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Automation of dust charging experiment
Pechal, Radim ; Pavlů, Jiří (advisor) ; Žilavý, Peter (referee)
Title: Automation of dust charging experiment Author: Radim Pechal Department: Department of Surface and Plasma Science Supervisor: RNDr. Jiří Pavlů, PhD. Supervisor's e-mail address: Jiri.Pavlu@mff.cuni.cz Abstract: Since the dust grains are expected to cause problems during operation of tokamaks, there is a developing research of these devices which raises interest in dust grain charging processes research as well. Clarification of the dust grain charging processes may help with their solutions. This thesis deals with an issue of designing a part of a new experimental setup for dust grain research built at the Department of Surface and Plasma Science, Charles University in Prague. The base of this experimental setup is original linear quadrupole trap enabling dust grain trapping and its charging by electron, ion, and UV beams. In the thesis, a method of stabilization of one part of grain oscillation frequency detection is described. The thesis is focused on a development of a control unit and high voltage power supply for an image intensifier. To measure charging processes tungsten dust grains were used. This material will be probably used in construction of ITER tomakak. Electron equilibrium characteristics and other parameters were measured. Two samples of tungsten dust grains were used for...
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Activation of collimating system of linear accelerator through photon radiation and its impact on the doses received by the staff.
KUBÍKOVÁ, Adéla
The diploma thesis on the topic "Activation of Collimating System of Linear Accelerator through Photon Radiation and its Impact on the Doses Received by the Staff" is divided into two parts, a theoretical and a practical part. The introductory theoretical part is devoted to the basic information about ionizing radiation. What are the types of ionizing radiation, its characteristics, properties and sources of ionizing radiation. Furthermore, there are mentioned direct and indirect interactions of ionizing radiation, a brief description of charged particle accelerators, collimator systems and radioisotope irradiation devices. Another part deals with radiation protection, basic legislation, methods and principles of radiation protection, personal dosimetry and medical supervision of radiation workers. Literary sources, available internet links and valid legal regulations were used for the work. In the practical part, a number of measurements were carried out to measure and to analyse the doses of secondary radiation of the linear accelerator collimator system for different photon beam energies, depending on time, distance from source, position of radiologic assistant around the table when working with the patient, as well as sizes of irradiated field. The aim of the work was to find out how large the doses of secondary radiation are, although measurable, but their values are not sufficient to be detected by personal dosimeters of radiological assistants. Confirm the hypothesis that the doses from the secondary radiation of the linear accelerator collimator system are so low that the dose power does not exceed 0.031 mGy/hr. The results obtained from various measurements are processed into transparent tables and graphically displayed. Based on the results of the measurements, the hypotheses were confirmed.
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Frames of Tennis Rackets
Rajdlík, Lukáš ; Němec, Karel (referee) ; Molliková, Eva (advisor)
This bachelor’s thesis deals with materials used for manufacturing of the frame of tennis rackets. The thesis informs about the frame of tennis rackets development, from the origins of tennis to these days, when there are modern technologies used. There are parts of the frame of a tennis racket and construction requirements defined. There are two samples of tennis rackets investigated and the both samples are compared with each other.
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Electron beam welding of ODS materials
Jankůj, Luděk ; Čížek, Jan (referee) ; Jan, Vít (advisor)
Thesis on Electron beam welding of ODS materials is divided into theoretical and experimental part. In the first part the theoretical research work focuses on the accurate description of the candidate materials in a research fusion reactor ITER. Following are detailed constructional ODS materials and tungsten alloy as a material of the first wall. The second part of the theoretical research deals with various possibilities of joining high-melting dissimilar materials such as brazing or electron beam welding as well, which will be established in the experimental section. The experimental part of the thesis deals with a joining ODS steel MA 956 with sintered carbide WC-Co and ODS tungsten. These materials are welded by electron beam. Individual samples are distinguished used filler material, preheating or welding parameters. This thesis contains photographic documentations of microstructure the welding samples, results from scanning electron microscopy, and measurements of microhardness across the weld metal.
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Tungsten wire surface cleaning using electropolishing process
Jurčík, M.
This article deals with the preparation of tungsten wires surface for electrochemical etching process via electropolishing process. Cleaning of the wire surface is very important for obtaining field emission cold cathodes with sharp tips and low contamination on its surface which are made from these tungsten wires. There are many ways to clean wire surface such as heating it in a ultra vacuum, using solutions and acids, mechanical cleaning etc. Each of these methods has advantages and disadvantages and due to electropolishing process quickness this method was selected for futher usage.
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Young's Modulus on the Interface of Elastic and Elastic-Plastic Material
Kocmanová, Lenka ; Haušild, P. ; Materna, A. ; Matějíček, Jiří
The paper is aimed at determining the Young's modulus at the sharp interface between two materials, where one material is elastic and the other elastic-plastic. To determine the Young's modulus was used 3D numerical model of nanoindentation with conical indenter. The interface between the materials with the normal plane perpendicular to the direction of penetration. The goal is to simulate the combination of metal and ceramic materials.\n Young modulus according to the standardized distance from the interface are approximated inverse beta distribution and is determined by the relation between parameters inverse beta distribution of the size of the area affected by the second phase
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Structural and Mechanical Characterization of Spark Plasma Sintered Tungsten
Čech, J. ; Haušild, P. ; Kocmanová, Lenka ; Matějíček, Jiří
The main objective of this paper is to describe the microstructure and mechanical properties of spark plasma sintered tungsten. The indentation tests, which are very advantageous because of their semi-nondestructive character and low requirements on the volume of investigated material, were carried out using Berkovich and spherical indenters. Indentation techniques with spherical indenters are less frequently used than those with sharp indenters but they offer variation of strain with the indentation depth and, therefore, they could be used for determination of stress-strain curves. Local stress-strain behavior obtained by this method showed good correspondence with the results of compression tests. Observation of the microstructure and the fracture surfaces helped to explain some phenomena which occurred during the mechanical testing
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THERMAL AND MECHANICAL PROPERTIES OF TUNGSTEN COMPACTS PREPARED BY SPS
Nevrlá, Barbara ; Vilémová, Monika ; Matějíček, Jiří
Tungsten is a promising candidate material for use in the tokamak device aimed at future production of nuclear fusion power. Here, tungsten is intended for the application in the part called first wall,with the function of a heat-resistant plasma facing armor.In the present work,two fractions of tungsten powder (2 and 4 μm) were used to prepare two consolidated samples by spark plasma sintering (SPS),using a combination of pressure,temperature and electric power.This sintering technique produces samples of near theoretical density which is positive for the application.Tungsten compacts were then studied to determine some basic thermal and mechanical properties, namely thermal conductivity using the laser-flash method and hardness by Vickers test.The measurements were focused on thermal conductivity of the compacts because high thermal conductivity is crucial for the material of tokamak first wall,loaded by high heat flux from the plasma.High hardness is desirable for good resistance
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