空间SCD质子辐照损伤实验研究

Dectection of space Low-energy X-ray is an important approach to studying cosmic soft X-ray background, pulsars and other related astrophysical focuses. Sweep Charge device (SCD), owing to good X-ray energy resolution and fast readout of whole chip, is an ideal detector for low-energy X-ray. In the radiation space, charged particles will damage SCD; in particular the protons will gradually reduce the performance of SCD. Therefore, studying proton radiation damage effects on SCD is extremely important for in-orbital operation of SCD. So far, both domestic and abroad researches in this area that studies proton radiation damage of space charge coupled device (CCD), mainly focus on the image X-ray CCD. It is still a lack of systematic study on proton damage of SCD. In this project, we address the physical damage issues of SCD, a special type of CCD. By using accelerator-based proton radiation method, we will acquire responses of proton radiation in several key parameters of SCD, such as readout noise, energy resolution, charge transfer efficiency, split events, etc. The major aim of this project is to illustrate the physical mechanism of proton radiation damage on SCD, meanwhile, the major results can provide important experimental data and data optimization method for the Hard X-ray Modulation Telescope (HXMT) and help to promote innovation and creativity of advanced technologies in China.

低能X射线空间探测，是研究宇宙低能X射线背景、脉冲星等相关天体物理热点的重要手段。扫式电荷器件（SCD）具有良好的X射线能量分辨能力和极快的整片读出速度，是理想的低能X 射线探测器。在空间辐照环境中，带电粒子对SCD会造成损伤，尤其是质子辐照，会逐渐降低SCD在轨性能。因此，开展SCD质子辐照损伤研究对优化SCD在轨运行具有重要意义。目前国内外研究空间电荷有耦合器件（CCD）质子辐照损伤集中在成像X射线CCD，尚无针对SCD质子损伤的系统研究。本项目专门针对SCD这一特殊CCD的辐照损伤问题，采用加速器质子辐照的方法，获取SCD读出噪声、能量分辨、电荷转移效率、分裂事例等指标，研究其质子损伤。本项目旨在系统研究质子辐照对SCD损伤的机理，同时，为硬X 调制望远镜（HXMT）重大项目提供重要实验数据和数据优化方法，有利于提升我国先进技术自主创新能力。

本项目在基金委的支持下，结合HXMT慧眼项目的研制过程，目的是掌握质子辐照对扫式电荷器件（SCD）的损伤机理。项目组通过数次质子束流辐照试验及实验前后详细真空低温性能测试，测定了SCD在承受在轨辐照剂量后的能量分辨（250eV@5.9keV，-40℃），使用多孔膜方法测定了SCD读出电极电荷转移效率（CTE），并排除了电荷转移“奇点”。分析实验数据，确定了HXMT慧眼使用的SCD在寿命末期依然可以达到性能指标要求（450eV@5.9keV，-40℃）。统计所有数据，发现了SCD辐照后性能的“退火”现象，并使用电荷注入的方式对SCD能量分辨进行一定改善。.通过本项目的研究，掌握了SCD的质子辐照损伤机理主要为电荷转移效率降低，完整电子云应有的信号幅度被降低，使得能谱主峰发生展宽。定量分析为HXMT慧眼提供了有利支撑，并且这套实验方法可以用到未来的X射线天文探测器卫星，如EP、eXTP等项目。