C., Hacker, P., Han, X., Harris, J. H., Hartmann, D., Hathiramani, D., Hein, B., Heinemann, B., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hollfeld, K. P., H��lting, A., H��schen, 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., Kenmochi, N., Killer, C., Kirschner, A., Klinger, T., Knauer, J., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., K��chl, F., Kolesnichenko, Y., K��nies, A., K��nig, R., Kornejew, P., Koschinsky, J.-P., K��ster, F., Kr��mer, M., Krampitz, R., Kr��mer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Ksiazek, I., Kubkowska, M., K��hner, G., Kurki-Suonio, T., Kurz, P. A., Landreman, M., Lang, P., Lang, R., 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., L��cke, A., Lumsdaine, A., Lutsenko, V., Maa��berg, 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., M��nnich, T., Morisaki, T., Moseev, D., Murakami, S., N��fr��di, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Ngo, T., Nicolai, D., Nielsen, S. K., Niemann, H., Nishizawa, T., Nocentini, R., N��hrenberg, C., N��hrenberg, J., Obermayer, S., Offermanns, G., Ogawa, K., ��lmanns, J., Ongena, J., Oosterbeek, J. W., Orozco, G., Otte, M., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfu��, D., Paqay, S., Pawelec, E., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., P��l��skei, P., Porkolab, M., Proll, J., Puiatti, M.-E., Puig Sitjes, A., Purps, F., Rack, M., R��csei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riedl, R., Riemann, J., Risse, K., Rohde, V., R��hlinger, H., Rom��, 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., S��nchez, E., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schlaich, A., Schlisio, G., Schluck, F., Schl��ter, K.-H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schr��der, M., Schr��der, T., Schroeder, R., Schumacher, H., Schweer, B., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Sipli��, S., Slaby, C., Sleczka, M., Spiess, W., Spong, D. A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Szab��, V., Szabolics, T., Szepesi, T., Sz��kefalvi-Nagy, Z., Tamura, N., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulip��n, S., Unterberg, B., Vakulchyk, I., Valet, S., Van��, L., Van Eeten, P., Van Milligen, B., Van Vuuren, A. J., Vela, L., Velasco, J.-L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Von Stechow, A., Vork��per, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Wauters, T., Wegener, L., Weggen, J., Wegner, T., 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., Wright, A., Wurden, G., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zanini, M., Zarnstorff, M., Zeitler, A., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., and Zuin, M.

Subjects
Chemical engineering, ddc:660
Published
2021

63. Impurity transport in ion- and electron-root confinement scenarios at Wendelstein 7-X

Author

W7-X Team, Langenberg, A., Wegner, Th., Marchuk, O., García-Regaña, J. M., Pablant, N. A., Fuchert, G., Bozhenkov, S., Damm, H., Pasch, E., Brunner, K.-J., Knauer, J., Beurskens, M., Reimold, F., Wolf, R. C., 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

Subjects
ddc:620, Engineering & allied operations
Published
2021
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64. High-performance ECRH at W7-X: experience and perspectives

Author

W7-X Team, Laqua, H. P., Baldzuhn, J., Braune, H., Bozhenkov, S., Brunner, K., Hirsch, M., Hoefel, U., Knauer, J., Langenberg, A., Marsen, S., Moseev, D., Pasch, E., Rahbarnia, K., Stange, T., Wolf, R. C., Pablant, N., Grulke, O., 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

Subjects
Technology, ddc:600
Published
2021

65. Frequency Stabilization of Megawatt-Class 140 GHz Gyrotrons at W7-X Using an Off-the-Shelf PLL System

Author

Krier, L., primary, Avramidis, K. A., additional, Braune, H., additional, Gantenbein, G., additional, Illy, S., additional, Ioannidis, Z., additional, Jelonnek, J., additional, Laqua, H. P., additional, Marsen, S., additional, Moseev, D., additional, Noke, F., additional, Pagonakis, I. Gr., additional, Ruess, T., additional, Rzesnicki, T., additional, Stange, T., additional, Thumm, M., additional, and Wolf, R. C., additional

Published
2021
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66. 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

