下一代康普顿望远镜的量能器探测单元研究

Study of the detection unit of the calorimeter for the next generation Compton telescope

MeV能区的γ射线天文研究远落后于其它能区,导致该能区的天文物理信息至今还没被充分挖掘,因此,研制下一代高灵敏度的康普顿望远镜对于开展MeV能区的γ射线天文研究具有重要的科学意义。量能器作为康普顿望远镜的重要组成部分,应具有高能量分辨率和高位置分辨率,为此,设计了一种双端读出的γ射线探测器作为量能器的基本探测单元,并对其进行细致的研究。结果表明:通过双端读出信号幅值,可以确定γ射线的总能量以及在晶体中的相互作用位置,采用硅光电倍增管(Silicon Photomultiplier,SiPM)匹配铊激活碘化铯(CsI(Tl))晶体时,探测单元获得比采用光电二极管(Photodiode,PD)和雪崩光电二极管(Avalanche Photodiode,APD)都更好的性能,对662 keVγ射线的能量分辨率可达5.9%(Full Width at Half Maxima,FWHM),位置分辨率约为5.7 mm(FWHM)。该探测单元能够很好地满足下一代康普顿望远镜对量能器的性能要求。

[Background]Compared with other energy regions,little research of gamma-ray astronomy in the MeV energy region has been carried out,hence insufficient exploration of astrophysical information is available in the MeV energy region.[Purpose]This study aims to investigate the gamma-ray astronomy of MeV energy region so as to provide reference for the design of the next generation Compton telescope calorimeter.[Methods]A dual-ended readout gamma-ray detector was designed as the elementary detection unit of a calorimeter.The detector was made of a long CsI(Tl)bar with the size of 10 mm×10 mm×80 mm and wrapped by the ESR film.The photodiode(PD),the avalanche photodiode(APD)and the silicon photomultiplier tube(SiPM)were used respectively as photoelectric converters for the detector,and they were tested by using 137Cs source at different positions on the detector.[Results]The results show that the total energy and interaction position of the incident gamma-ray can be determined by reading the signal amplitudes at two ends of the three photoelectric converters.The energy resolution for 662 keV gamma-ray is 5.9%(full width at half maxima,FWHM)and the position resolution is about 5.7 mm(FWHM),which is the best performance obtained in the case of SiPM readout.[Conclusions]The detection unit designed in this paper can meet the performance requirements of the calorimeter of the next generation Compton telescope.