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1. 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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2. Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry

Author

W7-X Team, Zhang, D., Burhenn, R., Beidler, C. D., Feng, Y., Thomsen, H., Brandt, C., Buller, S., Reimold, F., Hacker, P., Laube, R., Geiger, J., Regaña, J. M. García, Smith, H. M., König, R., Giannone, L., Penzel, F., Klinger, T., Baldzuhn, J., Bozhenkov, S., Bräuer, T., Brunner, J. K., Buttenschön, B., Damm, H., Endler, M., Effenberg, F., Fuchert, G., Gao, Y., Jakubowski, M., Knauer, J., Kremeyer, T., Krychowiak, M., Kwak, S., Laqua, H. P., Langenberg, A., Otte, M., Pablant, N., Pasch, E., Rahbarnia, K., Pavone, A., Rudischhauser, L., Svensson, J., Killer, C., Windisch, T., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Technology, Nuclear and High Energy Physics, business.industry, media_common.quotation_subject, Bolometer, Radiation, Condensed Matter Physics, 01 natural sciences, Asymmetry, 010305 fluids & plasmas, law.invention, Optics, law, 0103 physical sciences, Tomography, Wendelstein 7-X, 010306 general physics, business, ddc:600, media_common
Published
2021
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3. Wendelstein 7-X on the path to long-pulse high-performance operation

Author

W7-X Team, Endler, M., Baldzuhn, J., Beidler, C. D., Bosch, H.-S., Bozhenkov, S., Buttenschön, B., Dinklage, A., Fellinger, J., Feng, Y., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Hartmann, D., Jakubowski, M., König, R., Laqua, H. P., Lazerson, S., McNeely, P., Naujoks, D., Neuner, U., Otte, M., Pasch, E., Sunn Pedersen, T., Perseo, V., Puig Sitjes, A., Rahbarnia, K., Rust, N., Schmitz, O., Spring, A., Stange, T., Stechow, A. von, Turkin, Y., Wang, E., Wolf, R. C., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Technology, Optimisation, Steady-state, Stellarator, Wendelstein 7-X, Nuclear engineering, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Data acquisition, law, Range (aeronautics), 0103 physical sciences, Water cooling, General Materials Science, 010306 general physics, Civil and Structural Engineering, Steady state, Mechanical Engineering, Fusion power, Nuclear Energy and Engineering, Path (graph theory), ddc:600
Abstract

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

Published
2021
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4. Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase

