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1. Wendelstein 7-X on the path to long-pulse high-performance operation

Author

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., von Stechow, A., Turkin, Y., Wang, E., and Wolf, R.C.

Published
2021
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2. 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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4. Edge plasma measurements on the OP 1.2a divertor plasmas at W7-X using the combined probe

Author

Drews, P., Killer, C., Cosfeld, J., Knieps, A., Brezinsek, S., Jakubowski, M., Brandt, C., Bozhenkov, S., Dinklage, A., Cai, J., Endler, M., Hammond, K., Henkel, M., Gao, Y., Geiger, J., Grulke, O., Höschen, D., König, R., Krämer-Flecken, A., Liang, Y., Li, Y., Liu, S., Niemann, H., Nicolai, D., Neubauer, O., Neuner, U., Rack, M., Rahbarnia, K., Rudischhauser, L., Sandri, N., Satheeswaran, G., Schilling, S., Thomsen, H., Windisch, T., and Sereda, S.

Published
2019
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5. Theoretical interpretation of W soft X-ray spectra collected by the pulse height analysis system on Wendelstein 7-X stellarator.

Author

Syrocki, Ł., Kubkowska, M., Jabłoński, S., and Neuner, U.

Subjects
ELECTRON impact ionization, X-ray spectra, ENERGY levels (Quantum mechanics), NUCLEAR energy, ELECTRONIC excitation, ELECTRON temperature, SOFT X rays
Abstract

In many fusion devices, such as tokamaks or stellarators like Wendelstein 7-X (W7-X), soft x-ray pulse height analysis (PHA) system diagnostics are routinely used during the experiments. The PHA system is dedicated to providing information about the impurity content, and average along line-of-sight electron temperature in the plasma conditions. Moreover, it is also able to estimate impurity density and an average effective charge from the comparison of experimental spectra with the modeled ones. However, the experimental x-ray spectra can be interpreted in terms of interesting plasma parameters only when the theoretical radiation models first identify and then take into account all the relevant factors that affect the spectrum. Therefore, for this purpose, a theoretical model has been applied. Flexible Atomic Code, which allows for calculation of various atomic properties such as energy levels, cross sections for excitation and ionization by electron impact, transition probabilities for radiative transitions and autoionization, and any others as needed in the collisional–radiative approximation. The chosen spectra collected during the W7-X campaign (OP1.2b) were examined, trying to obtain an agreement between the observed and simulated spectra. The analysis carried out allowed for a reliable interpretation of experimental x-ray spectra, estimation of the electron temperature, and obtaining information on the content of tungsten impurities. [ABSTRACT FROM AUTHOR]

Published
2024
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7. 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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8. Engineering design for the magnetic diagnostics of Wendelstein 7-X

Author

Endler, M., Brucker, B., Bykov, V., Cardella, A., Carls, A., Dobmeier, F., Dudek, A., Fellinger, J., Geiger, J., Grosser, K., Grulke, O., Hartmann, D., Hathiramani, D., Höchel, K., Köppen, M., Laube, R., Neuner, U., Peng, X., Rahbarnia, K., Rummel, K., Sieber, T., Thiel, S., Vorköper, A., Werner, A., Windisch, T., and Ye, M.Y.

Published
2015
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9. 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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10. Plasma beta effects on the edge magnetic field structure and divertor heat loads in Wendelstein 7-X high-performance scenarios

Author

W7-X Team, Knieps, A., Suzuki, Y., Geiger, J., Dinklage, A., Zhou, S., Rahbarnia, K., Schilling, J., Neuner, U., Thomsen, H., Jakubowski, M., Koenig, R., Endler, M., Gao, Y., Sitjes, A. Puig, Niemann, H., Beurskens, M., Bozhenkov, S., Liang, Y., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Nuclear and High Energy Physics, Technology, Materials science, Divertor, Plasma, Edge (geometry), Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, Beta (plasma physics), 0103 physical sciences, Atomic physics, Wendelstein 7-X, 010306 general physics, ddc:600
Abstract

To support the scenario design for the upcoming long-pulse high-performance campaign of Wendelstein 7-X, this work presents a study of high-beta full-field 3D equilibria obtained with the HINT code. For three magnetic configurations of different edge-ι, the effects of both overall pressure and pressure profile changes on the magnetic topology are analyzed. Anisotropic diffusion modeling is used to obtain estimates of the conductive heat load distribution both on the divertor and other plasma-facing components in finite-beta magnetic configurations. For the magnetic standard configuration, limitations of the model are outlined by comparing measured and predicted heatloads by performing a linear regression of the main strike-line position against various plasma parameters in both the experimental and the simulated device.

