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The effect of the shape of the intake ports for pumping in a Scintillation detector.
Flídr, Karel ; Vyroubal, Petr (referee) ; Maxa, Jiří (advisor)
The thesis is concerned with the design of the shape of suction canals used for pumping in the scintillation detector. The goal is to perform analysis of the model of the detector according to the current conception and then perform an optimalisation of the suction canals as per demands to their function. In the beginning of the thesis the history of the microscope and electron microscopy is described. The next chapter is focused on a more detailed description of ESEM. The following charter is dedicated to describing the scintillation detector.The thesis recounts the kinds of liquid flow. In conclusion the programs SolidWorks and Ansys Fleunt are described. Next part of this thesis describes in detail parameters‘ settings of simulation calculation. Following chapter introduces designed changes of suction channels shape and its results are shown and described.
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Ionization detector of secondary electrons for environmental scanning electron microscope
Dušek, Petr ; Zimáková, Jana (referee) ; Čudek, Pavel (advisor)
This thesis deals with problematics of a detection of secondary electrons by ionization detector for environmental scanning electron microscope. In this thesis is described the difference between scanning electron microscope and environmental scanning electron microscope. Further there is described emission and detection of the choosen signals that arise while primary electrons are interacting with a specimen in scanning electron microscope. A special emphasis is placed on a description, sorting and on the form of detection of secondary electrons. In thesis there is described principle of a function of ionization a scintilation detectors. Experimental part of thesis describes design of 3 different elctrode systems of a tabular ionization detector, which will be intended to be placed in environmental scanning electron microscope. Based on measuring with the detectors, with experimental design, there is chosen one with the highest quality of signal detection.
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Influence of working conditions on the signal level detected by LVSTD detector
Tylich, Ondřej ; Zimáková, Jana (referee) ; Čudek, Pavel (advisor)
This bachelor project includes information about function of low vacuum scanning electron microscope and describes it’s parts. It explains the difference between low vacuum and high vacuum scannig electron microscope. Contains informations about creation and detection of secondary electrons using scintillation detectors. It describes the calculation of signal to noise ratio and the method for obtaining the values of signal. Project is focused to determine the value of signal with a change in working conditions obtained by using Low Vacuum Secondary Electron Detector TESCAN (LVSTD). The aim is to determine the stability of the effect of working conditions on LVSTD.
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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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Scintillation Secondary Electrons Detector for ESEM
Čudek, Pavel ; Kadlec, Jaromír (referee) ; Rek, Antonín (referee) ; Jirák, Josef (advisor)
The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Scintillation SE Detector for Variable Pressure SEM
Tihlaříková, Eva ; Neděla, Vilém (referee) ; Jirák, Josef (advisor)
This project deals with the theme of environmental scanning electron microscopy (EREM). This method allows the examination of insulators and wet specimens without pretreatment and modification like drying and metallization. The principle of this method consists in using higher pressure in a specimen chamber. The pressure is within the range of 100 – 200 Pa. However, the pressure in the specimen chamber restricts the signal detection interference. The objective of the work is to explore the possibility of interference in secondary electron route detection by way of electrostatic field. The electrostatic field was realized with the system consisting of four electrodes located in front of the scintillation detector. It should have interfered the secondary electron´s trajectory to the detector chamber. The optimization of voltage on the electrodes was made by simulation program called SIMION. The simulation results were experimentally verified with laboratory EREM.
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Multi-electrode system of ionization detector for environmental scanning electrone microscope
Uhlář, Vít ; Špinka, Jiří (referee) ; Jirák, Josef (advisor)
Thesis deals with environmental scanning electron microscopy and with detection of signal electrons by using ionization detector. First part talks about the principle of environmental scanning electron microscope. Second part describes signals generated by interaction of primary electron beam with sample. Third section explains the principle of impact ionization and ionization detector. Experimental part deals with usage of segmental ionization detector and with measuring of signal amplification from copper and platinum. Thesis also examines arrangement of electrodes of ionisation detector on material contrast and examines also on influence of voltage contrast on base - emitter junction of an NPN bipolar transistor. All experiments were carried out in dependency on saturated water vapour pressure in sample chamber.
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Signal Detection by Segmental Ionization Detector in Environmental SEM
Černoch, Pavel ; Jirák, Josef (advisor)
The dissertation thesis deals with signal detection by an ionization detector in the environmental scanning electron microscope and utilization of this detector to gain required information in a specimen image. Main interest is focused on the detector containing several electrodes with a varied geometry arrangement and voltages on these electrodes. The detector was named segmental ionization detector. Detection capabilities of the segmental ionization detector were studied through computer simulations and experiments in the microscope utilizing knowledge from a technical literature background. On the base of the accomplished experiments, the segmental ionization detector has been optimized for the secondary electron detection improvement and at another configuration optimized for a high material contrast acquisition of the specimen image. Consideration of benefits of the examined segmental ionization detectors is included in the work.
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Ionization detector for environmental scanning electron microscope
Melechovský, Ondřej ; Čudek, Pavel (referee) ; Jirák, Josef (advisor)
Presented work deals with environmental scanning electron microscopy. The construction of the device is described concisely in the beginning. Important part is devoted to interaction of electrons with specimen and signals emitted from the specimen. The work aims especially at detection of secondary electrons using the ionization detector. Experimentally is determined effect of working environment and size of electrode system of ionization detector on detected signal.
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