应用于激光聚变诊断的闪烁成像型质子能谱在线测量技术研究

The energy spectrum of the D-3He reaction protons is one of the key parameters in the laser driven D-3He fuel inertial confinement fusion (ICF) physics research and the fundamental high energy density physics research. At the large laser fusion facilities, including NIF and OMEGA facilities in USA, the D-3He reaction proton spectra are usually measured by a wedged-range-filter (WRF) proton spectrometer based on the CR39 nuclear track detector. There are some intrinsic problems in this spectrometer, such as the difficulty of online measurement, the inconsistency between different spectrometers due to the piece-to-piece variations in CR39, low accuracy and so on. A novel online proton spectra measurement technique based on the scintillation imaging is proposed in this project. Through the combination of a wedged range filter and a fast response scintillator film, the proton spectrum will be transformed to the spatial distribution of the light emission image in the scintillator. By the introduction of the time-gated technique, the background induced by the hard X-rays and some other particles in the pulsed field will be suppressed. An optimized proton spectrum reconstruction code will also be developed. As a result, an online technique for pulsed proton spectra measurement with a high signal-to-noise ratio will be issued for the laser driven fusion plasma diagnostics. The problem of the inconsistency between different spectrometers can also be solved, so that the diagnostics accuracy of the implosion asymmetry and some other physics parameter, which needs the correlation analysis of the proton emission spectra in multi-angles, can be improved.

D-3He聚变质子能谱是激光驱动D-3He燃料惯性约束聚变物理实验和高能量密度物理基础研究中的一项关键物理参数。包括NIF和OMEGA在内的大型激光聚变装置目前采用基于CR39探测器的楔形滤片质子谱仪开展D-3He反应质子能谱测量，一直存在无法在线测量、谱仪间系统一致性较差和可靠性偏低等困扰。本项目提出建立一种闪烁发光成像型质子能谱在线测量技术，通过楔形滤片和薄膜闪烁体的组合实现质子能谱到闪烁体发光图像的转换，通过建立门控测量技术降低激光聚变脉冲场中硬X射线等信号的本底干扰，并发展质子能谱重建算法，实现激光驱动D-3He燃料聚变质子能谱的具有较高信噪比的在线诊断技术，同时解决谱仪测量的系统一致性问题，提高内爆压缩不对称性等物理参数的诊断精度。

D-He3聚变质子是激光间接驱动惯性约束聚变（ICF）的一种重要聚变产物，D-He3聚变质子能谱测量则是非D-T燃料下激光驱动ICF内爆实验中靶丸总面密度诊断的主要技术途径。目前包括美国NIF和OMEGA装置在内的大型激光聚变装置都采用该方法进行D燃料实验的内爆面密度诊断，但现有聚变质子谱仪均采用了基于CR39探测器的楔形滤片质子谱仪技术方案，一直存在无法在线测量、谱仪间系统一致性较差和可靠性偏低等困扰。本项目开展了一种楔形滤片调制闪烁成像型质子能谱测量技术研究，提出利用楔形滤片调制单元和超快时间响应闪烁体薄膜组合的方法，建立一种新的脉冲场质子能谱探测方法，用于实现激光驱动ICF内爆质子能谱在线测量，解决质子能谱测量时效性差、系统一致性等方面的问题。本项目已初步掌握基于楔形滤片调制闪烁成像的脉冲场质子能谱测量方法，突破了该谱仪多项关键技术，建立了蒙特卡洛方法的质子能谱响应模拟程序并详细计算了8-19MeV质子能谱响应矩阵，发展了基于最大熵算法的质子能谱重建程序，通过细致评估得到本项目质子能谱测量方法的能谱分辨在0.5-0.7MeV@14.7MeV，可解决传统质子谱仪无法在线测量、不同探测器能谱测量的系统一致性问题。本项目还完成谱仪工程设计并搭建了一套质子能谱测量技术原理演示装置，开展了多项质子信号背景噪声降低技术研究和系统结构设计，为该质子谱仪走向脉冲场质子能谱测量实用化应用奠定了基础。本项目开展了神光装置上约100kJ激光驱动D-He3燃料聚变初级质子能谱和D-D燃料次级D-3He质子能谱测量，初步分析了不同实验条件下的内爆压缩面密度，开展了楔形滤片调制质子谱仪的内爆面密度诊断方法演示。本项目发展的新型脉冲场质子能谱测量技术，未来具备较高潜力应用于我国最大的激光聚变实验装置，为我国激光驱动ICF实验提供一种先进的质子能谱诊断方法。