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Diffusion of Particles from Tokamak by Stochastization of Magnetic Field Lines
Cahyna, Pavel ; Krlín, Ladislav (advisor) ; Rohlena, Karel (referee) ; Suttrop, Wolfgang (referee)
The thesis summarizes the current state of research of thermonuclear fusion with magnetic confinement and decribes the possible role of stochastization of magnetic field lines and magnetic perturbations in solving 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 diffusion 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 explaining 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.
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Hamiltonian chaos and its application to anomalous dynamics in turbulent environment
Kurian, Matúš ; Krlín, Ladislav (advisor) ; Rohlena, Karel (referee) ; Stöckel, Jan (referee)
(Hamiltonian chaos and its application to anomalous dynamics in turbulent environment) RMP-induced ELM control has been tested on several tokamaks. It is believed that increase of electron transport across the magnetic field plays an important role. Edge plasma turbulence also affects dynamics in the edge region of tokamak. We study the simultaneous effect of plasma turbulence and RMP-induced stochastic magnetic field within the single-particle framework. We find out that the plasma turbulence is an important element of dynamics that should be taken into account in further (especially single-particle) studies.
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Fourier transform infrared spectroscopy: application in a study of transient species in discharge and ablation plasma
Kubelík, Petr ; Civiš, Svatopluk (advisor) ; Wild, Jan (referee) ; Rohlena, Karel (referee)
The present dissertation consists of two thematically related parts. The first one (includes two publications) deals with the study of chemical pro- cesses and spectroscopy of highly reactive particles produced in the discharge plasma. This part includes the analysis of ro-vibronic CN radical transitions in the infrared region and the study of chemical reactions in pulsed dischar- ges. The discharge was used as a tool for research of decomposition of simple precursors (acetonitrile, formamide and BrCN) and the subsequent formation of intermediates and reaction products in plasma. The obtained experimental results were interpreted using a numerical model developed in context of this work and used to simulate the kinetics of the studied systems. The second part (includes seven works) is aimed at high-resolved spectro- scopy of metals in the ablation plasma. A total of six different metals were studied: Au, Ag, Cu, Cs, K and Na. The main motivation for spectroscopic research on metals in the infrared region is to obtain information on atomic metals transitions, which are particularly important for astronomical identi- fication of lines in the spectra of stars and their spectroscopic assignments. Each publication contains a summary of the analyzed atomic transitions of which a considerable portion had not...
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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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Large laser sparks for laboratory simulation of high-energy-density events in planetary atmospheres
Babánková, Dagmar ; Civiš, Svatopluk (advisor) ; Strauch, Bohuslav (referee) ; Špirko, Vladimír (referee) ; Rohlena, Karel (referee)
3 Conclusion The main goal of this doctoral thesis is to investigate the possibility of synthesis of simply organic molecules from inorganic gases such CO,CO2N2,NH3,CHa,H2O,H2, using the large laser sparks. The laser sparks provide a unique way to mimic the chemical effects of high-energy-density events in planetary atmospheres (cometary impact, lightning) matching the natural energy-density, its spatio-temporal evolution and plasma-volume scaling ofsuch events in a fully-controlled laboratory environment. Laser induced dielectric breakdown was induced by Š1kJ laser pulses in molecular gases and mixtures related to various planetary atmospheres. We believe that the single-shot experiments realized at the high-power laser facility simulate more realistically high-energy-density atmospheric events than similar experiments conducted with electrical discharges or experiments using low- energy pulses from high-repetition-rate lasers. In our case three different gaseous mixtures were used for these purposes; the strongly.reduced mixture NH3-Cř{4.H2-H2o, medium-reduced mixture CO-N2-H2O and mildly-reduced mixture CO2-N2-H2O. For all kind of my experiments the emission spectra w€re measured in different spectral regions. The motecular bands of CN and C2 radicals dominates in the visible spectra taken from the...
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Hamiltonian chaos and its application to anomalous dynamics in turbulent environment
Kurian, Matúš ; Krlín, Ladislav (advisor) ; Rohlena, Karel (referee) ; Stöckel, Jan (referee)
(Hamiltonian chaos and its application to anomalous dynamics in turbulent environment) RMP-induced ELM control has been tested on several tokamaks. It is believed that increase of electron transport across the magnetic field plays an important role. Edge plasma turbulence also affects dynamics in the edge region of tokamak. We study the simultaneous effect of plasma turbulence and RMP-induced stochastic magnetic field within the single-particle framework. We find out that the plasma turbulence is an important element of dynamics that should be taken into account in further (especially single-particle) studies.
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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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Fourier transform infrared spectroscopy: application in a study of transient species in discharge and ablation plasma
Kubelík, Petr ; Civiš, Svatopluk (advisor) ; Wild, Jan (referee) ; Rohlena, Karel (referee)
The present dissertation consists of two thematically related parts. The first one (includes two publications) deals with the study of chemical pro- cesses and spectroscopy of highly reactive particles produced in the discharge plasma. This part includes the analysis of ro-vibronic CN radical transitions in the infrared region and the study of chemical reactions in pulsed dischar- ges. The discharge was used as a tool for research of decomposition of simple precursors (acetonitrile, formamide and BrCN) and the subsequent formation of intermediates and reaction products in plasma. The obtained experimental results were interpreted using a numerical model developed in context of this work and used to simulate the kinetics of the studied systems. The second part (includes seven works) is aimed at high-resolved spectro- scopy of metals in the ablation plasma. A total of six different metals were studied: Au, Ag, Cu, Cs, K and Na. The main motivation for spectroscopic research on metals in the infrared region is to obtain information on atomic metals transitions, which are particularly important for astronomical identi- fication of lines in the spectra of stars and their spectroscopic assignments. Each publication contains a summary of the analyzed atomic transitions of which a considerable portion had not...
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Diffusion of Particles from Tokamak by Stochastization of Magnetic Field Lines
Cahyna, Pavel ; Krlín, Ladislav (advisor) ; Rohlena, Karel (referee) ; Suttrop, Wolfgang (referee)
The thesis summarizes the current state of research of thermonuclear fusion with magnetic confinement and decribes the possible role of stochastization of magnetic field lines and magnetic perturbations in solving 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 diffusion 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 explaining 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.
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