Author

Wolf, R. C., Alonso, A., Akaslompolo, S., Baldzuhn, J., Beurskens, M., Beidler, C. D., Biedermann, C., Bosch, H. -S., Bozhenkov, S., Brakel, R., Braune, H., Brezinsek, S., Brunner, K. -J., Damm, H., Dinklage, A., Drewelow, P., Effenberg, F., Feng, Y., Ford, O., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Harder, N., Hartmann, D., Helander, P., Heinemann, B., Hirsch, M., Hofel, U., Hopf, C., Ida, K., Isobe, M., Jakubowski, M. W., Kazakov, Y. O., Killer, C., Klinger, T., Knauer, J., Konig, R., Krychowiak, M., Langenberg, A., Laqua, H. P., Lazerson, S., Mcneely, P., Marsen, S., Marushchenko, N., Nocentini, R., Ogawa, K., Orozco, G., Osakabe, M., Otte, M., Pablant, N., Pasch, E., Pavone, A., Porkolab, M., Puig Sitjes, A., Rahbarnia, K., Riedl, R., Rust, N., Scott, E., Schilling, J., Schroeder, R., Stange, T., Von Stechow, A., Strumberger, E., Sunn Pedersen, T., Svensson, J., Thomson, H., Turkin, Y., Vano, L., Wauters, T., Wurden, G., Yoshinuma, M., Zanini, M., Zhang, D., Andreeva, T., Brandt, C., Burhenn, R., Buttenschon, B., Geiger, B., Tamura, N., Thomsen, H., Wegner, T., Abramovic, I., Alcuson, J., Aleynikov, P., Aleynikova, K., Ali, A., Anda, G., Ascasibar, E., Bahner, J. P., Baek, S. G., Balden, M., Banduch, M., Barbui, T., Behr, W., Beidler, C., Benndorf, A., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., Bockenhoff, D., Boswirth, B., Bottger, L. -G., Borchardt, M., Borsuk, V., Boscary, J., Brand, H., Brauer, T., Bussiahn, R., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., Carralero, D., Carraro, L., Carvalho, B., Castejon, F., Charl, A., Chaudhary, N., Chauvin, D., Chernyshev, F., Cianciosa, M., Citarella, R., Claps, G., Coenen, J., Cole, M., Cole, M. J., Cordella, F., Cseh, G., Czarnecka, A., Czerski, K., Czerwinski, M., Czymek, G., Da Molin, A., Da Silva, A., De La Pena, A., Degenkolbe, S., Dhard, C. P., Dibon, M., Dittmar, T., Drevlak, M., Drews, P., Durodie, F., Edlund, E., Van Eeten, P., Ehrke, G., Elgeti, S., Endler, M., Ennis, D., Esteban, H., Estrada, T., Fellinger, J., Flom, E., Fernandes, H., Fietz, W. H., Figacz, W., Fontdecaba, J., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Garcia Regana, J., Gates, D., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Guerard, C., Hacker, P., Han, X., Harris, J. H., Hathiramani, D., Hein, B., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hollfeld, K. P., Holting, A., Hoschen, D., Houry, M., Howard, J., Huang, X., Huang, Z., Hubeny, M., Huber, M., Hunger, H., 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., Kirschner, A., Kleiber, R., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., Kochl, F., Kolesnichenko, Y., Konies, A., Kornejew, P., Koschinsky, J. -P., Koster, F., Kramer, M., Krampitz, R., Kramer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Ksiazek, I., Kubkowska, M., Kuhner, G., Kurki-Suonio, T., Kurz, P. A., Kwak, S., Landreman, M., Lang, P., Lang, R., Langish, S., Laqua, H., Laube, R., 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., Lucke, A., Lumsdaine, A., Lutsenko, V., Maassberg, H., Marchuk, O., Matthew, J. H., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., Mccarthy, K., Meier, A., Mellein, D., Mendelevitch, B., Mertens, P., Mikkelsen, D., Mishchenko, A., Missal, B., Mittelstaedt, J., Mizuuchi, T., Mollen, A., Moncada, V., Monnich, T., Morisaki, T., Moseev, D., Murakami, S., Nafradi, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Ngo, T., Nicolai, D., Nielsen, S. K., Niemann, H., Nishizawa, T., Nuhrenberg, C., Nuhrenberg, J., Obermayer, S., Offermanns, G., Olmanns, J., Ongena, J., Oosterbeek, J. W., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfuss, D., Paqay, S., Pawelec, E., Pedersen, T. S., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., Poloskei, P., Proll, J., Puiatti, M. -E., Purps, F., Rack, M., Recsei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riemann, J., Risse, K., Rohde, V., Rohlinger, H., Rome, M., Rondeshagen, D., Rong, P., Roth, B., Rudischhauser, L., Rummel, K., Rummel, T., Runov, A., Ryc, L., Ryosuke, S., Sakamoto, R., Salewski, M., Samartsev, A., Sanchez, E., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schlaich, A., Schlisio, G., Schluck, F., Schluter, K. -H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schroder, M., Schroder, T., Schumacher, H., Schweer, B., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Siplia, S., Slaby, C., Sleczka, M., Smith, H., Spiess, W., Spong, D. A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Szabo, V., Szabolics, T., Szepesi, T., Szokefalvi-Nagy, Z., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulipan, S., Unterberg, B., Vakulchyk, I., Valet, S., Van Milligen, B., Van Vuuren, A. J., Vela, L., Velasco, J. -L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vorkoper, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Warmer, F., Wegener, L., Weggen, J., Wei, Y., Weir, G., Wendorf, J., Wenzel, U., Werner, A., White, A., Wiegel, B., Wilde, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, S., Wright, A., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zarnstorff, M., Zeitler, A., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., Zuin, M., Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

