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Analysis of the gas flow in the passage of the primary electron beam differentially pumped chamber depending on the shape of the nozzle inlet
Hladký, David ; Vaculík, Sebastian (referee) ; Maxa, Jiří (advisor)
It is necessary to separate sample chamber with pressure up to 2000 Pa and the surroundings of tube with pressure 0.01 Pa with help of a differential pumped chamber at the environmental scanning electron microscope This differential pumped chamber is to be designed so that it has to manage to separate sections with very different pressures sufficiently and in the trajectory of transitting (overflying) prime electrons the average value of pressure and density has to be as low as possible, so that it would occure the lowest diffusion of these electrons, which is caused by collisions of electrons and air molecules too. It were created axisymmetric 2D models variant of Differentially pumped chamber with different opening angles of the clone, which were analyzed to choose the best variant. The Ansys Fluent systeme using finite volume method for analysis of fluid flow was used for analysis.
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Comparison of flow conditions in the gas detector used in the aperture and screen
Hubáček, Jiří ; Špinka, Jiří (referee) ; Maxa, Jiří (advisor)
The first part of the thesis deals with electron microscopy and physical model fluid flow. In the next part, a three-dimensional model is created in programme SolidWorks. It is the model of scintilating detector with aperture or screen with three hundred little apertures. These models are submitted to analysis focusing on investigation of the gas flow at different pressure in chamber of specimen ESEM using Cosmos FloWorks system. The results of the analysis of both apertures variants are compared with the request to minimize the pressure in the trajectory of the secondary electrons as well as in the chamber of specimen.
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Construction scintillation detector with one aperture for environmental scanning electron microscope
Přichystal, Vít ; Vyroubal, Petr (referee) ; Maxa, Jiří (advisor)
The thesis is focused on the design of a scintillation detector with one screen for environmental scanning electron microscope. At the beginning of the work is an introduction to microscopy. Further work is focused on the description of ESEM microscope and a scintillation detector. The following chapter is devoted to the dynamics of flow. They list the types of flow and mathematical description of equations. The next chapter is about using the software and the way of solution of flow. In the following chapter describes a proposal of the diaphragm and extraction method of the detector area. They are described some of type aperture. The last chapter is the conclusion, where the work is summarized.
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FLOW ANALYSIS OF THE PRESSURE IN THE EXPERIMENTAL CHAMBER OF THE DIFFERENTIAL PUMPING
Šabacká, Pavla ; Bílek, Michal (referee) ; Maxa, Jiří (advisor)
The thesis deals with the effect of the critical flow, which is produced at pumping of the differential pumping chamber of the Environmental Scanning Electron Microscope (ESEM). The thesis compares the state of the flow in the area of pumped chamber at pressure ratio on the apertures when the critical flow occurs and its advantages in design of the chambers versus the flow without the clogging the nozzle. Problematics were solved using finite volume method by Ansys Fluent system.
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Using Cosmos FloWorks for analyse the detector.
Hladík, Jaroslav ; Špinka, Jiří (referee) ; Maxa, Jiří (advisor)
This work follow up gas fluxion problems in detector chamber of enviromental scanning electron microscope. Describes basic electron microscopes characteristic and evaluation output signal. Basic focus of this work is proposal placing screening in detector in surroundings programme SolidWorks 2008. There is by the help of system COSMOS FloWorks effected analysis pumping gas with different pressure and mutual position which has significant influence in given fluxion conditions. Programmatic surroundings makes it possible to simulation 3D and evaluation fluxion method final capacities by setting fundamental conditions of solving, which would have been next to real behaviour of gas in real detector.
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Observation of Insulators in ESEM
Matějka, Milan ; Špinka, Jiří (referee) ; Jirák, Josef (advisor)
This graduation theses in introduction deals with principle and problems of electron signal detection in scanning electron microscopy and charging of insulating specimens in SEM. The experimental part of the thesis describe the methods of qualification and quantification of insulating specimen charging effect observed in environmental scanning electron microscope through the use of ionisation and scintillation detector in dependence on water vapour pressure in specimen chamber. The goal of the thesis is formation of the methodics useful to evaluate charging effect at insulating specimens observing and on the basis of measuring, determine optimal conditions for insulating specimen observation with ionisation and scintillation detector.
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Detection of signal electrons in ESEM
Šváb, Martin ; Špinka, Jiří (referee) ; Jirák, Josef (advisor)
This bachelor's thesis deals with problems of environmental scanning electron microscopy and with detection of signal electrons at higher pressure in working chamber. In this thesis I will focus on comparison of detected signal level achieved under different working conditions.
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Analysis of pressure distribution in the variant detector with three aperture by CAE system
Tomášek, Martin ; Vyroubal, Petr (referee) ; Maxa, Jiří (advisor)
This master`s thesis analyzes the pressure distribution on the premises of scintillation detector secondary electron in the variant with three aperture. The aim of this study is analyzing the fluid flow depending on the application of the third aperture in the entrance of the detector, thus creating more self-pumped chamber, which is responsible for ensuring a better distribution of pressure in the premises of the detector. The result of the analysis would be determining how to change parameters within the detector. If it is found that application of the third aperture has a positive effect on water flow in the premises of the detector, this arrangement may be used for improvement of the detector. Master`s thesis is divided into several chapters. First describes the basic principles of electron microscopy, including sample preparation, conditions for the proper functioning of microscopes and sharing different types of electron microscopes. The next chapters describe briefly the physical descriptions of gases flow in low pressures and small apertures, the mathematical models and simulation software used in this analysis. The analysis is done in SolidWorks with the module called Cosmos FloSimulation. The conclusion summarizes the results of the analysis, including graphical representations of simulation.
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