67. 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

68. Ion temperature clamping in Wendelstein 7-X electron cyclotron heated plasmas

Author

Beurskens, M. N.A., Bozhenkov, S. A., Ford, O., Xanthopoulos, P., Zocco, A., Turkin, Y., Alonso, A., Beidler, C., Calvo, I., Carralero, D., Estrada, T., Fuchert, G., Grulke, O., Hirsch, M., Ida, K., Jakubowski, M., Killer, C., Krychowiak, M., Kwak, S., Lazerson, S., Langenberg, A., Lunsford, R., Pablant, N., Pasch, E., Pavone, A., Reimold, F., Romba, Th, Von Stechow, A., Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, D., Wolf, R. C., Beurskens, M. N.A., Bozhenkov, S. A., Ford, O., Xanthopoulos, P., Zocco, A., Turkin, Y., Alonso, A., Beidler, C., Calvo, I., Carralero, D., Estrada, T., Fuchert, G., Grulke, O., Hirsch, M., Ida, K., Jakubowski, M., Killer, C., Krychowiak, M., Kwak, S., Lazerson, S., Langenberg, A., Lunsford, R., Pablant, N., Pasch, E., Pavone, A., Reimold, F., Romba, Th, Von Stechow, A., Smith, H. M., Windisch, T., Yoshinuma, M., Zhang, D., and Wolf, R. C.

Published
2021

69. High-performance ECRH at W7-X:Experience and perspectives

Author

Laqua, H. P., Baldzuhn, J., Braune, H., Bozhenkov, S., Brunner, K., Hirsch, M., Hoefel, U., Knauer, J., Langenberg, A., Marsen, S., Moseev, D., Pasch, E., Rahbarnia, K., Stange, T., Wolf, R. C., Pablant, N., Grulke, O., Laqua, H. P., Baldzuhn, J., Braune, H., Bozhenkov, S., Brunner, K., Hirsch, M., Hoefel, U., Knauer, J., Langenberg, A., Marsen, S., Moseev, D., Pasch, E., Rahbarnia, K., Stange, T., Wolf, R. C., Pablant, N., and Grulke, O.

Abstract

The second operation phase of W7-X (OP1.2) showed the potential of exclusively electron cyclotron resonance heating (ECRH)-sustained plasma operations in stellarators. Employing multi-pass ECRH scenario in the second harmonic O-mode (O2-ECRH), stationary densities of up to 1.4 × 1020 m-3 could be achieved. This scenario also made stationary divertor detachment possible, which is a reactor-relevant scenario for power and particle exhaust. At high densities and with sufficiently high density gradients for an improved ion confinement, the coupling between the electrons and ions was strong enough to bring the ion temperature to values above 3 keV and to the neoclassical limit for some magnetic configurations, thus enabling to test the W7-X neoclassical optimization. The planned enhancement of the ECRH performance will enable to advance towards reactor-relevant beta values and to investigate their stability and confinement of fast particles, which is a priority goal of W7-X.

Published
2021

72. First Cosmology Results using Supernovae Ia from the Dark Energy Survey: Survey Overview, Performance, and Supernova Spectroscopy

