Rozložení tepelných toků na stěnu tokamaku způsobených okrajovými nestabilitami

Okrajové nestability (ELMy) jsou nebezpečím pro budoucí fúzní zařízení, jako např. ITER, kvůli velkým tepelným tokům, které náhle působí na povrch komponent vystavených plazmatu. Velmi slibnou metodou potlačení okrajových nestabilit je aplikace rezonančních magnetických perturbací (RMP). Tato metoda ovšem vede k vytváření lokalizovaných míst -- otiskům -- s vysokým tepelným tokem. Jak přítomnost ELMů tak RMP může omezit životnost fúzního zařízení. V této práci analyzujeme pomocí metody tangle distance prostorové a časové rozmístění otisků na tokamaku ITER s cílem zamezit krátkodobému přehřívání povrchů. Také zde analyzujeme quasi-double-null konfiguraci plazmatu tokamaku ITER, u které existuje obava z přehřívání horní stěny. Na základě modelování jsme ukázali potenciálně nebezpečné konfigurace RMP. Pomocí modelu ELMů zahrnutého v GPU kódu LOCUST studujeme prostorové a časové rozložení tepelných toků způsobených okrajovými nestabilitami v axiálně symetrickém i nesymetrickém plazmatu. Výsledky porovnáváme publikovanými experimentálními pozorováními. Powered by TCPDF (www.tcpdf.org)Edge localized modes (ELMs) are a concern for future magnetic fusion devices, such as ITER, due to the large transient heat loads they generate on the plasma facing components. A very promising method of ELM suppression is an application of resonant magnetic perturbations (RMP); however, such application leads to localized places of higher heat fluxes called footprints. Both ELMs and RMP could limit the operational lifetime of the device. In this thesis, we analyze the temporal and spatial distribution of footprints using the tangle distance method in the aim to prevent a transient overheating. We also analyze quasi-double-null configuration of the ITER plasma which can be expected to be the most susceptible to overheating of the upper wall. Based on the modelling, the potentially dangerous configurations of the RMP have been shown. Using the ELM filament model included in the LOCUST GPU code, we study temporal and spatial distribution of the heat fluxes caused by ELMs in the axially symmetric and the asymmetric magnetic field. The results are compared with published experimental observations. Powered by TCPDF (www.tcpdf.org)Katedra fyziky povrchů a plazmatuDepartment of Surface and Plasma ScienceMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Simulations of COMPASS vertical displacement events with a self-consistent model for halo currents including neutrals and sheath boundary conditions

The understanding of the halo current properties during disruptions is key to design and operate large scale tokamaks in view of the large thermal and electromagnetic loads that they entail. For the first time, we present a fully self-consistent model for halo current simulations including neutral particles and sheath boundary conditions. The model is used to simulate vertical displacement events (VDEs) occurring in the COMPASS tokamak. Recent COMPASS experiments have shown that the parallel halo current density at the plasma-wall interface is limited by the ion saturation current during VDE-induced disruptions. We show that usual magneto-hydrodynamic boundary conditions can lead to the violation of this physical limit and we implement this current density limitation through a boundary condition for the electrostatic potential. Sheath boundary conditions for the density, the heat flux, the parallel velocity and a realistic parameter choice (e.g. Spitzer's resistivity and Spitzer-Harm parallel thermal conductivity) extend present VDE simulations beyond the state of the art. Experimental measurements of the current density, temperature and heat flux profiles at the COMPASS divertor are compared with the results obtained from axisymmetric simulations. Since the ion saturation current density (Jsat) is shown to be essential to determine the halo current profile, parametric scans are performed to study its dependence on different quantities such as the plasma resistivity and the particle and heat diffusion coefficients. In this respect, the plasma resistivity in the halo region broadens significantly the Jsat profile, increasing the halo width at a similar total halo current

