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Studies of tokamak edge plasma and its interaction with the first wall
Komm, Michael ; Kudrna, Pavel (advisor) ; Hrach, Rudolf (referee) ; Svoboda, Vojtěch (referee)
Title: Studies of tokamak edge plasma and its interaction with the first wall Author: Michael Komm Department: Department of Surface and Plasma Science Thesis director: doc. Mgr. Pavel Kudrna, Dr. KFPP Thesis supervisor: Dr. Renaud Dejarnac, IPP CAS CR Abstract: This work presents results of simulations of nuclear fusion related problems, using both 2D PIC code (SPICE2) and full 3D code (SPICE3). The simulations allowed us to predict particle and heat loads coming from plasma onto the divertor tiles, which is a key problem for the next-step de- vices. The results of simulations contributed to the research of fuel retention in the gaps between divertor tiles. We we also able to explain the behaviour of the Katsumata probe and verify the validity of its measurements. Keywords: Tokamak, PIC, divertor, tritium, Katsumata
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Study of laser mixture in the large pressure region
Morávek, Matěj Jan ; Hrachová, Věra (advisor) ; Kudrna, Pavel (referee)
This work studies discharge plasma in a mixture of gases, similar to that used in the so-called CO2-lasers. This mixture consists of CO2, N2 and He. The effect of the mixture composition and discharge parameters (especially pressure, in the range of 266 Pa - 100 kPa) on the distribution of energy in the vibrational levels of nitrogen was examined. This is important parameter for modelling of the discharge plasma. The effect of the mixture composition on the degree of dissociation of the CO2 molecules was also studied. The relative concentration of CO was applied to find the conditions leading to a minimal dissociation of the carbon dioxide. Measurements of radial profiles were also made. Results from two discharge tubes made from different materials were compared. Two types of discharge were utilized to acquire a wide pressure range - low pressure DC glow discharge in the range of 266 Pa to 1330 Pa and dielectric barrier discharge in the range of 5 kPa to 100 kPa. Both discharges are used in commercial CO2-lasers. We observed a descending dependence of the vibrational temperature on the pressure and a big step caused by increased occurrence of standing ionizing waves in the mixtures with low nitrogen ratio. Vibrational temperature in the DBD was markedly lower than in the DC GD, because of the...
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Advanced techniques of computer modelling in low- and high-temperature plasma physics
Pekárek, Zdeněk ; Hrach, Rudolf (advisor) ; Kudrna, Pavel (referee) ; Hron, Jaroslav (referee)
This thesis identifies the obstacles in efficient modelling of interaction of plasma and solid surfaces. It presents an enhanced method of solving the Poisson equation optimized to meet the requirements of the Particle-in-Cell modelling approach. A number of applications are discussed, including models of the plasma-facing wall of the nuclear fusion device, tokamak, and its interaction with particle fluxes driven by the intrinsic magnetic field. Another area of applications covers the modelling of plasma probes deployed to diagnose properties of plasma in various experiments. The thesis also includes the computer library code and instructions enabling a rapid use of the Poisson solver method in a third party computer code which implements the PIC approach in a compatible manner.
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Depozition of hydrophobic fluorocarbon coatings by plasma polymerization methods
Petr, Martin ; Kylián, Ondřej (advisor) ; Kudrna, Pavel (referee)
In this work we study the deposition of hydrophobic fluorocarbon coatings by magnetron sputtering of polymeric PTFE target. We show what is the influence of the conditions of the deposition process - the pressure in the chamber, the RF power - on the properties of the resulting CFx thin films (their chemical composition, morphology, wettability, barrier and optical properties, stability and possible bio-aplications). In this work we use a novel way to control the morphology and the chemical composition of the surface of thin films independently by using nano-particles, both metal (Pt, Cu, Al) and polymeric (C:H, Nylon). With nano-particles we can control the hydrophobicity of thin films and we can prepare super-hydrophobic films. Work has an experimental character.
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Selected issues of thermonuclear fusion in tokamak-like magnetic containers
Ondáč, Peter ; Tichý, Milan (advisor) ; Kudrna, Pavel (referee)
In this thesis there are summarized in the form of basic knowledge the basic problems of fusion research. It serves as an introduction to this field of physics for beginners, but also intermediate candidates. The first two chapters set out the basic terms and ideas associated with controlled thermonuclear fusion. Further described is the magnetic confinement in tokamaks. Physically most important is the third chapter, which includes more advanced parts of physics. It discusses the main focus of this work, i.e. some of the major problems hindering fusion research. Final fourth chapter is relaxed. It discusses the ideas and visions for the near and distant future.
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Diagnostics of low-temperature plasma using the Langmuir and emissive probes
Klusoň, Jan ; Kudrna, Pavel (advisor) ; Tichý, Milan (referee)
Magnetron sputtering belongs to the most important methods of production of thin films with a wide range of physical properties. Examples include hard, wear-resistant coatings, low friction ones, corrosion resistant ones as well as coatings with specific electrical or optical properties. During the development the basic sputtering process has been significantly improved and nowadays there are a number of various techniques of magnetron sputtering. Pulsed magnetron sputtering presents one of these techniques. The pulsed regime is especially suitable for the deposition of insulating layers because there occurs no effect of charging up of the target followed by arc events. The fact that pulsed sputtering allows reducing the substrate temperature during the deposition is also important. This thesis deals with the low-temperature plasma in magnetron discharge generated by pulsed DC voltage. The measurement was carried out in the experimental apparatus of the cylindrical magnetron. The plasma diagnostics was performed by means of the electrostatic Langmuir and emissive probe. The dependencies of the basic plasma parameters, i.e. electron density, electron temperature and plasma potential, were evaluated with time and spatial resolution. The dependencies on pressure, length of the voltage pulse and the value of...
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