The Study Of Gamma Ray Imaging Detection Technology

Nuclear radiation imaging techniques, emerged from the traditional radiation detection technology with great improvement and enhancement, can provide not only the radiation dosages and varieties, but also the spatial distributions of radiation, thus can be widely applied to nuclear power plant(for nuclear material, spent fuel, reactor de-commissioning, decontamination, etc.), environmental protection, anti-terrorism and so on. Developing small modular imaging detector is the key to the development of high resolution and high sensitivity radiation imaging equipment. This thesis focuses on the modularized gamma-ray radiation imaging technology, a series of study was made for some key technical problems of small modular imaging detector, which includes: optimized readout circuit design of the imaging detector module, performance of lanthanum bromide(LaBr3) crystal detector, 2 ×2 array SPMArray4 imaging module and so on.Lanthanum bromide detector consists of one H8500 PSPMT(position sensitivity photomutiplier tube) and one high° density continuous La Br3 scintillation crystal. An optimized front-end electronics(FE) has been designed for the detector system to reduce the 64 anodes’ signals to 4 outputs by using resistor network and charge division circuit. Adjustment of the non-uniformity of H8500 PSPMT’s anodes gain is also implemented in the FE board. In the section of the position readout-circuit, the gain differences are normalized across all signal channels. The performance of the detector gets greatly improved, resulting system’s spatial resolution is less than 1.5 mm, and effective detection area reaches 40 mm × 40 mm.The La Br3 module detector, combined with a dedicated MURA collimator, was applied to the far field radiation imaging detection of remote radiation source. Two kinds of decoding matrix algorithms named: δ decoding algorithm and finely sampling balance decoding(FSBD) algorithm are used in image reconstruction. Comparison of performance between the two decoding algorithms was conducted by MATLAB, the results verified that FSBD algorithm is a better decoding approach for radiation imaging system using MURA coded aperture collimator. The La Br3 detector module was verified by the experiments, the angular resolution of the whole image system is less than 1.9 degree, and the field of view(FOV) of the detector attains 20-40 degree, which measured up to the design objects.To explore the new detector’s performance for radiation image detection, DPC readout circuit and SCD+TCOG circuit were designed for the arrays of 2×2 SMPArray4 imaging detection module. Experimental test results showed that the second method(SCD+TCOG) is better than the first one(DPC) in terms of overall imaging performance. It reduced the impact of a photomultiplier tube splice death zone, increased the effective detection area of the detector modules, reduced the compression effect detection module at the edges. The best energy resolution can reach 16.1%, make it a good candidate for large view radiation image detection.