Author

Smith, M., primary, D’Andrea, C. B., additional, Sullivan, M., additional, Möller, A., additional, Nichol, R. C., additional, Thomas, R. C., additional, Kim, A. G., additional, Sako, M., additional, Castander, F. J., additional, Filippenko, A. V., additional, Foley, R. J., additional, Galbany, L., additional, González-Gaitán, S., additional, Kasai, E., additional, Kirshner, R. P., additional, Lidman, C., additional, Scolnic, D., additional, Brout, D., additional, Davis, T. M., additional, Gupta, R. R., additional, Hinton, S. R., additional, Kessler, R., additional, Lasker, J., additional, Macaulay, E., additional, Wolf, R. C., additional, Zhang, B., additional, Asorey, J., additional, Avelino, A., additional, Bassett, B. A., additional, Calcino, J., additional, Carollo, D., additional, Casas, R., additional, Challis, P., additional, Childress, M., additional, Clocchiatti, A., additional, Crawford, S., additional, Frohmaier, C., additional, Glazebrook, K., additional, Goldstein, D. A., additional, Graham, M. L., additional, Hoormann, J. K., additional, Kuehn, K., additional, Lewis, G. F., additional, Mandel, K. S., additional, Morganson, E., additional, Muthukrishna, D., additional, Nugent, P., additional, Pan, Y.-C., additional, Pursiainen, M., additional, Sharp, R., additional, Sommer, N. E., additional, Swann, E., additional, Thomas, B. P., additional, Tucker, B. E., additional, Uddin, S. A., additional, Wiseman, P., additional, Zheng, W., additional, Abbott, T. M. C., additional, Annis, J., additional, Avila, S., additional, Bechtol, K., additional, Bernstein, G. M., additional, Bertin, E., additional, Brooks, D., additional, Burke, D. L., additional, Rosell, A. Carnero, additional, Kind, M. Carrasco, additional, Carretero, J., additional, Cunha, C. E., additional, Costa, L. N. da, additional, Davis, C., additional, Vicente, J. De, additional, Diehl, H. T., additional, Eifler, T. F., additional, Estrada, J., additional, Frieman, J., additional, García-Bellido, J., additional, Gaztanaga, E., additional, Gerdes, D. W., additional, Gruen, D., additional, Gruendl, R. A., additional, Gschwend, J., additional, Gutierrez, G., additional, Hartley, W. G., additional, Hollowood, D. L., additional, Honscheid, K., additional, Hoyle, B., additional, James, D. J., additional, Johnson, M. W. G., additional, Johnson, M. D., additional, Kuropatkin, N., additional, Li, T. S., additional, Lima, M., additional, Maia, M. A. G., additional, March, M., additional, Marshall, J. L., additional, Martini, P., additional, Menanteau, F., additional, Miller, C. J., additional, Miquel, R., additional, Neilsen, E., additional, Ogando, R. L. C., additional, Plazas, A. A., additional, Romer, A. K., additional, Sanchez, E., additional, Scarpine, V., additional, Schubnell, M., additional, Serrano, S., additional, Sevilla-Noarbe, I., additional, Soares-Santos, M., additional, Sobreira, F., additional, Suchyta, E., additional, Tarle, G., additional, Tucker, D. L., additional, and Wester, W., additional

Published
2020
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77. Charge exchange recombination spectroscopy at Wendelstein 7-X

Author

W7-X Team, Ford, O. P., Vanó, L., Alonso, J. A., Baldzuhn, J., Beurskens, M. N. A., Biedermann, C., Bozhenkov, S. A., Fuchert, G., Geiger, B., Hartmann, D., Jaspers, R. J. E., Kappatou, A., Langenberg, A., Lazerson, S. A., McDermott, R. M., McNeely, P., Neelis, T. W. C., Pablant, N. A., Pasch, E., Rust, N., Schroeder, R., Scott, E. R., Smith, H. M., Wegner, Th., Kunkel, F., Wolf, R. C., 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, Applied Physics and Science Education, Science and Technology of Nuclear Fusion, Sensorics for fusion reactors, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
010302 applied physics, Technology, Materials science, Plasma parameters, Plasma, 01 natural sciences, 010305 fluids & plasmas, Computational physics, law.invention, law, Electric field, 0103 physical sciences, Physics::Accelerator Physics, Emission spectrum, Wendelstein 7-X, Spectroscopy, ddc:600, Instrumentation, Stellarator, Beam (structure)
Abstract

The Charge Exchange Recombination Spectroscopy (CXRS) diagnostic has become a routine diagnostic on almost all major high temperature fusion experimental devices. For the optimized stellarator Wendelstein 7-X (W7-X), a highly flexible and extensive CXRS diagnostic has been built to provide high-resolution local measurements of several important plasma parameters using the recently commissioned neutral beam heating. This paper outlines the design specifics of the W7-X CXRS system and gives examples of the initial results obtained, including typical ion temperature profiles for several common heating scenarios, toroidal flow and radial electric field derived from velocity measurements, beam attenuation via beam emission spectra, and normalized impurity density profiles under some typical plasma conditions.

Published
2020

78. Collective Thomson Scattering Diagnostic for Wendelstein 7-X at 175 GHz

Author

Moseev, Dmitry, Laqua, H. P., Stange, T., Abramovic, I., Nielsen, S. K., Äkäslompolo, S., Avramidis, K., Braune, H., Gantenbein, G., Illy, S., Jelonnek, J., Jin, J., Kasparek, W., Krier, L., Korsholm, S.B., Lechte, C., Marek, Ales, Marsen, S., Nishiura, M., Pagonakis, I., Salewski, M., Rasmussen, J., Tancetti, A., Thumm, M., and Wolf, R. C.

