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

Author: W7-X Team, Beurskens, M. N. A., Angioni, C., Bozhenkov, S. A., Ford, O., Kiefer, C., Xanthopoulos, P., Turkin, Y., Alcusón, J. A., Baehner, J. P., Beidler, C., Birkenmeier, G., Fable, E., Fuchert, G., Geiger, B., Grulke, O., Hirsch, M., Jakubowski, M., Laqua, H. P., Langenberg, A., Lazerson, S., Pablant, N., Reisner, M., Schneider, P., Scott, E. R., Stange, T., Stechow, A. von, Stober, J., Stroth, U., Wegner, Th., Weir, G., Zhang, D., Zocco, A., Wolf, R. C., Zohm, H., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, ASDEX Upgrade Team, Max Planck Institute for Plasma Physics, Max Planck Society, and EUROfusion MST1 Team
Subjects: Technology, Nuclear and High Energy Physics, Turbulent transport, Materials science, Turbulence, Ion temperature clamping, Plasma, Electron, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Nuclear physics, Electron heating, ASDEX Upgrade, Physics::Plasma Physics, 0103 physical sciences, Stellarator transport, Wendelstein 7-X, ddc:620, 010306 general physics, ddc:600
Abstract: In electron (cyclotron) heated plasmas, in both ASDEX Upgrade (L-mode) and Wendelstein 7-X, clamping of the ion temperature occurs at T i ∼ 1.5 keV independent of magnetic configuration. The ions in such plasmas are heated through the energy exchange power as n e 2 ( T e − T i ) / T e 3 / 2 , which offers a broad ion heating profile, similar to that offered by alpha heating in future thermonuclear fusion reactors. However, the predominant electron heating may put an additional constraint on the ion heat transport, as the ratio T e/T i > 1 can exacerbates ITG/TEM core turbulence. Therefore, in practical terms the strongly ‘stiff’ core transport translates into T i-clamping in electron heated plasmas. Due to this clamping, electron heated L-mode scenarios, with standard gas fueling, in either tokamaks or stellarators may struggle to reach high normalized ion temperature gradients required in a compact fusion reactor. The comparison shows that core heat transport in neoclassically optimized stellarators is driven by the same mechanisms as in tokamaks. The absence of a strong H-mode temperature edge pedestal in stellarators, sofar (which, like in tokamaks, could lift the clamped temperature-gradients in the core), puts a strong requirement on reliable and sustainable core turbulence suppression techniques in stellarators.
Published: 2021
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2. Transition between Instability and Seeded Self-Modulation of a Relativistic Particle Bunch in Plasma

Author: Batsch, F, Muggli, P, Agnello, R, Ahdida, CC, Amoedo Goncalves, MC, Andrebe, Y, Apsimon, O, Apsimon, R, Bachmann, A-M, Baistrukov, MA, Blanchard, P, Braunmüller, F, Burrows, PN, Buttenschön, B, Caldwell, A, Chappell, J, Chevallay, E, Chung, M, Cooke, DA, Damerau, H, Davut, C, Demeter, G, Deubner, HL, Doebert, S, Farmer, J, Fasoli, A, Fedosseev, VN, Fiorito, R, Fonseca, RA, Friebel, F, Furno, I, Garolfi, L, Gessner, S, Gorgisyan, I, Gorn, AA, Granados, E, Granetzny, M, Graubner, T, Grulke, O, Gschwendtner, E, Hafych, V, Helm, A, Henderson, JR, Hüther, M, Kargapolov, I Yu, Kim, S-Y, Kraus, F, Krupa, M, Lefevre, T, Liang, L, Liu, S, Lopes, N, Lotov, KV, Martyanov, M, Mazzoni, S, Medina Godoy, D, Minakov, VA, Moody, JT, Moon, K, Morales Guzmán, PI, Moreira, M, Nechaeva, T, Nowak, E, Pakuza, C, Panuganti, H, Pardons, A, Perera, A, Pucek, J, Pukhov, A, Ramjiawan, RL, Rey, S, Rieger, K, Schmitz, O, Senes, E, Silva, LO, Speroni, R, Spitsyn, RI, Stollberg, C, Sublet, A, Topaloudis, A, Torrado, N, Tuev, PV, Turner, M, Velotti, F, Verra, L, Verzilov, VA, Vieira, J, Vincke, H, Welsch, CP, Wendt, M, Wing, M, Wiwattananon, P, Wolfenden, J, Woolley, B, Xia, G, Zepp, M, Zevi Della Porta, G, AWAKE Collaboration, and Collaboration, AWAKE
Subjects: Accelerator Physics (physics.acc-ph), Proton, Other Fields of Physics, Phase (waves), FOS: Physical sciences, General Physics and Astronomy, Ciências Naturais::Ciências Físicas [Domínio/Área Científica], 01 natural sciences, Instability, Relativistic particle, physics.plasm-ph, 0103 physical sciences, 010306 general physics, physics.acc-ph, Physics, acceleration, Plasma, electron-beam, Accelerators and Storage Rings, Physics - Plasma Physics, ddc, Plasma Physics (physics.plasm-ph), Transverse plane, Amplitude, Physics::Accelerator Physics, Physics - Accelerator Physics, Atomic physics, Event (particle physics)
Abstract: We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of a long proton bunch in plasma. We show experimentally that, with sufficient initial amplitude ($\ge(4.1\pm0.4)$ MV/m), the phase of the modulation along the bunch is reproducible from event to event, with 3 to 7% (of 2$\pi$) rms variations all along the bunch. The phase is not reproducible for lower initial amplitudes. We observe the transition between these two regimes. Phase reproducibility is essential for deterministic external injection of particles to be accelerated., Comment: Letter and Supplemental Material, 6 figures, 8 pages
Published: 2021
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3. Characterization of injection and confinement improvement through impurity induced profile modifications on the Wendelstein 7-X stellarato

Author: W7-X Team, Lunsford, R., Killer, C., Nagy, A., Gates, D. A., Klinger, T., Dinklage, A., Satheeswaran, G., Kocsis, G., Lazerson, S. A., Nespoli, F., Pablant, N. A., Stechow, A. von, Alonso, A., Andreeva, T., Beurskens, M., Biedermann, C., Brezinsek, S., Brunner, K. J., Buttenschön, B., Carralero, D., Cseh, G., Drewelow, P., Effenberg, F., Estrada, T., Ford, O. P., Grulke, O., Hergenhahn, U., Höefel, U., Knauer, J., Krause, M., Krychowiak, M., Kwak, S., Langenberg, A., Neuner, U., Nicolai, D., Pavone, A., Puig Sitjes, A., Rahbarnia, K., Schilling, J., Svensson, J., Szepesi, T., Thomsen, H., Wauters, T., Windisch, T., Winters, V., Zhang, D., Zsuga, L., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Technology, Electron density, Plasma, Boron carbide, Condensed Matter Physics, 01 natural sciences, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, Ion, chemistry.chemical_compound, chemistry, law, Electric field, 0103 physical sciences, ddc:530, Wendelstein 7-X, Atomic physics, 010306 general physics, ddc:600, Stellarator
Abstract: Pulsed injections of boron carbide granules into Wendelstein 7-X stellarator (W7-X) plasmas transiently increase the plasma stored energy and core ion temperatures above the reference W7-X experimental programs by up to 30%. In a series of 4 MW electron cyclotron resonance heating experiments, the PPPL Probe Mounted Powder Injector provided 50 ms bursts of 100 μm granules every 350 ms at estimated quantities ranging from approximately 1 mg/pulse to over 30 mg/pulse. For each injection, the stored energy was observed to initially drop and the radiated power transiently increased, while the radial electron density profile rose at the edge as material was assimilated. Once the injected boron carbide was fully absorbed, the density rise transitioned to the core while the stored energy increased above the previous baseline level by an amount linearly correlated with the injection quantity. During the injection, the ion temperature gradient steepened with peak core ion temperatures observed to increase from a nominal 1.7 keV to over 2.6 keV for the largest injection amounts. Enhanced performance is accompanied by a reversal of the radial electric field at ρ < 0.3, indicating that the core transport has switched to the ion root. These observations are suggestive of a change in transport and provide further evidence that externally induced profile modifications provide a possible path to enhanced W7-X performance metrics.I. INTRODUCTIO
Published: 2021
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4. Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X

Author: W7-X Team, Weir, G. M., Xanthopoulos, P., Hirsch, M., Höfel, U., Stange, T., Pablant, N., Grulke, O., Äkäslompolo, S., Alcusón, J., Bozhenkov, S., Beurskens, M., Dinklage, A., Fuchert, G., Geiger, J., Landreman, M., Langenberg, A., Lazerson, S., Marushchenko, N., Pasch, E., Schilling, J., Scott, E. R., Turkin, Y., Klinger, T., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Nuclear and High Energy Physics, Technology, Heat pulse, Electron, Collisionality, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, Atomic physics, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract: The optimized stellarator Wendelstein 7-X (W7-X) is designed to have an approximately quasi-isodynamic magnetic configuration with reduced neoclassical transport in comparison to a classical stellarator, and turbulent transport is expected to be a significant source of anomalous heat transport across the plasma minor radius. The ion temperature gradient driven mode and the trapped electron mode (TEM) are thought to be responsible for the ion-scale turbulence in W7-X plasmas with volume averaged pressure below 1%. In this work, the electron temperature gradient driven turbulence is shown to be a good candidate for the explanation of the observed electron heat flux, in the inner plasma region where the density gradient is weak (in the outer region, a relatively stronger density gradient would drive additional TEM turbulence). The experimental electron heat transport measured during electron cyclotron resonant heating power and plasma density scans is compared to neoclassical predictions, and the stiffness in the electron heat transport measured during transient transport experiments is presented in three common magnetic configurations of W7-X. In low-⟨β⟩ plasma discharges, the stiffness in the electron heat flux, quantified by the ratio of the heat pulse to power balance diffusivity, χ e H P / χ e P B , is measured to be less than 2, and trend downwards with increasing collisionality.
Published: 2021
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5. Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

