Si-PIN与CdTe探测器应用于X射线荧光能谱测量的研究

半导体探测器具有优异的性能因而被广泛应用于能量色散X射线荧光测量,以传统型Si-PIN半导体探测器与复合型CdTe半导体探测器为研究对象,分别从材料属性、探测效率、能量分辨率等方面对两种探测器进行对比,重点分析探测器灵敏区厚度、入射X射线能量、后级电路成型时间等因素对其性能的影响,并对由逃逸峰、空穴拖尾效应所导致的X射线荧光能谱的差异进行分析;同时,针对探测器空穴收集不完全的问题,基于FPGA设计了带有上升时间甄别功能的数字多道脉冲幅度分析器,能够有效消除空穴拖尾的影响,提高能量分辨率。从实验结果可知:对能量低于15keV的射线,Si-PIN与CdTe探测器的探测效率基本相当;对能量大于15keV的射线,CdTe探测器的的探测效率明显占优;Si-PIN探测器的最佳成形时间约为10μs,CdTe探测器的最佳成形时间约为2.6μs,因而CdTe探测器更适用于高计数率条件;对于不同能量的X射线,Si-PIN探测器的能量分辨率优于CdTe探测器;CdTe探测器具有明显的空穴拖尾效应,将CdTe探测器与带上升时间甄别功能的数字多道脉冲幅度分析器配合使用,其能量分辨率显著提高。

Study on Si-PIN and CdTe Detectors Used in Energy Dispersive X-Ray Fluorescence Measurements

Semiconductor detector is widely used in energy dispersive X-ray fluorescence measurementsdue to its excellent per-formance.In this paper,Si-PIN and CdTe semiconductor detectors were studied,performances of the two detectors were com-pared in material properties,detection efficiency,energy resolution and other aspects.Focused on the performance of the detec-tors influenced by the thickness of detector sensitive area,energy of incident X-ray,shaping time of post-stage circuit,and ana-lyzed the differences of energy spectrum caused by escape peaks and hole trailing.Aiming at the problem of incomplete hole col-lection in detector,a digital multi-channel analyzer (DMCA)based on FPGA with rise-time discriminator was designed,it could reduce the influence of hole trailing effectively and improve energy resolution.The experimentation results indicate that the de-tection efficiency of Si-PIN and CdTe is roughly equal when energy is below 1 5 keV while CdTe has much higher detection effi-ciency than Si-PIN when energy is above 15 keV.The optimum forming time of the Si-PIN detector is about 10μs,and the CdTe detector is about 2.6μs,so the CdTe detector is more suitable for the high count rate condition.Si-PIN detector has better ener-gy resolution than CdTe detector for different energy incident X-ray.CdTe detector has obvious hole tailing effect and the energy resolution of CdTe detector is significantly improved by using DMCA with rise-time discrimination.