Detection And Screening Of Mobile Target Weak Radiation Source

Radioisotopes are widely used in different fields and promote the development ofthe economic and technology. On the other hand, the illicit trafficking of nuclearmaterials has become one of the most serious security concerns in modern times. Largearea plastic scintillator detector was widely used in the detection of radioisotopes due tofast response, short decay time, stability, resistance to radiation cheap and so on. Thisstudy investigated the detection and screening of mobile radiation source based on thelarge volume plastic scintillator. The study compared detection efficiency between onephotomultiplier tube (PMT) and dual PMTs and investigated the gross-count algorithmbased on the measurement of ray intensity. This study designed and developed theintegrated electronics module in replace of NIM electronics plugin. In addition,energy-windowing algorithm was discussed in this study, the conclusion was alsoanalyzed based on the result of the experiment of spectrum measurement.The large volume plastic scintillator has poor resolution of spectrum. We couldn’tdirectly judge which radioisotope the target had. We always measured the intensity ofray to make decision. Dual PMTs were used to do a test. The results showed that it canimprove efficiency by30%and could also reduce the false negative rate by usinggross-count algorithm.The study designed and developed the integrated electronics module consist of thesignal processing module and linear power. The electronics module is consisted of thepreamplifier, amplifier and the discriminator. The microprocessor with serial portscommunicated with external digital, using RS-485interface and Modbus agreement.The computer can read, process and display using the real-time acquisition data. Theexperiment results showed that the designed integrated electronics module and the dataanalysis software can meet the needs of normal detection.The energy-windowing algorithm was developed based on the difference ofdifferent radioisotopes spectrum. It can help us to detect which radioisotope the target has by using the large volume plastic scintillator. The experiment was done by NIMelectronics plugin. The results showed that the spectrum of different radioisotopes isdifferent from each other. This result could be used to make more detailed analysis. Thestudy established the feature regions of133Ba,137Cs,60Coand also proposed formulas tomake the energy-windowing algorithm achievement. Energy-windowing algorithm iseffective to some extent, but the number of radioisotopes judgment is limited. If wecombine the gross-count algorithm and energy-windowing algorithm, the performanceof the large volume plastic scintillator could be optimized and more and more targetradioisotopes could be detected.