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Study of Equilibrium Magnetic Configuration in Tokamak Type Devices
Havlíček, Josef ; Tichý, Milan (advisor) ; Kubeš, Pavel (referee) ; Van Oost, Guido (referee)
This thesis presents the magnetic fields of the COMPASS tokamak and work done during the COMPASS reinstallation in the Czech Republic. The geometry, vacuum magnetic fields and Power Supplies for the poloidal field coils circuits are described in the technical part of the thesis. The design of Power Supplies filters and improvements in the controller algorithm are also introduced. The MHD equilibrium reconstruction code EFIT++ and implementation of the induced currents model are described in the physical part of the thesis. The EFIT++ code was adapted for COMPASS. The utilization of the EFIT++ code for the COMPASS operation is shown. The global power balance in the non-stationary phases of the tokamak discharge is explained and examples are shown. The attached articles describe Power Supplies and tokamak feedback system developed for the COMPASS plasma control. Powered by TCPDF (www.tcpdf.org)
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Development and application of methods for measurement of magnetic field on tokamaks
Kovařík, Karel ; Ďuran, Ivan (advisor) ; Mlynář, Jan (referee) ; Tichý, Milan (referee)
Title: Development and application of methods for measurement of magnetic field on tokamaks Author: Ing. Karel Kovařík Department: Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague Institute of Plasma Physics of the Czech Academy of Sciences, v. v. i. Supervisor: Ing. Ivan Duran, PhD. (Institute of Plasma Physics of the Czech Academy of Sciences, v. v. i.) Abstract: Thesis describes two parts of my work in frame of magnetic confined fusion research. First part describes irradiation testing of the Hall sensors based on InSb semiconductor. It evaluates radiation effects of fast and thermal neutrons on the Hall sensors sensitivity. Tests indicate low level of changes for fluence lower only by order of magnitude than expected in the whole lifetime of ITER tokamak. Second part describes measurement of turbulent plasma structures parameters in scrape--off layer of the COMPASS tokamak, particularly the parallel electric current flowing along them. Design of novel combined probe allowing measurement of not only electrostatic parameters but also the parallel electric current is presented. Evaluation of parallel electric current is discussed and compared with experiment. Statistical analysis of the plasma structures is presented. Empirical formulas of the...
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Rozložení tepelných toků na stěnu tokamaku způsobených okrajovými nestabilitami
Kripner, Lukáš ; Cahyna, Pavel (advisor) ; Urban, Jakub (referee)
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)
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Selected issues of thermonuclear fusion in tokamak-like magnetic containers
Ondáč, Peter ; Tichý, Milan (advisor) ; Kudrna, Pavel (referee)
In this thesis there are summarized in the form of basic knowledge the basic problems of fusion research. It serves as an introduction to this field of physics for beginners, but also intermediate candidates. The first two chapters set out the basic terms and ideas associated with controlled thermonuclear fusion. Further described is the magnetic confinement in tokamaks. Physically most important is the third chapter, which includes more advanced parts of physics. It discusses the main focus of this work, i.e. some of the major problems hindering fusion research. Final fourth chapter is relaxed. It discusses the ideas and visions for the near and distant future.
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Study of probe diagnostics of tokamak edge plasma via computer simulation
Podolník, Aleš ; Pánek, Radomír (advisor) ; Cavalier, Jordan (referee) ; Roučka, Štěpán (referee)
The aim of the thesis is to examine plasma-wall interaction using computer modeling. Tokamak- relevant plasma conditions are simulated using the particle-in-cell model family SPICE working in three or two dimensions. SPICE model was upgraded with a parallel Poisson equation solver and a heat equation solver module. Plasma simulation aimed at synthetic Langmuir probe measurements were performed. First set considered a flush-mounted probe and the effect of variable magnetic field angle was studied with aim to compare existing probe data evaluation techniques and assess their operational space, in which the plasma parameters estimation via fit to the current-voltage characteristic is accurate. Second simulation set studied a protruding probe pin. Effective collecting area of such probe was investigated with intentions of density measurement collection. This area was found to be influenced by a combination of two factors. First, the density dampening inside the magnetic pre-sheath of the probe head, and the second, the extension of the area caused by Larmor rotation. A comparison with experimental results obtained at COMPASS tokamak was was performed, confirming these results. Keywords Langmuir probe, simulation, particle-in-cell, tokamak, Poisson equation, COMPASS 1
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Anomalous diffusion of plasma in tokamak edge region
Seidl, Jakub ; Krlín, Ladislav (advisor) ; Hrach, Rudolf (referee) ; Rohlena, Karel (referee)
Title: Anomalous diffusion of plasma in tokamak edge region Author: Jakub Seidl Tutoring institution: Institute of Plasma Physics AS CR, v.v.i. Supervisor: Doc. Ing. Ladislav Krlín, DrSc., IPP AS CR Consultant: RNDr. Radomír Pánek, Ph.D., IPP AS CR Abstract: This work provides brief introduction to the topic of plasma turbu- lence in tokamak edge region and several aspects of anomalous plasma diffusion are discussed. We use numerical code ESEL to model interchange turbulence and investigate properties of turbulent structures in different regimes of parallel trans- port. Means of experimental verification of the results are discussed. Results of the modelling are then used to interpret unexpected results experimentally obtained by electrostatic ball-pen probes on tokamak ASDEX Upgrade, mainly appearance of a 'bump' in power spectra of measured plasma potential. Next, we explain be- haviour of cross-correlation function of density signals measured by two spatially separated Langmuir probes in the vicinity of magnetic separatrix and we point out an ambiguity in interpretation of results of vorticity measurement made by set of floating Langmuir probes. In the last part, transport of plasma impurities by electrostatic turbulent potential is modelled. We identify reversal of radial particle velocity for particles with...