Subjects
Physics::Plasma Physics, Physics::Accelerator Physics
Abstract

The Collective Thomson Scattering (CTS) diagnostic measures the scattering spectrum of incident radiation off collective fluctuations in plasmas. In Wendelstein 7-X (W7-X) the diagnostic uses a 140 GHz heating gyrotron as a source of the probing radiation. At this frequency, the CTS spectra are heavily affected by the electron cyclotron emission, and the microwave beam propagation is restricted at typical W7-X plasma parameters. The diagnostic was successfully commissioned in the last experimental campaign and demonstrated ion temperature measurements. However, the signal-to-noise ratio was too low for measuring other quantities such as the fast-ion velocity distribution function or the fuel ion ratio. Currently, the W7-X CTS diagnostic is undergoing an upgrade to a frequency of 175 GHz. This will increase the sensitivity of the diagnostic, since the noise due to electron cyclotron emission will be reduced, and it will relax the constraints on microwave beam propagation in W7-X. Here we present the salient features of the upgraded CTS system and discuss its prospects for both thermal-ion and fast-ion measurements.

Published
2020
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79. 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

80. Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X

Author

W7-X Team, Langenberg, A., Wegner, Th., Pablant, N. A., Marchuk, O., Geiger, B., Tamura, N., Bussiahn, R., Kubkowska, M., Mollén, A., Traverso, P., Smith, H. M., Fuchert, G., Bozhenkov, S., Damm, H., Pasch, E., Brunner, K.-J., Knauer, J., Beurskens, M., Burhenn, R., Wolf, R. C., 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, Range (particle radiation), Technology, Turbulence, Charge (physics), State (functional analysis), Condensed Matter Physics, 7. Clean energy, 01 natural sciences, Atomic mass, 010305 fluids & plasmas, law.invention, Impurity, law, 0103 physical sciences, Wendelstein 7-X, Atomic physics, 010306 general physics, ddc:600, Stellarator
Abstract

In this paper, the plasma volume averaged impurity confinement of selected charge states and impurity species has been characterized for the Stellarator Wendelstein 7-X (W7-X), covering a wide range of atomic charges ( Z = 12–44) and atomic masses ( M = 28–184). A comparison of the experimental findings to theoretical neoclassical and turbulent transport expectations suggests, aside from/in addition to the neoclassical transport, an additional significant anomalous transport mechanism, which is not inconsistent with the predictions of a turbulence dominated impurity transport and is in agreement with the experimental results from recent transport studies based on the direct measurements of impurity diffusion profiles, performed at W7-X.

Published
2020

81. Increasing the density in Wendelstein 7-X: benefits and limitations

Author

W7-X Team, Fuchert, G., Brunner, K. J., Rahbarnia, K., Stange, T., Zhang, D., Baldzuhn, J., Bozhenkov, S. A., Beidler, C. D., Beurskens, M. N. A., Brezinsek, S., Burhenn, R., Damm, H., Dinklage, A., Feng, Y., Hacker, P., Hirsch, M., Kazakov, Y., Knauer, J., Langenberg, A., Laqua, H. P., Lazerson, S., Pablant, N. A., Pasch, E., Reimold, F., Sunn Pedersen, T., Scott, E. R., Warmer, F., Winters, V. R., Wolf, R. C., 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, Range (particle radiation), Divertor, Plasma, Radiation, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Computational physics, law, 0103 physical sciences, Radiative transfer, ddc:620, Wendelstein 7-X, 010306 general physics, ddc:600, Energy (signal processing), Stellarator
Abstract

In stellarators, increasing the density is beneficial for the energy confinement. While there is no single reason for this observation, it is still very robust across different devices and this is reflected in the empirical energy confinement time scaling for stellarators, ISS04. In order to study whether this is also true for Wendelstein 7-X, the density scaling of the energy confinement time is analyzed and compared to ISS04 for the first divertor experiments. When the density is increased beyond a critical density, however, radiative collapses are frequently observed. Existing analytical models for the critical density are revisited to assess whether they can predict the accessible density range. Furthermore, since close to the collapse the radiation losses increase substantially, the impact on the global energy confinement is investigated. It is found that in plasmas with high radiation the density scaling of the energy confinement time becomes weaker, the reason for this observation is not yet clear. In the second half of the first divertor campaign, boronization was applied to W7-X for the first time. This broadened the operational window, allowing for operation at higher density and, hence, higher stored energy.

