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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Development of a gamma-ray beam profile monitor for the high-intensity gamma-ray source

Regier, Thomas Zachary 29 October 2003
Beam profile monitors provide position and ux distribution information to facilitate the configuration of an experimental apparatus and are an important component of any accelerator facilities beam diagnostic system. Nuclear physics experiments typically involve the incidence of high energy particles or gamma-rays on some target material and the detection of the products of the ensuing interactions. Therefore, knowing the profile of the incident radiation beam is desirable. To address the need for a profile monitor for the High-Intensity Gamma-Ray Source, development of a CCD-based gamma-ray beam profiler was undertaken. The profiler consisted of plastic scintillator, a lens system and a Starlight Express MX5 CCD camera, all contained within a light tight box. The scintillation pattern, created by the interaction between the incident gamma-rays and the scintillator, could be focused onto the CCD. Simulations were used to determine the amount of power that would be absorbed for different beam energies and scintillator thicknesses. The use of a converter material, placed directly against the scintillator to improve power deposition, was also investigated. The system was tested in order to and the camera noise characteristics, the optical resolution and magnification and the systems responsivity to power absorption in the scintillator. Using a 137Cs source, preliminary beam proles were obtained. By combining the results of the testing and simulation, predictions of the required length of exposure were made. It was determined that a beam with a flux of 10^6/s and a diameter of 2.5 cm could be profiled, using 6.0 mm of plastic scintillator and 0.6 mm of iron converter, to within 5% error per 0.64 mm x 0.91 mm resolving unit, in less than 1 minute.
112

Development of a gamma-ray beam profile monitor for the high-intensity gamma-ray source

Regier, Thomas Zachary 29 October 2003 (has links)
Beam profile monitors provide position and ux distribution information to facilitate the configuration of an experimental apparatus and are an important component of any accelerator facilities beam diagnostic system. Nuclear physics experiments typically involve the incidence of high energy particles or gamma-rays on some target material and the detection of the products of the ensuing interactions. Therefore, knowing the profile of the incident radiation beam is desirable. To address the need for a profile monitor for the High-Intensity Gamma-Ray Source, development of a CCD-based gamma-ray beam profiler was undertaken. The profiler consisted of plastic scintillator, a lens system and a Starlight Express MX5 CCD camera, all contained within a light tight box. The scintillation pattern, created by the interaction between the incident gamma-rays and the scintillator, could be focused onto the CCD. Simulations were used to determine the amount of power that would be absorbed for different beam energies and scintillator thicknesses. The use of a converter material, placed directly against the scintillator to improve power deposition, was also investigated. The system was tested in order to and the camera noise characteristics, the optical resolution and magnification and the systems responsivity to power absorption in the scintillator. Using a 137Cs source, preliminary beam proles were obtained. By combining the results of the testing and simulation, predictions of the required length of exposure were made. It was determined that a beam with a flux of 10^6/s and a diameter of 2.5 cm could be profiled, using 6.0 mm of plastic scintillator and 0.6 mm of iron converter, to within 5% error per 0.64 mm x 0.91 mm resolving unit, in less than 1 minute.
113

Heavy Oil Upgrading from Electron Beam (E-Beam) Irradiation

Yang, Daegil 2009 December 1900 (has links)
Society's growing demands for energy results in rapid increase in oil consumption and motivates us to make unconventional resources conventional resources. There are enormous amounts of heavy oil reserves in the world but the lack of cost effective technologies either for extraction, transportation, or refinery upgrading hinders the development of heavy oil reserves. One of the critical problems with heavy oil and bitumen is that they require large amounts of thermal energy and expensive catalysts to upgrade. This thesis demonstrates that electron beam (E-Beam) heavy oil upgrading, which uses unique features of E-Beam irradiation, may be used to improve conventional heavy oil upgrading. E-Beam processing lowers the thermal energy requirements and could sharply reduce the investment in catalysts. The design of the facilities can be simpler and will contribute to lowering the costs of transporting and processing heavy oil and bitumen. E-Beam technology uses the high kinetic energy of fast electrons, which not only transfer their energy but also interact with hydrocarbons to break the heavy molecules with lower thermal energy. In this work, we conducted three major stages to evaluate the applicability of E-Beam for heavy oil upgrading. First, we conducted laboratory experiments to investigate the effects of E-Beam on hydrocarbons. To do so, we used a Van de Graff accelerator, which generates the high kinetic energy of electrons, and a laboratory scale apparatus to investigate extensively how radiation effects hydrocarbons. Second, we studied the energy transfer mechanism of E-Beam upgrading to optimize the process. Third, we conducted a preliminary economic analysis based on energy consumption and compared the economics of E-Beam upgrading with conventional upgrading. The results of our study are very encouraging. From the experiments we found that E-Beam effect on hydrocarbon is significant. We used less thermal energy for distillation of n-hexadecane (n-C16) and naphtha with E-Beam. The results of experiments with asphaltene indicate that E-Beam enhances the decomposition of heavy hydrocarbon molecules and improves the quality of upgraded hydrocarbon. From the study of energy transfer mechanism, we estimated heat loss, fluid movement, and radiation energy distribution during the reaction. The results of our economic evaluation show that E-Beam upgrading appears to be economically feasible in petroleum industry applications. These results indicate significant potential for the application of E-Beam technology throughout the petroleum industry, particularly near production facilities, transportation pipelines, and refining industry.
114

Design and Fabrication of High-Coupling Efficiency Beam Expander Integrated Laser Diode