Author: W7-X Team, Beidler, C. D., Smith, H. M., Alonso, A., Andreeva, T., Baldzuhn, J., Beurskens, M. N. A., Borchardt, M., Bozhenkov, S. A., Brunner, K. J., Damm, H., Drevlak, M., Ford, O. P., Fuchert, G., Geiger, J., Helander, P., Hergenhahn, U., Hirsch, M., Höfel, U., Kazakov, Ye. O., Kleiber, R., Krychowiak, M., Kwak, S., Langenberg, A., Laqua, H. P., Neuner, U., Pablant, N. A., Pasch, E., Pavone, A., Pedersen, T. S., Rahbarnia, K., Schilling, J., Scott, E. R., Stange, T., Svensson, J., Thomsen, H., Turkin, Y., Warmer, F., Wolf, R. C., Zhang, D., Abramovic, I., Äkäslompolo, S., Alcusón, J., Aleynikov, P., Aleynikova, K., Ali, A., Anda, G., Ascasibar, E., Bähner, J. P., Baek, S. G., Balden, M., Banduch, M., Barbui, T., Behr, W., Benndorf, A., Biedermann, C., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., Böckenhoff, D., Böswirth, B., Böttger, L.-G., Borsuk, V., Boscary, J., Bosch, H.-S., Brakel, R., Brand, H., Brandt, C., Bräuer, T., Braune, H., Brezinsek, S., Brunner, K.-J., Burhenn, R., Bussiahn, R., Buttenschön, B., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., Carraro, L., Carvalho, B., Castejon, F., Charl, A., Chaudhary, N., Chauvin, D., Chernyshev, F., Cianciosa, M., Citarella, R., Claps, G., Coenen, J., Cole, M., Cole, M. J., Cordella, F., Cseh, G., Czarnecka, A., Czerski, K., Czerwinski, M., Czymek, G., Molin, A. da, Silva, A. da, Pena, A. de la, Degenkolbe, S., Dhard, C. P., Dibon, M., Dinklage, A., Dittmar, T., Drewelow, P., Drews, P., Durodie, F., Edlund, E., Effenberg, F., Ehrke, G., Elgeti, S., Endler, M., Ennis, D., Esteban, H., Estrada, T., Fellinger, J., Feng, Y., Flom, E., Fernandes, H., Fietz, W. H., Figacz, W., Fontdecaba, J., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Gao, Y., García Regaña, J., Gates, D., Geiger, B., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Grulke, O., Guerard, C., Hacker, P., Han, X., Harris, J. H., Hartmann, D., Hathiramani, D., Hein, B., Heinemann, B., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hollfeld, K. P., Hölting, A., Höschen, D., Houry, M., Howard, J., Huang, X., Huang, Z., Hubeny, M., Huber, M., Hunger, H., Ida, K., Ilkei, T., Illy, S., Israeli, B., Jablonski, S., Jakubowski, M., Jelonnek, J., Jenzsch, H., Jesche, T., Jia, M., Junghanns, P., Kacmarczyk, J., Kallmeyer, J.-P., Kamionka, U., Kasahara, H., Kasparek, W., Kenmochi, N., Killer, C., Kirschner, A., Klinger, T., Knauer, J., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., Köchl, F., Kolesnichenko, Y., Könies, A., König, R., Kornejew, P., Koschinsky, J.-P., Köster, F., Krämer, M., Krampitz, R., Krämer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Ksiazek, I., Kubkowska, M., Kühner, G., Kurki-Suonio, T., Kurz, P. A., Landreman, M., Lang, P., Lang, R., Langish, S., Laqua, H., Laube, R., Lazerson, S., Lechte, C., Lennartz, M., Leonhardt, W., Li, C., Li, Y., Liang, Y., Linsmeier, C., Liu, S., Lobsien, J.-F., Loesser, D., Loizu Cisquella, J., Lore, J., Lorenz, A., Losert, M., Lücke, A., Lumsdaine, A., Lutsenko, V., Maaßberg, H., Marchuk, O., Matthew, J. H., Marsen, S., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., McCarthy, K., McNeely, P., Meier, A., Mellein, D., Mendelevitch, B., Mertens, P., Mikkelsen, D., Mishchenko, A., Missal, B., Mittelstaedt, J., Mizuuchi, T., Mollen, A., Moncada, V., Mönnich, T., Morisaki, T., Moseev, D., Murakami, S., Náfrádi, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Ngo, T., Nicolai, D., Nielsen, S. K., Niemann, H., Nishizawa, T., Nocentini, R., Nührenberg, C., Nührenberg, J., Obermayer, S., Offermanns, G., Ogawa, K., Ölmanns, J., Ongena, J., Oosterbeek, J. W., Orozco, G., Otte, M., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfuß, D., Paqay, S., Pawelec, E., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., Pölöskei, P., Porkolab, M., Proll, J., Puiatti, M.-E., Puig Sitjes, A., Purps, F., Rack, M., Récsei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riedl, R., Riemann, J., Risse, K., Rohde, V., Röhlinger, H., Romé, M., Rondeshagen, D., Rong, P., Roth, B., Rudischhauser, L., Rummel, K., Rummel, T., Runov, A., Rust, N., Ryc, L., Ryosuke, S., Sakamoto, R., Salewski, M., Samartsev, A., Sanchez, M., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schlaich, A., Schlisio, G., Schluck, F., Schlüter, K.-H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schröder, M., Schröder, T., Schroeder, R., Schumacher, H., Schweer, B., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Sipliä, S., Slaby, C., Sleczka, M., Spiess, W., Spong, D. A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Szabó, V., Szabolics, T., Szepesi, T., Szökefalvi-Nagy, Z., Tamura, N., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulipán, S., Unterberg, B., Vakulchyk, I., Valet, S., Vanó, L., Eeten, P. van, Milligen, B. van, Vuuren, A. J. van, Vela, L., Velasco, J.-L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Stechow, A. von, Vorköper, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Wauters, T., Wegener, L., Weggen, J., Wegner, T., Wei, Y., Weir, G., Wendorf, J., Wenzel, U., Werner, A., White, A., Wiegel, B., Wilde, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, S., Wright, A., Wurden, G., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zanini, M., Zarnstorff, M., Zeitler, A., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., Zuin, M., W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, Applied Physics and Science Education, Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, and European Commission
Subjects: Magnetically Confined Plasmas, Tokamak, Design, Helias, Nuclear engineering, Magnetically confined plasmas, 01 natural sciences, 7. Clean energy, Article, Plasma physics, 010305 fluids & plasmas, law.invention, law, Physics::Plasma Physics, 0103 physical sciences, Nuclear fusion, 010306 general physics, Engineering & allied operations, Stellarator, Physics, Plasma fusion, Multidisciplinary, Toroid, biology, Plasma Physics, Física, Magnetic confinement fusion, Plasma, biology.organism_classification, Energía Nuclear, ddc:620, Wendelstein 7-X
Abstract: Research on magnetic confinement of high-temperature plasmas has the ultimate goal of harnessing nuclear fusion for the production of electricity. Although the tokamak1 is the leading toroidal magnetic-confinement concept, it is not without shortcomings and the fusion community has therefore also pursued alternative concepts such as the stellarator. Unlike axisymmetric tokamaks, stellarators possess a three-dimensional (3D) magnetic field geometry. The availability of this additional dimension opens up an extensive configuration space for computational optimization of both the field geometry itself and the current-carrying coils that produce it. Such an optimization was undertaken in designing Wendelstein 7-X (W7-X)2, a large helical-axis advanced stellarator (HELIAS), which began operation in 2015 at Greifswald, Germany. A major drawback of 3D magnetic field geometry, however, is that it introduces a strong temperature dependence into the stellarator’s non-turbulent ‘neoclassical’ energy transport. Indeed, such energy losses will become prohibitive in high-temperature reactor plasmas unless a strong reduction of the geometrical factor associated with this transport can be achieved; such a reduction was therefore a principal goal of the design of W7-X. In spite of the modest heating power currently available, W7-X has already been able to achieve high-temperature plasma conditions during its 2017 and 2018 experimental campaigns, producing record values of the fusion triple product for such stellarator plasmas3,4. The triple product of plasma density, ion temperature and energy confinement time is used in fusion research as a figure of merit, as it must attain a certain threshold value before net-energy-producing operation of a reactor becomes possible1,5. Here we demonstrate that such record values provide evidence for reduced neoclassical energy transport in W7-X, as the plasma profiles that produced these results could not have been obtained in stellarators lacking a comparably high level of neoclassical optimization., Previously documented record values of the fusion triple product in the stellarator Wendelstein 7-X are shown to be evidence for reduced neoclassical energy transport in this optimized device.
Published: 2021
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6. Experimental study of extended timescale dynamics of a plasma wakefield driven by a self-modulated proton bunch

Author: Chappell, J., Adli, E., Agnello, R., Aladi, M., Andrebe, Y, Apsimon, O., Apsimon, R., Bachmann, A.-M., Baistrukov, M. A., Batsch, F., Bergamaschi, M., Della Porta, G. Z., Blanchard, P., Burrows, P. N., Buttenschön, B., Caldwell, A., Chevallay, E., Chung, M., Cooke, D. A., Damerau, H., Davut, C., Demeter, G., Deubner, L. H., Dexter, A., Djotyan, G. P., Doebert. S., Farmer, J., Fasoli, A., Fedosseev, V. N., Fiorito, R., Fonseca, R. A., Friebel, F., Furno, I., Garolfi, L., Gessner, S., Goddard, B., Gorgisyan, I., Gorn, A. A., Granados, E., Granetzny, M., Grulke, O., Gschwendtner, E., Hafych, V., Hartin, A., Helm, A, Henderson, J. R., Howling, A., Hüther, M ., Jacquier, R., Jolly, S. W., Kargapolov, I. Y., Kedves, M. Á., Keeble, F., Kelisani, M. D., Kim, S.-Y, Krausz, F., Krupa, M., Lefevre, T ., Li, Y., Liang, L., Liu, S., Lopes, N. C., Lotov, K. V., Martyanov, M., Mazzoni, S., Medina Godoy, D., Militsyn, B. L., Minakov, V. A., Moody, J. T., Morales Guzmán, P. I., Moreira, M. T., Panuganti, H., Pardons, A., Peña Asmus, F., Perera, A., Petrenko, A., Pucek, J., Pukhov, A., Ráczkevi, B., Ramjiawan, R. L., Rey, S., Ruhl, H., Saberi, H., Schmitz, O., Senes, E., Sherwood, P., Silva, L. O., Spitsyn, R. I., Tuev, P. V., Velotti, F., Verra, L., Verzilov, V. A., Vieira, J., Welsch, C. P., Williamson, B., Wing, M., Wolfenden, J., Woolley, B., Xia, G. X., and Zepp, M.
Subjects: Accelerator Physics (physics.acc-ph), Nuclear and High Energy Physics, Physics and Astronomy (miscellaneous), Proton, Other Fields of Physics, FOS: Physical sciences, Electron, 01 natural sciences, law.invention, law, Electron injection, Physics::Plasma Physics, physics.plasm-ph, 0103 physical sciences, 010306 general physics, physics.acc-ph, Physics, 010308 nuclear & particles physics, Dynamics (mechanics), Surfaces and Interfaces, Plasma, Laser, Accelerators and Storage Rings, Physics - Plasma Physics, ddc, Plasma Physics (physics.plasm-ph), Amplitude, Physics::Accelerator Physics, Physics - Accelerator Physics, Atomic physics, Excitation
Abstract: Plasma wakefield dynamics over timescales up to 800 ps, approximately 100 plasma periods, are studied experimentally at the Advanced Wakefield Experiment (AWAKE). The development of the longitudinal wakefield amplitude driven by a self-modulated proton bunch is measured using the external injection of witness electrons that sample the fields. In simulation, resonant excitation of the wakefield causes plasma electron trajectory crossing, resulting in the development of a potential outside the plasma boundary as electrons are transversely ejected. Trends consistent with the presence of this potential are experimentally measured and their dependence on wakefield amplitude are studied via seed laser timing scans and electron injection delay scans., 11 pages, 8 figures
Published: 2021
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7. Design and characteristics of a low-frequency magnetic probe for magnetic profile measurements at Wendelstein 7-X

