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318 results on '"Laqua H. -P."'

1. Plasma Production in ICRF in the Uragan-2M Stellarator in Hydrogen–Helium Gas Mixture

Author

Moiseenko, V. E., Kovtun, Yu. V., Lozin, A. V., Pavlichenko, R. O., Shapoval, A. N., Grigor’eva, L. I., Kozulya, M. M., Maznichenko, S. M., Korovin, V. B., Kramskoy, E. D., Zamanov, N. V., Siusko, Y. V., Baron, D. I., Krasiuk, A. Yu., Romanov, V. S., Garkusha, I. E., Wauters, T., Alonso, A., Brakel, R., Dinklage, A., Hartmann, D., Kazakov, Ye., Laqua, H., Ongena, J., and Stange, T.

Published
2022
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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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3. Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X

Author

Ponomarenko, S., Moseev, D., Stange, T., Krier, L., Stordiau, P., Braune, H., Gantenbein, G, Jelonnek, J., Kuleshov, A., Laqua, H. P., Lechte, C., Marsen, S., Nielsen, S. K., Oosterbeek, J. W., Plaum, B., Ragona, R., Rasmussen, J., Ruess, T., Salewski, M, Thumm, M., Zimmermann, J., Ponomarenko, S., Moseev, D., Stange, T., Krier, L., Stordiau, P., Braune, H., Gantenbein, G, Jelonnek, J., Kuleshov, A., Laqua, H. P., Lechte, C., Marsen, S., Nielsen, S. K., Oosterbeek, J. W., Plaum, B., Ragona, R., Rasmussen, J., Ruess, T., Salewski, M, Thumm, M., and Zimmermann, J.

Abstract

In this paper, we present the design and commissioning results of the upgraded collective Thomson scattering diagnostic at the Wendelstein 7-X stellarator. The diagnostic has a new radiometer designed to operate between the second and third harmonics of the electron cyclotron emission from the plasma at 171-177 GHz, where the emission background has a minimum and is of order 10-100 eV. It allows us to receive the scattered electromagnetic field with a significantly improved signal-to-noise ratio and extends the set of possible scattering geometries compared to the case of the original instrument operated at 140 GHz. The elements of the diagnostic are a narrowband notch filter and a frequency stabilized probing gyrotron that will allow measuring scattered radiation spectra very close to the probing frequency. Here, we characterize the microwave components applied to the radiometer and demonstrate the performance of the complete system that was achieved during the latest experimental campaign, OP2.1.

Published
2024

4. The ECRH-Power Upgrade at the Wendelstein 7-X Stellarator

Author

Laqua H. P., Avramidis K. A., Braune H., Chelis I., Gantenbein G., Illy S., Ioannidis Z., Jelonnek J., Jin J., Krier L., Lechte C., Leggieri A., Legrand F., Marsen S., Moseev D., Oosterbeek H., Rzesnicki T., Ruess T., Stange T., Thumm M., Tigelis I., and Wolf R. C.

Subjects
Physics, QC1-999
Abstract

The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to other large fusion experiments, W7-X has a relatively low power-to-volume ratio. However high heating power is particularly necessary for achieving high plasma beta values, where the improved confinement of fast ions, one of the optimization criteria of W7-X, can be examined. It is therefore necessary to expand the ECRH systems in several consecutive steps. It is planned to increase the number of gyrotron positions from 10 to 12 and at the same time to evolve the gyrotron output power in several development steps from 1 MW to nominal 1.5 MW and, finally, up to 2 MW. At the same time, the transmission lines will also be upgraded for 2 MW operation. A special effort is also made to improve the reliability of the system by the fast control system.

