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1. Tungsten based divertor development for Wendelstein 7-X

Author: Joris Fellinger, M. Richou, G. Ehrke, M. Endler, F. Kunkel, D. Naujoks, Th. Kremeyer, A. Menzel-Barbara, Th. Sieber, J-F. Lobsien, R. Neu, J. Tretter, Z. Wang, J-H. You, H. Greuner, K. Hunger, P. Junghanns, O. Schneider, M. Wirtz, Th. Loewenhoff, A. Houben, A. Litnovsky, P-E. Fraysinnes, P. Emonot, S. Roccella, O. Widlund, B. Končar, and M. Tekavčič
Subjects: Wendelstein 7-X, Divertor, High heat flux, Additive manufacturing, Diffusion welding, Hot isostatic pressing, Nuclear engineering. Atomic power, TK9001-9401
Abstract: Wendelstein 7-X, the world’s largest superconducting stellarator in Greifswald (Germany), started plasma experiments with a water-cooled plasma-facing wall in 2022, allowing for long pulse operation. In parallel, a project was launched in 2021 to develop a W based divertor, replacing the current CFC divertor, to demonstrate plasma performance of a stellarator with a reactor relevant plasma facing materials with low tritium retention. The project consists of two tasks: Based on experience from the previous experimental campaigns and improved physics modelling, the geometry of the plasma-facing surface of the divertor and baffles is optimized to prevent overloads and to improve exhaust. In parallel, the manufacturing technology for a W based target module is qualified.This paper gives a status update of project. It focusses on the conceptual design of a W based target module, the manufacturing technology and its qualification, which is conducted in the framework of the EUROfusion funded WPDIV program. A flat tile design in which a target module is made of a single target element is pursued. The technology must allow for moderate curvatures of the plasma-facing surface to follow the magnetic field lines. The target element is designed for steady state heat loads of 10 MW/m2 (as for the CFC divertor). Target modules of a similar size and weight as for the CFC divertor are assumed (approx.
Published: 2023
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2. Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components

Author: O. Grulke, C. Albert, J.A. Alcuson Belloso, P. Aleynikov, K. Aleynikova, A. Alonso, G. Anda, T. Andreeva, M. Arvanitou, E. Ascasibar, E. Aymerich, K. Avramidis, J.-P. Bähner, S.-G. Baek, M. Balden, J. Baldzuhn, S. Ballinger, M. Banduch, S. Bannmann, A. Bañón Navarro, L. Baylor, C.D. Beidler, M. Beurskens, C. Biedermann, G. Birkenmeier, T. Bluhm, D. Boeckenhoff, D. Boeyaert, D. Bold, M. Borchardt, D. Borodin, H.-S. Bosch, H. Bouvain, S. Bozhenkov, T. Bräuer, H. Braune, C. Brandt, S. Brezinsek, K.J. Brunner, C. Büschel, R. Bussiahn, A. Buzás, B. Buttenschoen, V. Bykov, I. Calvo, A. Cappa, F. Carovani, D. Carralero, A. Carls, B. Carvalho, D. Castaño-Bardawil, N. Chaudhary, I. Chelis, S. Chen, D. Cipciar, J.W. Coenen, G. Conway, M. Cornelissen, Y. Corre, P. Costello, K. Crombe, G. Cseh, B. Csillag, H.I. Cu Castillo, G. Czymek, H. Damm, R.J. Davies, C. Day, S. Degenkolbe, R. De Wolf, W. Dekeyser, A. Demby, P. Despontin, C.P. Dhard, A. Dinklage, F.A. d’Isa, T. Dittmar, M. Dreval, M. Drevlak, P. Drews, J. Droste, D. Dunai, C. Dyhring, P. van Eeten, E. Edlund, M. Endler, D.A. Ennis, F.J. Escoto, M.S. Espinosa, T. Estrada, D. Fehling, L. Feuerstein, J. Fellinger, Y. Feng, D.L.C. Fernando, S. Fischer, E.R. Flom, O. Ford, T. Fornal, J. Frank, H. Frerichs, G. Fuchert, G. Gantenbein, Y. Gao, K. Garcia, I. García-Cortés, J.M. García-Regaña, B. Geiger, J. Geiger, P. Geissler, M. Gerard, G. Godino-Sedano, T. Gonda, A. González, A. Goriaev, D. Gradic, M. Grahl, H. Greuner, E. Grigore, M. Gruca, J.F. Guerrero Arnaiz, V. Haak, L. van Ham, K. Hammond, B. Hamstra, X. Han, S.K. Hansen, J. Harris, D. Hartmann, D. Hathiramani, S. Hegedus, S. Heinrich, P. Helander, F. Henke, S. Henneberg, L. Henschke, M. Hirsch, U. Hoefel, K. Hoefler, S. Hoermann, K.-P. Hollfeld, A. Holtz, D. Höschen, M. Houry, J. Huang, M. Hubeny, K. Hunger, D. Hwangbo, K. Ida, Y. Igitkhanov, S. Illy, Z. Ioannidis, M. Jablczynska, S. Jablonski, B. Jabłoński, B. Jagielski, M. Jakubowski, J. Jelonnek, F. Jenko, J. Jin, A. Johansson, G. Jouniaux, S. Kajita, J.-P. Kallmeyer, U. Kamionka, W. Kasparek, C. Kawan, Ye. O. Kazakov, N. Kenmochi, W. Kernbichler, A.K. Kharwandikar, M. Khokhlov, C. Killer, A. Kirschner, R. Kleiber, C.C. Klepper, T. Klinger, J. Knauer, A. Knieps, M. Kobayashi, G. Kocsis, Y. Kolesnichenko, A. Könies, J. Kontula, P. Kornejew, S.A. Korteweg, J. Koschinsky, J. Koster, Y. Kovtun, A. Krämer-Flecken, M. Krause, T. Kremeyer, L. Krier, D.M. Kriete, M. Krychowiak, I. Ksia¸zek, M. Kubkowska, M.D. Kuczyński, D. Kulla, A. Kumar, T. Kurki-Suonio, I. Kuzmych, S. Kwak, V. Lancelotti, A. Langenberg, H. Laqua, H.P. Laqua, M.R. Larsen, S. Lazerson, C. Lechte, B. Lee, A. LeViness, M. Lewerentz, Y. Liang, L. Liao, A. Litnovsky, J. Liu, J. Loizu, R. Lopez-Cansino, L.D. Lopez Rodriguez, A. Lorenz, R. Lunsford, Y. Luo, V. Lutsenko, N. Maaziz, M. Machielsen, R. Mackenbach, D. Makowski, E. Maragkoudakis, O. Marchuk, M. Markl, S. Marsen, J. Martínez, N. Marushchenko, S. Masuzaki, D.A. Maurer, M. Mayer, K.J. McCarthy, P. McNeely, D. Medina Roque, J. Meineke, S. Meitner, S. vaz Mendes, A. Menzel-Barbara, B. van Milligen, A. Mishchenko, V. Moiseenko, A. Möller, S. Möller, D. Moseev, G. Motojima, S. Mulas, P. Mulholland, M. Nagel, D. Nagy, Y. Narbutt, D. Naujoks, P. Nelde, R. Neu, O. Neubauer, U. Neuner, D. Nicolai, S. Nielsen, C. Nührenberg, R. Ochoukov, G. Offermanns, J. Ongena, J.W. Oosterbeek, M. Otte, N. Pablant, N. Panadero Alvarez, A. Pandey, G. Partesotti, E.A. Pasch, R. Pavlichenko, E. Pawelec, T.S. Pedersen, V. Perseo, B. Peterson, F. Pisano, B. Plaum, G. Plunk, L. Podavini, N.S. Polei, P. Poloskei, S. Ponomarenko, P. Pons-Villalonga, M. Porkolab, J. Proll, M.J. Pueschel, A. Puig Sitjes, R. Ragona, K. Rahbarnia, M. Rasiński, J. Rasmussen, D. Refy, F. Reimold, M. Richou, J.S. Riemann, K. Riße, J. de la Riva Villén, G. Roberg-Clark, E. Rodriguez, V. Rohde, J. Romazanov, T. Romba, D. Rondeshagen, M. Rud, T. Ruess, T. Rummel, A. Runov, C. Ruset, N. Rust, L. Ryc, T. Rzesnicki, M. Salewski, E. Sánchez, L. Sanchis Sanchez, G. Satheeswaran, J. Schacht, E. Scharff, J. Schilling, G. Schlisio, K. Schmid, J.C. Schmitt, O. Schmitz, M. Schneider, M. Van Schoor, T. Schröder, R. Schroeder, B. Schweer, S. Sereda, B. Shanahan, G. Sias, S. Simko, L. Singh, Y. Siusko, C. Slaby, M. Śle¸czka, B.S. Smith, D.R. Smith, H. Smith, M. Spolaore, A. Spring, T. Stange, A. von Stechow, I. Stepanov, M. Stern, U. Stroth, Y. Suzuki, C. Swee, L. Syrocki, T. Szabolics, T. Szepesi, R. Takacs, H. Takahashi, N. Tamura, C. Tantos, J. Terry, S. Thiede, H. Thienpondt, H. Thomsen, M. Thumm, T. Thun, S. Togo, T. Tork, H. Trimino Mora, A. Tsikouras, Y. Turkin, L. Vano, S. Varoutis, M. Vecsei, J.L. Velasco, M. Verstraeten, M. Vervier, E. Viezzer, J. Wagner, E. Wang, F. Wang, M. Wappl, F. Warmer, T. Wegner, Y. Wei, G. Weir, N. Wendler, U. Wenzel, A. White, F. Wilms, T. Windisch, A. Winter, V. Winters, R. Wolf, G. Wurden, P. Xanthopoulos, H.M. Xiang, S. Xu, H. Yamada, J. Yang, R. Yi, M. Yokoyama, B. Zamorski, M. Zanini, M. Zarnstorff, D. Zhang, S. Zhou, J. Zhu, J. Zimmermann, A. Zocco, and S. Zoletnik
Subjects: stellarator, long-pulse operation, magnetic fusion confinement, divertor detachment, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first long-pulse operation campaign. A maximum discharge length of 8 min was achieved with a total heating energy of 1.3 GJ. Safe divertor operation was demonstrated in attached and detached mode. Stable detachment is readily achieved in some magnetic configurations but requires impurity seeding in configurations with small magnetic pitch angle within the edge islands. Progress was made in the characterization of transport mechanisms across edge magnetic islands: Measurement of the potential distribution and flow pattern reveals that the islands are associated with a strong poloidal drift, which leads to rapid convection of energy and particles from the last closed flux surface into the scrape-off layer. Using the upgraded plasma heating systems, advanced heating scenarios were developed, which provide improved energy confinement comparable to the scenario, in which the record triple product for stellarators was achieved in the previous operation campaign. However, a magnetic configuration-dependent critical heating power limit of the electron cyclotron resonance heating was observed. Exceeding the respective power limit leads to a degradation of the confinement.
Published: 2024
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3. Conditions and benefits of X-point radiation for the island divertor

Author: Y. Feng, V. Winters, D. Zhang, J. Geiger, Y. Gao, D. Reiter, P. Helander, C.D. Beidler, M. Endler, D. Gradic, M. Jakubowski, R. König, T. Kremeyer, M. Krychowiak, D. Naujoks, M. Otte, V. Perseo, F. Reimold, G. Schlisio, and the W7-X Team
Subjects: W7-X, island divertor, EMC3-Eirene, detachment stability, X-point radiation, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: We present a method to geometrically quantify the three magnetic island chains with the poloidal mode numbers m = 4, 5, and 6 (referred to in this paper as high-iota, standard, and low-iota islands, respectively), on which the W7-X divertor relies. The focus is on a comparative study of their detachment performance using a series of models of different physical and geometrical complexity, ranging from one- to three-dimensional (1D to 3D). In particular, it aims to identify the key physical elements behind the correlation between impurity radiation and island geometry and the associated detachment stability. Assuming intrinsic carbon as a radiator, we scan the three island chains with the EMC3-Eirene code based on otherwise identical code inputs. We find that the three islands behave differently in the radiation distribution, in the development of the radiation zones during detachment, and in the ‘radiation costs’, defined as the product of impurity and electron density near the last closed flux surface. While the radiation costs for the iota = 5/4 and 5/5 island chains linearly increase with the total radiation, the low-iota island with iota = 5/6 shows a bifurcation behavior in the sense that the radiation costs initially increase and then decrease when the total radiation exceeds a critical level. Consistent with the numerical trends, stable detachment, which is experimentally easy and robust to achieve with the standard iota = 5/5 island chain, remains an experimental challenge with the low-iota configuration. Dedicated numerical experiments show that the recycling neutrals and the ratio of parallel to perpendicular heat transport, which depends closely on the field line pitch, play a significant role in the formation and evolution of the radiation layer. A deeper understanding of the underlying physics relies on simpler models that explain why and how flux expansion can reduce the radiation costs. From these insights, we derive the conditions in which detached plasmas can benefit from the expansion of flux surfaces around the X-point. We show and explain why the current divertor design limits the actual capability of the high-iota configuration and propose solutions. The work is presented within a theoretical/numerical framework but cites relevant experimental evidence to emphasize its practical significance.
Published: 2024
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4. First feedback-controlled divertor detachment in W7-X: Experience from TDU operation and prospects for operation with actively cooled divertor

Author: M. Krychowiak, R. König, T. Barbui, S. Brezinsek, J. Brunner, F. Effenberg, M. Endler, Y. Feng, E. Flom, Y. Gao, D. Gradic, P. Hacker, J.H. Harris, M. Hirsch, U. Höfel, M. Jakubowski, P. Kornejew, M. Otte, A. Pandey, T.S. Pedersen, A. Puig, F. Reimold, O. Schmitz, T. Schröder, V. Winters, and D. Zhang
Subjects: Plasma control, Detachment, Plasma fuelling and seeding, Nuclear engineering. Atomic power, TK9001-9401
Abstract: In the last experimental campaign (OP1.2b) of the stellarator Wendelstein 7-X (W7-X), boronisation as a mean for first wall conditioning was applied for the first time which led to strongly reduced impurity fluxes from plasma-facing components. Thermal detachment at the uncooled target plates of the test divertor unit (TDU) was reached at higher plasma densities and was accompanied by high recycling of neutrals at the target plate [1], [2]. A feedback control system was established in W7-X to actively control the gas injection (actuator) for plasma fuelling and impurity seeding [3] through the divertors. It allowed very successful stabilisation of the detached plasma condition state as well as mitigation of thermal overloads to some baffle tiles. Different routinely available diagnostic signals were used as input parameters (sensors). We describe the setup of the feedback control system, its performance and provide some example results with the main focus on the development of the control scheme which led to the detachment stabilisation over the entire longest (30 s) high-power discharge at W7-X so far. In view of the achieved very successful detachment stabilisation and the necessity to include simultaneous optimisation of the core performance in the future, the feedback control system is being upgraded for the upcoming campaign (OP2.1) in which the water cooled and hereby inherently steady-state capable divertor has been currently installed. The prospects and some experiment ideas for active detachment control are discussed.
Published: 2023
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5. Immediate IUD insertion after second trimester abortion: implications for service delivery

Author: O. Somefun, D. Constant, and M. Endler
Subjects: Second trimester medical abortion, Copper IUD, Immediate insertion, Implications for service delivery, South Africa, Public aspects of medicine, RA1-1270
Abstract: Abstract Background The availability of modern contraception including long-acting reversible contraceptives (LARC), is a fundamental component of postabortion care. Findings from a recent randomized controlled trial (RCT) in South Africa comparing immediate to delayed insertion of the copper intrauterine device (IUD) after medical abortion (MA) at 17-20 gestational weeks showed that immediate insertion resulted in higher IUD use at 6 weeks postabortion, but that expulsion rates were significantly higher than for delayed insertion. This study aims to explore barriers, facilitators, and context-specific factors relevant to the implementation of immediate IUD provision after second trimester medical abortion. Methods We performed a qualitative study alongside the RCT in which we conducted in-depth interviews with 14 staff providing healthcare to study participants and 24 study participants. Research questions explored barriers and facilitators to implementation of immediate IUD insertion, contraceptive decision-making, and the impact of context and supplementary trial activities on service provision. Interviews were recorded and transcribed, with translation into English if needed. We performed a triangulated thematic analysis at the level of the transcribed interview text. Results Contraceptive counselling at the abortion facility by a study nurse improved knowledge, corrected misconceptions, and increased demand for the IUD postabortion. Women expressed a clear preference for immediate insertion. Convenience, protection from pregnancy and privacy issues were paramount and women expressed preference for engagement with staff who knew their abortion history, and with whom they had an established connection. Doctors and nurses were generally in favour of immediate insertion and said it could be incorporated into standard care if women wanted this. This contrasted with the need for interventions by the research team to reinforce adherence by staff to provide contraception as allocated during the trial. Conclusions Women and staff favour immediate IUD insertion after second trimester medical abortion, but service delivery may require structures that ensure timely insertion postabortion, continuity of care, communication that mitigates loss to follow-up and training of staff to ensure competence.
Published: 2021
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6. Edge plasma measurements on the OP 1.2a divertor plasmas at W7-X using the combined probe

