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2D & 3D computer modelling of low-temperature plasma sheaths with a particular focus on their mutual interaction
Hromádka, Jakub ; Hrachová, Věra (advisor)
The presented thesis deals with the study of the sheath layer which is formed during the interaction of a low-temperature plasma with a solid object using computer modelling techniques. The theoretical part of the thesis summarizes knowledge about the physics of the sheath layer of electropositive and electronegative plasma and presents the theory of measuring plasma parameters using a Langmuir probe, including a discussion of the effect of collisions of charged particles with neutrals on the probe measurements. Further, theoretical descriptions of the plasma are presented which are the basis of the computer models created in the framework of the thesis: a particle model based on the Particle-in-Cell method and a fluid model of the drift-diffusion approximation of the plasma. The developed particle model works in 3D space, uses the null-collision Monte Carlo method to account for the effects of collisions of charged particles with neutrals and implements the Intel Math Kernel Library functions to solve the Poisson's equation. The fluid model is implemented using FeniCS software. At first, the developed models are used for the calculation of the sheath layer and the current-voltage characteristics of free-standing Langmuir probes of several types: a 1D model of an infinitely large planar probe, a 2D model of...
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2D & 3D computer modelling of low-temperature plasma sheaths with a particular focus on their mutual interaction
Hromádka, Jakub ; Hrachová, Věra (advisor) ; Novotný, Dušan (referee) ; Kudrna, Pavel (referee)
The presented thesis deals with the study of the sheath layer which is formed during the interaction of a low-temperature plasma with a solid object using computer modelling techniques. The theoretical part of the thesis summarizes knowledge about the physics of the sheath layer of electropositive and electronegative plasma and presents the theory of measuring plasma parameters using a Langmuir probe, including a discussion of the effect of collisions of charged particles with neutrals on the probe measurements. Further, theoretical descriptions of the plasma are presented which are the basis of the computer models created in the framework of the thesis: a particle model based on the Particle-in-Cell method and a fluid model of the drift-diffusion approximation of the plasma. The developed particle model works in 3D space, uses the null-collision Monte Carlo method to account for the effects of collisions of charged particles with neutrals and implements the Intel Math Kernel Library functions to solve the Poisson's equation. The fluid model is implemented using FeniCS software. At first, the developed models are used for the calculation of the sheath layer and the current-voltage characteristics of free-standing Langmuir probes of several types: a 1D model of an infinitely large planar probe, a 2D model of...
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Application of methods of computational physics for the study of plasma-solid interaction
Hromádka, Jakub ; Hrach, Rudolf (advisor) ; Novák, Stanislav (referee)
Low-temperature plasma and its interaction with immersed solids is studied in this work. The research of the physical processes on this interface is performed by two-dimensional particle computer model. The model uses molecular dynamic method. Mutual forces between particles are computed by Particle- in-Cell method. The main application of the model is in the area of the probe diagnostic of plasma. Simple problems are compared with theory and two dimensional effects are discused. Contribution of particle modeling to plasma research is showed on the problem of interaction of sheaths around cylidrical probes. We deal with question whether we are able to get some information about unevennesses at the surface of solid immersed in plasma by measuring probe characteristics in its surroundings. We also studied the influence of plasma electronegativity on the parameters of sheaths around cylidrical probes. Powered by TCPDF (www.tcpdf.org)
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Application of boundary element method for calculation of electric field in a radiofrequency ion trap
Vavřička, Radek ; Roučka, Štěpán (advisor) ; Hromádka, Jakub (referee)
In this thesis we explore numerical methods that could be used to solve La- place's equation. We compare the boundary element method (BEM), implemen- ted in Bempp library, and the finite element method (FEM), implemented in FEniCS library, by using them to solve Laplace's equation in the cases of a mul- tipole and a rf ion trap, which we create a model of through the use of Gmsh. In order to gauge effectiveness of a method, we measure the time of evaluation, me- mory usage and the squared deviation from theoretical values (if we know them) summed over the points of evaluation. In the end, we use the known values of electric field to simulate a charged particle moving within the trap, comparing evolution of its position and velocity for BEM and FEM. 1 2
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Application of methods of computational physics for the study of plasma-solid interaction
Hromádka, Jakub ; Hrach, Rudolf (advisor) ; Novák, Stanislav (referee)
Low-temperature plasma and its interaction with immersed solids is studied in this work. The research of the physical processes on this interface is performed by two-dimensional particle computer model. The model uses molecular dynamic method. Mutual forces between particles are computed by Particle- in-Cell method. The main application of the model is in the area of the probe diagnostic of plasma. Simple problems are compared with theory and two dimensional effects are discused. Contribution of particle modeling to plasma research is showed on the problem of interaction of sheaths around cylidrical probes. We deal with question whether we are able to get some information about unevennesses at the surface of solid immersed in plasma by measuring probe characteristics in its surroundings. We also studied the influence of plasma electronegativity on the parameters of sheaths around cylidrical probes. Powered by TCPDF (www.tcpdf.org)
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