Published
2023
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5. Progress in High Power Gyrotron Development Projects at KIT

Author

Gantenbein, G., primary, Avramidis, K., additional, Ell, B., additional, Delpech, L., additional, Feuerstein, L., additional, Illy, S., additional, Jelonnek, J., additional, Jin, J., additional, Krier, L., additional, Laqua, H. P., additional, Ruess, T., additional, Rzesnicki, T., additional, Stanculovic, S., additional, and Thumm, M., additional

Published
2023
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6. Observation of impurity accumulation and its compatibility with high plasma performance in W7-X

Author

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

Published
2023
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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. Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X

Author

Tancetti, A., Nielsen, S. K., Rasmussen, J., Moseev, D., Stange, T., Marsen, S., Vecséi, M., Killer, C., Wurden, G. A., Jensen, T., Stejner, M., Anda, G., Dunai, D., Zoletnik, S., Rahbarnia, K., Brandt, C., Thomsen, H., Hirsch, M., Hoefel, U., Chaudhary, N., Winters, V., Kornejew, P., Harris, J., Laqua, H. P., Tancetti, A., Nielsen, S. K., Rasmussen, J., Moseev, D., Stange, T., Marsen, S., Vecséi, M., Killer, C., Wurden, G. A., Jensen, T., Stejner, M., Anda, G., Dunai, D., Zoletnik, S., Rahbarnia, K., Brandt, C., Thomsen, H., Hirsch, M., Hoefel, U., Chaudhary, N., Winters, V., Kornejew, P., Harris, J., and Laqua, H. P.

Abstract

Experimental evidence of parametric decay instability (PDI) is observed in the Wendelstein 7-X stellarator, when high-power microwave beams cross a stationary magnetic island at the plasma edge. Here, trapping and build-up of upper hybrid waves within a density bump (measured within the island by alkali beam emission spectroscopy) is responsible for the reduction of the instability power threshold below the maximum gyrotron power. In this paper, we provide the first experimental evidence of the connection between the trapping mechanism in the island density bump and excitation of PDI-related signals. We show correlations of periodic crashes in the PDI-related signals with quasi-continuous fluctuations at the plasma edge, which, additionally, cause a flattening of the density profile in the island. We demonstrate that flattening of the experimental density profiles can suppress the trapping mechanism and inhibit the low-threshold PDI. PDI on the edge island could alter the power deposition profile and reduce the efficiency of the electron cyclotron resonance heating system, simultaneously posing a serious threat to the optimal operation of microwave-based diagnostics and plasma-facing components.

Published
2023

9. Short-pulse frequency stabilization of a MW-class ECRH gyrotron at W7-X for CTS diagnostic

Author

W7-X Team, Krier, L., Avramidis, K. A., Braune, H., Gantenbein, G., Illy, S., Jelonnek, J., Laqua, H. P., Marsen, S., Moseev, D., Noke, F., Ruess, T., Stange, T., Thumm, M., and Wolf, R. C.

Subjects
Technology, ddc:600
Abstract

At the Wendelstein 7-X stellarator, a 174 GHz Collective Thomson Scattering (CTS) diagnostic will be implemented. One of the 140 GHz Electron Cyclotron Resonance Heating (ECRH) gyrotrons will be operated at around 174 GHz in a higher cavity mode, using it as source for the CTS mm-wave probing beam. To prevent any damage to the CTS receiver, a notch filter cuts out the high-power gyrotron signal at the entrance of the receiver. The bandwidth of the gyrotron signal determines the notch filter bandwidth. First proof-of-principle experiments on frequency stabilization were conducted on W7-X ECRH gyrotrons employing Phase-Locked Loop techniques. The gyrotron output frequency was controlled with the accelerating voltage, which is applied between the anode and cathode of the gyrotron diode-type Magnetron Injection Gun. Frequency stabilization experiments with 10 ms pulses were conducted at the gyrotron nominal frequency of 140 GHz as well as at 174 GHz. It is concluded that the gyrotron frequency could be stabilized for at least 3 ms at 140 GHz and 8 ms at 174 GHz. In the frequency spectrum, a clear main peak of the gyrotron frequency at 140 GHz with a full -15 dB linewidth of below 500 Hz was achieved.

