Development Of Compton Scattering Imaging Detector

With the rapid development of nuclear science and nuclear technology,the use of various types of radioactive sources and safety issues are the focus of attention.The gamma ray imager has an irreplaceable position in the management of radioactive materials.It can quickly find the location of the radioactive source and play a very important role in the search for radioactive materials.The Compton scattering imaging system obtains the azimuth and energy information of the incident ray based on the kinetic principle that rays are scattered twice by multiple detectors.Because Compton cameras do not require heavy collimators to limit the field of view,their system weight is greatly reduced,they can be made more portable,and the imaging range is wider,the detection efficiency is higher,and the detectable ray energy is higher.At present,there are few studies on the overall system of Compton cameras in China,and there are no products that are independently developed and put into market applications.Only the relevant simulation and image reconstruction algorithms are studied.Therefore,the development of a new type of Compton camera with high detection efficiency,wide field of view,and high angular resolution is an important task.The detector is the core component of the Compton scattering imaging system.In this paper,according to the imaging principle of Compton camera,a Compton scattering imaging detector suitable for Compton camera is developed.This paper designs a front-end readout circuit,timing circuit and power supply module based on a scattering layer detector and an absorption layer detector made of SensL C-60035pixel type SiPM coupled GAGG:Ce scintillator,The performance of the detector is tested and acquired according to the detector,The data is filtered by the back-projection imaging algorithm to reconstruct the image.This paper provides a reference for the development of Compton scattering imaging system in China.The research comes from"Compton Scattering-Coded Aperture Composite Detection Imaging System"of the scientific equipment development project of the Chinese Academy of Sciences?project number:29201707??the national key research and development project“High-resolution aerial gamma spectrometry and airborne imaging spectroscopy”?project number:2017YFC0602100?and the national netural science fund project“Mathematical Construction and High-speed Real-Time Digital Reconstruction of Nuclear Pulse Signal Chain”?project number:41474159?.The experimental results of this article are:1.The ²²Na source was used to separately detect the scattering layer detector and the absorption layer.The scatter plots of the scattering layer detector and the absorption layer detector were clearly visible.The ratio of the peak to the valley of the scattering layer detector projection was 3.84:1.The peak-to-valley ratio of the absorption layer detector is 3.67:1.2.The scattering layer detector and the absorption layer detector were separately tested.The scattering layer detector had an average energy resolution of 10.65%for511 keV gamma rays and a 9.7 ray average energy resolution for 662 keV energy.The average energy resolution of the gamma ray with an energy of 511 keV is 11.93%for the absorption layer detector,and the average energy resolution for the gamma ray with an energy of 662 keV is 10.88%.3.The ²²Na source was used for the detection of the scattering layer detector and the absorption layer detector.The ratio of the peak to the valley of the projection of the scattering layer detector was 3.59:1,and the ratio of the peak to the valley of the layer detector of the absorption layer detector was 2.83:1.4.In order to understand the lower detection limit of the detector,the detectors were tested with 241Am source,57Co source,133Ba source,22Na source,and 137Cs source.The results show that the detection limit of the detector is greater than 365keV.5.The key points of the filtered back projection algorithm are studied.Eliminating the method of modeling with the convolution of the point spread function?PSF?,the spherical imaging surface is stereoscopically mapped to a plane,and each individual cone can be replaced with a plane that creates an equivalent ring on the image sphere.Experiments have shown that 137Cs other than 150mm can be imaged.