Published
2022

12. 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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13. 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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16. 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

17. Changes in the edge magnetic field of Wendelstein 7-X in high-beta plasmas

Author

Knieps, A., Liang, Y., Suzuki, Y., Andreeva, T., Drews, P., Gao, Y., Geiger, J., Grulke, O., Hollfeld, K., Jakubowski, M., Killer, C., Neubauer, O., Nicolai, D., Neuner, U., Niemann, H., Huang, Z., Rahbarnia, K., Satheeswaran, G., Schilling, J., Thomsen, H., Zhou, S., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2021

19. Fast characterization of plasma states in W7-X with permutation entropy.

Author

Guerrero Arnaiz, J F, Dinklage, A, Geiger, J, Hirsch, M, Höfel, U, Brandt, C, Thomsen, H, Schilling, J, Rahbarnia, K, Neuner, U, and Zanini, M

Subjects
BIG data, ENTROPY, PERMUTATIONS, ELECTRON emission, SOFT X rays, CYCLOTRONS
Abstract

Detecting changes in plasmas is compulsory for control and the detection of novelties. Moreover, automated novelty detection allows one to investigate large data sets to substantially enhance the efficiency of data mining approaches. To this end we introduce permutation entropy (PE) for the detection of changes in plasmas. PE is an information-theoretic complexity measure based in fluctuation analysis that quantifies the degree of randomness (resp. disorder, unpredictability) of the ordering of time series data. This method is computationally fast and robust against noise, which allows the evaluation of large data sets in an automated procedure. PE is applied on electron cyclotron emission and soft x-ray measurements in different Wendelstein 7-X low-iota configuration plasmas. A spontaneous transition to high core-electron temperature ( T e ) was detected, as well as a localized low-coherent intermittent oscillation which ceased when T e increased in the transition. The results are validated with spectrogram analysis and provide evidence that a complexity measure such as PE is a method to support in-situ monitoring of plasma parameters and for novelty detection in plasma data. Moreover, the acceleration in processing time offers implementations of plasma-state-detection that provides results fast enough to induce control actions even during the experiment. [ABSTRACT FROM AUTHOR]

Published
2022
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24. MHD activity during the recent divertor campaign at the Wendelstein 7-X stellarator

Author

Rahbarnia, K., Andreeva, T., Bluhm, T., Borchardt, M., Brandt, C., Carvalho, B., Hirsch, M., Kleiber, R., Könies, A., Laqua, H., Neuner, U., Schilling, J., Slaby, C., Stechow, A., Thomsen, H., Turkin, Y., Zanini, M., Zilker, M., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2019

25. 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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26. 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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35. 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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36. Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