Published
2023
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10. Numerical analyses of CVD diamond windows in high power microwave applications

Author

Aiello, Gaetano, Meier, Andreas, Scherer, Theo, Laqua, H. P., Schreck, Sabine, and Strauss, Dirk

Subjects
ddc:620, Engineering & allied operations
Abstract

Nuclear fusion reactors require electron cyclotron heating and current drive (EC H&CD) systems for plasma heating and stabilization. Chemical vapor deposition (CVD) polycrystalline diamond windows on both the torus and gyrotron sides of the reactors act as confinement and/or vacuum boundaries allowing the transmission of high-power microwave beams. For example, the beam power scenarios of 1.5 MW and 2 MW are the current targets considered respectively in Wendelstein 7-X and European DEMO fusion machines. In this work, with reference to both reactors, the numerical analyses required to verify the thermal and structural performance of the windows are discussed. Experimental measurements of loss tangent in diamond provided inputs for the numerical analyses. Sensitivity studies of the windows with respect to loss tangent and other parameters were also carried out to check the temperature reserve margins of the design.

Published
2023
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11. The ECRH-Power Upgrade at the Wendelstein 7-X Stellarator

Author

W7-X Team, Laqua, H. P., Avramidis, K. A., Braune, H., Chelis, I., Gantenbein, G., Illy, S., Ioannidis, Z., Jelonnek, J., Jin, J., Krier, L., Lechte, C., Leggieri, A., Legrand, F., Marsen, S., Moseev, D., Oosterbeek, H., Rzesnicki, T., Ruess, T., Stange, T., Thumm, M., Tigelis, I., Wolf, R. C., Poli, E., Liu, Y., and Udintsev, V.

Subjects
Technology, ddc:600, W7-X, ECRH
Abstract

The existing ECRH system at W7-X consists of 10 gyrotrons, with output power levels ranging from 0.6 MW up to 1.0 MW each at a frequency of 140 GHz, quasi-optical transmission lines and microwave launchers at the plasma vessel. Compared to other large fusion experiments, W7-X has a relatively low power-to-volume ratio. However high heating power is particularly necessary for achieving high plasma beta values, where the improved confinement of fast ions, one of the optimization criteria of W7-X, can be examined. It is therefore necessary to expand the ECRH systems in several consecutive steps. It is planned to increase the number of gyrotron positions from 10 to 12 and at the same time to evolve the gyrotron output power in several development steps from 1 MW to nominal 1.5 MW and, finally, up to 2 MW. At the same time, the transmission lines will also be upgraded for 2 MW operation. A special effort is also made to improve the reliability of the system by the fast control system.

Published
2023

13. Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X

Author

Tancetti, A, primary, Nielsen, S K, additional, Rasmussen, J, additional, Moseev, D, additional, Stange, T, additional, Marsen, S, additional, Vecséi, M, additional, Killer, C, additional, Wurden, G A, additional, Jensen, T, additional, Stejner, M, additional, Anda, G, additional, Dunai, D, additional, Zoletnik, S, additional, Rahbarnia, K, additional, Brandt, C, additional, Thomsen, H, additional, Hirsch, M, additional, Hoefel, U, additional, Chaudhary, N, additional, Winters, V, additional, Kornejew, P, additional, Harris, J, additional, and Laqua, H P, additional

Published
2022
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14. Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Author

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

Abstract

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

Published
2022

15. Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport

Author

Beurskens, M. N. A., Angioni, C., Bozhenkov, S. A., Ford, O., Kiefer, C., Xanthopoulos, P., Turkin, Y., Alcuson, J. A., Baehner, J. P., Beidler, C., Birkenmeier, G., Fable, E., Fuchert, G., Geiger, B., Grulke, O., Hirsch, M., Jakubowski, M., Laqua, H. P., Langenberg, A., Lazerson, S., Pablant, N., Reisner, M., Schneider, P., Scott, E. R., Stange, T., von Stechow, A., Stober, J., Stroth, U., Wegner, Th., Weir, G., Zhang, D., Zocco, A., Wolf, R. C., Zohm, H., Beurskens, M. N. A., Angioni, C., Bozhenkov, S. A., Ford, O., Kiefer, C., Xanthopoulos, P., Turkin, Y., Alcuson, J. A., Baehner, J. P., Beidler, C., Birkenmeier, G., Fable, E., Fuchert, G., Geiger, B., Grulke, O., Hirsch, M., Jakubowski, M., Laqua, H. P., Langenberg, A., Lazerson, S., Pablant, N., Reisner, M., Schneider, P., Scott, E. R., Stange, T., von Stechow, A., Stober, J., Stroth, U., Wegner, Th., Weir, G., Zhang, D., Zocco, A., Wolf, R. C., and Zohm, H.

