低能粒子探测器系统的研制

Performing β delayed particle spectroscopy in studying β delay particle emitters experiment over recent years, the high β background and detection efficient for low energy particle becomes a very severe problem. A novel detection system based GEM amplification stage for very low energy particle from β delayed particle decay is capable of observing low energy particle in high β background environment, for example, allowing the measurement of proton peaks as low as 200 keV with p(24Mg, 23Al)2n reaction. The main components of the detector system is drift region based on equipotential ring, gating grid (GG), and GEM detector (gas amplifier).The operating principle of the detector system is similar to that of a gas Time Projection Chamber (TPC), where drift electrons from the ionization of the gas created by particles losing energy in the active volume drift towards the GG and are collected on GEM detector. This excellent advantages is due to next factor: the GEM detector is a high gain and good charge resolution; the exotic nuclei are implanted inside the detector itself (no windows or dead layers for the particle emitted); gas detection is low sensitivity to the positions and gammas. It is not only upgraded to our experimental equipment, but also an excellent tool for the study of resonances of interest in nuclear astrophysics.

近年来在探测β延发粒子衰变的的在束实验中，一直面临着高β本底和探测效率等问题的困扰。本项目的低能粒子探测器系统是为β延发粒子衰变的低能质子和α粒子探测与鉴别的需要而研制, 该探测器的结构类似气体时间投影室内（TPC），有漂移区和具有GEM放大读出探测器构成。该探测器利用其门电极（GG）判选来获取β延发衰变的粒子能损∆E和E信号。它具有探测衰变的低能粒子特性，如在β延发质子（βp）衰变中，可探测到200keV左右能量的质子。其主要特点是： 高增益和良好的能量分辨，次级束核素在其腔体内衰变（避免了探测器窗、中间介质和死区等对衰变的低能粒子（如p和α）探测影响）以及对β粒子和γ射线的低灵敏性等方面。该低能粒子探测器系统的研制在国际上刚刚开始，获得相关的关键技术，不仅对我们现有的探测器装置的升级改造有非常重要的意义，也是天体核反应共振峰的研究中β延发粒子衰变低能粒子探测一种有效手段。

近年来在探测β延发粒子衰变实验中，一直受到高β本底和探测效率等问题的困扰。传统探测器技术因为探测效率低而无法达到测量的要求，时间投影室（Time Projection Chamber，TPC）是一致可以运用于粒子物理与核物理实验中的气体探测器，可以获得进入其漂移场内的带电粒子的三维径迹和能量损失，具有较好的能量分辨和很高的位置分辨能力。该项目中采用GEM读出TPC相对于传统丝室TPC具有明显的优势：二维读出各项同性，空间分辨在亚毫米量级已经能很好的抑制正离子反馈能力。通过对GEM读出TPC探测器的设计、搭建和各项测试，我们得到了各项参数，包括能量分辨和位置分辨等信息，并通过在束实验研制了该项目提出的探测器系统满足中低能核物理实验的要求，同时为今后有关TPC的搭建积累经验和提供实验测试参数。本项目探测器系统因为高探测器效率的优势可替代传统实验技术来满足实验的要求。