Universität Stuttgart
Permanent URI for this communityhttps://elib.uni-stuttgart.de/handle/11682/1
Browse
49 results
Search Results
Item Open Access Fusionsforschung : eine Einführung(2020) Köhn-Seemann, AlfIn diesem Vortrag wird ein Überblick und eine Einleitung in das Gebiet der Fusionsforschung gegeben.Item Open Access Overview of first Wendelstein 7-X high-performance operation(2019) Klinger, T.; Andreeva, T.; Bozhenkov, Sergey; Brandt, C.; Burhenn, R.; Buttenschön, Birger; Fuchert, G.; Geiger, B.; Grulke, O.; Laqua, H. P.; Pablant, N.; Rahbarnia, K.; Stange, T.; Stechow, A. von; Tamura, Naoki; Thomsen, H.; Turkin, Y.; Wegner, Thomas; Abramovic, I.; Äkäslompolo, S.; Alcuson, J.; Aleynikov, P.; Aleynikova, K.; Ali, A.; Alonso, A.; Anda, G.; Ascasibar, E.; Bähner, J. P.; Baek, S. G.; Balden, M.; Baldzuhn, J.; Banduch, M.; Barbui, T.; Behr, W.; Beidler, C.; Benndorf, A.; Biedermann, C.; Biel, W.; Blackwell, B.; Blanco, E.; Blatzheim, M.; Ballinger, S.; Bluhm, T.; Böckenhoff, D.; Böswirth, B.; Böttger, L.-G.; Borchardt, M.; Borsuk, V.; Boscary, J.; Bosch, H.-S.; Beurskens, M.; Brakel, R.; Brand, H.; Bräuer, T.; Braune, H.; Brezinsek, S.; Brunner, K.-J.; 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.; Damm, H.; de la Pena, A.; Degenkolbe, S.; Dhard, C. P.; Dibon, M.; Dinklage, A.; Dittmar, T.; Drevlak, M.; Drewelow, P.; Drews, P.; Durodie, F.; Edlund, E.; Eeten, P. van; 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.; Ford, O.; Fornal, T.; Frerichs, H.; Freund, A.; Funaba, T.; Galkowski, A.; Gantenbein, G.; Gao, Y.; García Regaña, J.; Gates, D.; Geiger, J.; 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.; Hartmann, D.; Hathiramani, D.; Hein, B.; Heinemann, B.; Helander, P.; Henneberg, S.; Henkel, M.; Hernandez Sanchez, J.; Hidalgo, C.; Hirsch, M.; Hollfeld, K. P.; Höfel, U.; 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, Walter; Kazakov, Y. O.; Kenmochi, N.; Killer, C.; Kirschner, A.; Kleiber, R.; 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.; Krychowiak, M.; Ksiazek, I.; Kubkowska, M.; Kühner, G.; Kurki-Suonio, T.; Kurz, P. A.; Kwak, S.; Landreman, M.; Lang, P.; Lang, R.; Langenberg, A.; Langish, S.; Laqua, H.; Laube, R.; Lazerson, S.; Lechte, Carsten; Lennartz, M.; Leonhardt, W.; Li, C.; 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.; Neuner, U.; 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.; Pasch, E.; Pavone, A.; Pawelec, E.; Pedersen, T. S.; Pelka, G.; Perseo, V.; Peterson, B.; Pilopp, D.; Pingel, S.; Pisano, F.; Plaum, Burkhard; 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, Felix; Renard, S.; Riedl, R.; Riemann, J.; Risse, K.; Rohde, V.; Röhlinger, Holger; Romé, M.; Rondeshagen, D.; Rong, P.; Roth, Bernhard; Rudischhauser, L.; Rummel, K.; Rummel, T.; Runov, A.; Rust, N.; Ryc, L.; Ryosuke, S.; Sakamoto, R.; Salewski, M.; Samartsev, A.; Sanchez, E.; Sano, F.; Satake, S.; Schacht, J.; Satheeswaran, G.; Schauer, F.; Scherer, T.; Schilling, J.; Schlaich, A.; Schlisio, G.; Schluck, F.; Schlüter, Karl-Heinz; 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.; Scott, E.; Sereda, S.; Shanahan, B.; Sibilia, M.; Sinha, P.; Sipliä, S.; Slaby, C.; Sleczka, M.; Smith, H.; Spiess, W.; Spong, D. A.; Spring, A.; Stadler, R.; Stejner, M.; Stephey, L.; Stridde, U.; Suzuki, C.; Svensson, J.; Szabó, V.; Szabolics, T.; Szepesi, T.; Szökefalvi-Nagy, Z.; 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.; Vano, L.; Milligen, B. van; Vuuren, A. J. van; Vela, L.; Velasco, J.-L.; Vergote, M.; Vervier, M.; Vianello, N.; Viebke, H.; Vilbrandt, R.; Vorköper, A.; Wadle, S.; Wagner, F.; Wang, E.; Wang, N.; Wang, Z.; Warmer, F.; Wauters, T.; 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, Stefan; Wolf, R. C.; Wright, A.; Wurden, G.; Xanthopoulos, P.; Yamada, H.; Yamada, I.; Yasuhara, R.; Yokoyama, M.; Zanini, M.; Zarnstorff, M.; Zeitler, Achim; Zhang, D.; Zhang, H.; Zhu, J.; Zilker, M.; Zocco, A.; Zoletnik, S.; Zuin, M.