Abstract

In electron (cyclotron) heated plasmas, in both ASDEX Upgrade (L-mode) and Wendelstein 7-X, clamping of the ion temperature occurs at Ti ∼ 1.5 keV independent of magnetic configuration. The ions in such plasmas are heated through the energy exchange power as ne2(Te-Ti)/Te3/2, which offers a broad ion heating profile, similar to that offered by alpha heating in future thermonuclear fusion reactors. However, the predominant electron heating may put an additional constraint on the ion heat transport, as the ratio Te/Ti > 1 can exacerbates ITG/TEM core turbulence. Therefore, in practical terms the strongly 'stiff' core transport translates into Ti-clamping in electron heated plasmas. Due to this clamping, electron heated L-mode scenarios, with standard gas fueling, in either tokamaks or stellarators may struggle to reach high normalized ion temperature gradients required in a compact fusion reactor. The comparison shows that core heat transport in neoclassically optimized stellarators is driven by the same mechanisms as in tokamaks. The absence of a strong H-mode temperature edge pedestal in stellarators, sofar (which, like in tokamaks, could lift the clamped temperature-gradients in the core), puts a strong requirement on reliable and sustainable core turbulence suppression techniques in stellarators.

Published
2022

16. Nonlinear decay of high-power microwaves into trapped modes in inhomogeneous plasma

Author

Tancetti, A., Nielsen, S. K., Rasmussen, J., Gusakov, E. Z., Popov, A. Yu, Moseev, D., Stange, T., Senstius, M. G., Killer, C., Vecséi, M., Jensen, T., Zanini, M., Abramovic, I., Stejner, M., Anda, G., Dunai, D., Zoletnik, S., Laqua, H. P., Tancetti, A., Nielsen, S. K., Rasmussen, J., Gusakov, E. Z., Popov, A. Yu, Moseev, D., Stange, T., Senstius, M. G., Killer, C., Vecséi, M., Jensen, T., Zanini, M., Abramovic, I., Stejner, M., Anda, G., Dunai, D., Zoletnik, S., and Laqua, H. P.

Abstract

We present novel experimental evidence of parametric decay instability of microwave beams in the plasma edge of the Wendelstein 7-X stellarator. We propose that the instability is sustained by trapping of only one daughter wave in the non-monotonic density profile measured with high spatial resolution within a stationary magnetic island. The power levels and spectral shapes of the detected microwave signal are reproduced by numerical modelling and a theoretical power threshold is predicted around 300 kW, comparable with observations. We predict a fraction of power drained by daughter waves around 4% in the experiments, potentially increasing above 50% for more hollow edge density profiles. Such absorption levels could significantly reduce the efficiency of the microwave heating and current-drive system in tokamaks and stellarators.

