基于微结构电子倍增器的弱光成像系统

Design a Microstructure Photomultiplier Assembly (MPA) that enables the effective conversion of light signals (received at the front of the assembly) into readily-detectable electrical signals. The MPA comprises a photocathode, followed by an electron-multiplying plate(s) made from an insulating substrate which does not emit sufficient contaminants to poison the photocathode. Each plate is coated with a conductive layer. The front face of each plate is further coated with a layer of secondary electron-emissive material which, when struck by an incoming electron, can produce secondary electrons. Each plate is perforated with channels. The channels are designed to promote the efficient transfer and acceleration of electrons through the channels, under an applied voltage differential across the plate(s). An anode (pixelated or not pixelated ) at the end of the last plate collects the electrons and generates an electrical signal. The MPA is contained within a vacuum enclosure.MPA relates to the field of photo-detectors and in particular to devices commonly called photomultipliers or microchannel plates Whose function is to convert a Weak light signal, as may be emitted by certain radiation scintillators (eg a NaI(TI) crystal), to an electronic pulse that can be readily processed by conventional analogue and digital electronics. Such devices are also used in the detection of light signals associated with industrial, medical, astronomy or optical communication.

本项目研制一套基于微结构板的光电倍增器（Microstructure Photomultiplier Assembly, MPA），MPA可以有效的将入射光信号转化成电信号，MPA由光阴极、电子倍增板、读出阳极板构成。电子倍增板为微孔结构绝缘板构成，双面幅度导电材料，且面向光阴极一侧涂覆易产生二次电子材料，电子倍增板的绝缘材料基材可以保证不会产生腐蚀物质损坏光阴极，光电子与电子倍增板作用后产生二次电子，通过板间的电压差加速吸出，实现电子倍增；阳极可由像素型或非像素型构成，用于收集光电子产生电信号。MPA与光电倍增管或微通道板的功能相同，主要功能为光子探测，其优点在于加工成本低，有效探测器面积大及位置灵敏，MPA将晶体产生的微弱荧光转化为可以被模拟电路与数字电路记录的电脉冲，同时此设备也可应用工业、医学以及天文观测等一切需要大面积，位置灵敏的弱光探测场合。

通过本基金的支持，完成硬件设计与性能研究两部分工作。.硬件设计部分，根据电子倍增器GEM 原理，研制一套基于双层THGEM 的弱光成像系统。目前已完成工作内容：成像系统腔体设计与加工，腔体由窗、THGEM1、THGEM2、十字交叉阳极板构成；128 路模拟信号获取系统，由两个模块构成，此电子学系统针对十字交叉型阳极信号读出设计，X、Y 方向分别为64 路，核心器件采用IDEAL 公司ASIC 芯片管芯，采用无管壳封装形式，以适应小体积、高密电子学系统设计，在线数据获取PC 端软件通过LABVIEW 编写，最多可获取7个64 数据获取模块数据；.性能研究部分，用55Fe 放射源，在流气模式下分别提取了Anode、THGEM2、THGEM1 的信号，记录了信号的幅度和时间信息，测量了该探测器在稳定工作区间的位置分辨，通过测试发现两个月内每次开机重复性好，条件稳定，且每次工作4小时或以上皆稳定。目前探测器本征位置分辨达到400μm，具备一定的成像能力，同时也研究了β射线在腔体灵敏空间内能量沉积响应，通过本项目的研究，为未来集成成像数字型探测器测量以及应用提供了一个较好的思路