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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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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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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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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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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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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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Infrared Thermography on the COMPASS Tokamak
Vondráček, Petr ; Horáček, Jan ; Cahyna, Pavel ; Pánek, Radomír ; Uličný, J.
This contribution describes a new slow infrared camera obtained by the COMPASS tokamak at IPP Prague. We focus on the camera limitations affecting the experimental data (temporal and spatial smoothing, time shift). Data time deconvolution used to correct the effect of the long response time of the camera detector is described. The second part of the contribution is devoted to the physic basis for the design of a new fast IR camera system planned for installation in COMPASS during the next year.
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Simulations of Runaway Electrons
Papřok, R. ; Krlín, Ladislav ; Cahyna, Pavel
In this paper we discuss current knowledge of phenomena of runaway electrons in tokamaks. We summarize experimental facts and investigate theoretical understanding of runaway electrons. We also present result of our recent work concerning influence of JET’s Error Filed Correction Coils on runaway electrons dynamics. At the end of our paper we describe our plan to study runaway electrons dynamic in time and space varying magnetic field during plasma disruption as obtained from global MHD code JOREK.
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Status of Magnetic Diagnostics on COMPASS
Havlíček, J. ; Kudláček, O. ; Janky, F. ; Horáček, Jan ; Beňo, R. ; Valcárcel, D.F. ; Fixa, J. ; Brotánková, Jana ; Zajac, Jaromír ; Hron, Martin ; Pánek, Radomír ; Cahyna, Pavel
The COMPASS tokamak is in a test operation after its reinstallation in Institute of Plasma Physics AS CR in Prague (IPP Prague) in the year 2008. This operation consists of commissioning of various diagnostics and tokamak auxiliary systems. This paper presents current status of magnetic diagnostics after its refurbishment, used method of the calibration and shows examples of magnetic diagnostics utilization for plasma position reconstruction as well as for vertical hydraulic preload interlock system.
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Pohyb nabitých částic v perturbovaných magnetických polích tokamaku
Papřok, R. ; Krlín, Ladislav ; Cahyna, Pavel ; Riccardo, V.
In this paper we present two Hamiltonian approaches–full and drift–for description of charged particles (e.g. electrons, D+) in magnetic field of a tokamak. We use a basic magnetic toroidal field configuration with shear plus overlapping island chains creating magnetic ergodic layer. We would like to use this apparatus for solving two physical problems. Firstly for an estimate of generation of electric field in edge plasma caused by addition of “ergodic coils”, which could serve as a mechanism for mitigation of ELMs and is will be studied on the COMPASS tokamak. Secondly we want to use the apparatus for tracing the influence on runaway electrons (energy 10 MeV) in the presence of magnetic field generated by Error Field Correction Coils (EFCCs) as are installed on JET Tokamak.
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