Published
2022

17. Microwave stray radiation losses in vacuum windows

Author

Oosterbeek, J. W., Stern, M., Braune, H., Ewert, K., Hirsch, M., Hollmann, F., Laqua, H. P., Marsen, S., Meier, A., Moseev, D., Noke, F., Reintrog, A., Stange, T., Wolf, R. C., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Loss tangent, Nuclear Energy and Engineering, Vacuum window losses, Mechanical Engineering, Microwave stray radiation, General Materials Science, ddc:620, Engineering & allied operations, W7-X, Civil and Structural Engineering, ECRH, Dielectric losses
Abstract

Vacuum windows are required in magnetically confined fusion experiments to provide possibilities to observe the plasma in a wide range of electromagnetic wavelengths. The window disk consists of a dielectric, e.g. Fused Silica (SiO$_2$), Sapphire or Chemically Vapourised Diamond (CVD). As electromagnetic waves pass through the disk, a fraction of the beam power is dissipated resulting in a temperature increase of the disk. In Electron Cyclotron Waves (ECW) heated plasmas the dissipation in the window disk can be very high. The computation of dielectric losses for a collimated beam with known incidence angle, polarisation and loss tangent (measure for the intrinsic dielectric loss) is well established. However, the dielectric losses in diagnostic windows mostly result from microwave stray radiation, which results from a modest, but inevitable, fraction of non-absorbed ECW. This fraction diffuses in the vessel by many reflections into rays with random k-vector and with random polarisation. In this work the thermal load on the window disk by microwave stray radiation is assessed. The load by a collimated beam is studied as a function of incidence angle and polarisation allowing to average over a distribution of incident rays. An experiment was commissioned measuring the loss tangent of a number of commercially available SiO$_2$ disks at low power in an open resonator, and subsequently measuring the dielectric heating of these disks at high power stray radiation using the facility ’MISTRAL’ at Wendelstein-7X. The experimental results are compared to modelling and it is demonstrated that, in the parameter range considered, single-pass fractional absorption may be applied while taking a safety margin that arises from the minima and maxima due to multiple reflections.

Published
2022
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18. Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport

Author

W7-X Team, Beurskens, M. N. A., Angioni, C., Bozhenkov, S. A., Ford, O., Kiefer, C., Xanthopoulos, P., Turkin, Y., Alcusón, J. A., Baehner, J. P., Beidler, C., Birkenmeier, G., Fable, E., Fuchert, G., Geiger, B., Grulke, O., Hirsch, M., Jakubowski, M., Laqua, H. P., Langenberg, A., Lazerson, S., Pablant, N., Reisner, M., Schneider, P., Scott, E. R., Stange, T., Stechow, A. von, Stober, J., Stroth, U., Wegner, Th., Weir, G., Zhang, D., Zocco, A., Wolf, R. C., Zohm, H., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team

Subjects
Technology, Nuclear and High Energy Physics, Turbulent transport, Materials science, Turbulence, Ion temperature clamping, Plasma, Electron, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Nuclear physics, Electron heating, ASDEX Upgrade, Physics::Plasma Physics, 0103 physical sciences, Stellarator transport, Wendelstein 7-X, ddc:620, 010306 general physics, ddc:600
Abstract

In electron (cyclotron) heated plasmas, in both ASDEX Upgrade (L-mode) and Wendelstein 7-X, clamping of the ion temperature occurs at T i ∼ 1.5 keV independent of magnetic configuration. The ions in such plasmas are heated through the energy exchange power as n e 2 ( T e − T i ) / T e 3 / 2 , which offers a broad ion heating profile, similar to that offered by alpha heating in future thermonuclear fusion reactors. However, the predominant electron heating may put an additional constraint on the ion heat transport, as the ratio T e/T i > 1 can exacerbates ITG/TEM core turbulence. Therefore, in practical terms the strongly ‘stiff’ core transport translates into T i-clamping in electron heated plasmas. Due to this clamping, electron heated L-mode scenarios, with standard gas fueling, in either tokamaks or stellarators may struggle to reach high normalized ion temperature gradients required in a compact fusion reactor. The comparison shows that core heat transport in neoclassically optimized stellarators is driven by the same mechanisms as in tokamaks. The absence of a strong H-mode temperature edge pedestal in stellarators, sofar (which, like in tokamaks, could lift the clamped temperature-gradients in the core), puts a strong requirement on reliable and sustainable core turbulence suppression techniques in stellarators.