Author: P. Drews, C. Killer, J. Cosfeld, A. Knieps, S. Brezinsek, M. Jakubowski, C. Brandt, S. Bozhenkov, A. Dinklage, J. Cai, M. Endler, K. Hammond, M. Henkel, Y. Gao, J. Geiger, O. Grulke, D. Höschen, R. König, A. Krämer-Flecken, Y. Liang, Y. Li, S. Liu, H. Niemann, D. Nicolai, O. Neubauer, U. Neuner, M. Rack, K. Rahbarnia, L. Rudischhauser, N. Sandri, G. Satheeswaran, S. Schilling, H. Thomsen, T. Windisch, and S. Sereda
Subjects: Nuclear engineering. Atomic power, TK9001-9401
Abstract: During its second operational campaign (OP 1.2a) W7-X operated with an edge island divertor. Much higher densities (1020m−3) than in to the previous, limiter campaign were achieved. In order to asses this improved performance and the nature of transport with regard to the expected higher densities and other parameters such as the electron and ion temperature, the electric field and plasma flow, measurements at the plasma edge were conducted with reciprocating probe, mounted on a Manipulator. The probe contains a set of Langmuir pins, Mach probes, compensation coils and a set of 3D pick up coils for the measurement of the local magnetic field and fluctuations, and an ion sensitive probe. It has been observed, in addition to differences due to the magnetic configurations, that the magnetic topology is sensitive to the plasma conditions, especially to changes due to a evolving toroidal plasma current. Measurements from divertor cameras showed that an increasing toroidal current in the standard configuration broadened the heat flux and shifted the strike line considerably. These down-stream observation can be complemented with the measurements at the mid-plane with the manipulator mounted probes. During the experiments the edge island remnant was identified with the measured edge plasma profiles and compared with the predictions from the field line tracing code. Those electron densities and temperatures have been used as an input for understanding edge transport with the EMC3-EIRENE modeling. The results from EMC3-EIRENE also help improve the caculated density profiles, since the modelling provides a profile of the effective charge Zeff. Keywords: W7-X, Langmuir probes, Magnetic islands, Plasma edge transport
Published: 2019
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7. Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Author: Thomas Sunn Pedersen, I. Abramovic, P. Agostinetti, M. Agredano Torres, S. Äkäslompolo, J. Alcuson Belloso, P. Aleynikov, K. Aleynikova, M. Alhashimi, A. Ali, N. Allen, A. Alonso, G. Anda, T. Andreeva, C. Angioni, A. Arkhipov, A. Arnold, W. Asad, E. Ascasibar, M.-H. Aumeunier, K. Avramidis, E. Aymerich, S.-G. Baek, J. Bähner, A. Baillod, M. Balden, J. Baldzuhn, S. Ballinger, M. Banduch, S. Bannmann, A. Banon Navarro, A. Bañón Navarro, T. Barbui, C. Beidler, C. Belafdil, A. Bencze, A. Benndorf, M. Beurskens, C. Biedermann, O. Biletskyi, B. Blackwell, M. Blatzheim, T. Bluhm, D. Böckenhoff, G. Bongiovi, M. Borchardt, D. Borodin, J. Boscary, H. Bosch, T. Bosmann, B. Böswirth, L. Böttger, A. Bottino, S. Bozhenkov, R. Brakel, C. Brandt, T. Bräuer, H. Braune, S. Brezinsek, K. Brunner, S. Buller, R. Burhenn, R. Bussiahn, B. Buttenschön, A. Buzás, V. Bykov, I. Calvo, K. Camacho Mata, I. Caminal, B. Cannas, A. Cappa, A. Carls, F. Carovani, M. Carr, D. Carralero, B. Carvalho, J. Casas, D. Castano-Bardawil, F. Castejon, N. Chaudhary, I. Chelis, A. Chomiczewska, J.W. Coenen, M. Cole, F. Cordella, Y. Corre, K. Crombe, G. Cseh, B. Csillag, H. Damm, C. Day, M. de Baar, E. De la Cal, S. Degenkolbe, A. Demby, S. Denk, C. Dhard, A. Di Siena, A. Dinklage, T. Dittmar, M. Dreval, M. Drevlak, P. Drewelow, P. Drews, D. Dunai, E. Edlund, F. Effenberg, G. Ehrke, M. Endler, D.A. Ennis, F.J. Escoto, T. Estrada, E. Fable, N. Fahrenkamp, A. Fanni, J. Faustin, J. Fellinger, Y. Feng, W. Figacz, E. Flom, O. Ford, T. Fornal, H. Frerichs, S. Freundt, G. Fuchert, M. Fukuyama, F. Füllenbach, G. Gantenbein, Y. Gao, K. Garcia, J.M. García Regaña, I. García-Cortés, J. Gaspar, D.A. Gates, J. Geiger, B. Geiger, L. Giudicotti, A. González, A. Goriaev, D. Gradic, M. Grahl, J.P. Graves, J. Green, E. Grelier, H. Greuner, S. Groß, H. Grote, M. Groth, M. Gruca, O. Grulke, M. Grün, J. Guerrero Arnaiz, S. Günter, V. Haak, M. Haas, P. Hacker, A. Hakola, A. Hallenbert, K. Hammond, X. Han, S.K. Hansen, J.H. Harris, H. Hartfuß, D. Hartmann, D. Hathiramani, R. Hatzky, J. Hawke, S. Hegedus, B. Hein, B. Heinemann, P. Helander, S. Henneberg, U. Hergenhahn, C. Hidalgo, F. Hindenlang, M. Hirsch, U. Höfel, K.P. Hollfeld, A. Holtz, D. Hopf, D. Höschen, M. Houry, J. Howard, X. Huang, M. Hubeny, S. Hudson, K. Ida, Y. Igitkhanov, V. Igochine, S. Illy, C. Ionita-Schrittwieser, M. Isobe, M. Jabłczyńska, S. Jablonski, B. Jagielski, M. Jakubowski, A. Jansen van Vuuren, J. Jelonnek, F. Jenko, T. Jensen, H. Jenzsch, P. Junghanns, J. Kaczmarczyk, J. Kallmeyer, U. Kamionka, M. Kandler, S. Kasilov, Y. Kazakov, D. Kennedy, A. Kharwandikar, M. Khokhlov, C. Kiefer, C. Killer, A. Kirschner, R. Kleiber, T. Klinger, S. Klose, J. Knauer, A. Knieps, F. Köchl, G. Kocsis, Ya.I. Kolesnichenko, A. Könies, R. König, J. Kontula, P. Kornejew, J. Koschinsky, M.M. Kozulia, A. Krämer-Flecken, R. Krampitz, M. Krause, N. Krawczyk, T. Kremeyer, L. Krier, D.M. Kriete, M. Krychowiak, I. Ksiazek, M. Kubkowska, M. Kuczynski, G. Kühner, A. Kumar, T. Kurki-Suonio, S. Kwak, M. Landreman, P.T. Lang, A. Langenberg, H.P. Laqua, H. Laqua, R. Laube, S. Lazerson, M. Lewerentz, C. Li, Y. Liang, Ch. Linsmeier, J. Lion, A. Litnovsky, S. Liu, J. Lobsien, J. Loizu, J. Lore, A. Lorenz, U. Losada, F. Louche, R. Lunsford, V. Lutsenko, M. Machielsen, F. Mackel, J. Maisano-Brown, O. Maj, D. Makowski, G. Manduchi, E. Maragkoudakis, O. Marchuk, S. Marsen, E. Martines, J. Martinez-Fernandez, M. Marushchenko, S. Masuzaki, D. Maurer, M. Mayer, K.J. McCarthy, O. Mccormack, P. McNeely, H. Meister, B. Mendelevitch, S. Mendes, A. Merlo, A. Messian, A. Mielczarek, O. Mishchenko, B. Missal, R. Mitteau, V.E. Moiseenko, A. Mollen, V. Moncada, T. Mönnich, T. Morisaki, D. Moseev, G. Motojima, S. Mulas, M. Mulsow, M. Nagel, D. Naujoks, V. Naulin, T. Neelis, H. Neilson, R. Neu, O. Neubauer, U. Neuner, D. Nicolai, S.K. Nielsen, H. Niemann, T. Nishiza, T. Nishizawa, C. Nührenberg, R. Ochoukov, J. Oelmann, G. Offermanns, K. Ogawa, S. Okamura, J. Ölmanns, J. Ongena, J. Oosterbeek, M. Otte, N. Pablant, N. Panadero Alvarez, A. Pandey, E. Pasch, R. Pavlichenko, A. Pavone, E. Pawelec, G. Pechstein, G. Pelka, V. Perseo, B. Peterson, D. Pilopp, S. Pingel, F. Pisano, B. Plöckl, G. Plunk, P. Pölöskei, B. Pompe, A. Popov, M. Porkolab, J. Proll, M.J. Pueschel, M.-E. Puiatti, A. Puig Sitjes, F. Purps, K. Rahbarnia, M. Rasiński, J. Rasmussen, A. Reiman, F. Reimold, M. Reisner, D. Reiter, M. Richou, R. Riedl, J. Riemann, K. Riße, G. Roberg-Clark, V. Rohde, J. Romazanov, D. Rondeshagen, P. Rong, L. Rudischhauser, T. Rummel, K. Rummel, A. Runov, N. Rust, L. Ryc, P. Salembier, M. Salewski, E. Sanchez, S. Satake, G. Satheeswaran, J. Schacht, E. Scharff, F. Schauer, J. Schilling, G. Schlisio, K. Schmid, J. Schmitt, O. Schmitz, W. Schneider, M. Schneider, P. Schneider, R. Schrittwieser, T. Schröder, M. Schröder, R. Schroeder, B. Schweer, D. Schwörer, E. Scott, B. Shanahan, G. Sias, P. Sichta, M. Singer, P. Sinha, S. Sipliä, C. Slaby, M. Sleczka, H. Smith, J. Smoniewski, E. Sonnendrücker, M. Spolaore, A. Spring, R. Stadler, D. Stańczak, T. Stange, I. Stepanov, L. Stephey, J. Stober, U. Stroth, E. Strumberger, C. Suzuki, Y. Suzuki, J. Svensson, T. Szabolics, T. Szepesi, M. Szücs, F.L. Tabarés, N. Tamura, A. Tancetti, C. Tantos, J. Terry, H. Thienpondt, H. Thomsen, M. Thumm, J.M. Travere, P. Traverso, J. Tretter, E. Trier, H. Trimino Mora, T. Tsujimura, Y. Turkin, A. Tykhyi, B. Unterberg, P. van Eeten, B.Ph. van Milligen, M. van Schoor, L. Vano, S. Varoutis, M. Vecsei, L. Vela, J.L. Velasco, M. Vervier, N. Vianello, H. Viebke, R. Vilbrandt, G. Vogel, N. Vogt, C. Volkhausen, A. von Stechow, F. Wagner, E. Wang, H. Wang, F. Warmer, T. Wauters, L. Wegener, T. Wegner, G. Weir, U. Wenzel, A. White, F. Wilde, F. Wilms, T. Windisch, M. Winkler, A. Winter, V. Winters, R. Wolf, A.M. Wright, G.A. Wurden, P. Xanthopoulos, S. Xu, H. Yamada, H. Yamaguchi, M. Yokoyama, M. Yoshinuma, Q. Yu, M. Zamanov, M. Zanini, M. Zarnstorff, D. Zhang, S. Zhou, J. Zhu, C. Zhu, M. Zilker, A. Zocco, H. Zohm, S. Zoletnik, L. Zsuga, Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya. GPI - Grup de Processament d'Imatge i Vídeo, Universitat Politècnica de Catalunya. GREO - Grup de Recerca en Enginyeria Òptica, 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, Fusion and Plasma Physics, Department of Applied Physics, National Institute for Fusion Science, Aalto-yliopisto, Aalto University, Science and Technology of Nuclear Fusion, Group Heemels, Control Systems Technology, and Turbulence in Fusion Plasmas
Subjects: Magnetic confinement, Nuclear and High Energy Physics, Technology, Materials science, Detachment, Nuclear engineering, Física::Física de partícules [Àrees temàtiques de la UPC], Imatges -- Processament, stellarator, Divertor, Image processing, Physics::Plasma Physics, divertor, Wendelstein 7-X, ddc:530, FIS/03 - FISICA DELLA MATERIA, Neoclassical optimization, Stellarators, Reactors de fusió, magnetic confinement, Enginyeria de la telecomunicació::Processament del senyal::Processament de la imatge i del senyal vídeo [Àrees temàtiques de la UPC], Condensed Matter Physics, ddc, Fusion reactors, Physics and Astronomy, detachment, neoclassical optimization, ddc:620, ddc:600, Paper, FEC 2020 Summaries and Overviews
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. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under Grant Agreement No. 633053. Peer Reviewed Article signat per 497 autors/es: Thomas Sunn Pedersen1,2,∗ , I. Abramovic3, P. Agostinetti4, M. Agredano Torres1, S. Äkäslompolo1, J. Alcuson Belloso1, P. Aleynikov1, K. Aleynikova1, M. Alhashimi1, A. Ali1, N. Allen5, A. Alonso6, G. Anda7, T. Andreeva1, C. Angioni8, A. Arkhipov8, A. Arnold1, W. Asad8, E. Ascasibar6, M.-H. Aumeunier9, K. Avramidis10, E. Aymerich11, S.-G. Baek3, J. Bähner1, A. Baillod12, M. Balden1, M. Balden8, J. Baldzuhn1, S. Ballinger3, M. Banduch1, S. Bannmann1, A. Banon Navarro8, A. Bañon Navarro ´ 1, T. Barbui13, C. Beidler1, C. Belafdil9, A. Bencze7, A. Benndorf1, M. Beurskens1, C. Biedermann1, O. Biletskyi14, B. Blackwell15, M. Blatzheim1, T. Bluhm1, D. Böckenhoff1, G. Bongiovi16, M. Borchardt1, D. Borodin17, J. Boscary8, H. Bosch1,18, T. Bosmann19, B. Böswirth8, L. Böttger1, A. Bottino8, S. Bozhenkov1, R. Brakel1, C. Brandt1, T. Bräuer1, H. Braune1, S. Brezinsek17, K. Brunner1, S. Buller1, R. Burhenn1, R. Bussiahn1, B. Buttenschön1, A. Buzás7, V. Bykov1, I. Calvo6, K. Camacho Mata1, I. Caminal20, B. Cannas11, A. Cappa6, A. Carls1, F. Carovani1, M. Carr21, D. Carralero6, B. Carvalho22, J. Casas20, D. Castano-Bardawil17, F. Castejon6, N. Chaudhary1, I. Chelis23, A. Chomiczewska24, J.W. Coenen13,17, M. Cole1, F. Cordella25, Y. Corre9, K. Crombe26, G. Cseh7, B. Csillag7, H. Damm1, C. Day10, M. de Baar27, E. De la Cal6, S. Degenkolbe1, A. Demby13, S. Denk3, C. Dhard1, A. Di Siena8,28, A. Dinklage12, T. Dittmar17, M. Dreval14, M. Drevlak1, P. Drewelow1, P. Drews17, D. Dunai7, E. Edlund3, F. Effenberg29, G. Ehrke1, M. Endler1, D.A. Ennis5, F.J. Escoto6, T. Estrada6, E. Fable8, N. Fahrenkamp1, A. Fanni11, J. Faustin1, J. Fellinger1, Y. Feng1, W. Figacz4, E. Flom13, O. Ford1, T. Fornal24, H. Frerichs13, S. Freundt1, G. Fuchert1, M. Fukuyama30, F. Füllenbach1, G. Gantenbein10, Y. Gao1, K. Garcia13, J.M. García Regaña6, I. García-Cortés6, J. Gaspar31, D.A. Gates29, J. Geiger1, B. Geiger13, L. Giudicotti32, A. González6, A. Goriaev26,33, D. Gradic1, M. Grahl1, J.P. Graves12, J. Green13, E. Grelier9, H. Greuner8, S. Groß1, H. Grote1, M. Groth34, M. Gruca24, O. Grulke1,35, M. Grün1, J. Guerrero Arnaiz1, S. Günter8, V. Haak1, M. Haas1, P. Hacker1, A. Hakola36, A. Hallenbert1, K. Hammond29, X. Han17,37, S.K. Hansen3, J.H. Harris38, H. Hartfuß1, D. Hartmann1, D. Hathiramani1, R. Hatzky8, J. Hawke39, S. Hegedus7, B. Hein8, B. Heinemann8, P. Helander12, S. Henneberg1, U. Hergenhahn8,40, C. Hidalgo6, F. Hindenlang8, M. Hirsch1, U. Höfel1, K.P. Hollfeld17, A. Holtz1, D. Hopf8, D. Höschen17, M. Houry9, J. Howard19, X. Huang41, M. Hubeny17, S. Hudson29, K. Ida9, Y. Igitkhanov10, V. Igochine8, S. Illy10, C. Ionita-Schrittwieser42, M. Isobe39, M. Jabłczynska ´ 24, S. Jablonski24, B. Jagielski1, M. Jakubowski1, A. 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Maisano-Brown3, O. Maj8, D. Makowski49, G. Manduchi50, E. Maragkoudakis6, O. Marchuk17, S. Marsen1, E. Martines4, J. Martinez-Fernandez6, M. Marushchenko1, S. Masuzaki41, D. Maurer5, M. Mayer8, K.J. McCarthy6, O. Mccormack4, P. McNeely1, H. Meister8, B. Mendelevitch8, S. Mendes1, A. Merlo1, A. Messian26, A. Mielczarek49, O. Mishchenko1, B. Missal1, R. Mitteau9, V.E. Moiseenko14, A. Mollen1, V. Moncada9, T. Mönnich1, T. Morisaki41, D. Moseev1, G. Motojima41, S. Mulas6, M. Mulsow1, M. Nagel1, D. Naujoks1, V. Naulin35, T. Neelis19, H. Neilson29, R. Neu8, O. Neubauer17, U. Neuner1, D. Nicolai17, S.K. Nielsen35, H. Niemann1, T. Nishiza1, T. Nishizawa1, T. Nishizawa8, C. Nührenberg1, R. Ochoukov8, J. Oelmann17, G. Offermanns17 K. Ogawa41, S. Okamura41, J. Ölmanns17, J. Ongena26, J. Oosterbeek1, M. Otte1, N. Pablant29, N. Panadero Alvarez6, N. Panadero Alvarez6, A. Pandey1, E. Pasch1, R. Pavlichenko14, A. Pavone1, E. Pawelec46, G. Pechstein1, G. Pelka24, V. Perseo1, B. Peterson41, D. Pilopp1, S. Pingel1, F. Pisano11, B. Plöckl8, G. Plunk1, P. Pölöskei1, B. Pompe2, A. Popov51, M. Porkolab3, J. Proll19, M.J. Pueschel19,27, M.-E. Puiatti52, A. Puig Sitjes1, F. Purps1, K. Rahbarnia1, M. Rasinski ´ 17, J. Rasmussen35, A. Reiman29, F. Reimold1, M. Reisner8, D. Reiter17, M. Richou9, R. Riedl8, J. Riemann1, K. Riße1, G. Roberg-Clark1, V. Rohde8, J. Romazanov17, D. Rondeshagen1, P. Rong1, L. Rudischhauser1, T. Rummel1, K. Rummel1, A. Runov1, N. Rust1, L. Ryc24, P. Salembier20, M. Salewski35, E. Sanchez6, S. Satake41, G. Satheeswaran17, J. Schacht1, E. Scharff1, F. Schauer8, J. Schilling1, G. Schlisio1, K. Schmid8, J. Schmitt5, O. Schmitz13, W. Schneider1, M. Schneider1, P. Schneider8, R. Schrittwieser42, T. Schröder1, M. Schröder1, R. Schroeder1, B. Schweer26, D. Schwörer1, E. Scott1, E. Scott8, B. Shanahan1, G. Sias11, P. Sichta29, M. Singer1, P. Sinha29, S. Sipliä34, C. Slaby1, M. Sleczka53, H. Smith1, J. Smoniewski54, E. Sonnendrücker8, M. Spolaore4, A. Spring1, R. Stadler8, D. Stanczak24, T. Stange1, I. Stepanov26, L. Stephey13, J. Stober8, U. Stroth8,55, E. Strumberger8, C. Suzuki41, Y. Suzuki41, J. Svensson1, T. Szabolics7, T. Szepesi7, M. Szücs7, F.L. Tabares6, N. Tamura41, A. Tancetti35, C. Tantos10, J. Terry3, H. Thienpondt6, H. Thomsen1, M. Thumm10, J.M. Travere9, P. Traverso5, J. Tretter8, E. Trier8, H. Trimino Mora1, T. Tsujimura41, Y. Turkin1, A. Tykhyi45, B. Unterberg17, P. van Eeten1, B.Ph. van Milligen6, M. van Schoor26, L. Vano1, S. Varoutis10, M. Vecsei7, L. Vela56, J.L. Velasco6, M. Vervier17, N. Vianello50, H. Viebke1, R. Vilbrandt1, G. Vogel8, N. Vogt1, C. Volkhausen1, A. von Stechow1, F. Wagner1, E. Wang17, H. Wang57, F. Warmer1, T. Wauters26, L. Wegener1, T. Wegner1, G. Weir1, U. Wenzel1, A. White3, F. Wilde1, F. Wilms1, T. Windisch1, M. Winkler1, A. Winter1, V. Winters1, R. Wolf118, A.M. Wright29, G.A. Wurden39, P. Xanthopoulos1, S. Xu17, H. Yamada58, H. Yamaguchi41, M. Yokoyama41, M. Yoshinuma41, Q. Yu8, M. Zamanov14, M. Zanini1, M. Zarnstorff29, D. Zhang1, S. Zhou17, J. Zhu1, C. Zhu29, M. Zilker8, A. Zocco1, H. Zohm8, S. Zoletnik7 and L. Zsuga7 // 1 Max Planck Institute for Plasma Physics, Garching and Greifswald, Germany: 2 University of Greifswald, Greifswald, Germany; 3 Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, United States of America; 4 Consorzio RFX, Corso Stati Uniti, 4-35127 Padova, Italy; 5 Auburn University, Auburn, AL 36849, United States of America; 6 CIEMAT, Avenida Complutense, 40, 28040 Madrid, Spain; 7 Center for Energy Research, Konkoly-Thegeut 29-33, 1121 Budapest, Hungary; 8 Max-Planck-Institute for Plasma Physics, Boltzmannstraße 2, 85748 Garching bei München, Germany; 9 CEA Cadarache, 13115 Saint-Paul-lez-Durance, France; 10 Karlsruhe Institute of Technology, Kaiserstr. 12, 76131 Karlsruhe, Germany; 11 University of Cagliari, Via Universita, 40, 09124 Cagliari, Italy; 12 École Polytechnique Fédérale de Lausanne, Swiss Plasma Center, CH-1015 Lausanne, Switzerland; 13 University of Wisconsin–Madison, Engineering Drive, Madison, WI 53706, United States of America; 14 Institute of Plasma Physics, National Science Center ‘Kharkiv Institute of Physics and Technology’, Kharkiv, Ukraine; 15 The Australian National University, Acton ACT 2601, Canberra, Australia; 16 Department of Engineering, University of Palermo, Viale delle Scienze, Edificio 6, Palermo, 90128, Italy; 17 Forschungszentrum Jülich GmbH, Institut für Energie-und Klimaforschung—Plasmaphysik, 52425 Jülich, Germany; 18 Technical University of Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany; 19 Eindhoven University of Technology, 5600 MB Eindhoven, Netherlands; 20 Universitat Politècnica de Catalunya. BarcelonaTech, C. Jordi Girona, 31, 08034 Barcelona, Spain; 21 Culham Center for Fusion Energy, Abingdon OX14 3EB, United Kingdom; 22 Instituto de Plasmas e Fusao Nuclear, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; 23 Department of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece; 24 Institute of Plasma Physics and Laser Microfusion, 23 Hery Str., 01-497 Warsaw, Poland; 25 ENEA—Centro Ricerche Frascati, Via Enrico Fermi, 45, 00044 Frascati RM, Italy; 26 Laboratory for Plasma Physics, LPP-ERM/KMS, TEC Partner, B-1000 Brussels, Belgium; 27 Dutch Institute for Fundamental Energy Research, PO Box 6336, 5600 HH Eindhoven, Netherlands; 28 University of Texas, Austin, TX, United States of America; 29 Princeton Plasma Physics Laboratory, Princeton, NJ 08543, United States of America; 30 Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan; 31 Aix-Marseille University, Jardin du Pharo, 58 Boulevard Charles Livon, 13007, Marseille, France; 32 Department of Physics and Astronomy, Padova University, Via Marzolo 8, 35131 Padova, Italy; 33 Department of Applied Physics, Ghent University, Sint-Pietersnieuwstraat 41 B4, 9000 Ghent, Belgium; 34 Aalto University, 02150 Espoo, Finland; 35 Department of Physics, Technical University of Denmark, Anker Engelunds Vej, 2800 Kgs Lyngby, Denmark; 36 VTT Technical Research Center of Finland Ltd., PO Box 1000, FI-02044 VTT, Finland; 37 Institute of Plasma Physics, Chinese Academy of Sciences, 230031 Hefei, Anhui, China; 38 Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37830, United States of America; 39 Los Alamos National Laboratory, NM 87545, United States of America; 40 Fritz-Haber-Institut der Max-Planck-Gesellschaft, 14195 Berlin, Germany; 41 National Institute for Fusion Science, National Institutes of Natural Sciences, 322-6 Oroshi-cho, Toki, Gifu Prefecture 509-5292, Japan; 42 Institute for Ion Physics and Applied Physics, University of Innsbruck, Innsbruck, Austria; 43 Graz University of Technology, Rechbauerstraße 12, 8010 GRAZ, Austria; 44 Austrian Academy of Science, Doktor-Ignaz-Seipel-Platz 2, 1010 Wien, Austria; 45 Institute for Nuclear Research, prospekt Nauky 47, Kyiv 03028, Ukraine; 46 University of Opole, plac Kopernika 11a, 45-001 Opole, Poland; 47 University of Maryland, Paint Branch Drive, College Park, MA 20742, United States of America; 48 National Research Nuclear University MEPhI, 115409 Moscow, Russian Federation; 49 Department of Microelectronics and Computer Science, Lodz University of Technology, Wolczanska 221/223, 90-924 Lodz, Poland; 50 Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro, 7, 00185 Roma, Italy; 51 Ioffe Physical-Technical Institute of the Russian Academy of Sciences, 26 Politekhnicheskaya, St Petersburg 194021, Russian Federation; 52 Istituto di Fisica del Plasma Piero Caldirola, Via Roberto Cozzi, 53, 20125 Milano, Italy; 53 University of Szczecin, 70-453, aleja Papieza Jana Pawła II 22A, Szczecin, Poland; 54 Lawrence University, 711 E Boldt Way, Appleton, WI 54911, United States of America; 55 Physik-Department E28, Technische Universität München, 85747 Garching, Germany; 56 Universidad Carlos III de Madrid, Av. de la Universidad, 30 Madrid, Spain; 57 Yale University, New Haven, CT 06520, United States of America; 58 University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chhiab 277-0882, Japan Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant::7.a - Per a 2030, augmentar la cooperació internacional per tal de facilitar l’accés a la investigació i a les tecnologies energètiques no contaminants, incloses les fonts d’energia renovables, l’eficiència energètica i les tecnologies de combustibles fòssils avançades i menys contaminants, i promoure la inversió en infraestructures energètiques i tecnologies d’energia no contaminant
Published: 2022
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8. Anisotropic diffusion as a proxy model for the estimation of heat-loads on plasma-facing components