Published
2020
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84. Wendelstein 7-X on the path to long-pulse high-performance operation

Author

W7-X Team, Endler, M., Baldzuhn, J., Beidler, C. D., Bosch, H.-S., Bozhenkov, S., Buttenschön, B., Dinklage, A., Fellinger, J., Feng, Y., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Hartmann, D., Jakubowski, M., König, R., Laqua, H. P., Lazerson, S., McNeely, P., Naujoks, D., Neuner, U., Otte, M., Pasch, E., Sunn Pedersen, T., Perseo, V., Puig Sitjes, A., Rahbarnia, K., Rust, N., Schmitz, O., Spring, A., Stange, T., Stechow, A. von, Turkin, Y., Wang, E., Wolf, R. C., 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, Optimisation, Steady-state, Stellarator, Wendelstein 7-X, Nuclear engineering, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Data acquisition, law, Range (aeronautics), 0103 physical sciences, Water cooling, General Materials Science, 010306 general physics, Civil and Structural Engineering, Steady state, Mechanical Engineering, Fusion power, Nuclear Energy and Engineering, Path (graph theory), ddc:600
Abstract

The Wendelstein 7-X project is aimed at demonstrating that an optimised stellarator is an attractive candidate for a fusion reactor. This requires the achievement of a number of technical and physics goals. Several of these goals have already been achieved in the first three experimental campaigns. We shall exemplify this by a number of results. One important goal is the demonstration of quasi-steady-state operation at high plasma density and temperature for half an hour, which encompasses the physical and technical requirements of stable operation with density and impurity control, cw heating, water-cooled targets, particle exhaust, and an appropriate control and data acquisition system for long-pulse operation. In the previous experimental campaigns, with uncooled targets, stationary discharges for up to 25 s with 5 MW heating power and up to 100 s with 2 MW heating power were achieved. For the next operational phase, to start in 2022, water-cooled targets are being installed, water cooling will be provided for all first-wall components, and a number of further upgrades to plasma heating, vacuum and fuelling systems as well as diagnostics will become available. With this equipment, the further goals of the project will be tackled, including the stepwise extension of discharge intervals to the multi-minute range. The experimental results so far have confirmed the neoclassical theory underlying several of the optimisation goals. At the same time, they showed that an optimisation is also required with respect to anomalous transport. In the future operational phases we aim at building a solid theoretical, experimental and technical foundation for the design of a next-step stellarator device.

Published
2021
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85. Neural network approximated Bayesian inference of edge electron density profiles at JET

Author

Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Comunidad Europea de la Energía Atómica. EURATOM. U.E., Pavone, A., Svensson, J., Kwak, S., Brix, M., Wolf, R. C, Jet Contributors, García Muñoz, Manuel, Viezzer, Eleonora, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Comunidad Europea de la Energía Atómica. EURATOM. U.E., Pavone, A., Svensson, J., Kwak, S., Brix, M., Wolf, R. C, Jet Contributors, García Muñoz, Manuel, and Viezzer, Eleonora

Abstract

A neural network (NN) has been trained on the inference of the edge electron density profiles from measurements of the JET lithium beam emission spectroscopy (Li-BES) diagnostic. The novelty of the approach resides in the fact that the network has been trained to be a fast surrogate model of an existing Bayesian model of the diagnostic implemented within the Minerva framework. Previous work showed the very first application of this method to an x-ray imaging diagnostic at the W7-X experiment, and it was argued that the method was general enough that it may be applied to different physics systems. Here, we try to show that the claim made there is valid. What makes the approach general and versatile is the common definition of different models within the same framework. The network is tested on data measured during several different pulses and the predictions compared to the results obtained with the full model Bayesian inference. The NN analysis only requires tens of microseconds on a GPU compared to the tens of minutes long full inference. Finally, in relation to what was presented in the previous work, we demonstrate an improvement in the method of calculation of the network uncertainties, achieved by using a state-of-the-art deep learning technique based on a variational inference interpretation of the network training. The advantage of this calculation resides in the fact that it relies on fewer assumptions, and no extra computation time is required besides the conventional network evaluation time. This allows estimating the uncertainties also in real time applications.

