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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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A source of cold hydrogen atoms
Podolník, Aleš ; Plašil, Radek (advisor) ; Kaňka, Adolf (referee)
Vodík v molekulární a atomární formě je nejčastější prvek ve vesmíru a proto jsou chemické reakce, ve kterých vystupuje, důležité pro pochopení nejen formace prvních hvězd a galaxií, ale i pro studium současných dějů v mezihvězdném plynu. Studium například reakce H- + H -> H2 + e- (asociativní odtržení) ujasňuje náhled na proces tvorby molekul vodíku a umožňuje upřesnění kvantově-mechanických modelů. Pro tento a další experimenty je na KFPP přítomen zdroj chladného atomárního vodíku. V práci je popsána aparatura zdroje a její operace, navrhováno a částečně realizováno zlepšení uspořádání vnitřní konstrukce a jsou proměřeny základní charakteristiky zdroje.
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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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A source of cold hydrogen atoms
Podolník, Aleš ; Plašil, Radek (advisor) ; Kaňka, Adolf (referee)
Vodík v molekulární a atomární formě je nejčastější prvek ve vesmíru a proto jsou chemické reakce, ve kterých vystupuje, důležité pro pochopení nejen formace prvních hvězd a galaxií, ale i pro studium současných dějů v mezihvězdném plynu. Studium například reakce H- + H -> H2 + e- (asociativní odtržení) ujasňuje náhled na proces tvorby molekul vodíku a umožňuje upřesnění kvantově-mechanických modelů. Pro tento a další experimenty je na KFPP přítomen zdroj chladného atomárního vodíku. V práci je popsána aparatura zdroje a její operace, navrhováno a částečně realizováno zlepšení uspořádání vnitřní konstrukce a jsou proměřeny základní charakteristiky zdroje.
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Poisson Equation Solver Parallelisation for Particle-in-Cell Model
Podolník, Aleš ; Komm, Michael ; Dejarnac, Renaud ; Gunn, J. P.
Numerical simulations based on PIC technique like the SPICE2 model developed at IPP ASCR are often used in tokamak plasma physics to investigate the interaction of edge plasma with plasma-facing components. The SPICE2 model has been parallelised with the exception of the Poisson equation solver which considerably slows down the simulations. It is now being upgraded to a parallelised version to be efficient enough to perform more demanding tasks like the ITER tokamak baseline scenario edge plasma whose conditions like high density (up to 1020 m−3) and low temperature (1–2 eV) result in simulations taking several months to compute. Performance and scaling are compared for different cases in order to choose the optimal candidate for aforementioned applications.
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Heat and Particle Deposition on the Plasma-Facing Components
Podolník, Aleš ; Pánek, Radomír ; Komm, Michael ; Dejarnac, Renaud ; Gunn, J. P.
The interaction of plasma with plasma-facing components (PFCs) in tokamaks is of increasing interest because of implications for ITER and next-step devices. The heat and particle fluxes interacting with solid objects can be studied by means of particle-in-cell (PIC) simulations. The aim of this work is to use the existing family of PIC codes SPICE to simulate the heat and particle flux distribution on PFCs. The output of the simulations is then used in new heat equation solver, which calculates the temperature of the PFCs. This solver provides us a testbed for the parallel sparse matrix code development as well as for the complex application aimed at study of the melting of tiles.
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