Author

Pedersen T. S., Otte M., Lazerson S., Helander P., Bozhenkov S., Biedermann C., Klinger T., Wolf R. C., Bosch H. -S., Abramovic I., Akaslompolo S., Aleynikov P., Aleynikova K., Ali A., Alonso A., Anda G., Andreeva T., Ascasibar E., Baldzuhn J., Banduch M., Barbui T., Beidler C., Benndorf A., Beurskens M., Biel W., Birus D., Blackwell B., Blanco E., Blatzheim M., Bluhm T., Bockenhoff D., Bolgert P., Borchardt M., Bottger L. -G., Brakel R., Brandt C., Brauer T., Braune H., Burhenn R., Buttenschon B., Bykov V., Calvo I., Cappa A., Carls A., De Carvalho B. B., Castejon F., Cianciosa M., Cole M., Costea S., Cseh G., Czarnecka A., Dal Molin A., De La Cal E., De La Pena A., Degenkolbe S., Dhard C. P., Dinklage A., Dostal M., Drevlak M., Drewelow P., Drews P., Dudek A., Durodie F., Dzikowicka A., Von Eeten P., Effenberg F., Endler M., Erckmann V., Estrada T., Fahrenkamp N., Fellinger J., Feng Y., Figacz W., Ford O., Fornal T., Frerichs H., Fuchert G., Garcia-Munoz M., Geiger B., Geiger J., Gierse N., Gogoleva A., Goncalves B., Gradic D., Grahl M., Gross S., Grote H., Grulke O., Guerard C., Haas M., Harris J., Hartfuss H. -J., Hartmann D., Hathiramani D., Hein B., Heirnich S., Henneberg S., Hennig C., Hernandez J., Hidalgo C., Hidalgo U., Hirsch M., Hofel U., Holbe H., Holting A., Houry M., Huber V., Ionita C., Israeli B., Jablonski S., Jakubowski M., Van Vuuren A. J., Jenzsch H., Kaczmarczyk J., Kallmeyer J. -P., Kamionka U., Kasahara H., Kenmochi N., Kernbichler W., Killer C., Kinna D., Kleiber R., Knauer J., Kochl F., Kocsis G., Kolesnichenko Y., Konies A., Konig R., Kornejew P., Koster F., Kramer-Flecken A., Krampitz R., Krawzyk N., Kremeyer T., Krychowiak M., Ksiazek I., Kubkowska M., Kuhner G., Kurki-Suonio T., Kurz P., Kuttler K., Kwak S., Landreman M., Langenberg A., Lapayese F., Laqua H., Laqua H. -P., Laube R., Laux M., Lentz H., Lewerentz M., Liang Y., Liu S., Lobsien J. -F., Cisquella J. L., Lopez-Bruna D., Lore J., Lorenz A., Lui S., Lutsenko V., Maassberg H., Maisano-Brown J., Marchuk O., Marrelli L., Marsen S., Marushchenko N., Masuzaki S., McCarthy K., McNeely P., Medina F., Milojevic D., Mishchenko A., Missal B., Mittelstaedt J., Mollen A., Moncada V., Monnich T., Moseev D., Nagel M., Naujoks D., Neilson G. H., Neubauer O., Neuner U., Ngo T. -T., Niemann H., Nuhrenberg C., Nuhrenberg J., Ochando M., Ogawa K., Ongena J., Oosterbeek H., Pablant N., Pacella D., Pacios L., Panadero N., Pasch E., Pastor I., Pavone A., Pawelec E., Pedrosa A., Perseo V., Peterson B., Pilopp D., Pisano F., Piulatti M. E., Plunk G., Preynas M., Proll J., Sitjes A. P., Purps F., Rack M., Rahbarnia K., Riemann J., Risse K., Rong P., Rosenberger J., Rudischhauser L., Rummel K., Rummel T., Runov A., Rust N., Ryc L., Saitoh H., Satake S., Schacht J., Schmitz O., Schmuck S., Schneider B., Schneider M., Schneider W., Schrittwieser R., Schroder M., Schroder T., Schroder R., Schumacher H. W., Schweer B., Seki R., Sinha P., Sipilae S., Slaby C., Smith H., Sousa J., Spring A., Standley B., Stange T., Von Stechow A., Stephey L., Stoneking M., Stridde U., Suzuki Y., Svensson J., Szabolics T., Szepesi T., Thomsen H., Travere J. -M., Traverso P., Mora H. T., Tsuchiya H., Tsuijmura T., Turkin Y., Valet S., Van Milligen B., Vela L., Velasco J. -L., Vergote M., Vervier M., Viebke H., Vilbrandt R., Von Thun C. P., Wagner F., Wang E., Wang N., Warmer F., Wauters T., Wegener L., Wegner T., Weir G., Wendorf J., Wenzel U., Werner A., Wie Y., Wiegel B., Wilde F., Windisch T., Winkler M., Winters V., Wright A., Wurden G., Xanthopoulos P., Yamada I., Yasuhara R., Yokoyama M., Zhang D., Zilker M., Zimbal A., Zocco A., Zoletnik S., W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, Massachusetts Institute of Technology. Department of