Subjects
Physics, Technology, Plasma parameters, Divertor, Nuclear engineering, Plasma, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, Magnetic field, law, 0103 physical sciences, Limiter, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract

Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future stellarator power plant. Plasma operation started in 2015 using a limiter configuration. After installing an uncooled magnetic island divertor, extending the energy limit from 4 to 80 MJ, operation continued in 2017. For this phase, the electron cyclotron resonance heating (ECRH) capability was extended to 7 MW, and hydrogen pellet injection was implemented. The enhancements resulted in the highest triple product (6.5 × 1019 keV m-3 s) achieved in a stellarator until now. Plasma conditions [Te(0) ≈ Ti(0) ≈ 3.8 keV, τE > 200 ms] already were in the stellarator reactor-relevant ion-root plasma transport regime. Stable operation above the 2nd harmonic ECRH X-mode cutoff was demonstrated, which is instrumental for achieving high plasma densities in Wendelstein 7-X. Further important developments include the confirmation of low intrinsic error fields, the observation of current-drive induced instabilities, and first fast ion heating and confinement experiments. The efficacy of the magnetic island divertor was instrumental in achieving high performance in Wendelstein 7-X. Symmetrization of the heat loads between the ten divertor modules could be achieved by external resonant magnetic fields. Full divertor power detachment facilitated the extension of high power plasmas significantly beyond the energy limit of 80 MJ.

Published
2019
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5. Investigation of the radiative power loss in the limiter plasmas of W7-X

Author

Zhang, D., Burhenn, R., Buttenschön, B., König, R., Laube, R., Jenszch, H., Giannone, L., Marquardt, M., Thomsen, H., Werner, A., Alonso, A., Biedermann, Ch, Bozhenkov, S., Brakel, R., Czarnecka, A., Fornal, T., Fuchert, G., Grulke, O., Hirsch, M., Knauer, J., Kubkowska, M., Langenberg, A., Laqua, H. P., Otte, M., Novimir Pablant, Pasch, E., Rahbarnia, K., Schröder, T., Svensson, J., Wenzel, U., Wurden, G. A., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

6. Core confinement in wendelstein 7-X limiter plasmas

Author

Dinklage, A., Alonso, A., Baldzuhn, J., Beidler, C. D., Biedermann, C., Blackwell, B., Bozhenkov, S., Brakel, R., Buttenschön, B., Feng, Y., Fuchert, G., Geiger, J., Helander, P., Hirsch, M., Hoefel, U., Knauer, J., Krämer-Flecken, A., Landreman, M., Langenberg, A., Laqua, H. P., Maaßberg, H., Pablant, N. A., Pasch, E., Rahbarnia, K., Rudischhauser, L., Smith, H., Stange, T., Stephey, L., Trimino-Mora, H., Turkin, Yu, Velasco, J. -L, Glen Wurden, Zhang, D., Andreeva, T., Beurskens, M., Blanco, E., Bosch, H. -S, Burhenn, R., Cappa, A., Czarnecka, A., Dostal, M., Drews, P., Endler, M., Estrada, T., Fornal, T., Grulke, O., Hartmann, D., Harris, J. H., Jakubowski, M., Klinger, T., Klose, S., Kocsis, G., König, R., Kornejew, P., Krawczyk, N., Krychowiak, M., Kubkowska, M., Ksiazek, I., Lazerson, S., Liang, Y., Liu, S., Marchuk, O., Marsen, S., Marushchenko, N., Moncada, V., Moseev, D., Naujoks, D., Niemann, H., Otte, M., Pedersen, T. S., Pisano, F., Riße, K., Rummel, T., Schmitz, O., Satake, S., Schröder, T., Szepesi, T., Thomsen, H., Traverso, P., Tsuchiya, H., Valson, P., Wang, N., Wauters, T., Weir, G., Wolf, R., Yokoyama, M., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

