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Monte-Carlo simulation of photodissociation spectra from molecular beam experiment
Košťál, Pavel ; Fárník, Michal (advisor) ; Havlíček, Josef (referee)
Within the framework of my BSc Thesis I became familiar with a unique molecular beam apparatus for cluster studies. I have learned about clusters and molecular beams, mass spectrometry, photodissociation and molecular dynamics. My specific task was to generace several computer programs for data acquisition and evaluation of~the~present experiments: (1) A program for TOF to mass spectra conversion. This program facilitated immediate evaluation of~the~measured mass spectra. (2) A program for TOF spectra conversion into the kinetic energy distribution KED of the fragments, which provides immediate information about the studied photochemical processes. The immediate information provided by both these programs enable a more effective control of the experiment. (3) Finally, I have modified Monte-Carlo simulation program. This program serves the ultimate TOF→ KED conversion of the experimental data. All the programs were tested with photodissociation of a well studied system of HBr cluster, and they have shown a good performance.
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MHD nestability plazmatu pozorované ve výbojích tokamaku COMPASS
Kripner, Lukáš ; Němeček, Zdeněk (advisor) ; Havlíček, Josef (referee)
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. 1
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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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Magnetic field Supported Discharge Based Plasma Sources
Havlíček, Josef ; Kudrna, Pavel (advisor) ; Tichý, Milan (referee)
Main aim of this work was measurement of a floating potential fluctuations in the cylindrical magnetron in classical configuration in neon. Two Langmuir probes were used for measurement of wave vector. The following values were measured: pressure p in range 1-7 Pa, magnetic induction B in range 10-40 mT, discharge current I in range 5-100 mA, discharge voltage U and floating potential Uf. Fluctuations were described by dependencies of power spectral density on frequency S(f) and by histograms S(k,f), where k is wave vector. Several discharge modes were observed in the magnetron. These are characterized by different values of discharge voltage, electric field in positive column, magnitude of the floating potential etc. The discharge conditions, where peaks were observed in spectra, were determined. Only one peak with frequency in range 4-16 kHz was mostly observed. Most of these peaks had zero wave vector in histogram S(k,f), i.e. the floating potential synchronously oscillated in the whole discharge area. For some discharge conditions histograms with non-zero wave vector for noise background were observed.
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RE beam generation in MGI disruptions on COMPASS.
Ficker, Ondřej ; Mlynář, Jan ; Macúšová, Eva ; Vlainić, M. ; Weinzettl, Vladimír ; Urban, Jakub ; Čeřovský, Jaroslav ; Farník, Michal ; Markovič, Tomáš ; Papřok, Richard ; Vondráček, Petr ; Imríšek, Martin ; Tomeš, Matěj ; Havlíček, Josef ; Varju, Jozef ; Varavin, Mykyta ; Bogár, Ondrej ; Havránek, Aleš ; Gospodarczyk, M. ; Rabinski, M. ; Jakubowski, M. ; Malinovski, K. ; Zebrowski, J. ; Plyusnin, V. ; Papp, G. ; Pánek, Radomír ; Hron, Martin
In the experiments with the massive gas injection (MGI) triggered disruptions in the COMPASS tokamak, post-disruptive runaway electron (RE) beams are generated occasionally. In this contribution, a relatively large set of discharges from the recent years is analysed in order to improve our understanding of the processes behind the beam generation. It seems that despite the low toroidal field applied in the discharges (typically 1.15 T) the magnetic perturbations may be small enough to allow the acceleration and confinement of the electrons. The influence of the different components and different sections of the frequency spectrum of the magnetic perturbations on the beam generation and RE beam current is examined. Fast visible camera images are also analysed. The relevance of COMPASS runaway electron experiments for large machines is discussed. Moreover, the potential of less common diagnostic tools (Cherenkov detector, vertical ECE, ...) to clarify the role of the pre-disruption fast electron population and the influence of prompt runaway electron losses in the current quench is discussed using the recent test measurements.
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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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Monte-Carlo simulation of photodissociation spectra from molecular beam experiment
Košťál, Pavel ; Fárník, Michal (advisor) ; Havlíček, Josef (referee)
Within the framework of my BSc Thesis I became familiar with a unique molecular beam apparatus for cluster studies. I have learned about clusters and molecular beams, mass spectrometry, photodissociation and molecular dynamics. My specific task was to generace several computer programs for data acquisition and evaluation of~the~present experiments: (1) A program for TOF to mass spectra conversion. This program facilitated immediate evaluation of~the~measured mass spectra. (2) A program for TOF spectra conversion into the kinetic energy distribution KED of the fragments, which provides immediate information about the studied photochemical processes. The immediate information provided by both these programs enable a more effective control of the experiment. (3) Finally, I have modified Monte-Carlo simulation program. This program serves the ultimate TOF→ KED conversion of the experimental data. All the programs were tested with photodissociation of a well studied system of HBr cluster, and they have shown a good performance.
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|
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MHD nestability plazmatu pozorované ve výbojích tokamaku COMPASS
Kripner, Lukáš ; Němeček, Zdeněk (advisor) ; Havlíček, Josef (referee)
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. 1
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Magnetic field Supported Discharge Based Plasma Sources
Havlíček, Josef ; Kudrna, Pavel (advisor) ; Tichý, Milan (referee)
Main aim of this work was measurement of a floating potential fluctuations in the cylindrical magnetron in classical configuration in neon. Two Langmuir probes were used for measurement of wave vector. The following values were measured: pressure p in range 1-7 Pa, magnetic induction B in range 10-40 mT, discharge current I in range 5-100 mA, discharge voltage U and floating potential Uf. Fluctuations were described by dependencies of power spectral density on frequency S(f) and by histograms S(k,f), where k is wave vector. Several discharge modes were observed in the magnetron. These are characterized by different values of discharge voltage, electric field in positive column, magnitude of the floating potential etc. The discharge conditions, where peaks were observed in spectra, were determined. Only one peak with frequency in range 4-16 kHz was mostly observed. Most of these peaks had zero wave vector in histogram S(k,f), i.e. the floating potential synchronously oscillated in the whole discharge area. For some discharge conditions histograms with non-zero wave vector for noise background were observed.
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