Development Of CeBr₃ Compact Gamma-ray Spectrometer Based On SiPM Readout

Based on the effective progress of the integrated modularization of the electronics industry,the compactness of the instrument has also become a trend.The reduction in the size of the gamma-ray spectrometers can reduce the burden on the staff,especially the geological surveyors,and it can also assist in efficient work.At present,common portable gamma-ray spectrometers mainly use NaI scintillator detectors.The energy resolution of NaI scintillator is poor,and the resolving power and nuclear recognition ability of the ray energy spectrum are weak.For the traditional gamma-ray spectrometers in the actual application of the volume is too large to carry,the data can not be timely transmission and other deficiencies.,in this paper,a compact gamma-ray spectrometer that is more suitable for carrying is developed from the aspects of improving detection efficiency,reducing instrument volume,designing low power consumption,facilitating real-time measurement and observing energy spectrum.The research comes from 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 main research contents and achievements of the compact gamma-ray spectrometer developed in this paper are as follows:1.Probe design:Based on the investigation of the portable gamma-ray spectrometers,a compact gamma-ray spectrometer was designed.A new type of inorganic scintillator,CeBr₃,was used instead of the conventional NaI scintillator to improve the energy resolving power of the detector.The multiplier tube replaces the traditional vacuum photomultiplier tube and reduces the detector volume.The bias power supply of less than 30V significantly reduces the power consumption of the power supply,and also increases the impact resistance and the magnetic field interference resistance.2.Hardware design:The analog circuits are designed for fast and slow filtering of the two channels.With respect to the differential shaping circuit,the slow channel realizes filter broadening and noise reduction.The fast channel is used for pulse shaping and particle event arrival time information extraction;8Msps A/D converter and STM32 are used.The microcontroller implements the peak sampling and estimation of the nuclear pulse signal,thereby realizing a low power consumption and small volume integrated multi-channel pulse amplitude analyzer.3.Software design:The software design includes the data transmission,storage and transmission part of the detector control end,and the data receiving and calculation and display part of the handheld end.The detector control end adopts DMA channel mode of STM32 to transmit the data collected by the external 8Msps parallel ADC,so that the CPU of the microcontroller can host the data acquisition and transmission work to the DMA controller,greatly reducing the time occupation for the CPU and improving the system response time and work efficiency.The spectrometer uses a micro-power Wi-Fi chip to realize data communication with the mobile phone,and has developed an Android mobile phone APP to realize convenient real-time energy spectral observations,dose equivalents,and nuclide recognition functions to achieve good human-computer interaction.4.The whole structure:Using a small detector,a compact circuit board design,a button cell,and a small Wi-Fi module,the small size of the compact gamma-ray spectrometer is achieved,reachingφ31.4mm×75.5mm,and the overall weight is92.6g.At the same time,the low power consumption of the compact gamma-ray spectrometer can be achieved from many aspects such as the selection of hardware low-power devices to the power-saving mode of the software,and the overall power consumption is only 296.57mW.5.Machine test and function features:After testing,the compact gamma-ray spectrometer has an energy resolution of 5.2%（137Cs 662keV energy gamma ray）and has the functions of energy spectrum measurement,dose equivalent rate display,and nuclide identification,while reducing power consumption and volume In terms of reduction,we have achieved a greater degree of improvement,facilitated human-computer interaction,and achieved more satisfactory results to achieve the original intention of design.