7. MAIN RESULTS OF THE FIRST EXPERIMENTAL CAMPAIGN IN THE STELLARATOR W7-X

Author

Marushchenko, N. B., Dinklage, A., Alonso, A., Baldzuhn, J., Beidler, C. D., Biedermann, C., Blackwell, B., Sergey Bozhenkov, Brakel, R., Buttenschön, B., Feng, Y., Fuchert, G., Geiger, J., Hirsch, M., Hoefel, U., Knauer, J., Krämer-Flecken, A., Langenberg, A., Laqua, H. P., Landreman, M., Maassberg, H., Pablant, N. A., Pasch, E., Rahbarnia, K., Rudischhauser, L., Stange, T., Stephey, L., Trimino-Mora, H., Turkin, Y., Velasco, J. -L, Wurden, G., Zhang, D., Andreeva, T., Beurskens, M., Blanco, E., Bosch, H. -S, Burhenn, R., Cappa, A., Czarnecka, A., Dostal, M., Drews, P., Endler, M., Estrada, T., Fornal, T., Grulke, O., Hartmann, D., Harris, J. H., Helander, P., Jakubowski, M., Klinger, T., Klose, S., Kocsis, G., König, R., Kornejew, P., Krawczyk, N., Krychowiak, M., Kubkowska, M., Kiazek, I., Lazerson, S., Liang, Y., Liu, S., Marchuk, O., Marsen, S., Moncada, V., Moseev, D., Naujoks, D., Niemann, H., Otte, M., Pedersen, T. S., Pisano, F., Riße, K., Rummel, T., Schmitz, O., Satake, S., Smith, H., Schröder, T., Szepesi, T., Thomsen, H., Traverso, P., Tsuchiya, M., Wang, N., Wauters, T., Weir, G., Wolf, R., and Yokoyama, M.

Subjects
Magnetic confinement
Abstract

A summary of the first operational phase (OP1.1) at the stellarator W7-X is given. The operational setup of heating and diagnostics as well the results of experiments are briefly described. Plasma parameters and confinement are better than expected: T(b)> 8 keV and T(i)> 2 keV at n(b)≈ 3×10¹⁹ m⁻³ yielding β0 ≈ 2.5 %. The results for ECR heating with X2-mode as well the ECCD are in good agreement with the theory predictions. The heating scenario with the O2-mode alone was successfully first time performed. Stellarator specific regime of core “electron root” confinement was obtained. Представлены итоги первой экспериментальной кампании (ОР1.1) на стеллараторе W7-X. Вкратце описана специфика эксперимента, методов нагрева и основных диагностик. Параметры плазмы и удержание, полученные в экспериментах, превысили ожидаемые: T(b)> 8 кэВ и T(i)> 2 кэВ при ≈ n(b)≈ 3×10¹⁹ m⁻³, что соответствует β0 ≈ 2.5 %. Результаты по ЭЦР-нагреву на Х2-моде, а также по токам увлечения согласуются с теорией. Впервые был успешно реализован сценарий нагрева на О2-моде. Был также получен специфический для стеллараторов режим "электронного корня" удержания. Представлені підсумки першої експериментальної кампанії (ОР1.1) на стелараторі W7-X. Коротко описана специфіка експерименту, методів нагріву та діагностики. Параметри плазми та удержання, отримані в експериментах, перевищили очікувані: T(b)> 8 кеВ та T(i)> 2 > 2 кеВ при ≈ n(b)≈ 3×10¹⁹ m⁻³, що відповідає β0 ≈ 2.5 %. Результати по ЕЦР-нагріву на Х2-моді, а також по струмам захоплення відповідають теорії. Вперше був успішно реалізований сценарій нагріву на О2-моді. Був також успішно реалізований специфічний для стелараторів режим "електронного кореня" утримання.

