Research On The Key Technologies Of X-ray Imaging Detection

X-ray imaging detecting technology has large potential on the nondestructive testing in industry,medical imaging and safety inspection.Because of its high quality images,scintillation imaging detection has great advantages over other kinds of imaging detections.The implementation of low-cost and miniaturization of scintillation imaging detection is the goal to X-ray imaging engineering field,and that is an important developing direction for X-ray imaging detecting.The high quality images of scintillation imaging detection benefits from the close match between the fluorescence emitted from scintillation screen and the detection wavelength band of image sensor.Therefor,the research on improving the scintillation characteristics of scintillation screen has great academic sigmificance and applicative value.This dissertation proposed the idea of using CsI:Tl membranous scintillation screen as the X-ray conversion screen and the direct coupling structure between the scintillation screen and image sensor,which aims at implementing the low-cost and miniaturization of scintillation imaging detection.The key technologies include building the microstructure model of CsI:Tl membranous scintillation screen,preparing CsI:Tl membranous scintillation screen samples by vacuum thermal evaporation,improving the microstructure of CsI:Tl membranous scintillation screen by interfacial tegulating,studing the moistureproof solution for CsI:Tl membranous scintillation screen,setting up the scintillation imaging detection system with direct coupling structure.This dissertation successfully acquire the images clearly apprearing the internal structure shape of an object through the CsI:Tl membranous scintillation screen of several microns thick,and impement the low-cost and miniaturization of scintillation imaging detection by direct coupling structure.The main research work are as follows:1.The research idea of utilizing CsI:Tl membranous scintillation screen as the X-ray conversion screen and the scintillation imaging detection system with direct coupling structure were proposed based on the objective of the low-cost and miniaturization of scintillation imaging detection.2.The supercells models of CsI:Tl scintillation crystals and the microcolumn structure model of CsI:Tl membranous scintillation screen were build.The electronic band structure and state density of the supercells models were caldulated to study the scintillation mechanism of CsI:Tl crystals and the impact of the doping concentration of Tl~+on the scintillation performance of CsI:Tl crystals.The image point structure of fluorescence was setting up to study the transmission path of fluorescence in the microcolumn structure model of CsI:Tl membranous scintillation screen.The relationship between the conversion efficiency and microstructure parameters for CsI:Tl membranous scintillation screen irradiated by X-ray can be calculated through Monte Carlo arithmetic.These results could provide theoeetical basis for the idea of using CsI:Tl membranous scintillation screen as the X-ray conversion screen.3.CsI:Tl membranous scintillation screen samples were prepared by vacuum thermal evaporation.The process conditions that could affect the fluorescence conversion performance of CsI:Tl membranous scintillation screen were gained through the research of growth mechanism of polycrystalline films deposited by vacuum thermal evaporation.The fluorescence smission spectrum,microstructure topography,crystalline characteristic of samples prepared under different process parameter were tested to study the impacet of process conditions on the fluorescence conversion performance of CsI:Tl membranous scintillation screen.4.The CsI:Tl membranous scintillation screen samples deposited on single crystal Si substrates were prepared.And the influence of single crystal Si substrates on the fluorescence conversion performance of CsI:Tl membranous scintillation screen was studied,which could provide the data to back the deposition process on photosensitive surface of image sensor and the integration of scintillation imaging detection system.5.The means of interfacial regulation and moistureproof was utilized to optimize the fluorescence conversion performance of CsI:Tl membranous scintillation screen.Based on the epitaxial growth mechanism of crystal films,the idea of regulating the microstructure with crystal interface was proposed to optimized the fluorescence conversion performance of CsI:Tl membranous scintillation screen.The pre-deposition technique was used to implement the idea of interfacial regulation.The CsI:Tl interface with island porphology was predeposited on the substrates on which the CsI:Tl membranous scintillation screen with regular and compact microstructure was achieved.Combined with the design of the Al high-reflective film on screen surface,Al layer with1 mm thickness was used to prevented the moistureproof of CsI:Tl membranous scintillation screen.For the the CsI:Tl membranous scintillation screen samples with and without the Al layers,the relative light output intensity of these samples exposed in the humid environment for different time were tested to verified the humidity resistance of Al layer.6.The miniaturization scintillation imaging detection system with direct coupling structure was setting up.Combined with the CsI:Tl membranous scintillation screen,the imaging of object internal structure was achieved to verified the the image performance of imaging system and CsI:Tl membranous scintillation screen.The scintillation imaging detection system with optical component coupling structure was build to verify the adcantages in terms of the imaging performance of the miniaturization scintillation imaging detection system.The imaging performance optimization of the CsI:Tl membranous scintillation screen prepared by predeposition technique was verified through the scintillation imaging detection system with two kinds of coupling structure.