Published
2021
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19. Inhibition of parametric decay in heating microwave beams during fluctuations of the density profile in the edge island of Wendelstein 7-X

Author

W7-X Team, Tancetti, A., Nielsen, S. K., Rasmussen, J., Moseev, D., Stange, T., Marsen, S., Vecséi, M., Killer, C., Wurden, G. A., Jensen, T., Stejner, M., Anda, G., Dunai, D., Zoletnik, S., Rahbarnia, K., Brandt, C., Thomsen, H., Hirsch, M., Hoefel, U., Chaudhary, N., Winters, V., Kornejew, P., Harris, J., Laqua, H. P., Gantenbein, Gerd, Illy, Stefan, Jelonnek, John, Krier, Laurent, and Thumm, Manfred

Subjects
Technology, Nuclear Energy and Engineering, Condensed Matter Physics, ddc:600
Abstract

Experimental evidence of parametric decay instability (PDI) is observed in the Wendelstein 7-X stellarator, when high-power microwave beams cross a stationary magnetic island at the plasma edge. Here, trapping and build-up of upper hybrid waves within a density bump (measured within the island by alkali beam emission spectroscopy) is responsible for the reduction of the instability power threshold below the maximum gyrotron power. In this paper, we provide the first experimental evidence of the connection between the trapping mechanism in the island density bump and excitation of PDI-related signals. We show correlations of periodic crashes in the PDI-related signals with quasi-continuous fluctuations at the plasma edge, which, additionally, cause a flattening of the density profile in the island. We demonstrate that flattening of the experimental density profiles can suppress the trapping mechanism and inhibit the low-threshold PDI. PDI on the edge island could alter the power deposition profile and reduce the efficiency of the electron cyclotron resonance heating system, simultaneously posing a serious threat to the optimal operation of microwave-based diagnostics and plasma-facing components.

Published
2022
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20. 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

21. 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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22. 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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23. 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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24. Thermographic reconstruction of heat load on the first wall of Wendelstein 7-X due to ECRH shine-through power

Author

W7-X Team, Corre, Y., Gaspar, J., Marsen, S., Moseev, D., Stange, T., Boscary, J., Drewelow, P., Gao, Y., Jakubowski, M., Hillairet, J., Laqua, H. P., Lechte, C., Moncada, V., Niemann, H., Preynas, M., Puig Sitjes, 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, Institut de Recherche sur la Fusion par confinement Magnétique (IRFM), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut universitaire des systèmes thermiques industriels (IUSTI), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Max-Planck-Institut für Plasmaphysik [Garching] (IPP), University of Stuttgart, ITER organization (ITER), European Project: 633053,H2020,EURATOM-Adhoc-2014-20,EUROfusion(2014), and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Ir thermography, [PHYS]Physics [physics], Nuclear and High Energy Physics, Technology, Materials science, business.industry, heat flux calculation, Condensed Matter Physics, 01 natural sciences, Electron Cyclotron Resonance Heating, 010305 fluids & plasmas, Power (physics), Optics, 0103 physical sciences, infrared thermography, Wendelstein 7-X, Heat load, 010306 general physics, business, ddc:600
Abstract

Electron cyclotron resonance heating (ECRH) is a powerful and flexible plasma heating technique that serves as the main heater at Wendelstein 7-X (W7-X) and will be used at ITER for start-up, heating, current drive and mitigation of plasma instabilities. In the case of poor or degraded microwave absorption, which is expected in the O2-mode heating scenario, a significant part of the beam directly hits the wall, leading to local overheating and potential damage. The ECRH shine-through power is mostly reflected onto the targets; only a small fraction is really absorbed through ohmic losses (typically 3% for graphite at 140 GHz). The ohmic losses do not only depend on the material properties and the frequency, but also on the polarization of the wave and the angle of incidence. This paper presents a thermographic analysis of ECRH experiments at W7-X, including heat load and temperature simulations of the first wall that include ECRH shine through. Two O-mode ECRH experiments with both a high temperature rise of the first wall and different angles of beam incidence on the wall’s surface are depicted. One experiment has 775 kW of power modulation (5 Hz) with mixed polarization (45% O-mode, 55% X-mode) and an EC beam angle almost normal to the first wall. The second has 550 kW of steady EC power with O-mode polarization, a shallow beam angle and increased power absorption by the material. It is shown that infrared thermography is a useful tool for measuring shine-through power and protecting wall components.