Author: W7-X Team, Knieps, A., Liang, Y., Drews, P., Endler, M., Grulke, O., Huang, Z., Killer, C., Liu, S., Nicolai, D., Rahbarnia, K., Sandri, N., Satheeswaran, G., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Losert, M., Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: 010302 applied physics, Technology, Materials science, Atmospheric-pressure plasma, Plasma, Low frequency, Kinetic energy, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, Computational physics, Reciprocating motion, Physics::Plasma Physics, 0103 physical sciences, Cutoff, ddc:620, Wendelstein 7-X, Instrumentation, ddc:600
Abstract: Equilibrium analysis in fusion devices usually relies on plasma pressure profiles and magnetic measurements outside the plasma. The kinetic profiles can give indirect information about the equilibrium magnetic field, while the stationary magnetic diagnostics cannot resolve current distributions on a smaller scale. This work presents a reciprocating magnetic probe, designed to provide direct plasma response measurements of the magnetic field in the scrape-off layer of Wendelstein 7-X. Hardware design and frequency characteristics are discussed, and a post-processing technique for extending the lower frequency cutoff of the integration scheme is presented.
Published: 2020
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8. Enhanced energy confinement after series of pellets in Wendelstein 7-X

Author: W7-X Team, Baldzuhn, J., Damm, H., Beidler, C. D., McCarthy, K., Panadero, N., Biedermann, C., Bozhenkov, S. A., Dinklage, A., Brunner, K. J., Fuchert, G., Kazakov, Y., Beurskens, M., Dibon, M., Geiger, J., Grulke, O., Höfel, U., Klinger, T., Köchl, F., Knauer, J., Kocsis, G., Kornejew, P., Lang, P. T., Langenberg, A., Laqua, H., Pablant, N. A., Pasch, E., Pedersen, T. S., Ploeckl, B., Rahbarnia, K., Schlisio, G., Scott, E. R., Stange, T., Von Stechow, A., Szepesi, T., Turkin, Y., Wagner, F., Winters, V., Wurden, G., Zhang, D., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Technology, Materials science, Series (mathematics), Pellets, Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Nuclear Energy and Engineering, Impurity, 0103 physical sciences, Wendelstein 7-X, Atomic physics, 010306 general physics, ddc:600, Energy (signal processing)
Abstract: A series of ice pellets was injected into the advanced stellarator Wendelstein 7-X (W7-X). Although the pellets were small and slow, deep and efficient particle fueling could be observed experimentally. The most striking feature appearing after the injection of the pellets, however, was a transient increase in the energy confinement time. This transient phase resembled in several aspects modes of enhanced confinement after gas-puff or pellet injection, as observed in other fusion experiments. All experimental attempts, to prolong this phase, failed. In this paper, discharges are described that show the enhanced energy confinement, and some conditions are summarized which seem to be essential in order to generate it. The focus here is on deep particle fueling by pellets, and shaping of the density profiles during and after the series of pellets. During this time, neutral gas particle re-fueling at the plasma edge is reduced, while density profile peaking and low impurity radiation losses are present.
Published: 2020

9. Statistical characteristics of the SOL turbulence in the first divertor plasma operation of W7-X using a reciprocating probe

Author: W7-X Team, Liu, S. C., Liang, Y., Wang, H. Q., Killer, C., Drews, P., Knieps, A., Han, X., Grulke, O., Krämer-Flecken, A., Xu, G. S., Yan, N., Höschen, D., Nicolai, D., Satheeswaran, G., Geiger, J., Henkel, M., Huang, Z., König, R., Li, Y., Neubauer, O., Rahbarnia, K., Sandri, N., Schweer, B., Wang, E. H., Wang, Y. M., Xu, S., Gao, X., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Technology, Cross-correlation, Field (physics), Turbulence, Divertor, Statistical parameter, Plasma, Condensed Matter Physics, 01 natural sciences, 010305 fluids & plasmas, Computational physics, Normal field, Physics::Fluid Dynamics, Reciprocating motion, Condensed Matter::Materials Science, Computer Science::Emerging Technologies, Physics::Plasma Physics, 0103 physical sciences, ddc:530, 010306 general physics, ddc:600
Abstract: The statistical characteristics of the scrape-off layer (SOL) turbulence have been investigated in the first divertor plasma operation of W7-X using a reciprocating probe. The turbulence spectra, auto-correlation time and the statistical parameters are analyzed in three magnetic configurations. In standard and high mirror configurations, the SOL turbulence can be classified into four patterns from the outer SOL to the inner SOL, and each pattern is characterized by the poloidal cross correlation spectrum and the turbulence propagation property. A strong dependence of the SOL turbulence on the magnetic topology is demonstrated experimentally. In high iota configuration, the SOL island is relatively narrow and consequently the fluctuation level of turbulence is weak in the far SOL but enhanced significantly in the near SOL. In the reversed field case, the SOL turbulence reveals similar propagation properties and statistical parameters with those in the normal field case, demonstrating the same turbulence structure in both toroidal field directions.
Published: 2020
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10. Correction to 'Proton-driven plasma wakefield acceleration in AWAKE' (vol 377, 20180418, 2019)

Author: Gschwendtner, E., Turner, M., Adli, E., Ahuja, A., Apsimon, O., Apsimon, R., Bachmann, A.-M., Batsch, F., Bracco, C., Braunmüller, F., Burger, S., Burt, G., Buttenschön, B., Caldwell, A., Chappell, J., Chevallay, E., Chung, M., Cooke, D., Damerau, H., Deubner, L. H., Dexter, A., Doebert, S., Farmer, J., Fedosseev, V. N., Fiorito, R., Fonseca, R. A., Garolfi, L., Gessner, S., Goddard, B., Gorgisyan, I., Gorn, A. A., Granados, E., Grulke, O., Hartin, A., Helm, A, Henderson, J. R., Hüther, M., Ibison, M., Jolly, S., Keeble, F., Kelisani, M. D., Kim, S.-Y., Krausz, F., Krupa, M., Lefevre, T., Liu, S., Lopes, N., Lotov, K., Martyanov, M., Mazzoni, S., Minakov, V., Molendijk, J. C., Moody, J. T., Moreira, M. T., Muggli, P., Panuganti, H., Pardons, A., Peña Asmus, F., Perera, A., Petrenko, A., Pukhov, A., Rey, S., Ruhl, H., Saberi, H., Sublet, A., Sherwood, P., Silva, L. O., Sosedkin, A. P., Tuev, P. V., Velotti, F., Verra, L., Verzilov, V. A., Vieira, J., Welsch, C. P., Wendt, M., Williamson, B., Wing, M., Woolley, B., Xia, G., and AWAKE Collaboration Team
Subjects: Accelerator Physics (physics.acc-ph), AWAKE Collaboration, Proton, General Science & Technology, General Mathematics, Engenharia e Tecnologia::Engenharia Civil [Domínio/Área Científica], FOS: Physical sciences, General Physics and Astronomy, Electron, plasma wakefield acceleration, Ciências Naturais::Ciências Físicas [Domínio/Área Científica], 01 natural sciences, 010305 fluids & plasmas, Nuclear physics, Ciências Naturais::Matemáticas [Domínio/Área Científica], Physics::Plasma Physics, AWAKE, 0103 physical sciences, 010306 general physics, Nuclear Experiment, physics.acc-ph, Physics, Large Hadron Collider, General Engineering, Plasma, Plasma acceleration, Accelerators and Storage Rings, Ciências Naturais::Outras Ciências Naturais [Domínio/Área Científica], seeded self modulation, Physics::Accelerator Physics, Physics - Accelerator Physics
Abstract: In this article, we briefly summarize the experiments performed during the first run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013–2018) was to demonstrate that 10– 20 MeV electrons can be accelerated to GeV energies in a plasma wakefield driven by a highly relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration'. In this article, we briefly summarize the experiments performed during the first Run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013 - 2018) was to demonstrate that 10-20 MeV electrons can be accelerated to GeV-energies in a plasma wakefield driven by a highly-relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future.
Published: 2019
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11. Wendelstein 7-X on the path to long-pulse high-performance operation

Author: W7-X Team, Endler, M., Baldzuhn, J., Beidler, C. D., Bosch, H.-S., Bozhenkov, S., Buttenschön, B., Dinklage, A., Fellinger, J., Feng, Y., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Hartmann, D., Jakubowski, M., König, R., Laqua, H. P., Lazerson, S., McNeely, P., Naujoks, D., Neuner, U., Otte, M., Pasch, E., Sunn Pedersen, T., Perseo, V., Puig Sitjes, A., Rahbarnia, K., Rust, N., Schmitz, O., Spring, A., Stange, T., Stechow, A. von, Turkin, Y., Wang, E., Wolf, R. C., Gantenbein, Gerd, Huber, Martina, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Mellein, Daniel, Papenfuß, Daniel, Scherer, Theo, Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Technology, Optimisation, Steady-state, Stellarator, Wendelstein 7-X, Nuclear engineering, 01 natural sciences, 7. Clean energy, 010305 fluids & plasmas, law.invention, Data acquisition, law, Range (aeronautics), 0103 physical sciences, Water cooling, General Materials Science, 010306 general physics, Civil and Structural Engineering, Steady state, Mechanical Engineering, Fusion power, Nuclear Energy and Engineering, Path (graph theory), ddc:600
Abstract: The Wendelstein 7-X project is aimed at demonstrating that an optimised stellarator is an attractive candidate for a fusion reactor. This requires the achievement of a number of technical and physics goals. Several of these goals have already been achieved in the first three experimental campaigns. We shall exemplify this by a number of results. One important goal is the demonstration of quasi-steady-state operation at high plasma density and temperature for half an hour, which encompasses the physical and technical requirements of stable operation with density and impurity control, cw heating, water-cooled targets, particle exhaust, and an appropriate control and data acquisition system for long-pulse operation. In the previous experimental campaigns, with uncooled targets, stationary discharges for up to 25 s with 5 MW heating power and up to 100 s with 2 MW heating power were achieved. For the next operational phase, to start in 2022, water-cooled targets are being installed, water cooling will be provided for all first-wall components, and a number of further upgrades to plasma heating, vacuum and fuelling systems as well as diagnostics will become available. With this equipment, the further goals of the project will be tackled, including the stepwise extension of discharge intervals to the multi-minute range. The experimental results so far have confirmed the neoclassical theory underlying several of the optimisation goals. At the same time, they showed that an optimisation is also required with respect to anomalous transport. In the future operational phases we aim at building a solid theoretical, experimental and technical foundation for the design of a next-step stellarator device.
Published: 2021
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12. Proton beam defocusing in AWAKE: comparison of simulations and measurements