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.Item Open Access Plasma electron acceleration in a non-resonant microwave heating scheme below the electron cyclotron frequency(2022) Köhn-Seemann, Alf; Birkenmeier, Gregor; Diez, Peter; Holzhauer, Eberhard; Merli, Stefan; Ramisch, Mirko; Sichardt, Garbriel; Stroth, UlrichMicrowave heating of over-dense plasmas is routinely achieved in the stellarator TJ-K. In contrast to usually applied heating scenarios in tokamaks or stellarators, an operational regime is described where the heating occurs well below the electron cyclotron frequency but still well above the lower hybrid frequency. Microwave energy is deposited at the so-called O-resonance, accompanied by a small population of high-energy electrons with an energy up to 100 keV. These electrons are responsible for a significant toroidal net current and the occurrence of hard x-rays. Requirements for achieving this heating regime are described together with a novel scheme for plasma-electron acceleration.Item Open Access Microwave absorption of layer materials(2026) Hentrich, Andreas; Tovar, Günter E. M. (Prof. Dr.)The influence of the production process of atmospheric plasma sprayed ceramic coatings on the resonant absorption of millimeter waves was investigated. The main focus of the work was the application of these coatings as microwave absorbers in nuclear fusion related experiments. The production and optimization process for these absorbers was described in detail and most practically relevant parameter dependencies were investigated both in experiment and model.Item Open Access Visualization of the O-X-B mode conversion process with a full-wave code(2008) Köhn, Alf; Holzhauer, Eberhard; Stroth, UlrichThe O-X-B mode conversion is a process to couple electromagnetic waves into an overdense plasma. At the vicinity of the cutoff, the wave is converted into a Bernstein wave, which is very well absorbed in the plasma without further density cutoff. Therefore, these waves are a promising tool to heat high-density plasmas. The conversion process has been investigated in great detail using a full-wave code, and for the first time, the time-dependent formation of the Bernstein waves has been visualized by using the data obtained with this simulation.Item Open Access Charakterisierung der elektromagnetischen Turbulenz im Torsatron TJ-K(2007) Rahbarnia, Kian; Stroth, Ulrich (Prof. Dr.)Es wird die elektromagnetische Turbulenz im Torsatron TJ-K gemessen und analysiert.Item Open Access Silicon integrated dual-mode interferometer with differential outputs(2017) Hoppe, Niklas; Scheck, Pascal; Sweidan, Rami; Diersing, Philipp; Rathgeber, Lotte; Vogel, Wolfgang; Riegger, Benjamin R.; Southan, Alexander; Berroth, ManfredThe dual-mode interferometer (DMI) is an attractive alternative to Mach-Zehnder interferometers for sensor purposes, achieving sensitivities to refractive index changes close to state-of-the-art. Modern designs on silicon-on-insulator (SOI) platforms offer thermally stable and compact devices with insertion losses of less than 1 dB and high extinction ratios. Compact arrays of multiple DMIs in parallel are easy to fabricate due to the simple structure of the DMI. In this work, the principle of operation of an integrated DMI with differential outputs is presented which allows the unambiguous phase shift detection with a single wavelength measurement, rather than using a wavelength sweep and evaluating the optical output power spectrum. Fluctuating optical input power or varying attenuation due to different analyte concentrations can be compensated by observing the sum of the optical powers at the differential outputs. DMIs with two differential single-mode outputs are fabricated in a 250 nm SOI platform, and corresponding measurements are shown to explain the principle of operation in detail. A comparison of DMIs with the conventional Mach-Zehnder interferometer using the same technology concludes this work.Item Open Access Ökobilanz für die Bioprozessoptimierung : Herstellung des Biotensids MEL(2024) Bippus, Lars; Briem, Ann-Kathrin; Beck, Alexander; Zibek, Susanne; Albrecht, StefanThis study evaluates the environmental impacts of producing mannosylerythritol lipids (MELs) using life cycle assessment (LCA) and kinetic models. MELs are microbial biosurfactants with various applications produced from biobased sources. The LCA results indicate that substrate provision, bioreactor aeration and solvent use for purification are major environmental impact sources. The findings highlight areas for improving the environmental sustainability of the production processes.Item Open Access Entwicklung und spektroskopische Untersuchung eines Mikrowellen-Plasmabrenners für die Schichtabscheidung aus Pulvern(2012) Kopecki, Jochen; Stroth, Ulrich (Prof. Dr.)Nachhaltige Energiekonzepte, wie die Verwendung von regenerativen Energien, spielen in Zeiten von immer größer werdendem Energiebedarf eine entscheidende Rolle. Insbesondere im Bereich der Photovoltaik hat