Published
2020

86. Plasma termination by excess pellet fueling and impurity injection in TJ-II, the Large Helical Device and Wendelstein 7-X

Author

Dinklage, A., McCarthy, K. J., Suzuki, C., Tamura, N., Wegner, Th., Yamada, H., Baldzuhn, J., Brunner, K. J., Buttenschön, B., Damm, H., Drewelow, P., Fuchert, G., Hirsch, M., Hoefel, U., Kasahara, H., Knauer, J., Maier, D., Miyazawa, J., Motojima, G., Oishi, T., Rahbarnia, K., Sunn Pedersen, T., Sakamoto, R., Wolf, R. C., 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, 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, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Large Helical Device, Impurity, law, 0103 physical sciences, Pellet, Atomic physics, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Published
2019

87. 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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88. Electron-cyclotron-resonance heating in Wendelstein 7-X

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, Y., Geiger, J., Hirsch, M., Hofel, U., Jakubowski, M., Jelonnek, J., Jensen, T., Kasparek, W., Knauer, J., Korsholm, S. B., Langenberg, A., Lechte, C., Leipold, F., Mora, H. T., Neuner, U., Nielsen, S. K., Moseev, D., Oosterbeek, H., Pablant, N., Pasch, E., Plaum, B., Pedersen, T. S., Sitjes, A. P., Rahbarnia, K., Rasmussen, J., Salewski, M., Schilling, J., Scott, E., Stejner, M., Thomsen, H., Thumm, M., Turkin, Y., Wilde, F., Giannella, V., Citarella, R., W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, and Science and Technology of Nuclear Fusion

Subjects
Physics, Technology, Cyclotron, Plasma, Collisionality, Fusion power, Condensed Matter Physics, 7. Clean energy, 01 natural sciences, Electron cyclotron resonance, Stellerator, 010305 fluids & plasmas, law.invention, Computational physics, Bootstrap current, stellarator, Nuclear Energy and Engineering, law, 0103 physical sciences, Electron temperature, Wendelstein 7-X, electron-cyclotron-resonance heating and current drive, 010306 general physics, ddc:600
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
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90. The ICRH system for the stellarator Wendelstein 7-X

Author

Ongena, J., primary, Messiaen, A., additional, Kazakov, Ye.O., additional, Schweer, B., additional, Stepanov, I., additional, Vervier, M., additional, Crombé, K., additional, Schoor, M. Van, additional, Borsuk, V., additional, Castaño-Bardawil, D., additional, Kraemer-Flecken, A., additional, Hollfeld, K. P., additional, Offermanns, G., additional, Hartmann, D. A., additional, Kallmeyer, J. P., additional, and Wolf, R. C., additional

Published
2020
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94. Steve: A Hierarchical Bayesian Model for Supernova Cosmology

Author

Hinton, S. R., primary, Davis, T. M., additional, Kim, A. G., additional, Brout, D., additional, D’Andrea, C. B., additional, Kessler, R., additional, Lasker, J., additional, Lidman, C., additional, Macaulay, E., additional, Möller, A., additional, Sako, M., additional, Scolnic, D., additional, Smith, M., additional, Wolf, R. C., additional, Childress, M., additional, Morganson, E., additional, Allam, S., additional, Annis, J., additional, Avila, S., additional, Bertin, E., additional, Brooks, D., additional, Burke, D. L., additional, Rosell, A. Carnero, additional, Kind, M. Carrasco, additional, Carretero, J., additional, Cunha, C. E., additional, Costa, L. N. da, additional, Davis, C., additional, Vicente, J. De, additional, DePoy, D. L., additional, Doel, P., additional, Eifler, T. F., additional, Flaugher, B., additional, Fosalba, P., additional, Frieman, J., additional, García-Bellido, J., additional, Gaztanaga, E., additional, Gerdes, D. W., additional, Gruendl, R. A., additional, Gschwend, J., additional, Gutierrez, G., additional, Hartley, W. G., additional, Hollowood, D. L., additional, Honscheid, K., additional, Krause, E., additional, Kuehn, K., additional, Kuropatkin, N., additional, Lahav, O., additional, Lima, M., additional, Maia, M. A. G., additional, March, M., additional, Marshall, J. L., additional, Menanteau, F., additional, Miquel, R., additional, Ogando, R. L. C., additional, Plazas, A. A., additional, Sanchez, E., additional, Scarpine, V., additional, Schindler, R., additional, Schubnell, M., additional, Serrano, S., additional, Sevilla-Noarbe, I., additional, Soares-Santos, M., additional, Sobreira, F., additional, Suchyta, E., additional, Tarle, G., additional, Thomas, D., additional, Vikram, V., additional, and Zhang, Y., additional

Published
2019
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96. First Cosmology Results using Type Ia Supernovae from the Dark Energy Survey: Constraints on Cosmological Parameters