Author: A Knieps, Y Liang, P Drews, M Endler, Y Gao, J Geiger, M Jakubowski, R Koenig, H Niemann, F Q Wang, S Xu, and S Zhou
Subjects: Nuclear Energy and Engineering, ddc:620, Condensed Matter Physics
Abstract: To facilitate the estimation of heat loads on plasma-facing components in fusion devices in various different magnetic geometries, a heat load proxy model was developed based on anisotropic diffusion. In this work, this model is compared to the so-called field-line diffusion approach. To facilitate the evaluation of these models, a novel synthetic camera-based approach for obtaining heat load distributions from Monte Carlo samples was also developed and implemented. With the assistance of this synthetic camera, heat load predictions for the Wendelstein 7-X divertor were obtained and compared with infrared camera observations. It was found that the anisotropic diffusion-based model achieved a closer match to infrared camera observations, while still being suitable in computational effort for large magnetic configuration database scans.
Published: 2022
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9. Overview of first Wendelstein 7-X high-performance operation

Author: V. Moncada, S. C. Liu, M. Winkler, P. Pölöskei, A. Tancetti, Naoki Tamura, H. Neilson, M. Krychowiak, Michael Drevlak, K. H. Schlüter, S. A. Henneberg, R. Vilbrandt, N. A. Pablant, M. Schröder, B. van Milligen, Bernd Heinemann, K. Rummel, Jonathan Schilling, Torsten Stange, G. Orozco, Christian Brandt, N. Krawczyk, Suguru Masuzaki, Yunfeng Liang, T. Estrada, Wolfgang Biel, J. H. Harris, B. Unterberg, M. Sleczka, M. Marushchenko, R. Lang, N. Rust, J. P. Kallmeyer, Laurie Stephey, P. Aleynikov, E. Blanco, Hans-Stephan Bosch, B. Buttenschön, D. Mellein, B. Shanahan, M. Vervier, M. Yokoyama, C. Suzuki, Seung Gyou Baek, A. Lücke, Felix Schauer, Ya. I. Kolesnichenko, V. Borsuk, Th. Rummel, B. Gonçalves, R. König, H. P. Laqua, G. Ehrke, K. J. McCarthy, Manfred Zilker, Venanzio Giannella, O. P. Ford, E. Flom, S. Murakami, Andreas Schlaich, P. Xanthopoulos, M. Zanini, E. Ascasíbar, C. Nührenberg, A. Carls, H. Viebke, Y. Feng, A. da Molin, H. Hunger, S. Paqay, Y. Wei, M. Blatzheim, M. W. Jakubowski, F. Köster, T. Wauters, J.C. Schmitt, M. Hubeny, P. van Eeten, H. Damm, Joris Fellinger, Gábor Cseh, Christoph Biedermann, G. Claps, L. Rudischhauser, R. Stadler, J. Mittelstaedt, Matteo Zuin, Z. Szökefalvi-Nagy, M. Knaup, Ch. Linsmeier, Francisco Castejón, J. P. Koschinsky, Bernardo B. Carvalho, L. Wegener, C. Guerard, J.M. Hernández Sánchez, B. Mendelevitch, A. Grosman, S. Pingel, Horacio Fernandes, M. Endler, N. Vianello, Jörg Schacht, Anett Spring, Yu Gao, V. Rohde, Samuel Lazerson, J.H. Matthew, W. Kasparek, R. Neu, R. Burhenn, N. Panadero, Jörg Weggen, P.A. Kurz, Walter H. Fietz, R. Schroeder, Andrea Pavone, G. Offermanns, Ryo Yasuhara, P. Sinha, Massimiliano Romé, José Luis Velasco, Carsten Killer, P. Drewelow, X. Han, T. Windisch, Nengchao Wang, Axel Könies, E.M. Edlund, K. P. Hollfeld, K. Aleynikova, Malte Henkel, Detlev Reiter, S. Brezinsek, Z. Huang, Heinz Grote, S. Langish, Matthias Otte, Alessandro Zocco, Daniel Papenfuß, G. Satheeswaran, Monika Kubkowska, S. Obermayer, G. A. Wurden, Carsten Lechte, F. Wagner, M. Gruca, H. Zhang, Olaf Neubauer, Peter Traverso, T. Ngo, V. Bykov, E. Sánchez, Matt Landreman, Dirk Naujoks, I. Vakulchyk, Andreas Langenberg, E. Wang, B. Hein, I. Ksiazek, S. Valet, Mark Cianciosa, G. Schlisio, Taina Kurki-Suonio, Oliver Schmitz, Adnan Ali, F. Reimold, Shinsuke Satake, Luis Vela Vela, C. Slaby, F. Remppel, David Gates, S. Schmuck, B. Roth, Zhirui Wang, Heinrich P. Laqua, F. Schluck, Olaf Grulke, S. Wadle, A. Runov, Manfred Thumm, Florian Effenberg, G. Fuchert, A. Vorköper, M. Banduch, Jonathan T. Green, J. Nührenberg, F. V. Chernyshev, H. Braune, Ewa Pawelec, David Maurer, A. Winter, A. Charl, Hiroshi Kasahara, T. Mizuuchi, D. Zhang, D. Höschen, J. Riemann, Thomas Klinger, W. Leonhardt, S. Sipliä, Katsumi Ida, T. Jesche, G. Pelka, U. Stridde, Riccardo Nocentini, Alexandra M. Freund, P. McNeely, A. Gogoleva, Victoria Winters, V. Szabó, Wolf-Dieter Schneider, D. A. Hartmann, Fabian Wilde, H. Schumacher, J. Howard, A. van Vuuren, J.L. Terry, M. Nagel, C. Hidalgo, Georg Kühner, S. Wolf, Boyd Blackwell, Michael Cole, Barbara Cannas, D. Rondeshagen, P. Hacker, Torsten Bluhm, J. Kacmarczyk, Kunihiro Ogawa, A. Zeitler, I. Yamada, P. Rong, Tamara Andreeva, Hiroshi Yamada, G. Anda, N. Panadero Alvarez, Wilfried Behr, F. Purps, H. Esteban, Dag Hathiramani, R. Bussiahn, David Ennis, A. H. Reiman, D. R. Mikkelsen, M. Borchardt, B. Israeli, M. Grahl, M. Losert, T. Dittmar, E. Pasch, U. Kamionka, Toru Ii Tsujimura, Gabriel G. Plunk, Felix Warmer, Jeremy Lore, F. Durodié, M. Balden, B.J. Peterson, J.P. Bähner, R. Schrittwieser, Morten Stejner, M.J. Cole, S. Zoletnik, Kian Rahbarnia, O. Marchuk, T. Bräuer, M. Hirsch, R. Riedl, W. Figacz, H. Trimino Mora, S. Degenkolbe, H. Greuner, B. Böswirth, B. Schweer, Dorothea Gradic, S. B. Ballinger, S. Ryosuke, B. Missal, Jiawu Zhu, J. H. E. Proll, M. Czerwinski, A. Cappa, B. Wiegel, J. Loizu Cisquella, Per Helander, Sehyun Kwak, S. Marsen, L. Carraro, T. Ilkei, D. Pilopp, Gábor Náfrádi, S. Récsei, M. Houry, A. de la Peña, Yu. Turkin, T.A. Scherer, T. Schröder, A. Galkowski, P. Drews, H. Frerichs, Benedikt Geiger, A. Krämer-Flecken, M. Dibon, L.-G. Böttger, A. Czarnecka, R. Krampitz, J. Wendorf, N. Chaudhary, T. Kremeyer, A. da Silva, R. Kleiber, R. Sakamoto, J.-M. Travere, I. Abramovic, T. Funaba, Andreas Meier, Fabio Pisano, Holger Niemann, Mirko Salewski, R. Brakel, M. Mayer, X. Huang, Stefan Illy, Ph. Mertens, Naoki Kenmochi, F. Köchl, Peter Lang, J. Geiger, Albert Mollén, A. Hölting, T. Barbui, M. Lennartz, T. Szabolics, Hayato Tsuchiya, S. Renard, A. Lorenz, J. Krom, C. D. Beidler, J. Cai, Andreas Dinklage, Anne White, Ye. O. Kazakov, P. Junghanns, W. Spiess, J. M. García Regaña, S. Elgeti, J. W. Coenen, Thomas Sunn Pedersen, C. Li, T. Mönnich, Miklos Porkolab, R. Laube, Burkhard Plaum, A. Benndorf, Michael Kramer, J. Ongena, J. Svensson, Dmitry Moseev, U. Wenzel, Chandra Prakash Dhard, S. Tulipán, M. C. Zarnstorff, M. Sibilia, A. von Stechow, G. M. Weir, H. Maaßberg, U. Höfel, P. Scholz, Alexey Mishchenko, R. C. Wolf, D. Carralero, G. Kocsis, Ivan Calvo, J. Tretter, Didier Chauvin, Y. Li, J. Boscary, A. Puig Sitjes, Fumimichi Sano, Andrey Samartsev, Tamás Szepesi, A. Kirschner, Dirk Nicolai, Francesco Cordella, M. Rack, A. Alonso, G. Czymek, E. R. Scott, M. E. Puiatti, Stefan Kragh Nielsen, M. Vergote, H. Schmitz, H. Jenzsch, Donald A. Spong, K. Czerski, A. Knieps, Arnold Lumsdaine, L. Ryć, M. N. A. Beurskens, Matthias F. Schneider, Simppa Äkäslompolo, Ulrich Neuner, V. Perseo, Jim-Felix Lobsien, Gerd Gantenbein, Roberto Guglielmo Citarella, L. Pacios Rodriguez, L. Vano, S. Bozhenkov, J. W. Oosterbeek, H. Röhlinger, J. P. Knauer, T. Nishizawa, A.H. Wright, M. Jia, A. Goriaev, H. Brand, D. Böckenhoff, H. M. Smith, J. P. Thomas, T. Fornal, J. Baldzuhn, D. Loesser, K. Risse, John Jelonnek, T. Wegner, S. Jablonski, Martina Huber, V. V. Lutsenko, S. Sereda, J. Ölmanns, Tomohiro Morisaki, H. Thomsen, J. A. Alcuson, P. Kornejew, J M Fontdecaba, Kai Jakob Brunner, A. Werner, T. Kobarg, European Commission, University of Greifswald, Max Planck Institute for Plasma Physics, Technical University of Denmark, Princeton University, National Institute for Fusion Science, CIEMAT, EURATOM HAS, Massachusetts Institute of Technology, University of Wisconsin-Madison, Research Center Julich, Australian National University, Eindhoven University of Technology, University of Cagliari, Consorzio RFX, Universidade de Lisboa, CEA Cadarache, St. Petersburg Scientific Centre, Oak Ridge National Laboratory, University of Salerno, ENEA Frascati Research Center, Institute of Plasma Physics and Laser Microfusion, University of Szczecin, University of Milano-Bicocca, Auburn University, Karlsruhe Institute of Technology, Universidad Carlos III de Madrid, University of Stuttgart, Austrian Academy of Sciences, National Academy of Sciences Ukraine, Technical University of Berlin, Opole University of Technology, Fusion and Plasma Physics, University of Maryland College Park, Consiglio Nazionale delle Ricerche (CNR), Kyoto University, Culham Centre for Fusion Energy, Physikalisch-Technische Bundesanstalt, Los Alamos National Laboratory, Department of Applied Physics, Aalto-yliopisto, and Aalto University
Subjects: Technology, CONFINEMENT, 01 natural sciences, impurities, 010305 fluids & plasmas, law.invention, ECR heating, Divertor, DENSITY LIMIT, law, Data_FILES, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 004 Datenverarbeitung, Informatik, Physics, Glow discharge, Condensed Matter Physics, Content (measure theory), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Electron temperature, Atomic physics, ddc:620, Stellarator, Impurities, Nuclear and High Energy Physics, Technology and Engineering, plasma performance, chemistry.chemical_element, Atmospheric-pressure plasma, PHYSICS, stellarator, Physics::Plasma Physics, NBI heating, 0103 physical sciences, divertor, 010306 general physics, Helium, Plasma performance, turbulence, Física, W7-X, Turbulence, TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES, chemistry, ddc:004, ddc:600, Energy (signal processing), SYSTEM
Abstract: The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.
Published: 2019
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10. Overview of the results from divertor experiments with attached and detached plasmas at Wendelstein 7-X and their implications for steady-state operation

