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Electron gun characterisation
Horák, Michal ; Lencová, Bohumila (referee) ; Zlámal, Jakub (advisor)
This thesis deals with problems of electron sources and electron optical systems. The theoretical part covers the derivation of properties of electrostatic and magnetic lenses, their aberrations and programs used for simulations in particle optics. The second part deals with the computation of properties of field emission electron gun.
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Scintillation SE Detector for VP SEM
Kozelský, Adam ; Čudek, Pavel (referee) ; Jirák, Josef (advisor)
This work contains description of basic properties and principles of electron microscopy focused on scanning electron microscopy. It describes construction solutions of a microscope, interaction between electron beam and sample, generation of backscattered and secondary electrons. Next chapters are dealing with development of electron microscopy and environmental scanning electron microscopy. The experimental part of this thesis is focuses on the detection of secondary electrons with scintillation detector in environmental scanning electron microscope at higher pressure in the specimen chamber. Concretely is focused on optimization of collecting grid voltage and measurement of pressure dependences.
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Coulomb Interactions in Electron Beams in the Vicinity of a Schottky and Cold Field Emission Sources
Liška, Ivo ; Kotačka, Libor (referee) ; Radlička, Tomáš (referee) ; Lencová, Bohumila (advisor)
Dizertační práce se zabývá problematikou výpočtu vlivu coulombovských interakcí částic na parametry emitovaného elektronového svazku v blízkosti Schottkyho a studené katody. Práce poskytuje základní předhled o problematice, popisuje vytvořené modely emisních zdrojů a metodu simulace Monte Carlo. Představuje novou metodu generování vstupních dat, která klade větší důraz na přesnou simulaci emisního procesu. Pozornost je zde věnována zejména vlivu interakcí na energiovou šířku, velikost virtuálního zdroje a jas katody v závislosti na velikosti poloměru hrotu a emisním proudu. Sledováním vývoje energiové šířky bylo zjištěno, že naprostá většina interakcí se odehrává v prostoru do několika mikrometrů od hrotu katody. Závislost spočtené celkové energiové šířky na úhlové intenzitě je ve shodě s dostupnými experimentálními daty. Spočtené energiové rozšíření vlivem coulombovských interakcí bylo srovnáno s hodnotami vypočtenými pomocí vzorců založených na analytických přiblíženích. Bylo zjištěno, že některé z nich přijatelně předpovídají trendy ale nemohou být použity pro kvantitativní odhad.
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Concept and Development of Single-purpose Scanning Electron Microscope
Foret, Zdeněk ; Vašina, Radovan (referee) ; Starý,, Vladimír (referee) ; Svoboda, Milan (referee) ; Švejcar, Jiří (advisor)
Electron microscopy has become an essential component in many scientific fields, in which it contributes to new discoveries. The microscopy itself is continually being developed and the limits, which seemed to be insurmountable, have been overcome. The instruments have become user friendlier and their mobility enables flexible practical use in the field. The subject of this work is the design of a scanning electron microscope, the calculation of a magnetic curcuit of an immersion objective combined with standard lens, the theoretical calculation of a microscope resolution and the design solution of the mechanical parts of the microscope with a sample manipulator. The thesis includes a description of the electron microscopy development summarizing it briefly from the very beginning up to now. It also deals with electron sources, especially the Shottky cathode, which is to be the main object observed by the proposed device. The work also contains a description of the calculation of the microscope resolution as a function of the current density distribution. Another interesting issue included in the theoretical part is the signal detection, a description of several types of detectors and possible signal processing. The solution of the thesis includes a description of the concept of the scanning electron microscope with an explanation of the distribution of combined lens functions. The optical diagram shows the arrangement of the electron optics system and the distibution of pressure in the chamber of the microscope. The theoretical calculation is devoted to the magnetic curcuit design of the objective and to the resolution of the microscope for a given extent of working distances. Two modifications of the lens were designed – a standard simple objective and a combination of the standard objective with the immersion magnetic one. The results of both modifications are given for the parameters to be compared. The combined objective was designed with the possibility of use in two modes, as a standard and immersion lens. The deflection system is also divided into two modes, as a single deflection for the standard lens and as a two-dimension deflection for the immersion lens. Detectors for secondary electrons (SE) and detectors for back scattered electrons (BSE) will be used for the signal detection. The design of the microscope is another large part, which gives details on the most significant components of the microscope. The content of the technical solution is a three-dimensional computer model, created in Autodesk Inventor, which also includes a sample manipulator driven by piezoelectric actuators.
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Coulomb Interactions in Electron Beams
Jánský, Pavel ; Janík,, Ján (referee) ; Kolařík,, Robert (referee) ; Lencová, Bohumila (advisor)
The thesis deals with numerical simulations of a hairpin thermionic electron gun, an electron source of the electron-beam welding machine. Simulations showed that the space charge in the electron gun has a significant influence on the beam current and electron trajectories. Simulation outputs are in a sufficient agreement with the experimental measurements.
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SMV-2020-17: Development of the electron gun for welding of the radioactive samples
Zobač, Martin ; Vlček, Ivan ; Dupák, Libor
The subject of the project was the research and development of the electron gun for electron beam welding with accelerating voltage 60 kV and maximal power 2 kW. The device was developed for work in so called "hot chamber", where it is exposed to radioactive radiation. The electron gun was equipped with new type of ceramic isolator. The project was characteristic by solving complex problems from different fields and resulted in construction of functional prototype, that was successfully tested in cooperation with the client.
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SMV-2017-17: Development of the electron gun for welding of the radioactive samples
Zobač, Martin ; Vlček, Ivan
The subject of the project was the research and development of the electron gun for electron beam welding with accelerating voltage 60 kV and maximal power 2 kW. The device was developed for work in so called hot chamber, where it is exposed to radioactive radiation. The electron gun was equipped with new type of ceramic isolator. The project was characteristic by solving complex problems from different fields and resulted in construction of functional prototype, that was successfully tested in cooperation with the client.
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