Study Of Temperature Drift Compensation Methods For GAGG(Ce)-SiPM Detectors

The SiPM（Silicon Photomultiplier）is a new type of photoelectric conversion device with the advantages of high gain,low power consumption,anti-magnetic interference,small size and wide spectral response range compared to the PMT（Photomultiplier Tube）.It is widely used in medical imaging,high energy physics,environmental monitoring and national defence and security.During the same period,the inorganic scintillator cerium-doped gadolinium gallium aluminium garnet[GAGG（Ce）]has been intensively studied and widely used because of its high atomic number,high density,fast flash,high photon yield and resistance to deliquescence.Therefore,GAGG（Ce）detectors coupled with SiPM[GAGG（Ce）-SiPM]are expected to bring new solutions for nuclear radiation monitoring when the detection efficiency,energy resolution and spatial resolution are combined under the constraints of power consumption,volume and arraying.The electronic gain stability of the SiPM,which is essentially a self-sustained quenched avalanche diode,is strongly influenced by temperature changes because temperature changes cause the SiPM reverse breakdown voltage(V_BR)to change,and the overvoltage(V_OV)to change while the bias voltage remains unchanged,and the overvoltage is linearly related to the electronic gain.the luminescence characteristics of the GAGG（Ce）crystal are also subject to gain drift as the ambient temperature The gain drift phenomenon occurs with the change of ambient temperature.Therefore,in this paper,based on the study of the temperature response characteristics of SiPM-GAGG（Ce）detectors,a detector gain stabilization method and algorithm based on the feedback adjustment of SiPM bias voltage by temperature parameters is designed and established,and the main research contents and conclusions are as follows:（1）The temperature drift phenomenon of the GAGG（Ce）-SiPM detector was investigated by studying the nuclear pulse amplitude response characteristics of the GAGG（Ce）-SiPM detector.The SiPM modules are 8×8 arrays with a single SiPM size of 6 mm×6 mm and the crystal size isΦ50 mm×50 mm.The data show that the rate of change of full energy peak channel address gradually decreases with time after the temperature change occurs,and after a constant temperature time of more than at least110 min,the results of three consecutive energy spectrum measurements show that the peak channel address fluctuates within 0.1 channel and full energy peak position reaches a basic stability.The measurements showed that the energy resolution of¹³⁷Cs@662 ke V varied by 6.5%over the temperature range of-20°C to+40°C.The average drift rates of the full-energy peak channel addresses of theγenergy spectra of the ²⁴¹Am,¹³⁷Cs and ⁶⁰Co sources were as follows:43.85%@59.5 ke V,45.34%@662ke V,45.13%@1173 ke V 44.98%@1332 ke V.（2）The GAGG（Ce）-SiPM detector temperature-gain compensation method and system were studied and designed and implemented.In this paper,a hardware and software linkage method is used to stabilise the detector gain,i.e.the bias voltage of the SiPM is adjusted by the temperature-gain variation law scale curve.The system study includes hardware design such as 12 V/5 A flyback power supply design,STM32minimum system design,high voltage power supply design,temperature acquisition circuit design,and embedded software and Lab VIEW upper computer control software design.The measurement results show that the output voltage accuracy of the flyback power supply is 0.56%,the load regulation rate is 2.56%,the output voltage ripple is126 m V at no load and 253 m V at full load 5 A;the maximum output ripple of both sets of high-voltage power supplies is less than 400μV,and the output ripple coefficient is less than 0.001%.（3）The experimental test of the stabilization effect of the GAGG（Ce）-SiPM detectorγenergy spectrometry system.The experimental results show that,after using the temperature-gain compensation method and system of the GAGG（Ce）-SiPM detector designed in this paper.in the temperature range of-20°C～+40°C,The energy resolution of ¹³⁷Cs@662 ke V changed by 0.93%.The average drift rates of the measured²⁴¹Am,¹³⁷Cs and ⁶⁰Co point sources were 0.57%@59.5 ke V,0.37%@662 ke V,0.37%@1173 ke V and 0.36%@1332 ke V,which significantly improved the stability of the GAGG（Ce）-SiPMγenergy spectrometry system.The temperature-gain compensation method and algorithm designed in this paper have the advantages of simplicity and convenience,large dynamic range of high-voltage output,and customizable temperature characteristic curves,which can be adapted to the objective fact that SiPM bias voltage varies significantly among different manufacturers,and can provide technical support for the future development of nuclear radiation monitoring equipment based on GAGG（Ce）-SiPM detectors.