Author: Gorn, A., Turner, M., Adli, E, Agnello, R., Aladi, M., Andrebe, Y., Apsimon, O., Apsimon, R., Bachmann, A. -M., Baistrukov, M. A., Batsch, F., Bergamaschi, M., Blanchard, P., Burrows, P. N., Buttenschön, B., Caldwell, A., Chappell, J., Chevallay, E., Chung, M., Cooke, D. A., Damerau, H., Davut, C., Demeter, G., Deubner, L. H., Dexter, A., Djotyan, G. P., Doebert, S., Farmer, J., Fasoli, A., Fedosseev, V. N., Fiorito, R., Fonseca, R. A., Friebel, F., Furno, I., Garolfi, L., Gessner, S., Goddard, B., Gorgisyan, I, Granados, E., Granetzny, M., Grulke, O., Gschwendtner, E.., Hafych, V., Hartin, A., Helm, A., Henderson, J. R., Howling, A., Hüther, M., Jacquier, R., Kargapolov, I. Y., Kedves, M. Á., Keeble, F., Kelisani, M. D., Kim, S. -Y, Krausz, F., Krupa, M., Lefevre, T., Liang, L., Liu, S., Lopes, N. C., Lotov, K., Martyanov, M., Mazzoni, S., Medina Godoy, D., Minakov, V. A., Moody, J. T., Morales Guzmán, P. I., Moreira, M., Nechaeva, T., Panuganti, H., Pardons, A., Peña Asmus, F., Perera, A., Petrenko, A., Pucek, J., Pukhov, A., Ráczkevi, B., Ramjiawan, R. L., Rey, S., Ruhl, H., Saberi, H., Schmitz, O., Senes, E., Sherwood, P., Silva, L. O., Spitsyn, R. I., Verra, L., Verzilov, V. A., Vieira, J., Tuev, P. V., Velotti, F., Welsch, C. P., Williamson, B., Wing, M., Wolfenden, J., Woolley, B., Xia, G., Zepp, M., Della Porta, G. Z., and The AWAKE collaboration
Subjects: Accelerator Physics (physics.acc-ph), Physics, Proton, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, Other Fields of Physics, FOS: Physical sciences, Condensed Matter Physics, Accelerators and Storage Rings, 01 natural sciences, 7. Clean energy, Physics - Plasma Physics, 010305 fluids & plasmas, 3. Good health, Plasma Physics (physics.plasm-ph), Nuclear Energy and Engineering, physics.plasm-ph, 0103 physical sciences, Physics::Accelerator Physics, Physics - Accelerator Physics, Atomic physics, Nuclear Experiment, Beam (structure), physics.acc-ph
Abstract: In 2017, AWAKE demonstrated the seeded self-modulation (SSM) of a 400 GeV proton beam from the Super Proton Synchrotron (SPS) at CERN. The angular distribution of the protons deflected due to SSM is a quantitative measure of the process, which agrees with simulations by the two-dimensional (axisymmetric) particle-in-cell code LCODE. Agreement is achieved for beam populations between $10^{11}$ and $3 \times 10^{11}$ particles, various plasma density gradients ($-20 \div 20\%$) and two plasma densities ($2\times 10^{14} \text{cm}^{-3}$ and $7 \times 10^{14} \text{cm}^{-3}$). The agreement is reached only in the case of a wide enough simulation box (at least five plasma wavelengths)., Comment: 8 pages, 9 figures, 1 table
Published: 2020
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13. Investigation of turbulence rotation and radial electric field in the island divertor and plasma edge at W7-X

Author: Krämer-Flecken, A., Han, X., Windisch, T., Cosfeld, J., Drews, P., Fuchert, G., Geiger, J., Grulke, O., Killer, C., Knieps, A., Liang, Y., Liu, S., Rack, M., Gantenbein, Gerd, Jelonnek, John, Thumm, Manfred, Dammertz, Günter, Hunger, Hermann, Illy, Stefan, Kern, Stefan, Prinz, Oliver, Schmid, Martin, Samartsev, Andrey, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Technology, Turbulence, Divertor, Condensed Matter Physics, Rotation, 01 natural sciences, 010305 fluids & plasmas, Plasma edge, law.invention, Computational physics, Nuclear Energy and Engineering, law, Electric field, 0103 physical sciences, 010306 general physics, ddc:600, Stellarator
Published: 2019
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14. Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities

Author: Adli, E, Ahuja, A, Apsimon, O, Apsimon, R, Bachmann, A-M, Barrientos, D, Barros, MM, Batkiewicz, J, Batsch, F, Bauche, J, Olsen, VK Berglyd, Bernardini, M, Biskup, B, Boccardi, A, Bogey, T, Bohl, T, Bracco, C, Braunmueller, F, Burger, S, Burt, G, Bustamante, S, Buttenschoen, B, Caldwell, A, Cascella, M, Chappell, J, Chevallay, E, Chung, M, Cooke, D, Damerau, H, Deacon, L, Deubner, LH, Dexter, A, Doebert, S, Farmer, J, Fedosseev, VN, Fior, G, Fiorito, R, Fonseca, RA, Friebel, F, Garolfi, L, Gessner, S, Gorgisyan, I, Gorn, AA, Granados, E, Grulke, O, Gschwendtner, E, Guerrero, A, Hansen, J, Helm, A, Henderson, JR, Hessler, C, Hofle, W, Huether, M, Ibison, M, Jensen, L, Jolly, S, Keeble, F, Kim, S-Y, Kraus, F, Lefevre, T, LeGodec, G, Li, Y, Liu, S, Lopes, N, Lotov, KV, Brun, L Maricalva, Martyanov, M, Mazzoni, S, Godoy, D Medina, Minakov, VA, Mitchell, J, Molendijk, JC, Mompo, R, Moody, JT, Moreira, M, Muggli, P, Mutin, C, Oez, E, Ozturk, E, Pasquino, C, Pardons, A, Asmus, F Pena, Pepitone, K, Perera, A, Petrenko, A, Pitman, S, Plyushchev, G, Pukhov, A, Rey, S, Rieger, K, Ruhl, H, Schmidt, JS, Shalimova, IA, Shaposhnikova, E, Sherwood, P, Silva, LO, Soby, L, Sosedkin, AP, Speroni, R, Spitsyn, RI, Tuev, PV, Turner, M, Velotti, F, Verra, L, Verzilov, VA, Vieira, J, Vincke, H, Welsch, CP, Williamson, B, Wing, M, Woolley, B, Xia, G, and Collaboration, AWAKE
Subjects: Accelerator Physics (physics.acc-ph), Proton, Other Fields of Physics, General Physics and Astronomy, FOS: Physical sciences, Plasma oscillation, Ciências Naturais::Ciências Físicas [Domínio/Área Científica], 01 natural sciences, law.invention, law, Physics::Plasma Physics, Ionization, physics.plasm-ph, 0103 physical sciences, 010306 general physics, physics.acc-ph, Physics, Plasma, Laser, Accelerators and Storage Rings, Physics - Plasma Physics, Pulse (physics), ddc, Plasma Physics (physics.plasm-ph), Modulation, Physics::Space Physics, Physics::Accelerator Physics, Physics - Accelerator Physics, Atomic physics, Frequency modulation
Abstract: We give direct experimental evidence for the observation of the full transverse self-modulation of a relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a density modulation resulting from radial wakefield effects with a period reciprocal to the plasma frequency. We show that the modulation is seeded by using an intense laser pulse co-propagating with the proton bunch which creates a relativistic ionization front within the bunch. We show by varying the plasma density over one order of magnitude that the modulation period scales with the expected dependence on the plasma density., Comment: 4 figures, AWAKE collaboration paper, Submitted to PRL
Published: 2018
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15. Letter

Author: The AWAKE Collaboration, Adli, E., Ahuja, A., Apsimon, O., Apsimon, R., Bachmann, A. -M., Barrientos, D., Batsch, F., Bauche, J., Olsen, V. K. Berglyd, Bernardini, M., Bohl, T., Bracco, C., Braunmueller, F., Burt, G., Buttenschoen, B., Caldwell, A., Cascella, M., Chappell, J., Chevallay, E., Chung, M., Cooke, D., Damerau, H., Deacon, L., Deubner, L. H., Dexter, A., Doebert, S., Farmer, J., Fedosseev, V. N., Fiorito, R., Fonseca, R. A., Friebel, F., Garolfi, L., Gessner, S., Gorgisyan, I., Gorn, A. A., Granados, E., Grulke, O., Gschwendtner, E., Hansen, J., Helm, A., Henderson, J. R., Huether, M., Ibison, M., Jensen, L., Jolly, S., Keeble, F., Kim, S. -Y., Kraus, F., Li, Y., Liu, S., Lopes, N., Lotov, K. V., Brun, L. Maricalva, Martyanov, M., Mazzoni, S., Godoy, D. Medina, Minakov, V. A., Mitchell, J., Molendijk, J. C., Moody, J. T., Moreira, M., Muggli, P., Oez, E., Pasquino, C., Pardons, A., Asmus, F. Pena, Pepitone, K., Perera, A., Petrenko, A., Pitman, S., Pukhov, A., Rey, S., Rieger, K., Ruhl, H., Schmidt, J. S., Shalimova, I. A., Sherwood, P., Silva, L. O., Soby, L., Sosedkin, A. P., Speroni, R., Spitsyn, R. I., Tuev, P. V., Turner, M., Velotti, F., Verra, L., Verzilov, V. A., Vieira, J., Welsch, C. P., Williamson, B., Wing, M., Woolley, B., and Xia, G.
Subjects: Accelerator Physics (physics.acc-ph), Letter, High energy particle, Proton, General Science & Technology, FOS: Physical sciences, Electron, 7. Clean energy, 01 natural sciences, High Energy Physics - Experiment, 010305 fluids & plasmas, Nuclear physics, High Energy Physics - Experiment (hep-ex), Acceleration, Affordable and Clean Energy, Physics::Plasma Physics, 0103 physical sciences, 010306 general physics, physics.acc-ph, Physics, Multidisciplinary, Large Hadron Collider, Plasma, Plasma acceleration, Accelerators and Storage Rings, Physics - Plasma Physics, Ciências Naturais::Outras Ciências Naturais [Domínio/Área Científica], Plasma Physics (physics.plasm-ph), Bunches, Physics::Accelerator Physics, Physics - Accelerator Physics, Experimental particle physics, Plasma-based accelerators
Abstract: High-energy particle accelerators have been crucial in providing a deeper understanding of fundamental particles and the forces that govern their interactions. To increase the energy of the particles or to reduce the size of the accelerator, new acceleration schemes need to be developed. Plasma wakefield acceleration1–5, in which the electrons in a plasma are excited, leading to strong electric fields (so called ‘wakefields’), is one such promising acceleration technique. Experiments have shown that an intense laser pulse6–9 or electron bunch10,11 traversing a plasma can drive electric fields of tens of gigavolts per metre and above—well beyond those achieved in conventional radio-frequency accelerators (about 0.1 gigavolt per metre). However, the low stored energy of laser pulses and electron bunches means that multiple acceleration stages are needed to reach very high particle energies5,12. The use of proton bunches is compelling because they have the potential to drive wakefields and to accelerate electrons to high energy in a single acceleration stage13. Long, thin proton bunches can be used because they undergo a process called self-modulation14–16, a particle–plasma interaction that splits the bunch longitudinally into a series of high-density microbunches, which then act resonantly to create large wakefields. The Advanced Wakefield (AWAKE) experiment at CERN17–19 uses high-intensity proton bunches—in which each proton has an energy of 400 gigaelectronvolts, resulting in a total bunch energy of 19 kilojoules—to drive a wakefield in a ten-metre-long plasma. Electron bunches are then injected into this wakefield. Here we present measurements of electrons accelerated up to two gigaelectronvolts at the AWAKE experiment, in a demonstration of proton-driven plasma wakefield acceleration. Measurements were conducted under various plasma conditions and the acceleration was found to be consistent and reliable. The potential for this scheme to produce very high-energy electron bunches in a single accelerating stage20 means that our results are an important step towards the development of future high-energy particle accelerators21,22., Electron acceleration to very high energies is achieved in a single step by injecting electrons into a ‘wake’ of charge created in a 10-metre-long plasma by speeding long proton bunches.
Published: 2018
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16. Magnetic configuration effects on the Wendelstein 7-X stellarator

