Using a LaBr3:Ce scintillator for positron annihilation lifetime spectroscopy

A LaBr₃:Ce scintillator has a high light output (~60000 p.e/MeV) and a short decay constant (<25 ns), which makes it good for time spectrometry. Compared with a BaF₂ scintillator, it can bear a much higher count rate, and can be coupled to photomultipliers without using a quartz window. In this work, a positron annihilation lifetime spectrometer (PALS) consisting of two bulks of φ25 mm×25 mm LaBr₃:Ce scintillator coupled to two XP20D0 photomultipliers, respectively, was built. A time resolution of FWHM=206 ps was measured for the PALS with a ⁶⁰Co source at the energy window for ²²Na. With this spectrometer, a reasonable lifetime value τ=221±4 ps in a pure Si sample is obtained, which means that the utilization of LaBr₃:Ce as the detector for a PALS is feasible.     

无线通信系统电磁脉冲传导防护组件设计与有效性试验验证

为提高甚高频无线通信系统的抗高空电磁脉冲能力,基于易损性分析结果,确定了瞬态泄流和稳态滤波联合防护的设计思路以及设计指标,并研制了防护样件。使用20 ns/500 ns传导注入波形开展防护组件脉冲注入试验,比系统原始防护器残余电流峰值减小60%,启动时间缩短75%,作用时间缩短80%,注入波形低频能量限制（20 MHz以下）提高1个量级;以某甚高频无线通信系统为被试品,开展了防护组件加固验证试验,防护组件残余电流控制在10 A水平以下,被试系统功能和性能指标正常,验证了防护组件设计的有效性。