Traffic - Road Network Simulation Game

The goal of this thesis was to implement the mobile game Traffic, in which the player controls a car and navigates through a road network. The general concept of the game is based on our vision of a game simulating the experience of driving that would be different from similar existing games. This vision proved to be overly complex. Therefore, we selected only a subset of its features while ensuring that the resulting game can serve as a basis for future extension towards the original vision. We targeted the Android operating system and used the Unity game engine and C# for implementation. In the resulting game, the player acts as a taxi driver, i.e. they pick up customers and drop them off at designated locations. The player receives game money and rating based on the quality of each ride. The game world contains roads, intersections, sidewalks, buildings and pedestrians. The game world can be edited by a game designer with no programming skills. The designer can shape the roads and sidewalks using Bézier curves and connect roads into intersections. The shape of intersections is generated automatically. 1Cílem této práce byla implementace mobilní hry Traffic, ve které hráč ovládá auto a projíždí herním světem po silniční síti. Její základní princip vychází z naší vize hry simulující řízení, která by obohatila nabídku již existujících her. Tato vize se ukázala jako příliš komplexní, a proto jsme z jejích funkcionalit vybrali pouze podmnožinu, přičemž jsme dbali na zachování rozšiřitelnosti směrem k původní vizi. Jako cílovou platformu jsme zvolili systém Android a jako implementační nástroj engine Unity spolu s jazykem C#. Ve výsledné hře je hráč v roli taxikáře, tj. převáží lidi na jimi určené destinace. Podle kvality jednotlivých jízd získává peníze a hodnocení. Při tom projíždí světem obsahujícím silnice, křižovatky, chodníky, budovy a chodce. Herní svět je připraven na modifikaci herním návrhářem, který ne nutně umí progra- movat. Návrhář silnicím a chodníkům přiřazuje libovolný tvar daný Bézierovou křivkou a silnice pak spojuje do křižovatek. Tvar křižovatek se automaticky určí z tvaru navazu- jících silnic. 1Department of Distributed and Dependable SystemsKatedra distribuovaných a spolehlivých systémůMatematicko-fyzikální fakultaFaculty of Mathematics and Physic

Rozložení tepelných toků na stěnu tokamaku způsobených okrajovými nestabilitami

Edge localized modes (ELMs) are a concern for future magnetic fusion devices, such as ITER, due to the large transient heat loads they generate on the plasma facing components. A very promising method of ELM suppression is an application of resonant magnetic perturbations (RMP); however, such application leads to localized places of higher heat fluxes called footprints. Both ELMs and RMP could limit the operational lifetime of the device. In this thesis, we analyze the temporal and spatial distribution of footprints using the tangle distance method in the aim to prevent a transient overheating. We also analyze quasi-double-null configuration of the ITER plasma which can be expected to be the most susceptible to overheating of the upper wall. Based on the modelling, the potentially dangerous configurations of the RMP have been shown. Using the ELM filament model included in the LOCUST GPU code, we study temporal and spatial distribution of the heat fluxes caused by ELMs in the axially symmetric and the asymmetric magnetic field. The results are compared with published experimental observations. Powered by TCPDF (www.tcpdf.org

Zur Foraminiferen-Fauna im Wattenmeer bei Sylt

Die Aufgabe dieser Arbeit besteht im wesentlichen darin, die rezente Foraminiferen-Fauna im Arbeitsgebiet zu erfassen und sie in Beziehung zu ökologischen Faktoren zu setzen. Das besondere Interesse kommt der Lebendfauna zu. Auf einen taxionomischen Teil wird im Rahmen dieser Arbeit verzichtet. Es sei hier auf die Veröffentlichungen von VOORT-HUYSEN (1960), HAAKE (1962) und LUTZE (1964) verwiesen, die einen ausführlichen taxionomischen Teil enthalten

MHD nestability plazmatu pozorované ve výbojích tokamaku COMPASS

Compass tokamak (R = 0.56 m, a = (0.23 × 0.38) m, Ip = 200 − 400 kA, BT = 1.2 − 2.1 T and pulse length up to 1 s) is the smallest device with ITER-relevant plasma geometry with scale 1:10 to the ITER size. A tokamak plasma confinement is strongly limited by an occurrence of magnetohydrodynamic (MHD) instabilities occurring during the discharge. In the thesis, theoretical considerations and a typical behaviour of the tokamak plasma MHD instabilites are summarized based on the lite- rature overview. This discussion is complemented with an overview of the Compass diagnostics and different data analysis techniques. Finally, the examples of the Compass plasma behaviour influenced by sawtooth instability and tearing modes are shown and discussed.

Traffic - Road Network Simulation Game

The goal of this thesis was to implement the mobile game Traffic, in which the player controls a car and navigates through a road network. The general concept of the game is based on our vision of a game simulating the experience of driving that would be different from similar existing games. This vision proved to be overly complex. Therefore, we selected only a subset of its features while ensuring that the resulting game can serve as a basis for future extension towards the original vision. We targeted the Android operating system and used the Unity game engine and C# for implementation. In the resulting game, the player acts as a taxi driver, i.e. they pick up customers and drop them off at designated locations. The player receives game money and rating based on the quality of each ride. The game world contains roads, intersections, sidewalks, buildings and pedestrians. The game world can be edited by a game designer with no programming skills. The designer can shape the roads and sidewalks using Bézier curves and connect roads into intersections. The shape of intersections is generated automatically.

Český inserát

Katedra psychologieFilozofická fakult