Author: Dinklage A., Beidler C.D., Helander P., Fuchert G., Maassberg H., Rahbarnia K., Sunn Pedersen T., Turkin Y., Wolf R.C., Alonso A., Andreeva T., Blackwell B., Bozhenkov S., Buttenschon B., Czarnecka A., Effenberg F., Feng Y., Geiger J., Hirsch M., Hofel U., Jakubowski M., Klinger T., Knauer J., Kocsis G., Kramer-Flecken A., Kubkowska M., Langenberg A., Laqua H.P., Marushchenko N., Mollen A., Neuner U., Niemann H., Pasch E., Pablant N., Rudischhauser L., Smith H.M., Schmitz O., Stange T., Szepesi T., Weir G., Windisch T., Wurden G.A., Zhang D., Abramovic I., Akaslompolo S., Ali A., Belloso J.A., Aleynikov P., Aleynikova K., Alzbutas R., Anda G., Ascasibar E., Assmann J., Baek S.-G., Baldzuhn J., Banduch M., Barbui T., Barlak M., Baumann K., Behr W., Beidler C., Benndorf A., Bertuch O., Beurskens M., Biedermann C., Biel W., Birus D., Blanco E., Blatzheim M., Bluhm T., Bockenhoff D., Bolgert P., Borchardt M., Borsuk V., Boscary J., Bosch H.-S., Bottger L.-G., Brakel R., Brand H., Brandt C., Brauer T., Braune H., Brezinsek S., Brunner K.-J., Brunner B., Burhenn R., Bussiahn R., Bykov V., Cai Y., Calvo I., Cannas B., Cappa A., Card A., Carls A., Carraro L., Carvalho B., Castejon F., Charl A., Chernyshev F., Cianciosa M., Citarella R., Ciupinski L., Claps G., Cole M.J., Cordella F., Cseh G., Czermak A., Czerski K., Czerwinski M., Czymek G., da Molin A., da Silva A., Dammertz G., de la Pena A., Degenkolbe S., Denner P., Dittmar T., Dhard C.P., Dostal M., Drevlak M., Drewelow P., Drews P., Dudek A., Dundulis G., Durodie F., van Eeten P., Ehrke G., Endler M., Ennis D., Erckmann E., Esteban H., Estrada T., Fahrenkamp N., Feist J.-H., Fellinger J., Fernandes H., Fietz W.H., Figacz W., Fontdecaba J., Ford O., Fornal T., Frerichs H., Freund A., Fuhrer M., Funaba T., Galkowski A., Gantenbein G., Gao Y., Regana J.G., Garcia-Munoz M., Gates D., Gawlik G., Geiger B., Giannella V., Gierse N., Gogoleva A., Goncalves B., Goriaev A., Gradic D., Grahl M., Green J., Grosman A., Grote H., Gruca M., Grulke O., Guerard C., Hacker P., Haiduk L., Hammond K., Han X., Harberts F., Harris J.H., Hartfuss H.-J., Hartmann D., Hathiramani D., Hein B., Heinemann B., Heitzenroeder P., Henneberg S., Hennig C., Sanchez J.H., Hidalgo C., Holbe H., Hollfeld K.P., Holting A., Hoschen D., Houry M., Howard J., Huang X., Huber M., Huber V., Hunger H., Ida K., Ilkei T., Illy S., Israeli B., Ivanov A., Jablonski S., Jagielski J., Jelonnek J., Jenzsch H., Junghans P., Kacmarczyk J., Kaliatka T., Kallmeyer J.-P., Kamionka U., Karalevicius R., Kasahara H., Kasparek W., Kazakov Y., Kenmochi N., Keunecke M., Khilchenko A., Killer C., Kinna D., Kleiber R., Knaup M., Knieps A., Kobarg T., Kochl F., Kolesnichenko Y., Konies A., Koppen M., Koshurinov J., Koslowski R., Konig R., Koster F., Kornejew P., Koziol R., Kramer M., Krampitz R., Kraszewsk P., Krawczyk N., Kremeyer T., Krings T., Krom J., Krychowiak M., Krzesinski G., Ksiazek I., Kuhner G., Kurki-Suonio T., Kwak S., Landreman M., Lang R., Langish S., Laqua H., Laube R., Lazerson S., Lechte C., Lennartz M., Leonhardt W., Lewerentz L., Liang Y., Linsmeier C., Liu S., Lobsien J.-F., Loesser D., Cisquella J.L., Lore J., Lorenz A., Losert M., Lubyako L., Lucke A., Lumsdaine A., Lutsenko V., Maisano-Brown J., Marchuk O., Mardenfeld M., Marek P., Marsen S., Marushchenko M., Masuzaki S., Maurer D., McCarthy K., McNeely P., Meier A., Mellein D., Mendelevitch B., Mertens P., Mikkelsen D., Mishchenko O., Missal B., Mittelstaedt J., Mizuuchi T., Moncada V., Monnich T., Morisaki T., Moseev D., Munk R., Murakami S., Musielok F., Nafradi G., Nagel M., Naujoks D., Neilson H., Neubauer O., Ngo T., Nocentini R., Nuhrenberg C., Nuhrenberg J., Obermayer S., Offermanns G., Ogawa K., Ongena J., Oosterbeek J.W., Orozco G., Otte M., Rodriguez L.P., Pan W., Panadero N., Alvarez N.P., Panin A., Papenfuss D., Paqay S., Pavone A., Pawelec E., Pelka G., Peng X., Perseo V., Peterson B., Pieper A., Pilopp D., Pingel S., Pisano F., Plaum B., Plunk G., Povilaitis M., Preinhaelter J., Proll J., Puiatti M.-E., Sitjes A.P., Purps F., Rack M., Recsei S., Reiman A., Reiter D., Remppel F., Renard S., Riedl R., Riemann J., Rimkevicius S., Risse K., Rodatos A., Rohlinger H., Rome M., Rong P., Roscher H.-J., Roth B., Rummel K., Rummel T., Runov A., Rust N., Ryc L., Ryosuke S., Sakamoto R., Samartsev A., Sanchez M., Sano F., Satake S., Satheeswaran G., Schacht J., Schauer F., Scherer T., Schlaich A., Schlisio G., Schluter K.-H., Schmitt J., Schmitz H., Schmuck S., Schneider M., Schneider W., Scholz M., Scholz P., Schrittwieser R., Schroder M., Schroder T., Schroeder R., Schumacher H., Schweer B., Shanahan B., Shikhovtsev I.V., Sibilia M., Sinha P., Siplia S., Skodzik J., Slaby C., Smith H., Spiess W., Spong D.A., Spring A., Stadler R., Standley B., Stephey L., Stoneking M., Stridde U., Sulek Z., Pedersen T.S., Suzuki Y., Svensson J., Szabo V., Szabolics T., Szokefalvi-Nagy Z., Tamura N., Terra A., Terry J., Thomas J., Thomsen H., Thumm M., von Thun C.P., Timmermann D., Titus P., Toi K., Travere J.M., Traverso P., Tretter J., Mora H.T., Tsuchiya H., Tsujimura T., Tulipan S., Turnyanskiy M., Unterberg B., Urban J., Urbonavicius E., Vakulchyk I., Valet S., van Milligen B., Vela L., Velasco J.-L., Vergote M., Vervier M., Vianello N., Viebke H., Vilbrandt R., Vorkorper A., Wadle S., Wang E., Wang N., Warmer F., Wauters T., Wegener L., Weggen J., Wegner T., Wei Y., Wendorf J., Wenzel U., Wiegel B., Wilde F., Winkler E., Winters V., Wolf R., Wolf S., Wolowski J., Wright A., Wurden G., Xanthopoulos P., Yamada H., Yamada I., Yasuhara R., Yokoyama M., Zajac J., Zarnstorff M., Zeitler A., Zhang H., Zhu J., Zilker M., Zimbal A., Zocco A., Zoletnik S., Zuin M., W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, Science and Technology of Nuclear Fusion, and Turbulence in Fusion Plasmas
Subjects: Physics, Tokamak, Field (physics), General Physics and Astronomy, Plasma, 7. Clean energy, 01 natural sciences, 010305 fluids & plasmas, Bootstrap current, Computational physics, Magnetic field, law.invention, Magnetic mirror, Wendelstein 7-X stellarator, Physics and Astronomy (all), law, Physics::Plasma Physics, 0103 physical sciences, Wendelstein 7-X plasmas, Wendelstein 7-X, 010306 general physics, Stellarator
Abstract: The two leading concepts for confining high-temperature fusion plasmas are the tokamak and the stellarator. Tokamaks are rotationally symmetric and use a large plasma current to achieve confinement, whereas stellarators are non-axisymmetric and employ three-dimensionally shaped magnetic field coils to twist the field and confine the plasma. As a result, the magnetic field of a stellarator needs to be carefully designed to minimize the collisional transport arising from poorly confined particle orbits, which would otherwise cause excessive power losses at high plasma temperatures. In addition, this type of transport leads to the appearance of a net toroidal plasma current, the so-called bootstrap current. Here, we analyse results from the first experimental campaign of the Wendelstein 7-X stellarator, showing that its magnetic-field design allows good control of bootstrap currents and collisional transport. The energy confinement time is among the best ever achieved in stellarators, both in absolute figures (τE > 100 ms) and relative to the stellarator confinement scaling. The bootstrap current responds as predicted to changes in the magnetic mirror ratio. These initial experiments confirm several theoretically predicted properties of Wendelstein 7-X plasmas, and already indicate consistency with optimization measures. Results from the first experimental campaign of the Wendelstein 7-X stellarator demonstrate that its magnetic-field design grants good control of parasitic plasma currents, leading to long energy confinement times.
Published: 2018
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17. Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