Physics, Maisano-Brown, Jeannette D., Science and Technology of Nuclear Fusion, Pedersen, T, Otte, M, Lazerson, S, Helander, P, Bozhenkov, S, Biedermann, C, Klinger, T, Wolf, R, Bosch, H, Abramovic, I, Akaslompolo, S, Aleynikov, P, Aleynikova, K, Ali, A, Alonso, A, Anda, G, Andreeva, T, Ascasibar, E, Baldzuhn, J, Banduch, M, Barbui, T, Beidler, C, Benndorf, A, Beurskens, M, Biel, W, Birus, D, Blackwell, B, Blanco, E, Blatzheim, M, Bluhm, T, Bockenhoff, D, Bolgert, P, Borchardt, M, Bottger, L, Brakel, R, Brandt, C, Brauer, T, Braune, H, Burhenn, R, Buttenschon, B, Bykov, V, Calvo, I, Cappa, A, Carls, A, De Carvalho, B, Castejon, F, Cianciosa, M, Cole, M, Costea, S, Cseh, G, Czarnecka, A, Dal Molin, A, De La Cal, E, De La Pena, A, Degenkolbe, S, Dhard, C, Dinklage, A, Dostal, M, Drevlak, M, Drewelow, P, Drews, P, Dudek, A, Durodie, F, Dzikowicka, A, Von Eeten, P, Effenberg, F, Endler, M, Erckmann, V, Estrada, T, Fahrenkamp, N, Fellinger, J, Feng, Y, Figacz, W, Ford, O, Fornal, T, Frerichs, H, Fuchert, G, Garcia-Munoz, M, Geiger, B, Geiger, J, Gierse, N, Gogoleva, A, Goncalves, B, Gradic, D, Grahl, M, Gross, S, Grote, H, Grulke, O, Guerard, C, Haas, M, Harris, J, Hartfuss, H, Hartmann, D, Hathiramani, D, Hein, B, Heirnich, S, Henneberg, S, Hennig, C, Hernandez, J, Hidalgo, C, Hidalgo, U, Hirsch, M, Hofel, U, Holbe, H, Holting, A, Houry, M, Huber, V, Ionita, C, Israeli, B, Jablonski, S, Jakubowski, M, Van Vuuren, A, Jenzsch, H, Kaczmarczyk, J, Kallmeyer, J, Kamionka, U, Kasahara, H, Kenmochi, N, Kernbichler, W, Killer, C, Kinna, D, Kleiber, R, Knauer, J, Kochl, F, Kocsis, G, Kolesnichenko, Y, Konies, A, Konig, R, Kornejew, P, Koster, F, Kramer-Flecken, A, Krampitz, R, Krawzyk, N, Kremeyer, T, Krychowiak, M, Ksiazek, I, Kubkowska, M, Kuhner, G, Kurki-Suonio, T, Kurz, P, Kuttler, K, Kwak, S, Landreman, M, Langenberg, A, Lapayese, F, Laqua, H, Laube, R, Laux, M, Lentz, H, Lewerentz, M, Liang, Y, Liu, S, Lobsien, J, Cisquella, J, Lopez-Bruna, D, Lore, J, Lorenz, A, Lui, S, Lutsenko, V, Maassberg, H, Maisano-Brown, J, Marchuk, O, Marrelli, L, Marsen, S, Marushchenko, N, Masuzaki, S, Mccarthy, K, Mcneely, P, Medina, F, Milojevic, D, Mishchenko, A, Missal, B, Mittelstaedt, J, Mollen, A, Moncada, V, Monnich, T, Moseev, D, Nagel, M, Naujoks, D, Neilson, G, Neubauer, O, Neuner, U, Ngo, T, Niemann, H, Nuhrenberg, C, Nuhrenberg, J, Ochando, M, Ogawa, K, Ongena, J, Oosterbeek, H, Pablant, N, Pacella, D, Pacios, L, Panadero, N, Pasch, E, Pastor, I, Pavone, A, Pawelec, E, Pedrosa, A, Perseo, V, Peterson, B, Pilopp, D, Pisano, F, Piulatti, M, Plunk, G, Preynas, M, Proll, J, Sitjes, A, Purps, F, Rack, M, Rahbarnia, K, Riemann, J, Risse, K, Rong, P, Rosenberger, J, Rudischhauser, L, Rummel, K, Rummel, T, Runov, A, Rust, N, Ryc, L, Saitoh, H, Satake, S, Schacht, J, Schmitz, O, Schmuck, S, Schneider, B, Schneider, M, Schneider, W, Schrittwieser, R, Schroder, M, Schroder, T, Schroder, R, Schumacher, H, Schweer, B, Seki, R, Sinha, P, Sipilae, S, Slaby, C, Smith, H, Sousa, J, Spring, A, Standley, B, Stange, T, Von Stechow, A, Stephey, L, Stoneking, M, Stridde, U, Suzuki, Y, Svensson, J, Szabolics, T, Szepesi, T, Thomsen, H, Travere, J, Traverso, P, Mora, H, Tsuchiya, H, Tsuijmura, T, Turkin, Y, Valet, S, Van Milligen, B, Vela, L, Velasco, J, Vergote, M, Vervier, M, Viebke, H, Vilbrandt, R, Von Thun, C, Wagner, F, Wang, E, Wang, N, Warmer, F, Wauters, T, Wegener, L, Wegner, T, Weir, G, Wendorf, J, Wenzel, U, Werner, A, Wie, Y, Wiegel, B, Wilde, F, Windisch, T, Winkler, M, Winters, V, Wright, A, Wurden, G, Xanthopoulos, P, Yamada, I, Yasuhara, R, Yokoyama, M, Zhang, D, Zilker, M, Zimbal, A, Zocco, A, Zoletnik, S, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Department of Applied Physics, Aalto-yliopisto, Aalto University, and Pacella, D.

