The work is devoted to problems of electron microscopy, focusing on the scintillation detector, which is located in chamber separating the field from different pressures. Using of the CAD and CAE was created 3D model of the detector, which took place on calculations focused to influence of the performance of different types of air pumps at gas flow between the chambers. The results of individual variants are compared in graphic form and evaluated.

Despite nuclear fission prominence in nuclear physics, there are still several fundamental open questions about this process. One uncertainty is the energy distribution of neutrons emitted immediately after fission. In particular the relative energy distribution of neutrons above 8~MeV has been difficult to measure. This experiment measured the prompt neutron energy spectrum of n+235U from 3-10~MeV. The measurement took place at Los Alamos National Laboratory (LANL) and used a double time-of-flight technique to measure both the beam and fission neutron kinetic energies. Fission event timing was measured with a parallel plate avalanche counter. The fission neutron time-of-flight was measured with 2~m long plastic scintillation detectors. By combining the time-of-flight information with a known flight path the kinetic energy spectrum of neutrons was measured. To eliminate backgrounds various time-of-flight and energy cuts were imposed and an accidental coincidence background was subtracted. An MCNP simulation, including the 2~m neutron detector geometry, was done using the Madland and Nix model as the input energy distribution for the simulated neutrons. Finally, the measured energy spectrum was compared with the MCNP simulated n+235U fission neutron energy spectrum.

This graduation thesis deals with the problem of voltage contrast in ESEM. The purpose of this work was to verify influence of used detectors in the dependence on conditions in specimen chamber on the size of voltage contrast. With the conditions in specimen chamber we understand pressure and working conditions of signal detection. We used power transistor as specimen.

This work deals with the flow of gas in the scintillation detector. Thesis describes the function of an electron microscope, the composition, distribution and development of microscopes from the earliest to modern. The work also includes familiarization with SolidWorks 3D modeling in which is the electron microscope modeled and Cosmos FloWorks in which they are carried out simulations of gas flow. The paper is focused on the flow of gas in various shapes of the screen and various pressures in chamber of specimen. The results of the analysis of both apertures variants are compared with the request to minimize the pressures in the trajectory of the secondary electrons of well as in the chamber of specimen.

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.

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.

<p>We investigated the use of multiplexing and an electro-optical coupling system in the design of magnetic resonance compatible positron emission tomography (PET) detectors. Reducing the number of output channels is an effective way to minimize cost and complexity and complements the substitution of coaxial cables for fiber optics. In this work, we first compared the system performance of two multiplexing schemes using both simulation and experimental studies. Simulations were performed using the LTSPICE environment to investigate differences in resulting flood histograms and rising edge slopes. Experiments were performed using Lutetium-Yttrium Oxyorthosilicate (LYSO) crystals of coupled to a SensL ArraySL-4 silicon photomultiplier (SiPM) connected to interchangeable circuit boards containing the two multiplexing schemes of interest. Three crystal configurations were tested: single crystal element (3x3x20 mm³), 2x2 array (crystal pitch: 3x3x20 mm³) and 6x6 array (crystal pitch: 2.1x2.1x20 mm³). Good agreement was found between the simulations and experiment results. The capacitive multiplexer is able to achieve improved time resolution of good uniformity (average of 1.11±0.01ns and 1.90±0.03ns for the arrays, respectively) and crystal separation, compared to the resistive multiplexing (average of 1.95±0.03ns and 3.33±0.10ns). The resistive multiplexing demonstrates slightly improved energy resolution (11±0.1% and 22±0.6%, compared to 12±0.1% and 24±0.4% for the capacitive array). The relevancy of this work to the PET block detector design using SiPM arrays is also discussed, including light sharing, edge compression and gain variation among SiPM pixels. This work also examines the effect of the electro-optical coupling system by comparing the system performance between cases with and without it. The coupling system is found to adversely affect performance, increasing global energy resolution by ~6%, average timing resolution by ~120% and distorting the flood histogram.</p> / Master of Applied Science (MASc)

First part of this thesis is a theoretical essay which deals with the basics of scanning electron microscopy, with structure and function of a scanning electron microscope, its’ special case of an various pressure scanning electron microscope, electron interaction with surrounding environment and with a scintillation detector. The applied part of the thesis is focused on evaluation of material contrast on Cu-W specimen. Material contrast is evaluated for different pressures of water vapors in the microscope specimen chamber and for different detection conditions.

No description available.

This thesis deals with the design, implementation and testing of an equipment that performs spectral analysis of a gamma radiation, based on the evaluation of pulses from a scintillation detector. The pulzes are pre-amplified and digitized, and their further processing takes place numerically in an FPGA, which allows a simple modification of the function of the developed device. After an introduction to the issue of gamma radiation spectroscopy with a focus on its detection, the thesis is devoted to the development of a multichannel analyzer hardware, whose individual parts are further described later. Next, the development of a digital signal processing system in the FPGA is described. Followed by an analysis of a microcontroller firmware, and a text protocol for the controlling of the device. Finally, the results of the work are discussed, with a focus on the test measurement of gamma radiation.