Author: M. Jakubowski, M. Endler, Y. Feng, Y. Gao, C. Killer, R. König, M. Krychowiak, V. Perseo, F. Reimold, O. Schmitz, T.S. Pedersen, S. Brezinsek, A. Dinklage, P. Drewelow, H. Niemann, M. Otte, M. Gruca, K. Hammond, T. Kremeyer, M. Kubkowska, S. Jabłoński, A. Pandey, G. Wurden, D. Zhang, S. Bozhenkov, D. Böckenhoff, C.P. Dhard, J. Baldzuhn, D. Gradic, F. Effenberg, P. Kornejew, S. Lazerson, J. Lore, D. Naujoks, A Puig Sitjes, G. Schlisio, M. Ślęczka, U. Wenzel, V. Winters, null the W7-X Team, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Nuclear and High Energy Physics, Steady state (electronics), Nuclear engineering, Divertor, Plasma, Condensed Matter Physics, 7. Clean energy, 01 natural sciences, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, ddc:620, Wendelstein 7-X, 010306 general physics, Stellarator
Abstract: Wendelstein 7-X (W7-X), the largest advanced stellarator, is built to demonstrate high power, high performance quasi-continuous operation. Therefore, in the recent campaign, experiments were performed to prepare for long pulse operation, addressing three critical issues: the development of stable detachment, control of the heat and particle exhaust, and the impact of leading edges on plasma performance. The heat and particle exhaust in W7-X is realized with the help of an island divertor, which utilizes large magnetic islands at the plasma boundary. This concept shows very efficient heat flux spreading and favourable scaling with input power. Experiments performed to overload leading edges showed that the island divertor yields good impurity screening. A highlight of the recent campaign was a robust detachment scenario, which allowed reducing power loads even by a factor of ten. At the same time, neutral pressures at the pumping gap entrance yielded the particle removal rate close to the values required for stable density control in steady-state operation.
Published: 2021
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11. Understanding detachment of the W7-X island divertor

Author: D. Mellein, M. Endler, G. Fuchert, U. Wenzel, W. Leonhardt, Oliver Schmitz, T. Kremeyer, T. Sunn Pedersen, Carsten Killer, K. J. Brunner, John Jelonnek, Rouven Lang, F. Reimold, Y. Feng, P. Drewelow, R. König, S. Wadle, E. Pasch, T. Kobarg, Yu Gao, Martina Huber, Florian Effenberg, Wendelstein X Team, G. Schlisio, Manfred Thumm, Kenneth Hammond, Gerd Gantenbein, M. Krychowiak, Detlev Reiter, Matthias Otte, Theo Scherer, Daniel Papenfuß, D. Zhang, Stefan Illy, Christoph Biedermann, L. Rudischhauser, Victoria Winters, M. W. Jakubowski, Per Helander, C. D. Beidler, J. P. Knauer, J. Geiger, S. A. Bozhenkov, Andreas Dinklage, Jörg Weggen, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Nuclear and High Energy Physics, Technology, Nuclear engineering, Divertor, 0103 physical sciences, 010306 general physics, Condensed Matter Physics, 01 natural sciences, ddc:600, 010305 fluids & plasmas
Abstract: The fundamental behavior of the W7-X island divertor under detached conditions, which has been theoretically predicted with the EMC3-Eirene code, is re-examined here under the experimental conditions achieved so far and compared with the first experimental results. Both simulations and experiments cover a range of divertor configurations and plasma parameters, and show the following common trends: (1) with rising impurity radiation, the target heat load decreases ‘uniformly’ over the entire target surface in the sense that both the peak and average heat loads can drop by an order of magnitude. Impurity radiation (mainly from intrinsic carbon) occurs primarily at the plasma edge and the resulting negative impact on the stored energy is less than 10%. (2) When the total radiation exceeds a critical level, the target particle flux (the recycling flux Γrecy) begins to fall and can drop by a factor of 3–5 at high radiation levels without an obvious indication of significant volume recombination. (3) While Γrecy decreases, the divertor neutral pressure continues to build up and reaches a maximum, at which point Γrecy has declined significantly. (4) During detachment, the electron temperature at the last closed flux surface falls in a way that is not quantitatively understandable from parallel classical heat conduction processes. This paper presents a physical explanation of the numerical/experimental results described above. Furthermore, using the EMC3-Eirene code as a diagnostic tool, we are able, apparently for the first time, to provide a full quantitative analysis of each transport channel in the island divertor, aiming to clarify how the island divertor plasma self-regulates to maintain particle, energy, and momentum balance under detached conditions.
Published: 2021

12. Assessment of potential heat flux overload of target and first wall components in Wendelstein 7-X finite-beta magnetic configurations and choice of locations for temperature monitoring

Author: M. Endler, J. Geiger, D. Böckenhoff, Joris Fellinger, West Team, G. Bongiovì, A. Carls, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Convection, Materials science, Convective heat transfer, Mechanical Engineering, Atmospheric-pressure plasma, Baffle, Mechanics, 01 natural sciences, 010305 fluids & plasmas, Nuclear Energy and Engineering, Heat flux, 0103 physical sciences, Heat shield, Water cooling, General Materials Science, Wendelstein 7-X, 010306 general physics, Civil and Structural Engineering
Abstract: Within the framework of R&D activities on the Wendelstein 7-X (W7-X) stellarator machine, the assessment of heat loads onto the plasma facing components (PFCs) is an important aspect. So far, W7-X was operated in short pulses without water cooling of the PFCs. Presently, the device is being prepared for future operation phases with water cooling. The target plates, which receive the highest heat loads, are monitored by a thermography system. The rest of the first wall (heat shield) is not designed to receive convective particle loads, and it is in part poorly monitored by the infrared cameras. Recent studies have shown that for many plasma configurations there are locations on the heat shield which do receive significant convective heat flux. This is in particular true for the heat shields adjacent to the target plates (called baffles) and for configurations with finite plasma pressure, where the magnetic configuration is modified by plasma currents. On the other side, the heat flux limit to the baffle tiles had to be reduced from 0.50 to 0.25 MW/m2. In this work an evaluation of the heat flux to targets and baffles in plasma configurations with finite plasma pressure is presented. To this end, Field Line Diffusion (FLD) calculations have been performed to obtain the heat load pattern distributions for the considered magnetic configurations. The results have been assessed statistically to achieve a measure of certainty in the prediction of an overload in a certain location. The possibility of overloads onto the baffles due to plasma radiation has also been investigated. The results of the entire analysis show that local temperature monitoring by thermocouples in a rather limited number of locations will be sufficient to avoid heat flux overloads of the baffles and heat shields in all magnetic configurations considered.
Published: 2020

13. Confinement in Wendelstein 7-X limiter plasmas

Author: Andreas Langenberg, Olaf Grulke, M. Krychowiak, Fabio Pisano, R. Brakel, N. Krawczyk, Monika Kubkowska, E. Blanco, Hans-Stephan Bosch, P. Kornejew, M. Hirsch, T. Fornal, J. Baldzuhn, Tamás Szepesi, Tamara Andreeva, Matthias Otte, H. P. Laqua, N. A. Pablant, A. Werner, M. W. Jakubowski, Nikolai B. Marushchenko, T. Schröder, C. D. Beidler, E. Pasch, A. Czarnecka, Samuel Lazerson, V. Moncada, Yu. Turkin, Torsten Stange, Christoph Biedermann, M. Endler, R. Burhenn, Dirk Naujoks, S. Marsen, J. Geiger, J. H. Harris, H. Trimino Mora, T. Estrada, A. Cappa, Andreas Dinklage, B. Buttenschön, R. König, Dmitry Moseev, H. Thomsen, G. M. Weir, J. P. Knauer, H. Maaßberg, A. Alonso, G. A. Wurden, S. A. Bozhenkov, D. Zhang, Thomas Sunn Pedersen, U. Wenzel, Hayato Tsuchiya, M. N. A. Beurskens, Laurie Stephey, Tom Wauters, Kian Rahbarnia, Thomas Klinger, G. Kocsis, I. Ksiazek, D. A. Hartmann, U. Höfel, A. Krämer-Flecken, G. Fuchert, R. C. Wolf, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Nuclear and High Energy Physics, stellarator, confinement, 0103 physical sciences, 010306 general physics, Condensed Matter Physics, 01 natural sciences, energy confinement, 010305 fluids & plasmas
Abstract: Observations on confinement in the first experimental campaign on the optimized Stellarator Wendelstein 7-X are summarized. In this phase W7-X was equipped with five inboard limiters only and thus the discharge length restricted to avoid local overheating. Stationary plasmas are limited to low densities
Published: 2017
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14. Tuning of the rotational transform in Wendelstein 7-X

Author: Yu Gao, Tamara Andreeva, Christoph Biedermann, L. Rudischhauser, Kenneth Hammond, M. Endler, Kian Rahbarnia, Fabio Pisano, R. König, Aleix Puig Sitjes, G. Satheeswaran, Samuel Lazerson, Monica Spolaore, P. Drewelow, Tamás Szepesi, Adnan Ali, S. Klose, Carsten Killer, G. A. Wurden, G. Kocsis, Kai Jakob Brunner, Ulrich Neuner, U. Wenzel, M. W. Jakubowski, Dirk Nicolai, Barbara Cannas, Holger Niemann, J. Geiger, J. P. Knauer, Boyd Blackwell, Olaf Grulke, G. Schlisio, Matthias Mulsow, S. A. Bozhenkov, H. Thomsen, Jonathan Schilling, Matthias Otte, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Nuclear and High Energy Physics, Thesaurus (information retrieval), superconducting coils, Nuclear engineering, Divertor, islands, error fields, magnetic field, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Magnetic field, stellarator, law, 0103 physical sciences, divertor, Wendelstein 7-X, 010306 general physics, Superconducting Coils, Stellarator
Abstract: The control of rotational transform in Wendelstein 7-X (W7-X) is key to both the island divertor operation and safety of plasma facing components. The island divenor concept in W7-X relies on an edge flux surface with rotational transform of t = 1 resonating with an intrinsic n/m = 5/5 resonance to form a five lobed island chain. This island chain intersects with divertor plates to give rise to the island divertor. Changes in the relative position of the rational surface and the divertor plates can result in changes in divenor performance, thus the control of the rotational transform is essential to operation of the W7-X device. During the first divertor campaign electromagnetic loads resulted in elastic deformations of the shaped modular stellarator coils. Such deformations made these coils more planar, reducing the vacuum rotational transform, subsequently shifting the t = 1 resonance outward. Unintended plasma wall interactions provided the first clear evidence of this effect during plasma operation. Flux surface measurements were utilized to estimate the correct level of current in the planar coils for correction of t, and found to be around similar to-100 A. Scans the planar coil current for iota correction were performed during plasma operation. These measurements suggest planar coil currents between -250 and similar to 0 A would place the strike lines at the designed distance from the pumping gaps. Divertor Langmuir and upstream probe measurements confirm these estimates along with measurements of divertor neutral gas pressure.
Published: 2019
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15. Effects of toroidal plasma current on divertor power depositions on Wendelstein 7-X

Author: M. Zanini, D. Zhang, Yunfeng Liang, Tamara Andreeva, Kian Rahbarnia, Holger Niemann, J. Geiger, Yu Gao, S. A. Bozhenkov, Aleix Puig Sitjes, Torsten Stange, Matthias Otte, P. Drewelow, Samuel Lazerson, M. Rack, Adnan Ali, Heinrich P. Laqua, M. W. Jakubowski, Kenneth Hammond, M. Endler, Ulrich Neuner, Fabio Pisano, Barbara Cannas, A. Knieps, Tamás Szepesi, S. Marsen, H. Thomsen, Carsten Killer, Y. Feng, Jonathan Schilling, Yasuhiro Suzuki, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Nuclear and High Energy Physics, Toroid, Materials science, Divertor, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, Power (physics), Heat flux, Physics::Plasma Physics, 0103 physical sciences, Wendelstein 7-X, Electric current, Atomic physics, ddc:620, 010306 general physics, Deposition (law)
Abstract: The paper presents experimental observations and simulations for the effects of toroidal plasma current on divertor power depositions on W7-X. With increasing toroidal current accompanying changes in the island geometry result in a sweep of the strike line and a redistribution of the heat flux footprints. Good agreement between experiments, which partly used electron cyclotron current drive to generate an additional toroidal current contribution, and modelling using field line tracing in vacuum magnetic fields including an ad-hoc toroidal current on the magnetic axis is found for both standard and low-iota magnetic configurations.
Published: 2019
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16. Upgrades of edge, divertor and scrape-off layer diagnostics of W7‐X for OP1.2

Author: D. Chauvin, S. Mohr, David Ennis, D. Pilopp, Adnan Ali, P. Kornejew, U. Wenzel, V. Perseo, Joris Fellinger, M. Toth, A. Dudek, G. Anda, M. Mayer, Laurie Stephey, B. Schweer, G. Kocsis, H. T. Lambertz, Olaf Neubauer, H. Jenzsch, J. H. Harris, Florian Effenberg, P. Drewelow, R. König, M. Endler, G. Czymek, G. Ehrke, Chandra Prakash Dhard, O. P. Ford, M. Krause, Tamás Szepesi, K. Grosser, M. Schülke, T. Sunn Pedersen, G. A. Wurden, Oliver Schmitz, S. Zoletnik, S. Freundt, T. Barbui, Christoph Biedermann, L. Rudischhauser, M. W. Jakubowski, H. Hölbe, A. Charl, Dorothea Gradic, M. Knaup, T. Kremeyer, Matthias Otte, M. Krychowiak, Dag Hathiramani, Alexis Terra, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Materials science, Mechanical Engineering, Nuclear engineering, Divertor, chemistry.chemical_element, Plasma, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Magnetic field, Nuclear Energy and Engineering, chemistry, law, 0103 physical sciences, Electromagnetic shielding, Limiter, Nuclear fusion, General Materials Science, ddc:530, 010306 general physics, Stellarator, Helium, Civil and Structural Engineering
Abstract: Wendelstein 7-X (W7‐X) is the world’s largest superconducting nuclear fusion experiment of the optimized stellarator type. In the first Operation Phase (OP1.1) helium and hydrogen plasmas were studied in limiter configuration. The heating energy was limited to 4 MJ and the main purpose of that campaign was the integral commissioning of the machine and diagnostics, which was achieved very successfully. Already from the beginning a comprehensive set of diagnostics was available to study the plasma. On the path towards high-power, high-performance plasmas, W7‐X will be stepwise upgraded from an inertially cooled (OP1.2, limited to 80 MJ) to an actively cooled island divertor (OP2, 10 MW steady-state plasma operation). The machine is prepared for OP1.2 with 10 inertially cooled divertor units, and the experimental campaign has started recently. The paper describes a subset of diagnostics which will be available for OP1.2 to study the plasma edge, divertor and scrape-off layer physics including those already available for OP1.1, plus modifications, upgrades and new systems. The focus of this summary will be on technical and engineering aspects, like feasibility and assembly but also on reliability, thermal loads and shielding against magnetic fields.
Published: 2018
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17. Error fields in the Wendelstein 7-X stellarator

Author: Tamara Andreeva, Fabio Pisano, Barbara Cannas, Samuel Lazerson, S. A. Bozhenkov, Adnan Ali, Aleix Puig Sitjes, P. Drewelow, M. Endler, Victor Bykov, M. W. Jakubowski, Ben Israeli, Matthias Otte, Holger Niemann, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, Computational physics, Magnetic field, Nuclear Energy and Engineering, law, Thermocouple, 0103 physical sciences, Measuring instrument, Limiter, Wendelstein 7-X, Diffusion (business), 010306 general physics, Stellarator
Published: 2018