Deutschland seit jeher eine Vorreiterrolle eingenommen. Damit ist Deutschland der zentrale Standort für Photovoltaikforschung. In der vorliegenden Arbeit wird eine Möglichkeit zur plasmagestützten Abscheidung von amorphem Silizium aus Pulver entwickelt und untersucht, um eine kostengünstige Alternative zu den bestehenden Verfahren zu finden. Die Plasmaquelle hierfür basiert auf einem Mikrowellenresonator, welcher mit Hilfe von numerischen Simulationen mit CST Microwave Studio dimensioniert wurde und für den Betrieb bei Atmosphärendruck ausgelegt ist. Mit diesem Plasmabrenner ist es möglich ein linear ausgedehntes, freistehendes Plasma zu erzeugen, in dem Si-Partikel verdampft werden können. Die Partikel werden hierfür über einen Trägergasstrom eingeblasen und müssen während ihrer Verweilzeit im Plasma die benötigte Energie zum Verdampfen aufnehmen. Dieser Prozess wird im Detail untersucht, da sich über die Plasmalänge und den Gasfluss die maximal verwendbare Partikelgröße einstellt und für die Abscheidung von qualitativ hochwertigem amorphen Silizium der Schichtbildner vollständig gasförmig sein muss. Die Plasmaparameter T_gas, T_e und n_e, welche ebenfalls ausschlaggebend für den Beschichtungsprozess sind und in die verwendeten Verdampfungsmodelle eingehen, werden mittels optischer Emissionsspektroskopie in Abhängigkeit der Gaszusammensetzung ermittelt. Hierfür werden sowohl die relativen Intensitäten sowie die Linienprofile der Atomlinien der Balmerserie gemessen und ausgewertet. Die abgeschiedenen Schichten wurden mittels REM-, FTIR- und XPS-Analyse sowie der Photospektroskopie analysiert, wobei eine Verunreinigung der Schichten mit Sauerstoff ermittelt wurde, welche negative Auswirkungen auf die Leitfähigkeit der Schicht hat. Dennoch ist die Morphologie sowie die optische Qualtität der Schichten vergleichbar mit den Ergebnissen gängiger PECVD-Verfahren.Item Open Access The role of MHD instabilities in the improved H-mode scenario(2009) Flaws, Asher; Stroth, Ulrich (Prof.)Recently a regime of tokamak operation has been discovered, dubbed the improved H-mode scenario, which simultaneously achieves increased energy confinement and stability with respect to standard H-mode discharges. It has been suggested that magnetohydrodynamic (MHD) instabilities play some role in establishing this regime. In this thesis MHD instabilities were identified, characterised, and catalogued into a database of improved H-mode discharges in order to statistically examine their behaviour. The onset conditions of MHD instabilities were compared to existing models based on previous H-mode studies. Slight differences were found, most notably a reduced $\beta_N$ onset threshold for the frequently interrupted regime for neoclassical tearing modes (NTM). This reduced threshold is due to the relatively low magnetic shear of the improved H-mode regime. This study also provided a first-time estimate for the seed island size of spontaneous onset NTMs, a phenomenon characteristic of the improved H-mode scenario. Energy confinement investigations found that, although the NTM impact on confinement follows the same model applicable to other operating regimes, the improved H-mode regime acts to mitigate the impact of NTMs by limiting the saturated island sizes for NTMs with toroidal mode number $n \geqslant 2$. Surprisingly, although a significant loss in energy confinement is observed during the sawtooth envelope, it has been found that discharges containing fishbones and low frequency sawteeth achieve higher energy confinement than those without. This suggests that fishbone and sawtooth reconnection may indeed play a role in establishing the high confinement regime. It was found that the time evolution of the central magnetic shear consistently locks in the presence of sawtooth and fishbone reconnection. Presumably this is due to the periodic redistribution of the central plasma current, an effect which is believed to help establish and maintain the characteristic current profile required for improved H-mode operation. A similar effect was proposed for the NTM instability whereby the magnetic island drives an additional toroidal current which flattens the central current density profile. However, it was found that the NTM impact on the toroidal current density could be accounted for purely in terms of the $3$ conventional current contributions, namely: ohmic, bootstrap, and auxiliary heating current drive, without requiring an additional current source.