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The effects of ionizing radiation on semiconductor devices properties
Yermalayeva, Darya ; Šteffan, Pavel (referee) ; Musil, Vladislav (advisor)
This master’s thesis deals with the problematics of influence of ionizing radiation on semiconductor devices and their properties. The aim of the thesis is to analyze the different types of radiation that can occur in the areas of application of these components. In the second part, the degradation processes are explored, with emphasis on the influence caused by the radiation dose. Also, the displacement damage and SEE effects are described, but just slightly, because they are not part of this work. The third part describes the device design process and harmful effects, that have to be considered during the design phase. In the forth and the fifth parts of this work were done modeling of radiation effects (influence of dose rate, Single-Event Upset and Total Ionizing Dose) in PSpice program and was carried out the possibility of designing a simple dosimeter with silicon diode. In conclusion, the results of the thesis are summarized and evaluated.
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The effects of ionizing radiation on semiconductor devices properties
Yermalayeva, Darya ; Šteffan, Pavel (referee) ; Musil, Vladislav (advisor)
This master’s thesis deals with the problematics of influence of ionizing radiation on semiconductor devices and their properties. The aim of the thesis is to analyze the different types of radiation that can occur in the areas of application of these components. In the second part, the degradation processes are explored, with emphasis on the influence caused by the radiation dose. Also, the displacement damage and SEE effects are described, but just slightly, because they are not part of this work. The third part describes the device design process and harmful effects, that have to be considered during the design phase. In the forth and the fifth parts of this work were done modeling of radiation effects (influence of dose rate, Single-Event Upset and Total Ionizing Dose) in PSpice program and was carried out the possibility of designing a simple dosimeter with silicon diode. In conclusion, the results of the thesis are summarized and evaluated.
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The feasibility of different biodosimetric methods for dose estimation in case of radiation accidents.
PAVEZKA, Luboš
A deterioration of the coincidental hazards linked to the use of ionizing radiation is currently observed for four reasons. First, the increasing demand for radiation sources in numerous industrial applications (food sterilization, construction, engineering) leads to an increasing likelihood of loss of the sources or abnormal/unsuitable use and storage. Second, advances in medicine generate new protocols and tools that are more efficient but also much more complex to execute, increasing the risk of accidental overexposure. Third, the possibility of a terrorist attack using radiological or nuclear devices has to be taken into account. Finally, recent events in Fukushima (Japan) highlight the risks of exposure in the case of nuclear power plant accidents. All these issues could lead to the accidental exposure of one to several thousand individuals not wearing dosimeters. Thus, it is essential to be able to assess the exposure level of victims. Nowadays, this evaluation is based on clinical diagnosis (mainly irradiation symptoms and hematological variations) supplemented with biological dosimetry andphysical dose reconstruction. Biological dosimetry is especially important when the personal dosimeter is lacking or when the accidental context is unclear. All this information should help the medical staff to deliver appropriate medical care and to manage the long-term medical follow-up, if required. To fulfil this task, the dose estimates has to be timely, exact and conclusively reached in large-scale disasters. In my bachelor thesis, I have focused on the applicability of the various techniques for different scenarios: small- and large-scale exposes to different levels of a radiation that could manage to the urgent radiation syndrome and exposures with lower doses that do not need direct care, but should be followed for evidence of long-term impacts. The principle of biodozimetry is to utilize changes caused in the individual by ionizing radiation to estimate the dose and, if feasible, to predict or reflect the clinically relevant reaction. Optimally, the changes should be specific for ionizing radiation, and the response should be unaffected by prior medical or physiological variations among subjects, including changes that might be caused by the stress and trauma from a radiation event. There are two basic types of biodozimetry with dissimilar and very often complementary characteristics: those based on changes in biological parameters such as gene activation or chromosomal abnormalities and those based on physical changes in tissues. Factors advised comprise: time interval when the assay is feasible biologically, time for sample preparation and analysis, dose finding limit, ease of use, logistical demands, potential efficiency, point-of-care eligibility, and the ability to support patient diagnosis and treatment within a therapeutically relevant time point. The development of of biodozimetry has been mainly encouraged by the needs after a large-scale accident, where it is essential to have a tool or device to identify those individuals who would profit to be brought into the medical care system.
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