| As a high-tech,nuclear technology is widely used in national defense,industry,resource exploration,nuclear medicine,security inspection and other fields.Nuclear instruments and equipment can be found in subway,airport,hospital and other occasions.Conventional nuclear instruments are mainly used to measure the energy,intensity,time and other parameters of nuclear radiation.With the rapid increase of demand for nuclear medical imaging,aviation nuclear emergency imaging,and nuclear power station radioactive hot spot imaging,the array imaging measurement of nuclear radiation has developed rapidly and become one of the hot directions of nuclear radiation measurement.With the rapid development of electronic technology and nuclear science industry,the integration degree of the circuit is higher and higher,and the nuclear measuring instrument is more and more precise,which makes the nuclear radiation array detection with small size and high modularity realized.Aiming at the disadvantages of complex electronic structure,large volume and more interference between channels of nuclear radiation array detection,this paper designs a gamma ray array detector which is composed of a GAGG scintillator crystal array and a 64 channels silicon photomultiplier array.Based on the ASIC chip SKIROC2,the signal readout circuit is designed and the corresponding upper computer software is written.Making full use of the functions of SKIROC2 chip,it can be applied to various occasions such as radiation array detection and ray imaging.The main research contents and achievements are as follows:1.Detector design: compared with the traditional scintillation crystal,GAGG crystal has higher detection efficiency and energy resolution,and will not deliquesce.Compared with the traditional photomultiplier PSPMT,the silicon photomultiplier MPPC has the advantages of high multiplication ratio,high photon detection efficiency,excellent time resolution,strong anti-interference ability and won't burn out due to the saturation of incident light.Therefore,this paper designs a 64 channels gamma ray array detector composed of GAGG crystal array coupled with MPPC,and a detector array unit test circuit composed of 16 4-channel operational amplifier chips OPA4354.2.Signal readout circuit design: compared with the bloated and complicated circuit design of the traditional nuclear signal front-end readout system.This paper designs a set of signal readout circuit around the 64 channels ASIC SKIROC2,which is simple,compact,greatly simplifies the electronic design.Considering the output data of SKIROC2 and the expansion demand in the future,the read-out circuit uses USB3.0 mode to communicate with the upper computer.As the control center,FPGA realizes the timing logic control of SKIROC2 and USB chip FT600 Q.3.Upper computer software design: using Visual Studio compiles Winform software and communicates with FPGA through USB interface.Its main function is to configure the parameters of SKIROC2 chip,receive the measurement data and display it in a graph.The software design integrates the traditional windows desktop development and the current popular web front-end development technology,which can display the measurement data intuitively,elegantly and comprehensively.SQLite database is embedded in the software to realize the data storage and history.4.System test and functional characteristics: after the completion of the development of the whole machine,the experimental test is carried out.The resolution of the detector is 13.835,the trigger threshold of the signal readout circuit is 0.2f C,the integral nonlinearity is less than 0.1%,and the electronic noise is less than 0.3f C.The test results show that the system can operate stably,locate the gamma ray incident on the scintillator detector accurately,and display the image directly and accurately. |
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