Published
2021
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25. Development of the ion cyclotron emission diagnostic for the W7-X stellarator

Author

W7-X Team, Moseev, D., Ochoukov, R., Bobkov, V., Dendy, R. O., Faugel, H., Hartmann, D., Kallmeyer, J.-P., Lansky, J., Laqua, H. P., Marsen, S., McClements, K. G., Nielsen, S. K., Reintrog, A., Salewski, M., Schmidt, B. S., Schulz, T., Stange, T., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, and Weggen, Jörg

Subjects
Technology, ddc:600
Published
2021

27. Plasma radiation behavior approaching high-radiation scenarios in W7-X

Author

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

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

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

Published
2021
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28. 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

30. 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

35. 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

36. Stray radiation energy fluxes in ITER based on a multiresonator model

Author

Moseev, D., Oosterbeek, J. W., Sirinelli, A., Corre, Y., Houry, M., Korsholm, S. B., Laqua, H. P., Marsen, S., Preynas, M., Rasmussen, J., Salewski, M., Stange, T., Udintsev, V., Moseev, D., Oosterbeek, J. W., Sirinelli, A., Corre, Y., Houry, M., Korsholm, S. B., Laqua, H. P., Marsen, S., Preynas, M., Rasmussen, J., Salewski, M., Stange, T., and Udintsev, V.

Abstract

Here we re-evaluate the stray radiation loads due to electron cyclotron resonance heating and diagnostic gyrotrons in ITER, as well as compute the stray radiation energy flux due to electron cyclotron emission. Microwave loads due to stray radiation were assessed in the past. We give here more comprehensive estimates, including spatial variations in the machine. We show that for the start-up phase in the First Plasma campaign the threshold of 100 kW/m2, which diagnostics have to be able to withstand, is not exceeded. For the later campaigns, the stray radiation energy flux during start-up and burnthrough will exceed 450 kW/m2. Stray radiation from electron cyclotron emission and from a diagnostic 60 GHz gyrotron can contribute to more than 140 kW/m2 combined.

Published
2021

37. 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

47. Spectra of highly ionized xenon (6–30 nm) excited in W7-AS plasmas

Author

Hacker, H.H., Burhenn, R., Kondo, K., Anton, M., Assmus, D., Baeumel, S., Beidler, C., Bindemann, T., Brakel, R., Cattanei, G., Dinklage, A., Dodhy, A., Dorst, D., Ehmler, H., Elsner, A., Endler, M., Engelhardt, K., Erckmann, V., Feng, Y., Fuchs, C., Gadelmeier, F., Geiger, J., Giannone, L., Grigull, P., Gruenwald, G., Grulke, O., Harmeyer, E., Hartfuss, H.J., Herrnegger, F., Hirsch, M., Hofner, J., Hollmann, F., Holzhauer, E., Igitkhanov, Y., Jaenicke, R., Karger, F., Kick, M., Kisslinger, J., Klose, S., Knauer, J., Kroiss, H., Kühner, G., Kus, A., Laqua, H., Liu, R., Maassberg, H., Marushchenko, N., McCormick, K., Michel, G., Noke, F., Ott, W., Otte, M., Pacco-Duechs, M.G., Penningsfeld, F.P., Polunovsky, E., Probst, F., Purps, F., Ruhs, N., Rust, N., Saffert, N.J., Salat, A., Sallander, J., Sardei, F., Schneider, F., Schubert, M., Sidorenko, I., Speth, E., Suess, R., Thomsen, H., Volpe, F., Wagner, F., Weller, A., Wendland, C., Werner, A., Wobig, H., Wuersching, E., and Zimmermann, D.

Published
2001
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