18. Overview of diagnostic performance and results for the first operation phase in Wendelstein 7-X (invited)

Author: Oliver Schmitz, E. Pasch, S. A. Bozhenkov, O. P. Ford, Ireneusz Książek, J. Svensson, Robert Wolf, M. Endler, R. Burhenn, G. M. Weir, Dirk Naujoks, Florian Effenberg, L. Ryć, M. N. A. Beurskens, Olaf Grulke, T. Sunn Pedersen, G. A. Wurden, S. Marsen, Ulrich Neuner, S. Jablonski, S. C. Liu, T. Fornal, J. Baldzuhn, B. Schweer, Yunfeng Liang, Thomas Klinger, T. Schröder, B. Wiegel, Monika Kubkowska, D. A. Hartmann, Boyd Blackwell, J. P. Knauer, H. Thomsen, A. Dzikowicka, A. O. Marchuk, M. W. Jakubowski, G. Fuchert, H.-J. Hartfuß, Dag Hathiramani, Gábor Cseh, U. Wenzel, A. Adnan, Helmut Schuhmacher, N. A. Pablant, A. Alonso, B. Standley, Philipp Drews, J. Kaczmarczyk, Matthias Otte, T. Kremeyer, Christoph Biedermann, T. Szabolics, P. Kornejew, Hayato Tsuchiya, V. Erckmann, A. Werner, M. Krychowiak, S. Schmuck, N. Krawczyk, Laurie Stephey, D. Zhang, Hans-Stephan Bosch, J. W. Oosterbeek, V. Moncada, J.-M. Travere, B. Buttenschön, H. Neilson, T. Estrada, A. Cappa, A. Krämer-Flecken, Andreas Langenberg, U. Höfel, H. P. Laqua, Samuel Lazerson, T. Bräuer, M. Hirsch, Torsten Stange, R. König, Olaf Neubauer, Wendelstein X Team, B. B. Carvalho, S. Zoletnik, Holger Niemann, Andreas Zimbal, J. Geiger, T. Barbui, A. Lorenz, Andreas Dinklage, Heinke Frerichs, Wolfgang Biel, J. H. Harris, Martin Laux, Wolf-Dieter Schneider, Tamara Andreeva, A. Czarnecka, T. Windisch, S. Klose, H. Trimino Mora, Fabio Pisano, R. Brakel, Tamás Szepesi, G. Kocsis, Kian Rahbarnia, Science and Technology of Nuclear Fusion, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, business.industry, Plasma parameters, Instrumentation, Plasma, 01 natural sciences, Radiation zone, 010305 fluids & plasmas, law.invention, Optics, law, 0103 physical sciences, Limiter, ddc:530, Plasma diagnostics, Wendelstein 7-X, 010306 general physics, business, Stellarator
Abstract: Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.
Published: 2016
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19. Histological Evaluation of a Chronically-implanted Electrocorticographic Electrode Grid in a Non-human Primate

Author: Wei Wang, James R. Eles, Elizabeth C. Tyler-Kabara, Ivan Smalianchuk, Alan D. Degenhart, Aaron P. Batista, Bridget M. Endler, X. Tracy Cui, Richard P. Dum, Robin C. Ashmore, Nicholas G. Hatsopoulos, and Jessica L Mischel
Subjects: 0301 basic medicine, Male, Foreign-body giant cell, Biomedical Engineering, Electrode Grid, Article, Collagen Type I, 03 medical and health sciences, Cellular and Molecular Neuroscience, 0302 clinical medicine, Medicine, Animals, Electrocorticography, Brain–computer interface, Non human primate, Microscopy, Confocal, biology, medicine.diagnostic_test, business.industry, Granuloma, Foreign-Body, Macrophages, Motor Cortex, biology.organism_classification, Hand, Immunohistochemistry, Macaca mulatta, Electrodes, Implanted, Rhesus macaque, 030104 developmental biology, medicine.anatomical_structure, Cerebral cortex, Brain-Computer Interfaces, Implant, business, Neuroscience, Microelectrodes, 030217 neurology & neurosurgery
Abstract: Objective Electrocorticography (ECoG), used as a neural recording modality for brain-machine interfaces (BMIs), potentially allows for field potentials to be recorded from the surface of the cerebral cortex for long durations without suffering the host-tissue reaction to the extent that it is common with intracortical microelectrodes. Though the stability of signals obtained from chronically implanted ECoG electrodes has begun receiving attention, to date little work has characterized the effects of long-term implantation of ECoG electrodes on underlying cortical tissue. Approach We implanted and recorded from a high-density ECoG electrode grid subdurally over cortical motor areas of a Rhesus macaque for 666 d. Main results Histological analysis revealed minimal damage to the cortex underneath the implant, though the grid itself was encapsulated in collagenous tissue. We observed macrophages and foreign body giant cells at the tissue-array interface, indicative of a stereotypical foreign body response. Despite this encapsulation, cortical modulation during reaching movements was observed more than 18 months post-implantation. Significance These results suggest that ECoG may provide a means by which stable chronic cortical recordings can be obtained with comparatively little tissue damage, facilitating the development of clinically viable BMI systems.
Published: 2016

20. The set of diagnostics for the first operation campaign of the Wendelstein 7-X stellarator

Author: S. Jablonski, H. P. Laqua, S. Klose, S. A. Bozhenkov, H. Thomsen, Andreas Langenberg, Olaf Grulke, V. Moncada, Helmut Schuhmacher, Ralf König, Torsten Stange, T. Estrada, P. Kornejew, Matthias Otte, G. A. Wurden, Wolf-Dieter Schneider, B. Buttenschön, A. Werner, E. Pasch, L. Ryć, Yunfeng Liang, Tamás Szepesi, A. Czarnecka, M. Hirsch, Ulrich Neuner, Wolfgang Biel, M. Krychowiak, Olaf Neubauer, S. Zoletnik, Oliver Schmitz, B. B. Carvalho, M. W. Jakubowski, J. Baldzuhn, T. Kremeyer, Hans-Stephan Bosch, A. Zimbal, T. Windisch, Gábor Cseh, J. Geiger, B. Wiegel, Robert Wolf, M. Endler, R. Burhenn, A. Lorenz, Thomas Sunn Pedersen, Christoph Biedermann, J. Kaczmarczyk, A. O. Marchuk, Martin Laux, U. Wenzel, N. A. Pablant, G. Kocsis, T. Bräuer, B. Schweer, Monika Kubkowska, V. Erckmann, Kian Rahbarnia, J. W. Oosterbeek, D. Zhang, J.-M. Travere, Thomas Klinger, Dag Hathiramani, D. A. Hartmann, A. Krämer-Flecken, Science and Technology of Nuclear Fusion, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Heating power, business.industry, Plasma parameters, Nuclear engineering, Nuclear instruments and methods for hot plasma diagnostics, Electrical engineering, 01 natural sciences, 010305 fluids & plasmas, law.invention, Plasma diagnostics - interferometry, spectroscopy and imaging, law, 0103 physical sciences, Plasma diagnostics - interferometry, spectroscopy and imaging, Limiter, Plasma diagnostics, Plasma diagnostics - probes, Wendelstein 7-X, 010306 general physics, business, Instrumentation, Mathematical Physics, Stellarator
Abstract: Wendelstein 7-X (W7-X) is a large optimized stellarator (B=2.5T, V=30m3) aiming at demonstrating the reactor relevance of the optimized stellarators. In 2015 W7-X will begin its first operation phase (OP1.1) with five inertially cooled inboard limiters made of graphite. Assuming the heat loads can be spread out evenly between the limiters, 1 second discharges at 2 MW of ECRH heating power could be run in OP1.1. The expected plasma parameters will be sufficient to demonstrate the readiness of the installed diagnostics and even to run a first physics program. The diagnostics available for this first operation phase, including some special limiter diagnostics, and their capabilities are being presented. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics
Published: 2015

21. Technical challenges in the construction of the steady-state stellarator Wendelstein 7-X

Author: H.-S. Bosch, R.C. Wolf, T. Andreeva, J. Baldzuhn, D. Birus, T. Bluhm, T. Bräuer, H. Braune, V. Bykov, A. Cardella, F. Durodié, M. Endler, V. Erckmann, G. Gantenbein, D. Hartmann, D. Hathiramani, P. Heimann, B. Heinemann, C. Hennig, M. Hirsch, D. Holtum, J. Jagielski, J. Jelonnek, W. Kasparek, T. Klinger, R. König, P. Kornejew, H. Kroiss, J.G. Krom, G. Kühner, H. Laqua, H.P. Laqua, C. Lechte, M. Lewerentz, J. Maier, P. McNeely, A. Messiaen, G. Michel, J. Ongena, A. Peacock, T.S. Pedersen, R. Riedl, H. Riemann, P. Rong, N. Rust, J. Schacht, F. Schauer, R. Schroeder, B. Schweer, A. Spring, A. Stäbler, M. Thumm, Y. Turkin, L. Wegener, A. Werner, D. Zhang, M. Zilker, T. Akijama, R. Alzbutas, E. Ascasibar, M. Balden, M. Banduch, Ch. Baylard, W. Behr, C. Beidler, A. Benndorf, T. Bergmann, C. Biedermann, B. Bieg, W. Biel, M. Borchardt, G. Borowitz, V. Borsuk, S. Bozhenkov, R. Brakel, H. Brand, T. Brown, B. Brucker, R. Burhenn, K.-P. Buscher, C. Caldwell-Nichols, A. Cappa, A. Carls, P. Carvalho, Ł. Ciupiński, M. Cole, J. Collienne, A. Czarnecka, G. Czymek, G. Dammertz, C.P. Dhard, V.I. Davydenko, A. Dinklage, M. Drevlak, S. Drotziger, A. Dudek, P. Dumortier, G. Dundulis, P.v. Eeten, K. Egorov, T. Estrada, H. Faugel, J. Fellinger, Y. Feng, H. Fernandes, W.H. Fietz, W. Figacz, F. Fischer, J. Fontdecaba, A. Freund, T. Funaba, H. Fünfgelder, A. Galkowski, D. Gates, L. Giannone, J.M. García Regaña, J. Geiger, S. Geißler, H. Greuner, M. Grahl, S. Groß, A. Grosman, H. Grote, O. Grulke, M. Haas, L. Haiduk, H.-J. Hartfuß, J.H. Harris, D. Haus, B. Hein, P. Heitzenroeder, P. Helander, R. Heller, C. Hidalgo, D. Hildebrandt, H. Höhnle, A. Holtz, E. Holzhauer, R. Holzthüm, A. Huber, H. Hunger, F. Hurd, M. Ihrke, S. Illy, A. Ivanov, S. Jablonski, N. Jaksic, M. Jakubowski, R. Jaspers, H. Jensen, H. Jenzsch, J. Kacmarczyk, T. Kaliatk, J. Kallmeyer, U. Kamionka, R. Karaleviciu, S. Kern, M. Keunecke, R. Kleiber, J. Knauer, R. Koch, G. Kocsis, A. Könies, M. Köppen, R. Koslowski, J. Koshurinov, A. Krämer-Flecken, R. Krampitz, Y. Kravtsov, M. Krychowiak, G. Krzesinski, I. Ksiazek, M. Kubkowska, A. Kus, S. Langish, R. Laube, M. Laux, S. Lazerson, M. Lennartz, C. Li, R. Lietzow, A. Lohs, A. Lorenz, F. Louche, L. Lubyako, A. Lumsdaine, A. Lyssoivan, H. Maaßberg, P. Marek, C. Martens, N. Marushchenko, M. Mayer, B. Mendelevitch, Ph. Mertens, D. Mikkelsen, A. Mishchenko, B. Missal, T. Mizuuchi, H. Modrow, T. Mönnich, T. Morizaki, S. Murakami, F. Musielok, M. Nagel, D. Naujoks, H. Neilson, O. Neubauer, U. Neuner, R. Nocentini, J.-M. Noterdaeme, C. Nührenberg, S. Obermayer, G. Offermanns, H. Oosterbeek, M. Otte, A. Panin, M. Pap, S. Paquay, E. Pasch, X. Peng, S. Petrov, D. Pilopp, H. Pirsch, B. Plaum, F. Pompon, M. Povilaitis, J. Preinhaelter, O. Prinz, F. Purps, T. Rajna, S. Récsei, A. Reiman, D. Reiter, J. Remmel, S. Renard, V. Rhode, J. Riemann, S. Rimkevicius, K. Riße, A. Rodatos, I. Rodin, M. Romé, H.-J. Roscher, K. Rummel, Th. Rummel, A. Runov, L. Ryc, J. Sachtleben, A. Samartsev, M. Sanchez, F. Sano, A. Scarabosio, M. Schmid, H. Schmitz, O. Schmitz, M. Schneider, W. Schneider, L. Scheibl, M. Scholz, G. Schröder, M. Schröder, J. Schruff, H. Schumacher, I.V. Shikhovtsev, M. Shoji, G. Siegl, J. Skodzik, M. Smirnow, E. Speth, D.A. Spong, R. Stadler, Z. Sulek, V. Szabó, T. Szabolics, T. Szetefi, Z. Szökefalvi-Nagy, A. Tereshchenko, H. Thomsen, D. Timmermann, H. Tittes, K. Toi, M. Tournianski, U.v. Toussaint, J. Tretter, S. Tulipán, P. Turba, R. Uhlemann, J. Urban, E. Urbonavicius, P. Urlings, S. Valet, D. Van Eester, M. Van Schoor, M. Vervier, H. Viebke, R. Vilbrandt, M. Vrancken, T. Wauters, M. Weissgerber, E. Weiß, A. Weller, J. Wendorf, U. Wenzel, T. Windisch, E. Winkler, M. Winkler, J. Wolowski, J. Wolters, G. Wrochna, P. Xanthopoulos, H. Yamada, M. Yokoyama, D. Zacharias, J. Zajac, G. Zangl, M. Zarnstorff, H. Zeplien, S. Zoletnik, M. Zuin, Control Systems Technology, Science and Technology of Nuclear Fusion, Soft Matter and Biological Physics, Sensorics for fusion reactors, and Publica
Subjects: Nuclear and High Energy Physics, Steady state (electronics), LIMIT ANALYSIS, PLASMA, Nuclear engineering, MAGNET SYSTEM, Plasma, Fusion power, Condensed Matter Physics, W7-X, Electron cyclotron resonance, law.invention, PHYSICS, Data acquisition, Heating system, law, Wendelstein 7-X, Stellarator
Abstract: The next step in the Wendelstein stellarator line is the large superconducting device Wendelstein 7-X, currently under construction in Greifswald, Germany. Steady-state operation is an intrinsic feature of stellarators, and one key element of the Wendelstein 7-X mission is to demonstrate steady-state operation under plasma conditions relevant for a fusion power plant. Steady-state operation of a fusion device, on the one hand, requires the implementation of special technologies, giving rise to technical challenges during the design, fabrication and assembly of such a device. On the other hand, also the physics development of steady-state operation at high plasma performance poses a challenge and careful preparation. The electron cyclotron resonance heating system, diagnostics, experiment control and data acquisition are prepared for plasma operation lasting 30 min. This requires many new technological approaches for plasma heating and diagnostics as well as new concepts for experiment control and data acquisition.
Published: 2013
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22. Diagnostics development for quasi-ready-state operation of the Wendelstein 7-X stellarator (invited)

Author: D. Zhang, R. König, A. Weller, D. Hildebrandt, M. Endler, R. Burhenn, T. Richert, A. Werner, M. W. Jakubowski, S. Zoletnik, J. Baldzuhn, Robert Wolf, P. Kornejev, H. Thomsen, M. Krychowiak, Wolf-Dieter Schneider, J. W. Oosterbeek, Christoph Biedermann, Martin Laux, Dag Hathiramani, S. A. Bozhenkov, E. Pasch, A. Cardella, H. J. Hartfuss, T. Sunn-Pedersen, G. Kocsis, M. Hirsch, H. P. Laqua, and Science and Technology of Nuclear Fusion
Subjects: Physics, Nuclear magnetic resonance, law, Nuclear engineering, Steady State theory, Plasma diagnostics, Wendelstein 7-X, Instrumentation, Stellarator, law.invention
Abstract: The critical issues in the development of diagnostics, which need to work robust and reliable under quasi-steady state conditions for the discharge durations of 30 min and which cannot be maintained throughout the one week duration of each operation phase of the Wendelstein 7-X stellarator, are being discussed.
Published: 2012
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23. Preparing diagnostics for long pulse operation at W7-X

Author: R. König, M. Schülke, K. Grosser, E. Pasch, A. Cardella, M. Hirsch, Robert Wolf, Stefan Thiel, D. Pilopp, West Team, Dag Hathiramani, H. Thomsen, Ulrich Neuner, M. Endler, D. Zhang, B. Brucker, and W7-X Team
Subjects: Materials science, Thomson scattering, Mechanical Engineering, Nuclear engineering, Heat sink, Thermal conduction, Electromagnetic radiation, Nuclear magnetic resonance, Nuclear Energy and Engineering, Thermal radiation, Electromagnetic shielding, Heat transfer, General Materials Science, Microwave, Civil and Structural Engineering
Abstract: s Long pulse operation considerably increases the thermal load on in-vessel components. Diagnostic front-ends formerly employed at short pulse machines therefore have to be considerably re-designed for installation in the stellarator W7-X that is currently being built at Greifswald, Germany. The strategy applied to cope with the thermal load is threefold: to reduce the influx of heat on the component, to conduct the heat inside the component to suitable heat sinks and to choose suitable materials for sensitive components. The first is achieved by the shielding against microwave stray radiation, plasma radiation, thermal radiation and particle fluxes and by absorbing residual microwave stray radiation in the immediate vicinity of sensitive components. The second task, suitable heat conduction, enforces severe restrictions on the use of any thin parts like foils or meshes. Thirdly, in order for a component to survive the residual loads, materials must be chosen that absorb only a small fraction of the microwave stray radiation flux, conduct heat well enough, and survive high temperatures and large temperature gradients. Examples are provided from bolometry, magnetic diagnostics, soft X-ray diagnostics and Thomson scattering. Measurements of microwave stray radiation effects are presented, in particular the effectiveness of several shielding concepts.
Published: 2012