Author

Abbott, T. M. C., Allam, S., Andersen, P., Angus, C., Asorey, J., Avelino, A., Avila, S., Bassett, B. A., Bechtol, K., Bernstein, G. M., Bertin, E., Brooks, D., Brout, D., Brown, P., Burke, D. L., Calcino, J., Carnero Rosell, A., Carollo, D., Kind, M. Carrasco, Carretero, J., Casas, R., Castander, F. J., Cawthon, R., Challis, P., Childress, M., Clocchiatti, A., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Davis, C., Davis, T. M., De Vicente, J., DePoy, D. L., Desai, S., Diehl, H. T., Doel, P., Drlica-Wagner, A., Eifler, T. F., Evrard, A. E., Fernandez, E., Filippenko, A., V, Finley, D. A., Flaugher, B., Foley, R. J., Fosalba, P., Frieman, J., Galbany, L., Garcia-Bellido, J., Gaztanaga, E., Giannantonio, T., Glazebrook, K., Goldstein, D. A., Gonzalez-Gaitan, S., Gruen, D., Gruendl, R. A., Gschwend, J., Gupta, R. R., Gutierrez, G., Hartley, W. G., Hinton, S. R., Hollowood, D. L., Honscheid, K., Hoormann, J. K., Hoyle, B., James, D. J., Jeltema, T., Johnson, M. W. G., Johnson, M.D., Kasai, E., Kent, S., Kessler, R., Kim, A. G., Kirshner, R. P., Kovacs, E., Krause, E., Kron, R., Kuehn, K., Kuhlmann, S., Kuropatkin, N., Lahav, O., Lasker, J., Lewis, G. F., Li, T. S., Lidman, C., Lima, M., Lin, H., Macaulay, E., Maia, M. A. G., Mandel, K. S., March, M., Marriner, J., Marshall, J. L., Martini, P., Menanteau, F., Miller, C. J., Miquel, R., Miranda, V, Mohr, J. J., Morganson, E., Muthukrishna, D., Moller, A., Neilsen, E., Nichol, R. C., Nord, B., Nugent, P., Ogando, R. L. C., Palmese, A., Pan, Y-C, Plazas, A. A., Pursiainen, M., Romer, A. K., Roodman, A., Rozo, E., Rykoff, E. S., Sako, M., Sanchez, E., Scarpine, V, Schindler, R., Schubnell, M., Scolnic, D., Serrano, S., Sevilla-Noarbe, I, Sharp, R., Smith, M., Soares-Santos, M., Sobreira, F., Sommer, N. E., Spinka, H., Suchyta, E., Sullivan, M., Swann, E., Tarle, G., Thomas, D., Thomas, R. C., Troxel, M. A., Tucker, B. E., Uddin, S. A., Walker, A. R., Wester, W., Wiseman, P., Wolf, R. C., Yanny, B., Zhang, B., Zhang, Y., Abbott, T. M. C., Allam, S., Andersen, P., Angus, C., Asorey, J., Avelino, A., Avila, S., Bassett, B. A., Bechtol, K., Bernstein, G. M., Bertin, E., Brooks, D., Brout, D., Brown, P., Burke, D. L., Calcino, J., Carnero Rosell, A., Carollo, D., Kind, M. Carrasco, Carretero, J., Casas, R., Castander, F. J., Cawthon, R., Challis, P., Childress, M., Clocchiatti, A., Cunha, C. E., D'Andrea, C. B., da Costa, L. N., Davis, C., Davis, T. M., De Vicente, J., DePoy, D. L., Desai, S., Diehl, H. T., Doel, P., Drlica-Wagner, A., Eifler, T. F., Evrard, A. E., Fernandez, E., Filippenko, A., V, Finley, D. A., Flaugher, B., Foley, R. J., Fosalba, P., Frieman, J., Galbany, L., Garcia-Bellido, J., Gaztanaga, E., Giannantonio, T., Glazebrook, K., Goldstein, D. A., Gonzalez-Gaitan, S., Gruen, D., Gruendl, R. A., Gschwend, J., Gupta, R. R., Gutierrez, G., Hartley, W. G., Hinton, S. R., Hollowood, D. L., Honscheid, K., Hoormann, J. K., Hoyle, B., James, D. J., Jeltema, T., Johnson, M. W. G., Johnson, M.D., Kasai, E., Kent, S., Kessler, R., Kim, A. G., Kirshner, R. P., Kovacs, E., Krause, E., Kron, R., Kuehn, K., Kuhlmann, S., Kuropatkin, N., Lahav, O., Lasker, J., Lewis, G. F., Li, T. S., Lidman, C., Lima, M., Lin, H., Macaulay, E., Maia, M. A. G., Mandel, K. S., March, M., Marriner, J., Marshall, J. L., Martini, P., Menanteau, F., Miller, C. J., Miquel, R., Miranda, V, Mohr, J. J., Morganson, E., Muthukrishna, D., Moller, A., Neilsen, E., Nichol, R. C., Nord, B., Nugent, P., Ogando, R. L. C., Palmese, A., Pan, Y-C, Plazas, A. A., Pursiainen, M., Romer, A. K., Roodman, A., Rozo, E., Rykoff, E. S., Sako, M., Sanchez, E., Scarpine, V, Schindler, R., Schubnell, M., Scolnic, D., Serrano, S., Sevilla-Noarbe, I, Sharp, R., Smith, M., Soares-Santos, M., Sobreira, F., Sommer, N. E., Spinka, H., Suchyta, E., Sullivan, M., Swann, E., Tarle, G., Thomas, D., Thomas, R. C., Troxel, M. A., Tucker, B. E., Uddin, S. A., Walker, A. R., Wester, W., Wiseman, P., Wolf, R. C., Yanny, B., Zhang, B., and Zhang, Y.