8. Compatibility of high-Z impurity accumulation with high plasma performance in ECR-heated W7-X plasmas

Author

Zhang, D., Beurskens, M. N. A., Alcusón, J. A., Wurden, G., Buttenschön, B., Jablonski, S., Kubkowska, M., Langenberg, A., Rahbarnia, K., Reimold, F., Pavone, A., Kwak, S., Smith, H. M., Beidler, C. D., Bozhenkov, S. A., Ford, O., Biedermann, C., Brunner, K. J., Burhenn, R., Feng, Y., Fuchert, G., Gao, Y., Geiger, J., Giannone, L., Udo Höfel, Hirsch, M., Huang, Z., Knauer, J., Kornejew, P., Kremeyer, T., Krychowiak, M., König, R., Laqua, H. P., Laube, R., Naujoks, D., Pablant, N., Pasch, E., Penzel, F., Stechow, A., Thomsen, H., Wegner, Th, Weir, G., Winters, V., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

12. Plans for the first plasma operation of Wendelstein 7-X

Author

Pedersen, T. Sunn, Andreeva, T., Bosch, H. -S., Bozhenkov, S., Effenberg, F., Endler, M., Feng, Y., Gates, D. A., Geiger, J., Hartmann, D., Hoelbe, H., Jakubowski, M., Koenig, R., Laqua, H. P., Lazerson, S., Otte, M., Preynas, M., Schmitz, O., Stange, T., Turkin, Y., and W7-X Team

Subjects
operation, stellarator, Wendelstein 7-X, planning, limiter
Abstract

Wendelstein 7-X (W7-X) is currently under commissioning in preparation for its initial plasma operation phase, operation phase 1.1 (OP1.1). This first phase serves primarily to provide an integral commissioning of all major systems needed for plasma operation, as well as systems, such as diagnostics, that need plasma operation to verify their foreseen functions. In OP1.1, W7-X will have a reduced set of in-vessel components. In particular, five graphite limiter stripes replace the later foreseen divertor. This paper describes the expected machine capabilities in OP1.1, as well as a selection of physics topics that can be addressed in OP1.1, despite the simplified configuration and the reduced machine capabilities. Physics topics include the verification and adjustment of the magnetic topology, the testing of the foreseen plasma start-up scenarios and the feed-forward control of plasma density and temperature evolution, as well as more advanced topics such as scrape-off layer (SOL) studies at short connection lengths and transport studies. Plasma operation in OP1.1 will primarily be performed in helium, with a hydrogen plasma phase at the end.

14. MAIN RESULTS OF THE FIRST EXPERIMENTAL CAMPAIGN IN THE STELLARATOR W7-X

Author

Marushchenko, N. B., Dinklage, A., Alonso, A., Baldzuhn, J., Beidler, C. D., Biedermann, C., Blackwell, B., Bozhenkov, S., Brakel, R., Buttenschoen, B., Feng, Y., Fuchert, G., Geiger, J., Hirsch, M., Hoefel, U., Knauer, J., Kraemer-Flecken, A., Langenberg, A., Laqua, H. P., Landreman, M., Maassberg, H., Novimir Pablant, Pasch, E., Rahbarnia, K., Rudischhauser, L., Stange, T., Stephey, L., Trimino-Mora, H., Turkin, Yu, Velasco, J. -L, Wurden, G., Zhang, D., Andreeva, T., Beurskens, M., Blanco, E., Bosch, H. -S, Burhenn, R., Cappa, A., Czarnecka, A., Dostal, M., Drews, P., Endler, M., Estrada, T., Fornal, T., Grulke, O., Hartmann, D., Harris, J. H., Helander, P., Jakubowski, M., Klinger, T., Klose, S., Kocsis, G., Koenig, R., Kornejew, P., Krawczyk, N., Krychowiak, M., Kubkowska, M., Kiazek, Z., Lazerson, S., Liang, Y., Liu, S., Marchuk, O., Marsen, S., Moncada, V., Moseev, D., Naujoks, D., Niemann, H., Otte, M., Pedersen, T. S., Pisano, F., Risse, K., Rummel, T., Schmitz, O., Satake, S., Smith, H., Schroeder, T., Szepesi, T., Thomsen, H., Traverso, P., Tsuchiya, M., Wang, N., Wauters, T., Weir, G., Wolf, R., Yokoyama, M., and X Team, W.

16. 140 GHz high-power gyrotron development for the stellarator W7-X

Author

Dammertz, G., Alberti, S., Bariou, D., Brand, P., Braune, H., Erckmann, V., Gantenbein, G., Giguet, E., Heidinger, R., Hogge, J. P., Kasparek, W., Laqua, H. P., Lievin, C., Leonhardt, W., Michel, G., Muller, G., Neffe, G., Piosczyk, B., Schmid, M., and Thumm, M.