24. Diagnostics development for steady state operation of the stellarator Wendelstein 7-X

Author: Wolfgang Biel, Robert Wolf, H. P. Laqua, P. Kornejew, R. König, M. Krychowiak, H. J. Hartfuss, R. Jimenez-Gomez, E. Pasch, D. Zhang, A. Werner, Wolf-Dieter Schneider, J. W. Oosterbeek, M. Endler, R. Burhenn, K. Grosser, D. Hildebrandt, M. Laux, H. Dreier, J. Baldzuhn, H. Thomsen, M. Hirsch, A. Weller, and Science and Technology of Nuclear Fusion
Subjects: Steady state (electronics), Materials science, law, Electromagnetic coil, Divertor, Nuclear engineering, Electromagnetic shielding, Plasma, Wendelstein 7-X, Condensed Matter Physics, Stellarator, Microwave, law.invention
Abstract: The gain in experience with long-pulse operation under fusion relevant plasma conditions is an important step towards successful sustainment of future steady state reactor plasmas. The stellarator Wendelstein 7-X (W7-X) [1], presently being under construction, is already equipped with a superconducting coil system and principally capable of quasi-continuous operation. Like other long pulse devices, W7-X is faced with new enhanced technical requirements which have to be met by plasma facing components as well as the diagnostic systems in general. Water-cooled windows were qualified up to 60 kW/m2 thermal load, and shutters against evaporation of sensitive elements outside the attended time of the diagnostic as well as for baseline control had been developed. Shielding of in-vessel components against damage by absorption of microwave stray radiation originating from the heating systems appears to be one of the most challenging tasks. Experiments using a microwave test chamber identify critical materials and approved the necessity for careful shielding of both, sensitive diagnostics and cables. Spectroscopic systems for monitoring the impurity content and divertor load as well as for robust density measurement are presented (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Published: 2011

25. Diagnostics design for steady-state operation of the Wendelstein 7-X stellarator

Author: P. Kornejev, G. Kocsis, D. Hildebrandt, S. A. Bozhenkov, D.H. Zhang, H. Dreier, A. Werner, R. Jimenez-Gomez, R. König, M. Hirsch, B. Schweer, Wolfgang Biel, H. P. Laqua, M. Endler, J. W. Oosterbeek, M. Krychowiak, R. Burhenn, J. Cantarini, E. Pasch, H.-J. Hartfuss, T. Richert, J. Svensson, M. Laux, H. Thomsen, C. Biedermann, R. Wolf, A. Weller, M. W. Jakubowski, S. Zoletnik, J. Baldzuhn, W. Schneider, and Science and Technology of Nuclear Fusion
Subjects: Physics, Steady state (electronics), Nuclear engineering, Pulse duration, High density, Stray radiation, law.invention, law, Electromagnetic shielding, Plasma diagnostics, Atomic physics, Wendelstein 7-X, Instrumentation, Stellarator
Abstract: The status of the diagnostic developments for the quasistationary operable stellarator Wendelstein 7-X (maximum pulse length of 30 min at 10 MW ECRH heating at 140 GHz) will be reported on. Significant emphasis is being given to the issue of ECRH stray radiation shielding of in-vessel diagnostic components, which will be critical at high density operation requiring O2 and OXB heating. © 2010 American Institute of Physics
Published: 2010

26. Measurements investigating the embedding procedure of the Wendelstein 7-X non-planar coils

Author: L. Wegener, M. Endler, T. Kluck, J. Müller, and T. Bräuer
Subjects: Materials science, Mechanical Engineering, Nuclear engineering, Superconducting magnet, Fusion power, Temperature measurement, law.invention, Nuclear magnetic resonance, Planar, Nuclear Energy and Engineering, law, Embedding, General Materials Science, Wendelstein 7-X, Casing, Stellarator, Civil and Structural Engineering
Abstract: One manufacturing step of the Wendelstein 7-X non-planar coils is intended to generate a mechanical prestress between winding pack and casing. To document this “embedding” procedure, we performed several temperature and electric resistivity measurements and geometric surveys before, during and after the embedding. We also investigated the behaviour of quartz sand, used to fill the gap between winding pack and casing, under pressure. The results of the whole body of investigations are consistent with the assumption that the achieved prestress is significantly lower than initially intended.
Published: 2009

27. The parallel dynamics of drift wave turbulence in the WEGA Stellarator

Author: M. Endler, Matthias Otte, Friedrich E. Wagner, and S. Marsen
Subjects: Physics, Field (physics), business.industry, Field line, Wave turbulence, Condensed Matter Physics, law.invention, Magnetic field, Computational physics, Wavelength, Optics, Nuclear Energy and Engineering, law, Temporal resolution, Wavenumber, business, Stellarator
Abstract: The three-dimensional structure of turbulence in the edge (inside the last closed flux surface) of the WEGA stellarator is studied focusing on the parallel dynamics. WEGA as a small stellarator with moderate plasma parameters offers the opportunity to study turbulence with Langmuir probes providing high spatial and temporal resolution. Multiple probes with radial, poloidal and toroidal resolution are used to measure density fluctuations. Correlation analysis is used to reconstruct a 3D picture of turbulent structures. We find that these structures originate predominantly on the low field side and have a three-dimensional character with a finite averaged parallel wavenumber. The ratio between the parallel and perpendicular wavenumber component is in the order of 10?2. The parallel dynamics are compared at magnetic inductions of 57 and 500?mT. At 500?mT, the parallel wavelength is in the order of the field line connection length . A frequency resolved measure of k?/k? shows a constant ratio in this case. At 57?mT the observed k? is much smaller than at 500?mT. However, the observed small average value is due to an averaging over positive and negative components pointing parallel and antiparallel to the magnetic field vector.
Published: 2009

28. Spatio-temporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

Author: M. Endler, W As Team, M. Schubert, H. Thomsen, and W7-AS Team
Subjects: Plasma parameters, Transducers, Sensitivity and Specificity, law.invention, symbols.namesake, Magnetics, Nuclear magnetic resonance, Optics, Physics::Plasma Physics, law, Langmuir probe, Instrumentation, Electrical impedance, Physics, business.industry, Reproducibility of Results, Biasing, Plasma, Equipment Design, Equipment Failure Analysis, Thermography, symbols, Plasma diagnostics, business, Stellarator, Voltage
Abstract: Stationary Langmuir probe measurements of ion saturation current and floating potential in a plasma cannot give direct information on density and plasma potential fluctuations in the presence of temperature fluctuations. This problem can be avoided if the probe bias voltage is continuously swept faster than the fluctuation time scale, recording the current-voltage characteristic. This article reports the development of a spatiotemporal highly resolving Langmuir probe array with 15 fast swept tips, operating in the strongly magnetized, collisionless edge plasma of the Wendelstein 7-AS stellarator [Plasma Phys. Controlled Fusion 31, 1579 (1989)]. The probe tips are aligned in the poloidal direction, the tip spacing is 2 mm, and the sweeping frequency is 1.4 MHz. Current and voltage data are sampled with 50 MHz. The high bandwidth of the measurement is achieved by placing miniaturized differential amplifiers close to the probe tips in order to do an impedance transform. The surface-mounting technology and an additional inverse feedback module are utilized, allowing for an input voltage range of +/-100 V, and a common mode rejection rate of 55 dB at 4 MHz, which is sufficient to resolve the nonlinear probe characteristic. For the evaluation of the data, a fit model for stationary probes is employed and found adequate. Changes of the plasma parameters during one voltage sweep are taken into account by a linear interpolation of the fit parameters. Spatio-temporal fluctuation data gained by a fast swept Langmuir probe array, which can be relevant for the turbulent radial transport of particles and energy, are presented.
Published: 2007

29. Self-similarity of the plasma edge fluctuations

Author: Thomas Klinger, V. Antoni, M. A. Pedrosa, G. F. Matthews, M. Frances, S. Davies, David E. Newman, J. Bleuel, C. Ricardi, I. García-Cortés, C. Hidalgo, B. Ph. van Milligen, Benjamin A. Carreras, Emilio Martines, R. Balbín, A. Latten, E. Sánchez, M. Endler, Carreras, B, van Milligen, B, Pedrosa, M, Balbin, R, Hidalgo, C, Newman, D, Sanchez, E, Frances, M, Garcia-Cortes, I, Bleuel, V, Endler, M, Riccardi, C, Davies, S, Matthews, G, Martines, E, Antoni, A, Latten, A, and Klinger, T
Subjects: Physics, Tokamak, Reversed field pinch, Condensed matter physics, self-similarity, Autocorrelation, turbulence, Spectral density, Plasma, Condensed Matter Physics, Power law, Computational physics, law.invention, FIS/01 - FISICA SPERIMENTALE, Physics::Plasma Physics, law, Pinch, magnetoplasma, Decorrelation, FIS/03 - FISICA DELLA MATERIA
Abstract: The rescaled range analysis techniques are used to investigate long-range dependence in plasma edge fluctuations [Mandelbrot and Wallis, Water Resources Res. 4, 909 (1969)]. This technology has been applied to data from several confinement devices such as tokamaks, stellarators, and reversed-field pinch. The results reveal the self-similar character of the electrostatic fluctuations at the plasma edge with self-similarity parameters ranging from 0.62 to 0.72. These results show that the tail of the autocorrelation function decays as a power law for time lags longer than the decorrelation time and as long as times of the order of the confinement time. In cold plasma devices (Te< eV at the core), there is no evidence of algebraic tails in the autocorrelation function. Some other characteristic features of the autocorrelation function and power spectrum have been investigated. All of these features are consistent with plasma transport as characterized by self-organized criticality.
Published: 1998

30. Bose-Einstein correlations inpp collisions at 400 GeV/c

Author: J. J. Hernandez, M. Iori, F. Simonetto, H. Novak, V. A. Stopchenko, R. Contri, N. Sotnikova, A. A. Batalov, L. C. Oliveira, L. Montanet, Gianni Zumerle, P. Poropat, E. P. Kistenev, Simonetta Gentile, Paolo Checchia, R. Monge, K. E. Johansson, P. Pilette, Ugo Gasparini, S. O. Holmgren, V. M. Perevoztchikov, J. Duboc, N. Colino, U. Trevisan, Josef Hrubec, E. A. De Wolf, H. Rohringer, S. Kitamura, M. Sessa, A. M. Endler, F. Fontanelli, T. Kageya, Yu Fisyak, P. E. Ermolov, J. V. Yarba, M. E. Michalon-Mentzer, Edoardo Castelli, A. De Angelis, F. Verbeure, S. Saran, Speranza Falciano, M. Mazzucato, M. I. Josa, S. Squarcia, J. Salicio, A. De Roeck, N. De Seriis, W.W.M. Allison, Elizaveta Shabalina, C. Troncon, A. Michalon, H. K. Nguyen, M. Aguilar-Benitez, A. Gurtu, Alan Poppleton, S. N. Ganguli, Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), and Heyd, Yvette
Subjects: Physics, Particle physics, Physics and Astronomy (miscellaneous), Spectrometer, [PHYS.NEXP] Physics [physics]/Nuclear Experiment [nucl-ex], Nuclear Theory, Bose–Einstein correlations, Lorentz covariance, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Charged particle, Nuclear physics, Pion, Reference sample, Average size, High Energy Physics::Experiment, Multiplicity (chemistry), Nuclear Experiment, Engineering (miscellaneous), Particle Physics - Experiment
Abstract: Bose-Einstein correlations among identically charged pions produced in pp collisions at 400 GeV/c are studied using the EHS spectrometer. Employing the Kopylov-Podgoretskii parametrization, the average size of the emitting region r(k) and its lifetime tau for pion production were determined to be r(k) = 1.71 +/- 0.04 fm and c-tau = 0.89 +/- 0.05 fm. The average size r(g) in terms of the Lorentz invariant Goldhaber parametrization was determined to be r(g) = 1.20 +/- 0.03 fm. A decrease of the size with increasing momentum of the pions was observed. The size and the incoherence parameter of the pion emitting region were determined as a function of the charged particle multiplicity and the momentum of the pions. Identified charged kaons were used to study Bose-Einstein correlations among identically charged kaons K+/- K+/-. The average size of the emitting region for kaon production was determined to be r(k) = 1.87 +/- 0.33 fm in terms of the Kopylov-Podgoretskii parametrization. A study of the influence of a reference sample is presented.
Published: 1992

31. The fine structure of ELMs in the scrape-off layer.

Author: M Endler, I García-Cortés, C Hidalgo, G F Matthews, and ASDEX Team and JET Team
Published: 2005

32. Vector meson production in $\pi^{-}$p interactions at 360 GeV/c

Author: L. Montanet, K. E. Johannson, A. Michalon-Mentzer, P. Pilette, S. O. Holmgren, H. K. Nguyen, Josef Hrubec, Edoardo Castelli, F. Fontanelli, F. Verbeure, Gianni Zumerle, E. P. Kistenev, P. Poropat, V. A. Stopchenko, A. De-Angelis, J. Salicio, Yu. Fisjak, M. Aguilar-Benitez, Yu. A. Golubkov, N. DeSeriis, H. Nowak, A. Gurtu, S. Squarcia, Speranza Falciano, A. DeRoeck, M. Mazzucato, M. I. Josa, S. Saran, Nicanor Colino, Alan Poppleton, V. M. Perevoztchikov, U. Trevisan, F. Simonetto, S. N. Ganguli, J. Duboc, Elizaveta Shabalina, C. Troncon, A. Michalon, J. L. Bailly, Ugo Gasparini, A. M. Endler, J. J. Hernandez, M. Iori, Simonetta Gentile, P. V. Chliapnikov, H. Rohringer, J. V. Yarba, R. Contri, R. Monge, Paolo Checchia, P.F. Ermolov, N. Sotnikova, A. A. Batalov, L. C. Oliveira, M. Sessa, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherches Subatomiques (IReS), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Cancéropôle du Grand Est-Université Louis Pasteur - Strasbourg I-Centre National de la Recherche Scientifique (CNRS), and LEBC-EHS
Subjects: Physics, Particle physics, Large Hadron Collider, Physics and Astronomy (miscellaneous), Meson, 010308 nuclear & particles physics, Elementary particle, 01 natural sciences, 7. Clean energy, Momentum, 0103 physical sciences, [PHYS.HEXP]Physics [physics]/High Energy Physics - Experiment [hep-ex], Field theory (psychology), Production (computer science), Vector meson, Quantum field theory, 010306 general physics, Engineering (miscellaneous), Particle Physics - Experiment
Abstract: The inclusive production of vector mesons (charged ρ(770), ω(783), ϕ(1020) and neutralK*(892)) in π−p interactions at 360 GeV/c is studied. The data are based on 160 000 reconstructed events recorded in the NA 27 Experiment using the LEBC-EHS facility at CERN. The production cross sections in the forward hemisphere in c.m.s. and the longitudinal momentum distributions are determined. The results are compared with data obtained at lower energies.
Published: 1989

33. Scenario with combined density and heating control to reduce the impact of the bootstrap current in Wendelstein 7-X.

Author: P. Sinha, D. Böckenhoff, M. Endler, J. Geiger, H. Hölbe, H.M. Smith, T.S. Pedersen, Y. Turkin, and Team, W7-X
Subjects: HEATING control, PLASMA boundary layers, POWER density, DENSITY, PROOF of concept, HEAT recovery
Abstract: Wendelstein 7-X is a low-shear stellarator with an island divertor, formed by natural magnetic islands at the plasma edge and ten modular divertor units for particle and energy exhaust. For the island divertor concept to work properly, the device is optimized for small internal currents. In particular, the bootstrap current is minimized. Previous studies predicted a thermal overload of the targets at a particular location, due to the slow evolution of the toroidal net current in the initial phase of certain otherwise desirable high-power discharges. The present numerical study explores the neoclassical predictions for the bootstrap current in more detail and demonstrates, as a proof of principle, that a path from low density and low heating power to high density and full heating power exists, on which the bootstrap current remains constant. This offers the possibility to reach the predetermined toroidal net current at low heating power, where no overload will occur in the transient phase. [ABSTRACT FROM AUTHOR]
Published: 2019
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34. Drift effects on W7-X divertor heat and particle fluxes.

Author: K C Hammond, Y Gao, M Jakubowski, C Killer, H Niemann, L Rudischhauser, A Ali, T Andreeva, B D Blackwell, K J Brunner, B Cannas, P Drewelow, P Drews, M Endler, Y Feng, J Geiger, O Grulke, J Knauer, S Klose, and S Lazerson
Subjects: HEAT flux, PLASMA flow, MAGNETIC fields, ELECTRIC fields, PLASMA boundary layers, POLOIDAL magnetic fields
Abstract: Classical particle drifts are known to have substantial impacts on fluxes of particles and heat through the edge plasmas in both tokamaks and stellarators. Here we present results from the first dedicated investigation of drift effects in the W7-X stellarator. By comparing similar plasma discharges conducted with a forward- and reverse-directed magnetic field, the impacts of drifts could be isolated through the observation of up-down asymmetries in flux profiles on the divertor targets. In low-density plasmas, the radial locations of the strike lines (i.e. peaks in the target heat flux profiles) exhibited discrepancies of up to 3 cm that reversed upon magnetic field reversal. In addition, asymmetric heat loads were observed in regions of the target that are shadowed by other targets from parallel flux from the core plasma. A comparison of these asymmetric features with the footprints of key topological regions of the edge magnetic field on the divertor suggests that the main driver of the asymmetries at low density is poloidal E × B drift due to radial electric fields in the scrape-off layer and private flux region. In higher-density plasmas, upper and lower targets collected non-ambipolar currents with opposite signs that also inverted upon field reversal. Overall, in these experiments, almost all up-down asymmetry could be attributed to the field reversal and, therefore, field-dependent drifts. [ABSTRACT FROM AUTHOR]
Published: 2019
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35. Managing leading edges during assembly of the Wendelstein 7-X divertor.