Author: Pedersen T. S., Otte M., Lazerson S., Helander P., Bozhenkov S., Biedermann C., Klinger T., Wolf R. C., Bosch H. -S., Abramovic I., Akaslompolo S., Aleynikov P., Aleynikova K., Ali A., Alonso A., Anda G., Andreeva T., Ascasibar E., Baldzuhn J., Banduch M., Barbui T., Beidler C., Benndorf A., Beurskens M., Biel W., Birus D., Blackwell B., Blanco E., Blatzheim M., Bluhm T., Bockenhoff D., Bolgert P., Borchardt M., Bottger L. -G., Brakel R., Brandt C., Brauer T., Braune H., Burhenn R., Buttenschon B., Bykov V., Calvo I., Cappa A., Carls A., De Carvalho B. B., Castejon F., Cianciosa M., Cole M., Costea S., Cseh G., Czarnecka A., Dal Molin A., De La Cal E., De La Pena A., Degenkolbe S., Dhard C. P., Dinklage A., Dostal M., Drevlak M., Drewelow P., Drews P., Dudek A., Durodie F., Dzikowicka A., Von Eeten P., Effenberg F., Endler M., Erckmann V., Estrada T., Fahrenkamp N., Fellinger J., Feng Y., Figacz W., Ford O., Fornal T., Frerichs H., Fuchert G., Garcia-Munoz M., Geiger B., Geiger J., Gierse N., Gogoleva A., Goncalves B., Gradic D., Grahl M., Gross S., Grote H., Grulke O., Guerard C., Haas M., Harris J., Hartfuss H. -J., Hartmann D., Hathiramani D., Hein B., Heirnich S., Henneberg S., Hennig C., Hernandez J., Hidalgo C., Hidalgo U., Hirsch M., Hofel U., Holbe H., Holting A., Houry M., Huber V., Ionita C., Israeli B., Jablonski S., Jakubowski M., Van Vuuren A. J., Jenzsch H., Kaczmarczyk J., Kallmeyer J. -P., Kamionka U., Kasahara H., Kenmochi N., Kernbichler W., Killer C., Kinna D., Kleiber R., Knauer J., Kochl F., Kocsis G., Kolesnichenko Y., Konies A., Konig R., Kornejew P., Koster F., Kramer-Flecken A., Krampitz R., Krawzyk N., Kremeyer T., Krychowiak M., Ksiazek I., Kubkowska M., Kuhner G., Kurki-Suonio T., Kurz P., Kuttler K., Kwak S., Landreman M., Langenberg A., Lapayese F., Laqua H., Laqua H. -P., Laube R., Laux M., Lentz H., Lewerentz M., Liang Y., Liu S., Lobsien J. -F., Cisquella J. L., Lopez-Bruna D., Lore J., Lorenz A., Lui S., Lutsenko V., Maassberg H., Maisano-Brown J., Marchuk O., Marrelli L., Marsen S., Marushchenko N., Masuzaki S., McCarthy K., McNeely P., Medina F., Milojevic D., Mishchenko A., Missal B., Mittelstaedt J., Mollen A., Moncada V., Monnich T., Moseev D., Nagel M., Naujoks D., Neilson G. H., Neubauer O., Neuner U., Ngo T. -T., Niemann H., Nuhrenberg C., Nuhrenberg J., Ochando M., Ogawa K., Ongena J., Oosterbeek H., Pablant N., Pacella D., Pacios L., Panadero N., Pasch E., Pastor I., Pavone A., Pawelec E., Pedrosa A., Perseo V., Peterson B., Pilopp D., Pisano F., Piulatti M. E., Plunk G., Preynas M., Proll J., Sitjes A. P., Purps F., Rack M., Rahbarnia K., Riemann J., Risse K., Rong P., Rosenberger J., Rudischhauser L., Rummel K., Rummel T., Runov A., Rust N., Ryc L., Saitoh H., Satake S., Schacht J., Schmitz O., Schmuck S., Schneider B., Schneider M., Schneider W., Schrittwieser R., Schroder M., Schroder T., Schroder R., Schumacher H. W., Schweer B., Seki R., Sinha P., Sipilae S., Slaby C., Smith H., Sousa J., Spring A., Standley B., Stange T., Von Stechow A., Stephey L., Stoneking M., Stridde U., Suzuki Y., Svensson J., Szabolics T., Szepesi T., Thomsen H., Travere J. -M., Traverso P., Mora H. T., Tsuchiya H., Tsuijmura T., Turkin Y., Valet S., Van Milligen B., Vela L., Velasco J. -L., Vergote M., Vervier M., Viebke H., Vilbrandt R., Von Thun C. P., Wagner F., Wang E., Wang N., Warmer F., Wauters T., Wegener L., Wegner T., Weir G., Wendorf J., Wenzel U., Werner A., Wie Y., Wiegel B., Wilde F., Windisch T., Winkler M., Winters V., Wright A., Wurden G., Xanthopoulos P., Yamada I., Yasuhara R., Yokoyama M., Zhang D., Zilker M., Zimbal A., Zocco A., Zoletnik S., W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society, Massachusetts Institute of Technology. Department of Physics, Maisano-Brown, Jeannette D., Science and Technology of Nuclear Fusion, Pedersen, T, Otte, M, Lazerson, S, Helander, P, Bozhenkov, S, Biedermann, C, Klinger, T, Wolf, R, Bosch, H, Abramovic, I, Akaslompolo, S, Aleynikov, P, Aleynikova, K, Ali, A, Alonso, A, Anda, G, Andreeva, T, Ascasibar, E, Baldzuhn, J, Banduch, M, Barbui, T, Beidler, C, Benndorf, A, Beurskens, M, Biel, W, Birus, D, Blackwell, B, Blanco, E, Blatzheim, M, Bluhm, T, Bockenhoff, D, Bolgert, P, Borchardt, M, Bottger, L, Brakel, R, Brandt, C, Brauer, T, Braune, H, Burhenn, R, Buttenschon, B, Bykov, V, Calvo, I, Cappa, A, Carls, A, De Carvalho, B, Castejon, F, Cianciosa, M, Cole, M, Costea, S, Cseh, G, Czarnecka, A, Dal Molin, A, De La Cal, E, De La Pena, A, Degenkolbe, S, Dhard, C, Dinklage, A, Dostal, M, Drevlak, M, Drewelow, P, Drews, P, Dudek, A, Durodie, F, Dzikowicka, A, Von Eeten, P, Effenberg, F, Endler, M, Erckmann, V, Estrada, T, Fahrenkamp, N, Fellinger, J, Feng, Y, Figacz, W, Ford, O, Fornal, T, Frerichs, H, Fuchert, G, Garcia-Munoz, M, Geiger, B, Geiger, J, Gierse, N, Gogoleva, A, Goncalves, B, Gradic, D, Grahl, M, Gross, S, Grote, H, Grulke, O, Guerard, C, Haas, M, Harris, J, Hartfuss, H, Hartmann, D, Hathiramani, D, Hein, B, Heirnich, S, Henneberg, S, Hennig, C, Hernandez, J, Hidalgo, C, Hidalgo, U, Hirsch, M, Hofel, U, Holbe, H, Holting, A, Houry, M, Huber, V, Ionita, C, Israeli, B, Jablonski, S, Jakubowski, M, Van Vuuren, A, Jenzsch, H, Kaczmarczyk, J, Kallmeyer, J, Kamionka, U, Kasahara, H, Kenmochi, N, Kernbichler, W, Killer, C, Kinna, D, Kleiber, R, Knauer, J, Kochl, F, Kocsis, G, Kolesnichenko, Y, Konies, A, Konig, R, Kornejew, P, Koster, F, Kramer-Flecken, A, Krampitz, R, Krawzyk, N, Kremeyer, T, Krychowiak, M, Ksiazek, I, Kubkowska, M, Kuhner, G, Kurki-Suonio, T, Kurz, P, Kuttler, K, Kwak, S, Landreman, M, Langenberg, A, Lapayese, F, Laqua, H, Laube, R, Laux, M, Lentz, H, Lewerentz, M, Liang, Y, Liu, S, Lobsien, J, Cisquella, J, Lopez-Bruna, D, Lore, J, Lorenz, A, Lui, S, Lutsenko, V, Maassberg, H, Maisano-Brown, J, Marchuk, O, Marrelli, L, Marsen, S, Marushchenko, N, Masuzaki, S, Mccarthy, K, Mcneely, P, Medina, F, Milojevic, D, Mishchenko, A, Missal, B, Mittelstaedt, J, Mollen, A, Moncada, V, Monnich, T, Moseev, D, Nagel, M, Naujoks, D, Neilson, G, Neubauer, O, Neuner, U, Ngo, T, Niemann, H, Nuhrenberg, C, Nuhrenberg, J, Ochando, M, Ogawa, K, Ongena, J, Oosterbeek, H, Pablant, N, Pacella, D, Pacios, L, Panadero, N, Pasch, E, Pastor, I, Pavone, A, Pawelec, E, Pedrosa, A, Perseo, V, Peterson, B, Pilopp, D, Pisano, F, Piulatti, M, Plunk, G, Preynas, M, Proll, J, Sitjes, A, Purps, F, Rack, M, Rahbarnia, K, Riemann, J, Risse, K, Rong, P, Rosenberger, J, Rudischhauser, L, Rummel, K, Rummel, T, Runov, A, Rust, N, Ryc, L, Saitoh, H, Satake, S, Schacht, J, Schmitz, O, Schmuck, S, Schneider, B, Schneider, M, Schneider, W, Schrittwieser, R, Schroder, M, Schroder, T, Schroder, R, Schumacher, H, Schweer, B, Seki, R, Sinha, P, Sipilae, S, Slaby, C, Smith, H, Sousa, J, Spring, A, Standley, B, Stange, T, Von Stechow, A, Stephey, L, Stoneking, M, Stridde, U, Suzuki, Y, Svensson, J, Szabolics, T, Szepesi, T, Thomsen, H, Travere, J, Traverso, P, Mora, H, Tsuchiya, H, Tsuijmura, T, Turkin, Y, Valet, S, Van Milligen, B, Vela, L, Velasco, J, Vergote, M, Vervier, M, Viebke, H, Vilbrandt, R, Von Thun, C, Wagner, F, Wang, E, Wang, N, Warmer, F, Wauters, T, Wegener, L, Wegner, T, Weir, G, Wendorf, J, Wenzel, U, Werner, A, Wie, Y, Wiegel, B, Wilde, F, Windisch, T, Winkler, M, Winters, V, Wright, A, Wurden, G, Xanthopoulos, P, Yamada, I, Yasuhara, R, Yokoyama, M, Zhang, D, Zilker, M, Zimbal, A, Zocco, A, Zoletnik, S, Universidad de Sevilla. Departamento de Física Atómica, Molecular y Nuclear, Department of Applied Physics, Aalto-yliopisto, Aalto University, and Pacella, D.
Subjects: Tokamak, Plasma parameters, Science, General Physics and Astronomy, Topology (electrical circuits), Topology, 7. Clean energy, 01 natural sciences, Article, General Biochemistry, Genetics and Molecular Biology, 010305 fluids & plasmas, law.invention, law, 0103 physical sciences, 010306 general physics, Physics, Fusion, Wendelstein7-X, Stellarator, Multidisciplinary, ta114, General Chemistry, Plasma, Fusion power, Magnetic field, Erratum, Wendelstein 7-X, Stellarator
Abstract: Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good confinement is realized, and that the measured deviations are smaller than one part in 100,000. This is a significant step forward in stellarator research, since it shows that the complicated and delicate magnetic topology can be created and verified with the required accuracy., Early stellarator designs suffered from high particle losses, an issue that can be addressed by optimization of the coils. Here the authors measure the magnetic field lines in the Wendelstein 7-X stellarator, confirming that the complicated design of the superconducting coils has been realized successfully.
Published: 2016

18. Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase

Author: Wolf, R. C., Alonso, A., Akaslompolo, S., Baldzuhn, J., Beurskens, M., Beidler, C. D., Biedermann, C., Bosch, H. -S., Bozhenkov, S., Brakel, R., Braune, H., Brezinsek, S., Brunner, K. -J., Damm, H., Dinklage, A., Drewelow, P., Effenberg, F., Feng, Y., Ford, O., Fuchert, G., Gao, Y., Geiger, J., Grulke, O., Harder, N., Hartmann, D., Helander, P., Heinemann, B., Hirsch, M., Hofel, U., Hopf, C., Ida, K., Isobe, M., Jakubowski, M. W., Kazakov, Y. O., Killer, C., Klinger, T., Knauer, J., Konig, R., Krychowiak, M., Langenberg, A., Laqua, H. P., Lazerson, S., Mcneely, P., Marsen, S., Marushchenko, N., Nocentini, R., Ogawa, K., Orozco, G., Osakabe, M., Otte, M., Pablant, N., Pasch, E., Pavone, A., Porkolab, M., Puig Sitjes, A., Rahbarnia, K., Riedl, R., Rust, N., Scott, E., Schilling, J., Schroeder, R., Stange, T., Von Stechow, A., Strumberger, E., Sunn Pedersen, T., Svensson, J., Thomson, H., Turkin, Y., Vano, L., Wauters, T., Wurden, G., Yoshinuma, M., Zanini, M., Zhang, D., Andreeva, T., Brandt, C., Burhenn, R., Buttenschon, B., Geiger, B., Tamura, N., Thomsen, H., Wegner, T., Abramovic, I., Alcuson, J., Aleynikov, P., Aleynikova, K., Ali, A., Anda, G., Ascasibar, E., Bahner, J. P., Baek, S. G., Balden, M., Banduch, M., Barbui, T., Behr, W., Beidler, C., Benndorf, A., Biel, W., Blackwell, B., Blanco, E., Blatzheim, M., Ballinger, S., Bluhm, T., Bockenhoff, D., Boswirth, B., Bottger, L. -G., Borchardt, M., Borsuk, V., Boscary, J., Brand, H., Brauer, T., Bussiahn, R., Bykov, V., Cai, J., Calvo, I., Cannas, B., Cappa, A., Carls, A., Carralero, D., Carraro, L., Carvalho, B., Castejon, F., Charl, A., Chaudhary, N., Chauvin, D., Chernyshev, F., Cianciosa, M., Citarella, R., Claps, G., Coenen, J., Cole, M., Cole, M. J., Cordella, F., Cseh, G., Czarnecka, A., Czerski, K., Czerwinski, M., Czymek, G., Da Molin, A., Da Silva, A., De La Pena, A., Degenkolbe, S., Dhard, C. P., Dibon, M., Dittmar, T., Drevlak, M., Drews, P., Durodie, F., Edlund, E., Van Eeten, P., Ehrke, G., Elgeti, S., Endler, M., Ennis, D., Esteban, H., Estrada, T., Fellinger, J., Flom, E., Fernandes, H., Fietz, W. H., Figacz, W., Fontdecaba, J., Fornal, T., Frerichs, H., Freund, A., Funaba, T., Galkowski, A., Gantenbein, G., Garcia Regana, J., Gates, D., Giannella, V., Gogoleva, A., Goncalves, B., Goriaev, A., Gradic, D., Grahl, M., Green, J., Greuner, H., Grosman, A., Grote, H., Gruca, M., Guerard, C., Hacker, P., Han, X., Harris, J. H., Hathiramani, D., Hein, B., Henneberg, S., Henkel, M., Hernandez Sanchez, J., Hidalgo, C., Hollfeld, K. P., Holting, A., Hoschen, D., Houry, M., Howard, J., Huang, X., Huang, Z., Hubeny, M., Huber, M., Hunger, H., Ilkei, T., Illy, S., Israeli, B., Jablonski, S., Jakubowski, M., Jelonnek, J., Jenzsch, H., Jesche, T., Jia, M., Junghanns, P., Kacmarczyk, J., Kallmeyer, J. -P., Kamionka, U., Kasahara, H., Kasparek, W., Kenmochi, N., Kirschner, A., Kleiber, R., Knaup, M., Knieps, A., Kobarg, T., Kocsis, G., Kochl, F., Kolesnichenko, Y., Konies, A., Kornejew, P., Koschinsky, J. -P., Koster, F., Kramer, M., Krampitz, R., Kramer-Flecken, A., Krawczyk, N., Kremeyer, T., Krom, J., Ksiazek, I., Kubkowska, M., Kuhner, G., Kurki-Suonio, T., Kurz, P. A., Kwak, S., Landreman, M., Lang, P., Lang, R., Langish, S., Laqua, H., Laube, R., Lechte, C., Lennartz, M., Leonhardt, W., Li, C., Li, Y., Liang, Y., Linsmeier, C., Liu, S., Lobsien, J. -F., Loesser, D., Loizu Cisquella, J., Lore, J., Lorenz, A., Losert, M., Lucke, A., Lumsdaine, A., Lutsenko, V., Maassberg, H., Marchuk, O., Matthew, J. H., Marushchenko, M., Masuzaki, S., Maurer, D., Mayer, M., Mccarthy, K., Meier, A., Mellein, D., Mendelevitch, B., Mertens, P., Mikkelsen, D., Mishchenko, A., Missal, B., Mittelstaedt, J., Mizuuchi, T., Mollen, A., Moncada, V., Monnich, T., Morisaki, T., Moseev, D., Murakami, S., Nafradi, G., Nagel, M., Naujoks, D., Neilson, H., Neu, R., Neubauer, O., Neuner, U., Ngo, T., Nicolai, D., Nielsen, S. K., Niemann, H., Nishizawa, T., Nuhrenberg, C., Nuhrenberg, J., Obermayer, S., Offermanns, G., Olmanns, J., Ongena, J., Oosterbeek, J. W., Pacios Rodriguez, L., Panadero, N., Panadero Alvarez, N., Papenfuss, D., Paqay, S., Pawelec, E., Pedersen, T. S., Pelka, G., Perseo, V., Peterson, B., Pilopp, D., Pingel, S., Pisano, F., Plaum, B., Plunk, G., Poloskei, P., Proll, J., Puiatti, M. -E., Purps, F., Rack, M., Recsei, S., Reiman, A., Reimold, F., Reiter, D., Remppel, F., Renard, S., Riemann, J., Risse, K., Rohde, V., Rohlinger, H., Rome, M., Rondeshagen, D., Rong, P., Roth, B., Rudischhauser, L., Rummel, K., Rummel, T., Runov, A., Ryc, L., Ryosuke, S., Sakamoto, R., Salewski, M., Samartsev, A., Sanchez, E., Sano, F., Satake, S., Schacht, J., Satheeswaran, G., Schauer, F., Scherer, T., Schlaich, A., Schlisio, G., Schluck, F., Schluter, K. -H., Schmitt, J., Schmitz, H., Schmitz, O., Schmuck, S., Schneider, M., Schneider, W., Scholz, P., Schrittwieser, R., Schroder, M., Schroder, T., Schumacher, H., Schweer, B., Sereda, S., Shanahan, B., Sibilia, M., Sinha, P., Siplia, S., Slaby, C., Sleczka, M., Smith, H., Spiess, W., Spong, D. A., Spring, A., Stadler, R., Stejner, M., Stephey, L., Stridde, U., Suzuki, C., Szabo, V., Szabolics, T., Szepesi, T., Szokefalvi-Nagy, Z., Tancetti, A., Terry, J., Thomas, J., Thumm, M., Travere, J. M., Traverso, P., Tretter, J., Trimino Mora, H., Tsuchiya, H., Tsujimura, T., Tulipan, S., Unterberg, B., Vakulchyk, I., Valet, S., Van Milligen, B., Van Vuuren, A. J., Vela, L., Velasco, J. -L., Vergote, M., Vervier, M., Vianello, N., Viebke, H., Vilbrandt, R., Vorkoper, A., Wadle, S., Wagner, F., Wang, E., Wang, N., Wang, Z., Warmer, F., Wegener, L., Weggen, J., Wei, Y., Weir, G., Wendorf, J., Wenzel, U., Werner, A., White, A., Wiegel, B., Wilde, F., Windisch, T., Winkler, M., Winter, A., Winters, V., Wolf, S., Wright, A., Xanthopoulos, P., Yamada, H., Yamada, I., Yasuhara, R., Yokoyama, M., Zarnstorff, M., Zeitler, A., Zhang, H., Zhu, J., Zilker, M., Zocco, A., Zoletnik, S., Zuin, M., Science and Technology of Nuclear Fusion, Turbulence in Fusion Plasmas, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Physics, Technology, Plasma parameters, Divertor, Nuclear engineering, Plasma, Condensed Matter Physics, 01 natural sciences, 7. Clean energy, Electron cyclotron resonance, 010305 fluids & plasmas, law.invention, Magnetic field, law, 0103 physical sciences, Limiter, Wendelstein 7-X, 010306 general physics, ddc:600, Stellarator
Abstract: Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future stellarator power plant. Plasma operation started in 2015 using a limiter configuration. After installing an uncooled magnetic island divertor, extending the energy limit from 4 to 80 MJ, operation continued in 2017. For this phase, the electron cyclotron resonance heating (ECRH) capability was extended to 7 MW, and hydrogen pellet injection was implemented. The enhancements resulted in the highest triple product (6.5 × 1019 keV m-3 s) achieved in a stellarator until now. Plasma conditions [Te(0) ≈ Ti(0) ≈ 3.8 keV, τE > 200 ms] already were in the stellarator reactor-relevant ion-root plasma transport regime. Stable operation above the 2nd harmonic ECRH X-mode cutoff was demonstrated, which is instrumental for achieving high plasma densities in Wendelstein 7-X. Further important developments include the confirmation of low intrinsic error fields, the observation of current-drive induced instabilities, and first fast ion heating and confinement experiments. The efficacy of the magnetic island divertor was instrumental in achieving high performance in Wendelstein 7-X. Symmetrization of the heat loads between the ten divertor modules could be achieved by external resonant magnetic fields. Full divertor power detachment facilitated the extension of high power plasmas significantly beyond the energy limit of 80 MJ.
Published: 2019
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19. Observation of anomalous impurity transport during low-density experiments in W7-X with laser blow-off injections of iron

Author: W7-X Team, Geiger, B., Wegner, Th., Beidler, C. D., Burhenn, R., Buttenschön, B., Dux, R., Langenberg, A., Pablant, N. A., Pütterich, T., Turkin, Y., Windisch, T., Winters, V., Beurskens, M., Biedermann, C., Brunner, K. J., Cseh, G., Damm, H., Effenberg, F., Fuchert, G., Grulke, O., Harris, J. H., Killer, C., Knauer, J., Kocsis, G., Krämer-Flecken, A., Kremeyer, T., Krychowiak, M., Marchuk, O., Nicolai, D., Rahbarnia, K., Satheeswaran, G., Schilling, J., Schmitz, O., Schröder, T., Szepesi, T., Thomsen, H., Trimino Mora, H., Traverso, P., Zhang, D., Baumann, Klaus, Dammertz, Günter, Gantenbein, Gerd, Huber, Martina, Hunger, Hermann, Illy, Stefan, Jelonnek, John, Kobarg, Thorsten, Lang, Rouven, Leonhardt, Wolfgang, Losert, M., Mellein, Daniel, Papenfuß, Daniel, Smartsev, A., Scherer, Theo, Schlaich, Andreas, Spieß, W., Thumm, Manfred, Wadle, Simone, Weggen, Jörg, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Technology, Nuclear and High Energy Physics, Materials science, Turbulence, Condensed Matter Physics, Laser, 01 natural sciences, 010305 fluids & plasmas, law.invention, Strahl, Impurity, law, 0103 physical sciences, Low density, Atomic physics, 010306 general physics, ddc:600, Stellarator
Published: 2019
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20. AWAKE readiness for the study of the seeded self-modulation of a 400\,GeV proton bunch