Subjects
Tokamak, Plasma parameters, Science, General Physics and Astronomy, Topology (electrical circuits), Topology, 7. Clean energy, 01 natural sciences, Article, General Biochemistry, Genetics and Molecular Biology, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, 010306 general physics, Physics, Fusion, Wendelstein7-X, Stellarator, Multidisciplinary, ta114, General Chemistry, Plasma, Fusion power, Magnetic field, Erratum, Wendelstein 7-X, Stellarator
Abstract

Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good confinement is realized, and that the measured deviations are smaller than one part in 100,000. This is a significant step forward in stellarator research, since it shows that the complicated and delicate magnetic topology can be created and verified with the required accuracy., Early stellarator designs suffered from high particle losses, an issue that can be addressed by optimization of the coils. Here the authors measure the magnetic field lines in the Wendelstein 7-X stellarator, confirming that the complicated design of the superconducting coils has been realized successfully.

Published
2016

38. ECCD operations in the second experimental campaign at W7-X.

Author

Poli, E., Laqua, H., Oosterbeek, J., 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
STELLARATORS, ELECTRON cyclotron resonance heating, PLASMA radiation, TOROIDAL plasma, ROTATIONAL transitions (Molecular physics)
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. [ABSTRACT FROM AUTHOR]

Published
2019
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40. Status and prospects of the MHD diagnostics at Wendelstein 7-X stellarator

Author

Thomsen, H., Andreeva, T., Brandt, C., Neuner, U., Rahbarnia, K., Alonso, A., Broszat, T., Endler, M., Geiger, J., Grahl, M., Klinger, T., Laqua, H., Stange, T., Svensson, J., Turkin, Y., Werner, A., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Published
2016

44. Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X.

Author

Wegner, Th., Geiger, B., Kunkel, F., Burhenn, R., Schröder, T., Biedermann, C., Buttenschön, B., Cseh, G., Drews, P., Grulke, O., Hollfeld, K., Killer, C., Kocsis, G., Krings, T., Langenberg, A., Marchuk, O., Neuner, U., Nicolai, D., Offermanns, G., and Pablant, N. A.