Author: M Endler, J Fellinger, H Hölbe, T Sunn Pedersen, S Bozhenkov, J Geiger, M Grahl, and Team, W7-X
Subjects: *MAGNETIC fields, *HEAT transfer, *PLASMA gases, *MAGNETIC resonance imaging, *X-ray diffraction
Abstract: Divertor target plates of magnetic confinement experiments are usually intersected by the magnetic field under a shallow angle. If steps are present in the target surface, the resulting leading edges will receive a strongly increased heat load as compared with the surrounding target surface. A very precise alignment of the target components is required to limit the height of leading edges in all magnetic configurations. In preparation of the initial divertor operation phase of the Wendelstein 7-X stellarator, we combined a model calculating the thermal load pattern on the targets for each magnetic configuration with a time-dependent model for heat transport within the targets, with a model for carbon sublimation and with measurements of step heights between target components to estimate the carbon sublimation rates to be expected. In a few locations of the as-built and as-installed divertor, these were found to be critically high, such that a limitation of plasma performance might have resulted. By re-aligning one type of target component according to the results of our modelling, the expected carbon sublimation rates were strongly reduced to uncritical levels. [ABSTRACT FROM AUTHOR]
Published: 2019
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36. Diamagnetic energy measurement during the first operational phase at the Wendelstein 7-X stellarator.

Author: K. Rahbarnia, H. Thomsen, U. Neuner, J. Schilling, J. Geiger, G. Fuchert, T. Andreeva, M. Endler, D. Hathiramani, T. Bluhm, M. Zilker, B.b. Carvalho, A. Werner, and Team, Wendelstein 7-X.
Subjects: DIAMAGNETIC materials, STELLARATORS, MAGNETIC flux, THOMSON scattering, X-ray imaging
Abstract: The magnetic diagnostic system at the Wendelstein 7-X stellarator includes three diamagnetic loops to measure magnetic flux changes in the plasma. Their signals are directly related to the plasma energy. The diagnostic design with respect to materials, component cooling and data acquisition is built to be fully steady-state capable within the harsh environment of a fusion plasma device. During the first operational phase, two diamagnetic loops have been put into operation, each of them close to one of the up-down symmetric main planes of the plasma column with a bean-shaped and triangular-shaped cross-section, respectively. Both loops measured reliable energies in accordance to theoretical expectations. The triangular-shaped diamagnetic loop is equipped with four compensation coils. They are used to compensate errors during the energy measurement due to small fluctuations of externally driven currents in the main superconducting magnetic field coils and eddy currents in the adjacent vacuum vessel and thereby increase the time-resolution allowing to measure fast changes of the plasma energy. The diamagnetic flux measurements agree well with corresponding estimations of diamagnetic signals using three-dimensional Biot–Savart calculations. A consistency check for the diamagnetic energy is performed by a reconstruction of the associated Pfirsch–Schlüter current distribution and a comparison of predicted signals with measurements of an arrangement of eight plasma encircling Rogowski coil segments. Additionally, the measured diamagnetic energy is compared to kinetic energy calculations based on density and temperature measurements performed by the Thomson scattering diagnostic and the x-ray imaging crystal spectrometer diagnostic. The resulting energy confinement times are similar to predictions of empirical scaling laws, like ISS04. For upcoming operational periods of Wendelstein 7-X, the diamagnetic energy measurement will be used to generate an interlock signal, which will turn off the main plasma heating systems in case of a sudden, unwanted plasma collapse. [ABSTRACT FROM AUTHOR]
Published: 2018
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37. Special Topic

Author: D. A. Hartmann, Florian Effenberg, H. Hölbe, D.A. Gates, H. P. Laqua, Samuel Lazerson, S. A. Bozhenkov, Hans-Stephan Bosch, Yuriy Turkin, Thomas Sunn Pedersen, M. Preynas, Matthias Otte, Torsten Stange, Oliver Schmitz, R. König, J. Geiger, Y. Feng, M. Endler, Tamara Andreeva, M. W. Jakubowski, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Nuclear and High Energy Physics, Computer science, Nuclear engineering, Divertor, Phase (waves), chemistry.chemical_element, Topology (electrical circuits), Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, law.invention, chemistry, law, 0103 physical sciences, Limiter, Wendelstein 7-X, 010306 general physics, Stellarator, Helium
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.
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38. Major results from the first plasma campaign of the Wendelstein 7-X stellarator

Author: H. Maaßberg, M. Grahl, V. Moncada, Marek Scholz, Naoki Tamura, H. Neilson, R. Koziol, M. Krychowiak, A. Lücke, T. Estrada, R. Munk, M. Marushchenko, K. Toi, Heinrich P. Laqua, S. Paqay, Olaf Grulke, K. Baumann, A. Czermak, Ivan Calvo, Yasuhiro Suzuki, P.J. Heitzenroeder, H. Hölbe, G. Offermanns, Gintautas Dundulis, U. Stridde, H. Hunger, S. Valet, P. Denner, N. Krawczyk, O. Mishchenko, Andrey Samartsev, Mantas Povilaitis, Andrea Pavone, H. Schumacher, P. Aleynikov, H. P. Laqua, U. Wenzel, M. Sibilia, J. Ongena, Kian Rahbarnia, A. Galkowski, T.A. Scherer, C. Slaby, J. Nührenberg, H.-J. Roscher, Martin Köppen, L.-G. Böttger, A. Czarnecka, R. Krampitz, M. Zilker, T. Kremeyer, J. Wendorf, V. Bykov, A. Goriaev, Josef Preinhaelter, A. Alonso, Peter Titus, G. Czymek, Andreas Langenberg, Matteo Zuin, A. Gogoleva, F. Musielok, A. Zeitler, Andreas Schlaich, P. Xanthopoulos, Victoria Winters, M. Losert, D. A. Hartmann, Roberto Guglielmo Citarella, L. Pacios Rodriguez, Boyd Blackwell, E. Blanco, Hans-Stephan Bosch, R. König, R. Stadler, J. Mittelstaedt, Ch. Linsmeier, U. Höfel, N. Panadero Alvarez, E. Pasch, Francesco Cordella, M. Knaup, Fabian Wilde, M. C. Zarnstorff, B. Mendelevitch, Toru Ii Tsujimura, T. Szabolics, Hayato Tsuchiya, J.C. Schmitt, Tadas Kaliatka, Sadayoshi Murakami, Samuel Lazerson, W. Spiess, J. M. García Regaña, P. Junghans, María Sánchez, A. Grosman, I. Yamada, K. P. Hollfeld, K. Aleynikova, Gábor Náfrádi, T. Krings, Daniel Papenfuß, José Luis Velasco, P. Drewelow, N. A. Pablant, S. Renard, Alessandro Zocco, F. Wagner, D. Böckenhoff, S. Ryosuke, Michael Kramer, A. Vorkörper, M. Turnyanskiy, R. Riedl, W. Figacz, H. Trimino Mora, A. da Silva, D. Gradic, M. Keunecke, A. Pieper, M. Houry, S. Pingel, K. H. Schlüter, J. Loizu Cisquella, L. Carraro, S. Schmuck, M. Banduch, Sehyun Kwak, T. Ilkei, X. Huang, Stefan Illy, N. Fahrenkamp, I. Vakulchyk, G. Kocsis, Ph. Mertens, T. Morizaki, K. Czerski, F. V. Chernyshev, Bernd Heinemann, L. Lewerentz, B.J. Peterson, Francisco Castejón, Olaf Neubauer, D. Zhang, Torsten Bluhm, F. Köchl, C.P. von Thun, Michael Cole, Fabio Pisano, R. Brakel, Peter Traverso, G. Orozco, Wolf-Dieter Schneider, A. A. Ivanov, S. Sipliä, V. Szabó, D. Pilopp, A. Cappa, G. Anda, H. Braune, A. Krämer-Flecken, R. Sakamoto, A. Charl, Hiroshi Kasahara, Massimiliano Romé, J.-H. Feist, Mark Cianciosa, M. Führer, G. Schlisio, Taina Kurki-Suonio, F. Purps, H. Esteban, A. H. Reiman, J. Krom, C. D. Beidler, D. Loesser, H. M. Smith, Nengchao Wang, Axel Könies, Oliver Schmitz, T. Bräuer, M. Hirsch, Gabriel G. Plunk, Felix Warmer, R. Karalevicius, Riccardo Nocentini, J.L. Terry, John Jelonnek, Arnold Lumsdaine, L. Ryć, M. N. A. Beurskens, H. Jenzsch, Z. Sulek, Donald A. Spong, A. Khilchenko, P. Marek, R. Schroeder, T. Schröder, B. Standley, Manfred Thumm, B. Brünner, T. Fornal, Benedikt Geiger, H. Frerichs, R. Kleiber, T. Funaba, Andreas Meier, S. Degenkolbe, P. Rong, Dag Hathiramani, Matthias F. Schneider, Simppa Äkäslompolo, M. R. Stoneking, A. Dudek, Jiawu Zhu, X. Han, T. Windisch, Y. Wei, Detlev Reiter, J. Tretter, N. Rust, J. P. Kallmeyer, J. Baldzuhn, P. Bolgert, Dirk Timmermann, Shinsuke Satake, Luis Vela Vela, Yu. Turkin, Z. Szökefalvi-Nagy, Sigitas Rimkevicius, Naoki Kenmochi, Ulrich Neuner, M. Garcia-Munoz, V. Perseo, Matthias Otte, A. Puig Sitjes, Tamás Szepesi, A. da Molin, Alexis Terra, C. Guerard, J.M. Hernández Sánchez, A. Rodatos, J. Assmann, D. Höschen, Albert Mollén, A. Hölting, Tom Wauters, Adnan Ali, Ewa Pawelec, W. Kasparek, Ryo Yasuhara, D. Kinna, P. Sinha, B. Wiegel, Horacio Fernandes, M. E. Puiatti, S. Récsei, E. Ascasíbar, J.-M. Travere, C. Hidalgo, Joris Fellinger, H. Schmitz, Suguru Masuzaki, Katsumi Ida, G. Pelka, Jim-Felix Lobsien, S. Wolf, Jörg Schacht, J. Koshurinov, Han Zhang, P. Kornejew, J M Fontdecaba, T. Ngo, E. Wang, B. Hein, Gerd Gantenbein, Michael Drevlak, M. Vervier, J. W. Oosterbeek, H. Röhlinger, J. P. Knauer, B. Schweer, Jakub Urban, David Maurer, I. Ksiazek, David Gates, S. C. Liu, S. Massidda, F. Remppel, A.H. Wright, G. Satheeswaran, Monika Kubkowska, K. Rummel, Kai Jakob Brunner, Torsten Stange, J. Riemann, Thomas Klinger, S. Obermayer, H. Brand, Christine Hennig, A. Werner, N. Gierse, S. A. Henneberg, R. Vilbrandt, J. Wolowski, T. Sunn Pedersen, M. Dostal, G. A. Wurden, I. Abramovic, Carsten Lechte, R. Lang, S. A. Bozhenkov, G. Ehrke, K. J. McCarthy, Egidijus Urbonavicius, M. Schröder, S. Jablonski, Martina Huber, M. Nagel, Yunfeng Liang, O. P. Ford, Barbara Cannas, T. Mizuuchi, Anatoly Panin, Jan Skodzik, V. V. Lutsenko, R. Koslowski, R. Laube, Jonathan T. Green, B. Unterberg, Jeremy Lore, Laurie Stephey, J. H. E. Proll, M. Czerwinski, Venanzio Giannella, Jörg Weggen, S. Marsen, Clifford M Surko, Grzegorz Gawlik, B. Roth, D. Birus, Ch. Brandt, M. Mardenfeld, K. Riße, Y. Feng, Alexandra M. Freund, M. Vergote, S. Wadle, H. Thomsen, Wilfried Behr, A. Runov, L. Wegener, Burkhard Plaum, J. Svensson, Dmitry Moseev, Łukasz Ciupiński, G. M. Weir, E. Winkler, W. Pan, E. Erckmann, D. Mellein, B. Shanahan, Th. Kobarg, Marek Barlak, John Howard, Günter Dammertz, M. Endler, D.P. Dhard, N. Vianello, L. V. Lubyako, R. Burhenn, J. Thomas, N. Panadero, M. Gruca, T. Mönnich, J. Majano-Brown, Wolfgang Biel, S. Tulipán, J. H. Harris, C. Nührenberg, A. Carls, H. Viebke, Walter H. Fietz, L. Haiduk, S. Brezinsek, Heinz Grote, S. Langish, V. Huber, Jacek Jagielski, David Ennis, P. Kraszewsk, J. Kacmarczyk, Kunihiro Ogawa, U. Kamionka, O. Bertuch, F. Durodié, B. Missal, A. de la Peña, Robertas Alzbutas, Anett Spring, Yu Gao, Matt Landreman, Dirk Naujoks, Florian Effenberg, P. McNeely, Ya. I. Kolesnichenko, B. Gonçalves, B. van Millingen, M. Blatzheim, X. Peng, F. Harberts, M. W. Jakubowski, F. Köster, Gábor Cseh, Ph. Drews, Christoph Biedermann, G. Claps, L. Rudischhauser, Bernardo B. Carvalho, M. Yokoyama, Seung Gyou Baek, Felix Schauer, V. Borsuk, Th. Rummel, J. Boscary, Fumimichi Sano, J. R. Danielson, M. Rack, G. Fuchert, H.-J. Hartfuß, W. Leonhardt, Georg Kühner, D. R. Mikkelsen, M. Borchardt, A. Benndorf, P. Scholz, R. C. Wolf, I.V. Shikhovtsev, Holger Niemann, Andreas Zimbal, J. Geiger, T. Barbui, M. Lennartz, A. Lorenz, Andreas Dinklage, G. Krzesiński, J. Zajac, B. Israeli, R. Schrittwieser, M.J. Cole, S. Zoletnik, O. Marchuk, Per Helander, B. Buttenschön, P. van Eeten, Tamara Andreeva, Hiroshi Yamada, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Max-Planck-Institut fur Plasmaphysik Teilinstitut Greifswald, Wendelsteinstr. 1, 17491 Greifswald, Germany, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), KFKI Research Institute for Particle and Nuclear Physics (KFKI-RMKI), Forschungszentrum Julich GmbH, Institut fur Energie- und Klimaforschung---Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), Wilhelm-Johnen-Strase, 52428 Julich, Germany, University of Maryland, Princeton, Laboratory for Plasma Physics of the Ecole Royale Militaire/Koninklijke Militaire School (LPP-ERM/KMS), Avenue de la Renaissance 30, 1000 Bruxelles, Belgien, Los Alamos National Laboratory (LANL), Institute of Physics, Massachusetts Institute of Technology, Cambridge, University of Wisconsin-Madison, National Centre for Nuclear Research (NCBJ), Institut für Experimentelle Kernphysik, Universität Karlsruhe (IEKP), Geoscience Australia, Max Planck Institut für Plasma Physik and Excellence Cluster, Eindhoven University of Technology, Università degli Studi di Cagliari = University of Cagliari (UniCa), Consorzio Interuniversitario per la Fisica Spaziale (CIFS), Instituto Superior Técnico, Universidade de Lisboa (IST), A.F. Ioffe Physical-Technical Institute, Russian Academy of Sciences [Moscow] (RAS), Computer Science and Mathematics Division, Oak Ridge National Laboratory, Università di Milano, Warsaw University of Technology, ENEA-Frascati, IPPLM Institute of Plasma Physics and Laser Microfusion, 23 Hery Str., 01-497 Warsaw, Poland, Institute of Nuclear Physics PAN, University of Szczecin, 70-453, aleja Papieza Jana Pawla II 22A, Szczecin, Poland, Milano, University of California [San Diego] (UC San Diego), University of California (UC), International Center for Climate and Global Change Research and School of Forestry and Wildlife Sciences, Auburn University, Brandenburg University of Technology Cottbus-Senftenberg, Universitatsplatz 1, 01968 Senftenberg, Germany, National Institute for Fusion Science (NIFS), 322-6 Oroshicho, Toki, Gifu Prefecture 509-5202, Japan, Universidad Carlos III de Madrid (UC3M), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Budker Institute of Nuclear Physics (BINP), 11, akademika Lavrentieva prospect, Novosibirsk, 630090, Russian Federation, Institut für Raumfahrtsysteme, Universität Stuttgart (IRS), Fraunhofer-Institut fur Schicht- und Oberflachentechnik IST, Bienroder Weg 54 E, 38108 Braunschweig, Germany, Institut für Weltraumforschung, Österreichische Akademie der Wissenschaften (IWF), Kiev Institute for Nuclear Research, A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP), Institut für Optik und Atomare Physik, Technische Universität Berlin, University of Opole, plac Kopernika 11a, 45-001 Opole, Poland, School of Electrical Engineering, Aalto University, Physikalisch-Technische Bundesanstalt (PTB), Kyoto University, Institute of Plasma Physics, Chinese Academy of Sciences, 350 Shushanhu Rd., Hefei, Anhui 230031, People's Republic of China, Institute of Plasma Physics of the Czech Academy of Science, Za Slovankou 1782/3, 182 00 Prague 8---Liben, Czechia, Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche (IFP-CNR), Fraunhofer-Institut fur Werkzeugmaschinen und Umformtechnik IWU, Reichenhainer Strase 88, 09126 Chemnitz, Germany, Universität Rostock, Wayne State University, Consiglio Nazionale delle Ricerche, Piazzale Aldo Moro, 7, 00185 Roma, Italy, Max Planck Institute for Plasma Physics, CIEMAT, Wigner Research Centre for Physics, Jülich Research Centre, University of Maryland, College Park, Princeton University, Royal Military Academy, Los Alamos National Laboratory, Lithuanian Energy Institute, Massachusetts Institute of Technology, Narodowe Centrum Badań Jadrowych, Karlsruhe Institute of Technology, Australian National University, University of Cagliari, National Research Council of Italy, Instituto Superior Tecnico Lisboa, Ioffe Institute, Oak Ridge National Laboratory, University of Salerno, Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, Soltan Institute for Nuclear Studies, The Henryk Niewodniczanski Institute of Nuclear Physics of the Polish Academy of Sciences, University of Szczecin, University of Milan - Bicocca, University of California San Diego, Auburn University, Brandenburg University of Technology, National Institute for Fusion Science, Universidad Carlos III de Madrid, CEA, Culham Centre for Fusion Energy, RAS - Budker Institute of Nuclear Physics, University of Stuttgart, Fraunhofer Institute for Surface Engineering and Thin Films, Austrian Academy of Sciences, NASU - Institute of Nuclear Research, RAS - Institute of Applied Physics, Technical University of Berlin, University of Opole, Department of Applied Physics, Physikalisch-Technische Bundesanstalt, CAS - Institute of Plasma Physics, Czech Academy of Sciences, Istituto di Fisica Del Plasma Piero Caldirola, Fraunhofer Institute for Machine Tools and Forming Technology, University of Rostock, Lawrence University, Aalto-yliopisto, Aalto University, Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, Claps, G., and Cordella, F
Subjects: Magnetic confinement, Nuclear and High Energy Physics, Technology and Engineering, Plasma heating, Cyclotron resonance, CONFINEMENT, 01 natural sciences, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, PHYSICS, Nuclear physics, stellarator, current drive, magnetic confinement, plasma heating, Condensed Matter Physics, law, 0103 physical sciences, ddc:530, 010306 general physics, tellarator, Stellarator, Physics, Magnetic confinement fusion, Plasma, 530 Physik, TRANSPORT, Current drive, Electron temperature, Plasma diagnostics, Atomic physics, Wendelstein 7-X, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 × 1019 m−3 , central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre. EURATOM 633053
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39. Scenario with combined density and heating control to reduce the impact of the bootstrap current in Wendelstein 7-X

Author: P. Sinha, D. Böckenhoff, H. Hölbe, Thomas Sunn Pedersen, H. M. Smith, Yuriy Turkin, M. Endler, J. Geiger, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Nuclear and High Energy Physics, Toroid, Divertor, Mechanics, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Bootstrap current, Physics::Plasma Physics, law, 0103 physical sciences, Transient (oscillation), Current (fluid), Wendelstein 7-X, Electric current, 010306 general physics, Stellarator
Abstract: Wendelstein 7-X is a low-shear stellarator with an island divertor, formed by natural magnetic islands at the plasma edge and ten modular divertor units for particle and energy exhaust. For the island divertor concept to work properly, the device is optimized for small internal currents, in particular, the bootstrap current is minimized. Previous studies predicted a thermal overload of the targets at a particular location, due to the slow evolution of the toroidal net current in the initial phase of certain otherwise desirable high-power discharges. The present numerical study explores the neoclassical predictions for the bootstrap current in more detail and demonstrates, as a proof of principle, that a path from low density and low heating power to high density and full heating power exists, on which the bootstrap current remains constant. This offers the possibility to reach the predetermined toroidal net current at low heating power, where no overload will occur in the transient phase.
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40. Confinement in Wendelstein 7-X limiter plasmas.

