ADS中检测快中子束的GEM探测器的研制

ADS need neutron detectors working on a wide energy range and quite insensitive to X- and gamma-rays. GEM （Gas Electron Multiplier）technology has beem proposed to achieve this goal.A new GEM based neutron detector will designed and it gives the possobility to get integrated neutron fluxes from thermal to fast neutron. Owing to their excellent position resolution and high rate capability,GEM detectors are widely used for the tracking of charged particles in high-energy physics. With appropriate deposits on the electrodes or additional converter sheets, the device is used for detection and localization of neutrons. To compensate for the low efficiency of a single element, multi-layer structures can be made, with stacks of several converter GEM pairs, ionization released by a neutron conversion anywhere in the stack is transported through the structure to an end-cap position-sensitive GEM multiplier.Compared to the existing neutron detector,the more important advantage of the system is relatively simple structure,economy prices,high counting rate,good timing resolution and spatial resolution.

ADS（Accelerator Driven Sub-critical System）需要可测量中子能量范围广并且对光子不敏感的中子探测器。GEM型探测器就可满足其要求并对中子通量进行监测。GEM（Gas Electron Multiplier）型气体探测器是上世纪90年代研发的一种高计数率、良好的时间和空间分辨的粒子探测器。其抗辐射、读出方便，广泛的应用于高能物理的粒子监测。本项目将结合ADS项目的基础研究，在GEM探测器基础上增加中子转换层,研制高计数率率、高位置分辨的用于测试快中子通量的GEM中子探测器。此探测器可在极端条件下对中子通量分布进行检测。级联GEM膜的采用提供了中子探测效率。相对于其他中子探测器，其具有结构简单，价格便宜，高计数率以及良好的时间和空间分辨等优点。

GEM气体探测器的抗辐射、方便读出等优点使其作为中子探测器成为可能。本项开展一种新型多层聚乙烯转化结构的GEM读出的快中子探测器的基础研究。在国内首次使用了多层高密度聚乙烯（ Multi layers High Density Polyethylene）作为高效快中子转化新结构。通过软件 ANSYS、Garfield++和 Geant4 对它的合理性和性能进行了详细地建模和理论计算。完成了多层 HDPE 转化结构的快中子探测器的设计、加工和测试。为下一步研发一种性能可靠的新型快中子检测系统打下良好的理论与技术基础。