Subjects
NEODYMIUM lasers, STELLARATORS, PLASMA gases, LASER ablation, LASER pulses
Abstract

We present a detailed overview and first results of the new laser blow-off system on the stellarator Wendelstein 7-X. The system allows impurity transport studies by the repetitive and controlled injection of different tracer ions into the plasma edge. A Nd:YAG laser is used to ablate a thin metal film, coated on a glass plate, with a repetition rate of up to 20 Hz. A remote-controlled adjustable optical system allows the variation of the laser spot diameter and enables the spot positioning to non-ablated areas on the target between laser pulses. During first experiments, clear spectral lines from higher ionization stages of the tracer ions have been observed in the X-ray to the extreme ultraviolet spectral range. The temporal behavior of the measured emission allows the estimate of transport properties, e.g., impurity transport times in the order of 100 ms. Although the strong injection of impurities is well detectable, the global plasma parameters are barely changed. [ABSTRACT FROM AUTHOR]

Published
2018
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48. Optimizing the CERN plasma lens for antiproton collection

Author

Kowalewicz, R, Lubrano di Scampamorte, M, Maury, S, Milner, S, Riege, H, Christiansen, J, Frank, K, Neuner, U, Stetter, M, Tkotz, R, Wenninger, M, Boggasch, E, and Tauschwitz, A

Subjects
Accelerators and Storage Rings
Published
1993

49. Video Diagnostic for W7-X Stellarator.

Author

Sárközi, J., Grosser, K., Kocsis, G., König, R., Neuner, U., Molnár, Á., Petravich, G., Por, G., Porempovics, G., Récsei, S., Szabó, V., Szappanos, A., and Zoletnik, S.

Subjects
PLASMA diagnostics, STELLARATORS, GEOMETRY, DETECTORS, CAMERAS
Abstract

The video diagnostics for W7-X—which is under development—is devoted to observe plasma and frrst wall elements during operation, to warn in case of hot spots and dangerous heat load and to give information about the plasma size, position, edge structure, the geometry and location of magnetic islands and distribution of impurities. The video diagnostics will be mounted on the tangential AEQ-ports of the torus that are not straight and have about 2m length and a typical diameter of 0.1m which makes its realization more difficult. The geometry of the 10 tangential views of the AEQ-ports allows giving an almost complete overview of the vessel interior making this diagnostic indispensable for the machine operation. Different concepts of the diagnostics were investigated and finally the following design was selected. As a large heat load is expected on the optical window located at the plasma-facing end of the AEQ-port, the port window is protected by a cooled pinhole. An uncooled shutter located behind the pinhole can be closed to prevent window contamination during vessel conditioning discharges (glow discharge cleaning) and from inter-pulse deposition of soft a-C:H layers. The imaging optics and the detection sensor are located behind the port window in the port tube, which will be under atmospheric pressure. To detect the visible radiation distribution a new camera system called Event Detection Intelligent Camera (EDICAM) is under development. The system is divided into three major separated components. The Sensor Module contains only the selected CMOS sensor, the analog digital converters and the minimal electronics necessary for the communication with the subsequent camera system module called Image Processing and Control Unit (IPCU). Its simple structure makes the Sensor Module suitable to operate despite being exposed to ionizing (neutron, γ-) radiation. The IPCU, which can be located far from the Sensor Module and therefore far from the plasma, is designed to perform real time evaluation of the images detecting predefined events, managing the sensor read-out and the input triggers and producing the output triggers generated by the detected events. The IPCU can also be used to reduce the amount of the stored data. A Standard 10 Gigabit Ethernet fiber optics connection connects the IPCU module to the PC with GigEVision communication protocol. [ABSTRACT FROM AUTHOR]

Published
2008
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50. Response of converters to heating by intense heavy ion beams.

Author

Neuner, U., Bock, R., Roth, M., Wahl, H., Constantin, C., Dewald, E., Funk, U.N., Geissel, M., Hakuli, S., Hoffmann, D.H.H., Jacoby, J., Knobloch, R., Kozyreva, A., Penache, D., Pirzadeh, P., Rosmej, F.B., Rosmej, O., Tahir, N.A., Tauschwitz, A., and Udrea, S.

Abstract

The high current upgrade of the accelerator facilities at GSI Darmstadt, Germany, has created possibilities for a new class of experiments with heavy ion beams. Intense pulses of heavy ion beams can rapidly heat converters to high temperatures. The energy deposition of heavy ion beams as well as the hydrodynamic response of the converters and the radiation emitted from the converters are investigated experimentally. [ABSTRACT FROM PUBLISHER]

Published
2000

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