Abstract

Electron cyclotron resonance heating (ECRH) has proven to be one of the most attractive heating schemes for stellarators. Therefore, ECRH was chosen to be the main heating method for the Wendelstein 7-X stellarator (W7-X) now under construction at IPP Greifswald, Germany. A 10 MW ECRH system with continuous wave (CW) possibilities, operating at 140 GHz will be built up to meet the scientific goals of the stellarator. Two prototype gyrotrons with an output power of I MW were developed in collaboration between European research laboratories and European industry (Thales Electron Devices, France). The gyrotrons are equipped with a single-stage depressed collector, an optimised quasi-optical mode converter and a CVD-diamond window. The prototypes have been successfully tested at FZK. With the second one, an output power of 0.89 MW at a pulse duration of 3 min and an output power of 0.54 MW for about 15 min have been obtained. (c) 2005 Elsevier B.V. All rights reserved.

17. Power balance analysis of wendelstein 7-X plasmas using profile diagnostics

Author

Bozhenkov, S. A., Fuchert, G., Niemann, H., Beurskens, M., Feng, Y., Ford, O. P., Geiger, J., Hirsch, M., Höfel, U., Marcin Jakubowski, Knauer, J., Kornejew, P., Langenberg, A., Laqua, H. P., Maassberg, H., Marushchenko, N. B., Moseev, D., Pablant, N., Pasch, E., Rahbarnia, K., Stange, T., Svensson, J., Mora, H. T., Valson, P., Wurden, G., Zhang, D., Wolf, R. C., and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society

18. Electron cyclotron heating for W7-X: Physics and technology

Author

Erckmann, V., Brand, P., Braune, H., Dammertz, G., Gantenbein, G., Kasparek, W., Laqua, H. P., Maassberg, H., Nikolai Marushchenko, Michel, G., Thumm, M., Turkin, Y., Weissgerber, M., Weller, A., W7-X ECRH Team, and IPF Stuttgart

19. Experiments close to the beta-limit in W7-AS

Author

Weller, A., Geiger, J., Werner, A., Zarnstorff, M. C., Nührenberg, C., Sallander, E., Baldzuhn, J., Brakel, R., Burhenn, R., Dinklage, A., Fredrickson, E., Gadelmeier, F., Giannone, L., Grigull, P., Hartmann, D., Jaenicke, R., Klose, S., Knauer, J. P., Könies, A., Kolesnichenko, Ya I., Laqua, H. P., Lutsenko, V. V., Mccormick, K., Monticello, D., Osakabe, M., Pasch, E., Reiman, A., Rust, N., Spong, D. A., Wagner, F., and Yurii Yakovenko

21. Electron Bernstein Wave Core Deposition via O-X-B Double Mode Conversion in TCV

Author

Curchod, L, Pochelon, A, Coda, S, Decker, J, Goodman, T P, Laqua, H P, Moret, J M, Porte, L, Udintsev, V S, and Volpe, F

Subjects
Bernstein, EBW, heating, O-X-B, tokamak, plasma
Abstract

In the first results of electron Bernstein wave heating (EBWH) via O-X-B double mode conversion in a medium aspect ratio tokamak performed in TCV, the total power absorption efficiency was typically 60% and the deposition was made off-axis to avoid the central sawteeth perturbation that would prevent a clear detection of the deposition location. Central power deposition is however needed to maximize the global EBWH effects. Therefore, initial experiments have been started to optimize central deposition using an equatorial rather than poloidally oblique launch. A toroidal field scan provided promising central deposition results within a small database, in preparation for dedicated central high power deposition. The deposition location in presence of strong sawteeth could be determined from the slope break of soft X-ray traces at the EC power switch-ON times, in conditions where usual methods failed. Further analysis of these discharges will be presented. In particular, the difference between the experimental results and the non-relativistic calculations of deposition locations appears more significant than in the earlier off-axis deposition experiments, which provides a good opportunity for the simulation of relativistic ray propagation effects.

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