Author: M. Hirsch, A. Dinklage, A. Alonso, G. Fuchert, S. Bozhenkov, U. Höfel, T. Andreeva, J. Baldzuhn, M. Beurskens, H.-S. Bosch, C.D. Beidler, C. Biedermann, E. Blanco, R. Brakel, R. Burhenn, B. Buttenschön, A. Cappa, A. Czarnecka, M. Endler, and T. Estrada
Subjects: PLASMA confinement, PLASMA gases, STELLARATORS, ELECTRONS, PLASMA currents
Abstract: Observations on confinement in the first experimental campaign on the optimized Stellarator Wendelstein 7-X are summarized. In this phase W7-X was equipped with five inboard limiters only and thus the discharge length restricted to avoid local overheating. Stationary plasmas are limited to low densities <2–3 · 1019 m−3. With the available 4.3 MW ECR Heating core Te ~ 8 keV, Ti ~ 1–2 keV are achieved routinely resulting in energy confinement time τE between 80 ms to 150 ms. For these conditions the plasmas show characteristics of core electron root confinement with peaked Te-profiles and positive Er up to about half of the minor radius. Profiles and plasma currents respond to on- and off-axis heating and co- and counter ECCD respectively. [ABSTRACT FROM AUTHOR]
Published: 2017
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41. Plans for the first plasma operation of Wendelstein 7-X.

Author: T. Sunn Pedersen, T. Andreeva, H.-S. Bosch, S. Bozhenkov, F. Effenberg, M. Endler, Y. Feng, D.A. Gates, J. Geiger, D. Hartmann, H. Hölbe, M. Jakubowski, R. König, H.P. Laqua, S. Lazerson, M. Otte, M. Preynas, O. Schmitz, T. Stange, and Y. Turkin
Subjects: PLASMA physics, STELLARATORS, PLASMA confinement devices, FUSION reactor limiters, FUSION reactor materials
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. [ABSTRACT FROM AUTHOR]
Published: 2015
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42. Tracking of the magnet system geometry during Wendelstein 7-X construction to achieve the designed magnetic field.

Author: T. Andreeva, T. Bräuer, V. Bykov, K. Egorov, M. Endler, J. Fellinger, J. Kißlinger, M. Köppen, and F. Schauer
Subjects: MAGNETS, MAGNETIC fields, STELLARATORS, MANUFACTURING processes
Abstract: Wendelstein 7-X, currently under commissioning at the Max-Planck-Institut für Plasmaphysik in Greifswald, Germany, is a modular advanced stellarator, combining the modular coil concept with optimized properties of the plasma. Most of the envisaged magnetic configurations of the machine are rather sensitive to symmetry breaking perturbations which are the consequence of unavoidable manufacturing and assembly tolerances. This overview describes the successive tracking of the Wendelstein 7-X magnet system geometry starting from the manufacturing of the winding packs up to the modelling of the influence of operation loads. The deviations found were used to calculate the resulting error fields and to compare them with the compensation capacity of the trim coils. [ABSTRACT FROM AUTHOR]
Published: 2015
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43. Major results from the stellarator Wendelstein 7-AS.

Author: M Hirsch, J Baldzuhn, C Beidler, R Brakel, R Burhenn, A Dinklage, H Ehmler, M Endler, V Erckmann, Y Feng, J Geiger, L Giannone, G Grieger, P Grigull, J Hartfu, D Hartmann, R Jaenicke, R K, H P Laqua, and H Maa
Subjects: PHYSICS research, STELLARATORS, MAGNETOHYDRODYNAMICS, PLASMA devices
Abstract: Wendelstein 7-AS was the first modular stellarator device to test some basic elements of stellarator optimization: a reduced Shafranov shift and improved stability properties resulted in b-values up to 3.4% (at 0.9 T). This operational limit was determined by power balance and impurity radiation without noticeable degradation of stability or a violent collapse. The partial reduction of neoclassical transport could be verified in agreement with calculations indicating the feasibility of the concept of drift optimization. A full neoclassical optimization, in particular a minimization of the bootstrap current was beyond the scope of this project. A variety of non-ohmic heating and current drive scenarios by ICRH, NBI and in particular, ECRH were tested and compared successfully with their theoretical predictions. Besides, new heating schemes of overdense plasmas were developed such as RF mode conversion heating--Ordinary mode, Extraordinary mode, Bernstein-wave (OXB) heating--or 2nd harmonic O-mode (O2) heating. The energy confinement was about a factor of 2 above ISS95 without degradation near operational boundaries. A number of improved confinement regimes such as core electron-root confinement with central Te [?] 7 keV and regimes with strongly sheared radial electric field at the plasma edge resulting in Ti [?] 1.7 keV were obtained. As the first non-tokamak device, W7-AS achieved the H-mode and moreover developed a high density H-mode regime (HDH) with strongly reduced impurity confinement that allowed quasi-steady-state operation (t [?] 65 · tE) at densities \bar {n}_{\rme} \cong 4 \times 10^{20}\,\mbox{m}^{-3} (at 2.5 T). The first island divertor was tested successfully and operated with stable partial detachment in agreement with numerical simulations. With these results W7-AS laid the physics background for operation of an optimized low-shear steady-state stellarator. [ABSTRACT FROM AUTHOR]
Published: 2008

44. A silent pandemic of violence against providers in obstetrics and gynecology: A mixed-methods study based on a global survey.

Author: Endler M, Ramirez-Negrin A, and Sohail R
Abstract: Objectives: To quantify and qualify the experience of workplace violence (WPV) in a global sample of providers in obstetrics and gynecology (OBGYN)., Methods: We performed a mixed-methods analysis on data from a global survey. Survey content was designed around categorical and open-ended questions in relation to WPV; the occurrence and character, the physical and psychological consequences, training and support structures, and perceived triggers of the experience of WPV. Quantitative data were analyzed using descriptive statistics and text data using mixed deductive-inductive content analysis. These data were integrated using convergent joint display., Results: Between October 2023 and January 2024, survey responses were collected from 77 individual countries. Among the final sample, 764/1016 (75.2%) had experienced WPV, 699/1016 (68.8%) verbal, and 123/1016 (12.1%) physical violence. The violence affected physical health, psychological health, or job satisfaction for 106/764 (13.9%), 36/7642 (47.4%), and 222/764 (29.1%) of individuals respectively; 216/764 (28.3%) received support. Main WPV triggers were staff shortages, lack of security personnel, and long waiting times, identified by 38.8%, 37.5%, and 37.3% of respondents respectively. Qualitative data indicated that violence caused severe and long-lasting suffering. Catalysts for WPV were often reported as complex interplays between unmet or unrealistic expectations and insufficient resources. Lack of support for WPV was explained as violence being "part of the job" and a culture of assumed resilience among providers., Conclusion: WPV against OBGYN providers seems to be ubiquitous, arises from a complex interplay of factors, and causes significant injury while receiving insufficient mitigation and support., (© 2024 The Author(s). International Journal of Gynecology & Obstetrics published by John Wiley & Sons Ltd on behalf of International Federation of Gynecology and Obstetrics.)
Published: 2024
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45. No test medical abortion - a review of the evidence on selective use of preabortion testing.

Author: Cleeve A, Wallengren E, Brandell K, Lee S, Endler M, and Reynolds-Wright J
Subjects: Humans, Female, Pregnancy, Health Services Accessibility, Pregnancy, Ectopic diagnosis, Abortion Applicants psychology, Abortion, Induced, Telemedicine
Abstract: Purpose of Review: The last decade has seen a cascade of different telemedicine models for medical abortion (MA) being tested and implemented. Among these service delivery models is the 'no-test' MA model, in which care is provided remotely and eligibility for the MA is based on history alone. The purpose of this review is to provide an overview of the existing evidence for no-test MA., Recent Findings: The evidence base for no-test MA relies heavily on cohort and noncomparative studies predominantly from high resource settings. Recent findings indicate that no-test MA is safe, effective, and highly acceptable. Diagnoses of ectopic pregnancy and underestimation of gestational age were rare. Identified advantages included shortening time to access MA and mitigating access barriers such as cost, and geographical barriers. Abortion seekers valued omitting the ultrasound citing reasons such as privacy concerns, costs, more flexibility, and control. The impacts of no-test MA on unscheduled postabortion contacts and visits and on contraceptive use were unclear due to limited evidence., Summary: No-test MA can be provided to complement other care pathways including those with some or no in-person care. Further research is needed to allow for widespread adoption of no-test MA and scale-up in a variety of contexts, including low-resource settings., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)
Published: 2024
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46. Pop-up Langmuir probe diagnostic in the water cooled divertor of Wendelstein 7-X.

Author: Pandey A, Bohm S, Carls A, Cordes C, Endler M, Fellinger J, Freundt S, Gallowski K, Hammond K, Hathiramani D, Isberner G, Kallmeyer JP, Krause M, Kügler J, Otte M, Pedersen TS, Rondeshagen D, Ruhnau J, Schröder T, Sieber T, and Wendorf J
Abstract: The design, development, and successful implementation of pop-up Langmuir probes installed in the water-cooled divertor of W7-X are described. The probes are controlled by drive coils (actuators) installed behind the divertor plates. These drive coils make use of the magnetic field in W7-X to move the probe tips into and out of the plasma. The drive coils were installed in the vacuum vessel after extensively testing the durability of the coils and analyzing the criteria for safe operation. The probe design is carefully tailored for each of the 36 probe tips in order to be suitable for the different magnetic field configurations used in W7-X and ensure that the probes do not present leading edges to the magnetic flux tubes. An electronic bridge circuit is used for measurement to compensate for the effects of signal propagation time on the long cable lengths used. The diagnostic is integrated with the segment control of W7-X for automated operation and control of the diagnostic. The evaluation of the results from the plasma operation is presented after accounting for appropriate sheath expansion for negative bias voltage on the probes., (© 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).)
Published: 2024
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47. "I hope to all the world they don't forget women of Afghanistan": An interrupted survey among doctors in Afghanistan.

Author: Endler M, Hassan L, Gemzell-Danielsson K, Babak S, and Sohail R
Subjects: Humans, Female, Pregnancy, Afghanistan epidemiology, Cross-Sectional Studies, Prenatal Care, Surveys and Questionnaires, Reproductive Health Services
Abstract: Objective: To assess current access to essential sexual and reproductive health (SRHR) services in Afghanistan and how access has changed with the transition of power., Methods: This is a cross-sectional study based on data from an anonymous survey among doctors in Afghanistan in May 2022, analyzed using descriptive statistics. The survey recorded subjective estimates of access to SRHR services, barriers to access, extent of maternal mortality or near miss due to preventable factors, and the effect of the regime change on access., Results: The data collection was interrupted after 60 responses. A majority of providers responded that their population went hungry often or always. According to our criteria for "access", that 75% or more of the population was estimated to have it, no respondents (0%) assessed that access existed for services for gender-based violence. The corresponding proportion responding that access existed was 3.4% for services after rape, 12.6% for legal abortion, 13.3% for antenatal care, and 20% for labor care. According to 41.7% of respondents, untreated postpartum hemorrhage accounted for a large or very large proportion of preventable maternal mortality or near miss. Almost half of respondents (47.4%) reported the same for lack of skilled providers, 66.2% reported it for the concept "too many pregnancies", and 55% reported it for malnutrition and poor health. According to 43.3% of respondents, the regime change had reduced access to labor care to a large extent, 33.9% of respondents said this in relation to access to contraceptives, and 43.1% for overall access for internally displaced persons., Conclusion: Interim data suggest that women in some settings in Afghanistan have no access to SRHR services, that preventable factors account for a large portion of maternal deaths or near miss, and that access has deteriorated since the transition of power., (© 2023 The Authors. International Journal of Gynecology & Obstetrics published by John Wiley & Sons Ltd on behalf of International Federation of Gynecology and Obstetrics.)
Published: 2023
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48. Editorial: Women facing crises.

Author: Endler M, Ramirez-Negrin A, and Johnson TRB
Published: 2023
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49. Are sexual and reproductive health and rights taught in medical school? Results from a global survey.

Author: Endler M, Al-Haidari T, Benedetto C, Chowdhury S, Christilaw J, El Kak F, Galimberti D, Gutierrez M, Ibrahim S, Kumari S, McNicholas C, Flores DM, Muganda J, Ramirez-Negrin A, Senanayake H, Sohail R, Temmerman M, and Gemzell Danielsson K
Subjects: Pregnancy, Female, Humans, Schools, Medical, Reproductive Rights, Surveys and Questionnaires, Reproductive Health, Sexual Health
Abstract: Our aim was to investigate the inclusion of sexual and reproductive health and rights (SRHR) topics in medical curricula and the perceived need for, feasibility of, and barriers to teaching SRHR. We distributed a survey with questions on SRHR content, and factors regulating SRHR content, to medical universities worldwide using chain referral. Associations between high SRHR content and independent variables were analyzed using unconditional linear regression or χ 2 test. Text data were analyzed by thematic analysis. We collected data from 219 respondents, 143 universities and 54 countries. Clinical SRHR topics such as safe pregnancy and childbirth (95.7%) and contraceptive methods (97.2%) were more frequently reported as taught compared with complex SRHR topics such as sexual violence (63.8%), unsafe abortion (65.7%), and the vulnerability of LGBTQIA persons (23.2%). High SRHR content was associated with high-income level (P = 0.003) and low abortion restriction (P = 0.042) but varied within settings. Most respondents described teaching SRHR as essential to the health of society. Complexity was cited as a barrier, as were cultural taboos, lack of stakeholder recognition, and dependency on fees and ranking., (© 2022 The Authors. International Journal of Gynecology & Obstetrics published by John Wiley & Sons Ltd on behalf of International Federation of Gynecology and Obstetrics.)
Published: 2022
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50. Impact of the COVID-19 pandemic on access to and utilisation of services for sexual and reproductive health: a scoping review.

Author: VanBenschoten H, Kuganantham H, Larsson EC, Endler M, Thorson A, Gemzell-Danielsson K, Hanson C, Ganatra B, Ali M, and Cleeve A
Subjects: Adolescent, Adult, Female, Humans, Middle Aged, Pandemics, Pregnancy, Reproductive Health, Young Adult, COVID-19, Reproductive Health Services, Sexual Health, Sexually Transmitted Diseases prevention & control
Abstract: Introduction: The COVID-19 pandemic has negatively impacted health systems globally and widened preexisting disparities. We conducted a scoping review on the impact of the COVID-19 pandemic on women and girls' access to and utilisation of sexual and reproductive health (SRH) services for contraception, abortion, gender-based and intimate partner violence (GBV/IPV) and sexually transmitted infections (STIs)., Methods: We systematically searched peer reviewed literature and quantitative reports, published between December 2019 and July 2021, focused on women and girls' (15-49 years old) access to and utilisation of selected SRH services during the COVID-19 pandemic. Included studies were grouped based on setting, SRH service area, study design, population and reported impact. Qualitative data were coded, organised thematically and grouped by major findings., Results: We included 83 of 3067 identified studies and found that access to contraception, in-person safe abortion services, in-person services for GBV/IPV and STI/HIV testing, prevention and treatment decreased. The geographical distribution of this body of research was uneven and significantly less representative of countries where COVID-19 restrictions were very strict. Access was limited by demand and supply side barriers including transportation disruptions, financial hardships, limited resources and legal restrictions. Few studies focused on marginalised groups with distinct SRH needs., Conclusion: Reports indicated negative impacts on access to and utilisation of SRH services globally, especially for marginalised populations during the pandemic. Our findings call for strengthening of health systems preparedness and resilience to safeguard global access to essential SRH services in ongoing and future emergencies., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)
Published: 2022
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