Published
2019

97. Collective Thomson scattering diagnostic at Wendelstein 7-X

Author

Moseev, D., Stejner, M., Stange, T., Abramovic, I., Laqua, H. P., Marsen, S., Schneider, N., Braune, H., Hoefel, U., Kasparek, W., Korsholm, Søren Bang, Lechte, C., Leipold, Frank, Nielsen, S. K., Salewski, Mirko, Rasmussen, J., Weißgerber, M., Wolf, R. C., Moseev, D., Stejner, M., Stange, T., Abramovic, I., Laqua, H. P., Marsen, S., Schneider, N., Braune, H., Hoefel, U., Kasparek, W., Korsholm, Søren Bang, Lechte, C., Leipold, Frank, Nielsen, S. K., Salewski, Mirko, Rasmussen, J., Weißgerber, M., and Wolf, R. C.

Abstract

A Collective Thomson Scattering (CTS) diagnostic is installed at Wendelstein 7-X for ion temperature measurements in the plasma core. The diagnostic utilizes 140 GHz gyrotrons usually used for electron cyclotron resonance heating (ECRH) as a source of probing radiation. The CTS diagnostic uses a quasi-optical transmission line covering a distance of over 40 m. The transmission line is shared between the ECRH system and the CTS diagnostic. Here we elaborate on the design, installation, and alignment of the CTS diagnostic and present the first measurements at Wendelstein 7-X.

Published
2019

98. 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

99. Neural network surrogates of Bayesian diagnostic models for fast inference of plasma parameters.

Author

Pavone, A., Svensson, J., Krychowiak, M., Hergenhahn, U., Winters, V., Kornejew, P., Kwak, S., Hoefel, U., Koenig, R., and Wolf, R. C.

Subjects
ARTIFICIAL neural networks, NUCLEAR fusion, DISTRIBUTION (Probability theory), PLASMA flow
Abstract

We present a framework for training artificial neural networks (ANNs) as surrogate Bayesian models for the inference of plasma parameters from diagnostic data collected at nuclear fusion experiments, with the purpose of providing a fast approximation of conventional Bayesian inference. Because of the complexity of the models involved, conventional Bayesian inference can require tens of minutes for analyzing one single measurement, while hundreds of thousands can be collected during a single plasma discharge. The ANN surrogates can reduce the analysis time down to tens/hundreds of microseconds per single measurement. The core idea is to generate the training data by sampling them from the joint probability distribution of the parameters and observations of the original Bayesian model. The network can be trained to learn the reconstruction of plasma parameters from observations and the model joint probability distribution from plasma parameters and observations. Previous work has validated the application of such a framework to the former case at the Wendelstein 7-X and Joint European Torus experiments. Here, we first give a description of the general methodological principles allowing us to generate the training data, and then we show an example application of the reconstruction of the joint probability distribution of an effective ion charge Zeff-bremsstrahlung model from data collected at the latest W7-X experimental campaign. One key feature of such an approach is that the network is trained exclusively on data generated with the Bayesian model, requiring no experimental data. This allows us to replicate the training scheme and generate fast, surrogate ANNs for any validated Bayesian diagnostic model. [ABSTRACT FROM AUTHOR]

Published
2021
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