Optimization Design Of Scintillator Detector Based On SiPM

In recent years,silicon photomultiplier tube?SiPM?has been widely used in many fields such as nuclear medical imaging and nuclear detection.As a semiconductor device,SiPM is composed of a series of avalanche diode?g-apd?arrays.It is used at room temperature.When the ambient temperature changes,the breakdown voltage of SiPM changes accordingly,which affects the gain of SiPM and leads to large errors in energy spectrum measurement.In addition,SiPM has noise composed of dark counting,crosstalk between avalanche diodes,and post-pulse,which also causes trouble in promoting the use of SiPM.The main research content of this paper is that when SiPM ACTS as a photomultiplier device for scintillator detector,it optimizes the detector design according to the photoelectric characteristics of SiPM and obtains scintillator detector with stable performance and good energy resolution.The paper will explore from the following two directions:first,to stabilize the gain of SiPM at different temperatures;second,to reduce the influence of internal dark noise of SiPM and improve the energy resolution of scintillator detector.According to SenSL SiPM product manual,the gain of SiPM is positively correlated with the bias voltage,while the breakdown voltage of SiPM is linearly correlated with the temperature change.Based on the temperature characteristics,the paper designs a bias power supply based on the positive temperature coefficient thermistor?LPTC type?.The results showed that the scintillation detector made of LYSO crystal and SiPM was used to measure the ¹³⁷Cs all-powerful peak from 26?to 53?in the thermostatic chamber.It was found that when the temperature compensation circuit was added,the relative change of the ¹³⁷Cs all-powerful peak peak location was reduced from 1.18%/?to 0.05%/?,which achieved the effect of stabilizing the SiPM gain at different temperatures.Using FPGA development board design digital coincidence circuit,amplitude analysis method were used respectively to analysis method?PHA?and area?PAA?,measuring signal generator to generate the simulation of nuclear pulse,and single input,double road input meets sum measurements,the results show that PAA comply with the summation method and dual input measurement successfully reduce the almighty peak resolution.LYSO scintillator detector with single channel SiPM and NaI?Tl?scintillator detector with dual channel SiPM were used to measure energy spectra of ²²Na and¹³⁷Cs with PHA and PAA methods,respectively.The results showed that the PAA method,baseline recovery algorithm and the summation method of the two-channel measurement were in good agreement with the summation method for improving the energy resolution of the scintillator detector.The algorithm can effectively reduce the influence of internal dark current noise of SiPM and improve the detector energy spectrum.It lays a foundation for SiPM to replace PMT in scintillator detector.