Author: Muggli, P., Adli, E., Apsimon, R., Asmus, F., Baartman, R., Bachmann, A.-M., Barros Marin, M., Batsch, F., Bauche, J., Berglyd Olsen, V. K., Bernardini, M., Turner, M., Verzilov, V., Vieira, J., Vincke, H., Welsch, C. P., Williamson, B., Wing, M., Xia, G. X., Zhang, H., The AWAKE collaboration, Biskup, B., Blanco Vinuela, E., Boccardi, A., Bogey, T., Bohl, T., Bracco, C., Braunmuller, F., Burger, S., Burt, G., Bustamante, S., Buttenschön, B., Butterworth, A., Caldwell, A., Cascella, M., Chevallay, E., Chung, M., Damerau, H., Deacon, L., Dexter, A., Dirksen, P., Doebert, S., Farmer, J., Fedosseev, V., Feniet, T., Fior, G., Fiorito, R., Fonseca, R. A., Friebel, F., Gander, P., Gessner, S., Gorgisyan, I., Gorn, A. A., Grulke, O., Gschwendtner, E., Guerrero, A., Hansen, J., Hessler, C., Hofle, W., Holloway, J., Hüther, M., Ibison, M., Islam, M. R., Jensen, L., Jolly, S. W., Kasim, M., Keeble, F., Kim, S.-Y., Krausz, F., Lasheen, A., Lefevre, T., LeGodec, G., Li, Y., Liu, S., Lopes, N. C., Lotov, K., Martyanov, M., Mazzoni, S., Medina Godoy, D., Mete, O., Minakov, V. A., Mompo, R., Moody, J. T., Moreira, M. T., Mitchell, J., Mutin, C., Norreys, P., Öz, E., Ozturk, E., Pauw, W., Pardons, A., Pasquino, C., Pepitone, K., Petrenko, A., Pitmann, S., Plyushchev, G., Pukhov, A., Rieger, K., Ruhl, H., Schmidt, J., Shalimova, I. A., Shaposhnikova, E., Sherwood, P., Silva, L., Sosedkin, A. P., Speroni, R., Spitsyn, R. I., Szczurek, K., Thomas, J., Tuev, P. V., and AWAKE Collaboration
Subjects: Accelerator Physics (physics.acc-ph), Proton, Particle acceleration, Other Fields of Physics, chemistry.chemical_element, FOS: Physical sciences, 01 natural sciences, Ciências Naturais::Ciências Físicas [Domínio/Área Científica], 010305 fluids & plasmas, law.invention, Rubidium, law, Physics::Plasma Physics, Seeded self-modulation, Ionization, physics.plasm-ph, Plasma wakefields driven by protons, 0103 physical sciences, Physics::Atomic Physics, 010306 general physics, Nuclear Experiment, physics.acc-ph, Physics, Plasma, Plasma-based accelerator, Condensed Matter Physics, Plasma acceleration, Laser, Accelerators and Storage Rings, Physics - Plasma Physics, Pulse (physics), Plasma Physics (physics.plasm-ph), Nuclear Energy and Engineering, chemistry, Physics::Accelerator Physics, Seeding, Physics - Accelerator Physics, Plasma wakefields seeding, Atomic physics
Abstract: AWAKE is a proton-driven plasma wakefield acceleration experiment. % We show that the experimental setup briefly described here is ready for systematic study of the seeded self-modulation of the 400\,GeV proton bunch in the 10\,m-long rubidium plasma with density adjustable from 1 to 10$\times10^{14}$\,cm$^{-3}$. % We show that the short laser pulse used for ionization of the rubidium vapor propagates all the way along the column, suggesting full ionization of the vapor. % We show that ionization occurs along the proton bunch, at the laser time and that the plasma that follows affects the proton bunch. %, Comment: Presented as an invited talk at the EPS=Plasma Physics Conference 2017
Published: 2017
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21. Investigation of turbulence rotation in the SOL and plasma edge of W7-X for different magnetic configurations

Author: W7-X Team, Krämer-Flecken, A., Han, X., Otte, M., Anda, G., Bozhenkov, S. A., Dunai, D., Fuchert, G., Geiger, J., Grulke, O., Pasch, E., Scott, E. R., Trier, E., Vécsei, M., Windisch, T., Zoletnik, S., Gantenbein, Gerd, Jelonnek, John, Thumm, Manfred, and W7-X Team, Max Planck Institute for Plasma Physics, Max Planck Society
Subjects: Technology, Materials science, Turbulence, chemistry.chemical_element, Plasma, Condensed Matter Physics, Rotation, 01 natural sciences, 010305 fluids & plasmas, law.invention, chemistry, law, Electrical equipment, 0103 physical sciences, Measuring instrument, Graphite, Atomic physics, 010306 general physics, ddc:600, Carbon, Stellarator
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22. High Resolution Probe for filament transport and current density study at the edge region of W7-X

Author: Samuel Lazerson, Emilio Martines, Olaf Grulke, R. Ghirardelli, Roberto Cavazzana, M. Brombin, Carsten Killer, Dirk Nicolai, Piero Agostinetti, N. Vianello, M. Moresco, B. Schweer, G. Satheeswaran, Olaf Neubauer, Monica Spolaore, Michele Visentin, G. Grenfell, Spolaore, M, Agostinetti, P, Killer, C, Moresco, M, Brombin, M, Cavazzana, R, Ghirardelli, R, Grenfell, G, Grulke, O, Lazerson, S, Martines, E, Neubauer, O, Nicolai, D, Satheeswaran, G, Schweer, B, Vianello, N, and Visentin, M
Subjects: Ion sources (positive ions, Materials science, Ion sources (positive ions, negative ions, electron cyclotron resonance (ECR), electron beam (EBIS)), Edge region, High resolution, negative ions, electron beam (EBIS)), 01 natural sciences, Molecular physics, 010305 fluids & plasmas, Protein filament, 0103 physical sciences, Plasma diagnostics - probes, electron cyclotron resonance (ECR), 010306 general physics, Instrumentation, Current density, Plasma diagnostics-probe, Mathematical Physics
Abstract: For the study of electrostatic and magnetic properties of filaments characterizing the edge region of the stellarator experiment W7-X, a specifically designed insertable probe head was constructed within the framework of EUROfusion WP.S1 work package in collaboration between Consorzio RFX, IPP Greifswald and Forschungszentrum Mich. The probe head, named High Resolution Probe (HRP), was conceived to be installed on the mid-plane multi-purpose fast reciprocating manipulator on W7-X. Electromagnetic filamentary turbulent structures are found to characterize the edge region of different magnetic configurations including Reversed Field Pinch, stellarator and tokamak, where strong currents are associated also to ELM filamentary structures. The study of those phenomena in W7-X stellarator is of particular interest as the electromagnetic features of filaments are expected to become more relevant with the increase of the local plasma beta. In particular the aim is to provide information about the presence and the features of parallel current density associated to filamentary turbulent or ELM-like structures. Furthermore, the possibility to measure the time evolution of the flow radial profiles using the Mach probe array was considered as a further interesting part of the study, given the strong interplay expected between the turbulent fluctuations and the average flows. Further important information provided is the radial propagation of turbulent flux. The contribution will present the design development, the R&D studies and the applied solutions for the sensors embedded in the probe head. In particular, the presence of 140 GHz ECRH plasma environment represents one of the main challenges for reliable magnetic fluctuation measurements. First measurements were performed during the W7-X experimental campaign OP1.2b, where electromagnetic features of turbulence were measured with the probe, at different magnetic configurations.
Published: 2019
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23. Design of a High Resolution Probe Head for Electromagnetic Turbulence Investigations in W7-X

Author: M. Brombin, Carsten Killer, Piero Agostinetti, Simone Peruzzo, M. Moresco, Michele Visentin, Monica Spolaore, Nicola Vianello, Olaf Grulke, L. Franchin, V. Cervaro, Emilio Martines, Agostinetti, P, Spolaore, M, Brombin, M, Cervaro, V, Franchin, L, Grulke, O, Killer, C, Martines, E, Moresco, M, Peruzzo, S, Vianello, N, and Visentin, M
Subjects: Physics, Nuclear and High Energy Physics, Turbulence, Resolution (electron density), Edge region, High resolution, Mechanical engineering, Electromagnetic Turbulence, Condensed Matter Physics, 01 natural sciences, Electromagnetic fluctuations, W7-X, 010305 fluids & plasmas, Wendelstein 7-X (W7-X), stellarator, 0103 physical sciences, Head (vessel), Electromagnetic fluctuation, Work program, Manipulator, insertable probe, 010306 general physics, Engineering design process, High Resolution Probe
Abstract: A multi-purpose manipulator (MPM) system has been developed and installed on the W7-X vessel, aimed at investigating the edge plasmas of the stellarator. It is a flexible tool for integration of a variety of different diagnostics as e. g. electrical probes, probing magnetic coils, material collection, or material exposition probes, and gas injection. In the framework of the EUROfusion S1 work program for the preparation and exploitation of W7-X campaigns, a diagnostic insertable probe head called HRP (High Resolution Probe) has been developed by Consorzio RFX in collaboration with IPP Greifswald, to study the electrostatic and electromagnetic features of turbulence in the edge region of W7-X using the MPM.
Published: 2017
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23 results on '"Grulke O."'

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

2. Transition between Instability and Seeded Self-Modulation of a Relativistic Particle Bunch in Plasma

3. Characterization of injection and confinement improvement through impurity induced profile modifications on the Wendelstein 7-X stellarato

4. Heat pulse propagation and anomalous electron heat transport measurements on the optimized stellarator W7-X

5. Demonstration of reduced neoclassical energy transport in Wendelstein 7-X

6. Experimental study of extended timescale dynamics of a plasma wakefield driven by a self-modulated proton bunch

7. Design and characteristics of a low-frequency magnetic probe for magnetic profile measurements at Wendelstein 7-X

8. Enhanced energy confinement after series of pellets in Wendelstein 7-X

9. Statistical characteristics of the SOL turbulence in the first divertor plasma operation of W7-X using a reciprocating probe

10. Correction to 'Proton-driven plasma wakefield acceleration in AWAKE' (vol 377, 20180418, 2019)

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

12. Proton beam defocusing in AWAKE: comparison of simulations and measurements

13. Investigation of turbulence rotation and radial electric field in the island divertor and plasma edge at W7-X

14. Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities

15. Letter

16. Magnetic configuration effects on the Wendelstein 7-X stellarator

17. Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000

18. Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase

19. Observation of anomalous impurity transport during low-density experiments in W7-X with laser blow-off injections of iron

20. AWAKE readiness for the study of the seeded self-modulation of a 400\,GeV proton bunch

21. Investigation of turbulence rotation in the SOL and plasma edge of W7-X for different magnetic configurations

22. High Resolution Probe for filament transport and current density study at the edge region of W7-X

23. Design of a High Resolution Probe Head for Electromagnetic Turbulence Investigations in W7-X

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23 results on '"Grulke O."'

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