Wu, Chun-Ta 08 July 2004 (has links)
The purpose of this thesis is to design and fabricate the S-shaped profile in depth. The results are applied to design a beam expander. In the experiments, we use the local etch-rate control, i.e. diffusion-limited etching, to fabricate the S-shaped profile. The etchant solution and recipe is H3PO4:H2O2:H2O =98:1:1 at 21¢J without stirring. The diffusion length of the etchant solution is 12.5mm. The device includes active semiconductor laser and passive tapered waveguide (beam expander). The design of the passive waveguide includes the lateral and vertical directions. In the lateral aspect, we use FimmWave to simulate the best symmetrical far field angle. When the waveguide width is 2.5mm and the etching depth is 1.4mm, we can get the best symmetrical far field angle which is lateral 27.88¢X and vertical 27.76¢X. In the vertical aspect, we use diffusion-limited etching to fabricate the depth changing. In this thesis, we use the beam expander length 350, 400, 450, 500mm.
115

The Analysis of Smoke Detection on Performance of Smoke Exhaust System in Buildings with Atrium

Tai, Wen-sheng 31 May 2005 (has links)
Recently, plenty of large/public buildings have been completed in Taiwan. For bright indoor environment and comfortable feelings, these buildings often utilized lots of large spaces such as atria. However, it is difficult to maintain tenable conditions within atria and large spaces in case of fire. Therefore, the alert of smoke detectors and the efficiency of smoke control systems are both very important when a fire occurred and people needed to evacuate. In large space buildings, the smoke exhaust fan and smoke storage are major design concepts of the passive smoke management systems in order to maintain tenable conditions in means of egress. In this research, the operation strategies of passive smoke management and fire detection systems in large space buildings will be systematically analyzed. The full-scale hot smoke test can be performed to evaluate the temperature distribution of smoke layer and the smoke descending rate at ABRI large space fire lab in Tainan. In the other hand, the beam detectors can not only detect smoke layer by fire more earlier but show excellent smoke rejection if they can be effectually connected with passive smoke control systems. It is anticipated that through the execution of this research project, the concept developed in this study can be applied to improve the passive smoke management performance of large space buildings in Taiwan.
116

Process and analysis of nano wire in InGaAs/AlInAs by focused ion beam

Yu, Chien-Pang 19 July 2006 (has links)
On InGaAs/AlInAs heterostructures we made nanowires which were made by focus ion beam (FIB) and the width of nanowires making by FIB were 40nm¡B70nm¡B100nm and 200nm respectively. we studied electronic characterization of nanowires using Shubnikov-de Haas(SdH).In our research,by using SdH method there are no signal in our sample which processed by FIB,then we changed to process technology in our sample.For example: Increase thickness of the protection layer,size of change channel,etc.
117

Design of strained ¢»-¢½ epitaxial structures and the MBE growth

Liao, Cheng-Hsien 09 July 2002 (has links)
The work of this thesis includes molecular beam epitaxy (MBE) and optical study of strained InGaAs and InGaAlAs multiple quamtum well (MQW) structures. Two strained layer structures suitable for devices applications have been designed, grown, and investigated. The first one is a 0.98-
118

Application of Electron-Beam Lithography to the Fabrication of Electroabsorption Modulators

Chen, Hung-Ping 30 June 2003 (has links)
none
119

Synthesis and cure characterization of high temperature polymers for aerospace applications

Li, Yuntao 12 April 2006 (has links)
The E-beam curable BMI resin systems and phenylethynyl terminated AFR-PEPA-4 oligomer together with an imide model compound N-phenyl-[4-(phenylethynyl) phthalimide] were synthesized and characterized. E-beam exposure cannot propagate the polymerization of BMI system until the temperature goes up to 100oC. However, a small amount of oligomers may be generated from solid-state cure reaction under low E-beam intensity radiation. Higher intensity E-beam at 40 kGy per pass can give above 75% reaction conversion of BMI with thermal cure mechanism involved. NVP is a good reactive diluent for BMI resin. The cure extents of BMI/NVP increase with the increase of the dosage and applied dosage per pass. The reaction rate is much higher at the beginning of the E-beam cure and slows down after 2 dose passes due to diffusion control. Free radical initiator dicumyl peroxide can accelerate the reaction rate at the beginning of E-beam cure reaction but doesn’t affect final cure conversion very much. According to the results from FT-IR, 200 kGy total dosage E- beam exposure at 10 kGy per pass can give 70% reaction conversion of BMI/NVP with the temperature rise no more than 50oC. The product has a Tg of 180oC. The predicted ultimate Tg of cured AFR-PEPA-4 polyimide is found to be 437.2oC by simulation of DSC Tg as a function of cure. The activation energy of thermal cure reaction of AFR-PEPA-4 oligomer is 142.6 ± 10.0 kJ/mol with the kinetic order of 1 when the reaction conversion is less than 80%. The kinetics analysis of the thermal cure of N-phenyl-[4-(phenylethynyl) phthalimide] was determined by FT-IR spectroscopy by following the absorbance of the phenylethynyl triple bond and conjugated bonds. The thermal crosslinking of N-phenyl-[4-(phenylethynyl) phthalimide] through phenylethynyl addition reaction has a reaction order of 0.95 and an activation energy of 173.5 ± 8.2 kJ/mol. The conjugated bond addition reactions have a lower reaction order of 0.94 and lower activation energy (102.7 ± 15.9 kJ/mol). The cure reaction of N-phenyl-[4-(phenylethynyl) phthalimide] can be described as a fast first-order reaction stage followed by a slow second stage that is kinetically controlled by diffusion.
120

Anwendung des in-beam PET Therapiemonitorings auf Präzisionsbestrahlungen mit Helium-Ionen

Fiedler, F. 31 March 2010 (has links) (PDF)
No description available.

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