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Diffusion of Particles from Tokamak by Stochastization of Magnetic Field Lines
Cahyna, Pavel
Diffusion of particles from tokamak by stochastization of magnetic field lines Pavel Cahyna Abstract: The thesis summarizes the current state of research of ther- monuclear fusion with magnetic confinement and decribes the possible role of stochastization of magnetic field lines and magnetic perturbations in solv- ing some of the problems that are encountered on the road to the exploitation of fusion. It presents a theoretical introduction to deterministic chaos and explains the connection of this theory to magnetic perturbations in tokamak. The results are presented mainly in the form of publications in journals and conference proceedings. Among them are: the comparison of chaotic dif- fusion of particles and field lines, where significant differences were found; the application of chaotic diffusion of particles to the problem of runaway electrons originating in disruptions, where our simulations contributed to ex- plaining the experimental results from the JET tokamak; the calculation of spectra of perturbations for the COMPASS tokamak, done as a preparation for the upcoming experiments; and modelling of screening of perturbations by plasma, where the observations of divertor footprints show as a promising method to detect the screening. 1
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Utilization and Suppression of Birefringence Phenomena in Optical Fiber Sensory Applications
Motúz, Rastislav ; Hudcová, Lucie (referee) ; Vlček, Čestmír (referee) ; Drexler, Petr (advisor)
The thesis deals with integral and distributed optical fiber sensors of electric current. In the area of integral sensors the analysis is performed by Jones matrix calculus and the simultaneous influence of induced circular and undesired linear birefringence using an ortho-conjugation retroreflector. Furthermore, the proposed conjugation loop variant using half-wave phase retarders is analyzed. The theoretical conclusions are confirmed by simulation and experimental measurement. In the field of distributed fiber optic sensors, analysis and simulation for the detection of plasma currents in thermonuclear fusion reactors, based on the POTDR technique, is performed. An improvement procedure is proposed for circular-shaped vacuum vessel reactors. Plasma current detection procedure in divertor-type reactors have been newly designed and simulated to investigate the effect of the OTDR detector noise on plasma current detection accuracy.
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Study of probe diagnostics of tokamak edge plasma via computer simulation
Podolník, Aleš ; Pánek, Radomír (advisor) ; Cavalier, Jordan (referee) ; Roučka, Štěpán (referee)
The aim of the thesis is to examine plasma-wall interaction using computer modeling. Tokamak- relevant plasma conditions are simulated using the particle-in-cell model family SPICE working in three or two dimensions. SPICE model was upgraded with a parallel Poisson equation solver and a heat equation solver module. Plasma simulation aimed at synthetic Langmuir probe measurements were performed. First set considered a flush-mounted probe and the effect of variable magnetic field angle was studied with aim to compare existing probe data evaluation techniques and assess their operational space, in which the plasma parameters estimation via fit to the current-voltage characteristic is accurate. Second simulation set studied a protruding probe pin. Effective collecting area of such probe was investigated with intentions of density measurement collection. This area was found to be influenced by a combination of two factors. First, the density dampening inside the magnetic pre-sheath of the probe head, and the second, the extension of the area caused by Larmor rotation. A comparison with experimental results obtained at COMPASS tokamak was was performed, confirming these results. Keywords Langmuir probe, simulation, particle-in-cell, tokamak, Poisson equation, COMPASS 1
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Plasma Heat Flux to Solid Structures in Tokamaks
Vondráček, Petr ; Horáček, Jan (advisor) ; Gunn, James P. (referee) ; Svoboda, Vojtěch (referee)
Plasma Heat Flux to Solid Structures in Tokamaks Petr Vondráček Energy and particle exhaust is the key issue for future fusion reactors based on magnetic plasma confinement, namely for tokamaks. Good understanding of processes controlling plasma heat fluxes impinging the first wall of tokamaks is of a main concern for fusion research. This doctoral thesis is focused on experimental investigation of plasma heat fluxes in different locations of the COMPASS tokamak. A new infrared thermography system was built for this purpose as a part of this PhD research. There are four main topics studied using the system. First of all, a narrow near-SOL heat flux channel with a very steep radial profile is characterised in HFS limited discharges. It is shown that the near-SOL heat flux decay length is consistent with the drift-based model of the SOL heat transport. Secondly, heat loading of leading edges of misaligned limiters is broadly studied. The optical approximation of the heat flux distribution around a poloidal leading edge is confirmed as a valid approach. Heat loading of a magnetically shadowed side of a toroidal limiter gap is observed experimentally for the first time confirming predictions of particle-in-cell code simulations. Thirdly, localised hot-spots caused by the impact of runaway electrons as well as...
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