| Industrial Computed Tomography(ICT), compared to conventional radiogram technology, produces accurate images of the internal features of objects, as well as information about the defect's property and position . ICT technology is considered one of the best nondestructive testing methods. The high energy X-ray Industrial Computed Tomography (HECT) system with an electron linear accelerator is developed to image cross-sections of large scale and high density materials. Owing to strong radiation penetrability as well as high spatial resolution and fast scanning speed, HECT is broadly applicable to various fields as an important tool for nondestructive testing (NDT) and nondestructive evaluation(NDE), such as automobile engine, high speed railroad casting and solid fuel rocket motors and so on .The detection system is the key parts of HECT because the high spatial resolution, rapid inspects efficiency, flexible scan mode and low price of HECT are determined by the detection system. However, nowadays, the level of the detection technology is not satisfied the requests of the development of HECT. The scintillator detectors which are most commonly used have many shortcomings such as poor radiation resistance, great cross-talk, high environment condition, costliness, narrow dynamic range and so on. The gaseous detectors have many merits such as low cross-talk and wide dynamic range, but some serious defects are their low detection efficiency and big volume. In certain extent, the shortcoming of the detector is the most reason which restricts the development of HECT technology and holds back the broadly applicable to some fields. Currently, the study of the detection technology of HECT became an important part of HECT research work.Due to the restriction of the detection principle and the material performance the improvement of scintillator detectors is very hard. However, the gaseous detectors have great development space if we can conquer the two shortcomings, the low detection efficiency and the big volume. In this dissertation, supported by National Natural Science Foundation of China and by Tackling Key Problems of Science and Technology of ChongQing, the principle of the high energy X-ray detection and the mechanism of gaseous detector and gas electron multiplier (GEM) are studied, and a new type of solid-conversion gaseous detector was investigated. Some valuable results have been obtained. The main work is provided as follows: ?By analyzing the problems which have been meet in the development of the HECT, and by analyzing the disadvantages of the HECT detectors which have been widely used currently, we put forward key points in this dissertation.?A new type solid-conversion gaseous detector for HECT has been proposed based on the profound analysis of the theory about the pulse X-ray and the GEM. In this detector, a tungsten slab is employed as a radiation conversion medium, and makes the GEM as electron amplifier to resolve the contravention of the size and the detection efficiency of the gas detector.?The feasibility of the solid-conversion gaseous detector is analyzed and demonstrated by the model based on the GEM with theory analysis methods and computer simulation methods.?The sample of the solid-conversion gaseous detector has been designed and produced according to the results of computer simulation and the theoretical calculation . In addition, we set up a trial platform and contrive some experimental schemes. In the experiment, the analog signals waves of the detector unit were shown in distinctly, and the experiments proved that the output of the detector is proportion to the intensity of the incident X-ray. The results of the experiments show that the schemes of gas-solid electron multiplier detector of high energy x-ray industrial CT are reasonable.At last, this thesis reviews the whole research work, summing up innovations as well as shortcomings in it, some important issues are expected to be perfected and lucubrated in the near future. |
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