基于X射线能谱的内爆热斑混合诊断方法研究

Mix is one of the key factors which limit the performance of the inertial confined fusion, and it is of critical importance to study the relationship between mix and fusion power. Mix is induced by hydrodanamic instabilties, including Rayleigh-Taylor instability,Richtmyer-Meshkov instability and Kelvin-Helmoltz instablity. Although discovered at the beginning phase of inertial confined fusion, the underlying physics of mix still remains ambiguous, while the corresponding diagnosis is also rudimentary. In this application, an experiemntal technique based on continuous X-ray energy spectrum measurement for mix mass diagnosis is proposed. A model will be established for the assessment of the mix mass with the ratio between the X-ray yield and neutron yield.An elliptical crystall spectrometer will be employed for the energy spectrum measurement of the X-ray emission for the implosion core. The relationship between the integrated diffraction efficiency and the curvature of the elliptical crystall will be investigated, and the absolute detection efficicency of the spectrometer will be obtained in combination with theoretical study and experimental measurement.With this research, it is expected that the relationship between the mix mass and the implosion performance would be obtained experimentally.

内爆热斑混合是影响惯性约束聚变等离子体压缩的关键因素，是激光惯性约束聚变领域的研究热点与难点。内爆热斑混合由流体力学不稳定性引起，其物理机制十分复杂，相关诊断实验长期以来非常缺乏。本项目拟通过连续谱X射线产额测量，开展诊断混合质量的实验方法研究。建立连续谱X射线与中子产额比和混合质量之间的理论模型，依据实验结果给出混合质量。使用椭圆晶体谱仪测量X射线连续谱，深入研究椭圆晶体谱仪积分衍射效率与椭圆曲率的关系，并结合标定实验给出椭圆晶体谱仪绝对探测效率。预期通过本项目的研究，从实验上给出混合质量与聚变功率之间的关系。

本项目开展了惯性约束聚变实验方法研究，建立了内爆热斑均匀混合模型，在考虑热斑及推进层材料不透明度的情况下，计算了不同热斑温度、密度条件下连续谱X射线产额，给出了连续谱X射线产额与中子产额比与混合质量之间关系的理论模型。完成了椭圆晶体谱仪物理设计和工程研制，在同济大学X射线管实验室开展了测试实验，表明椭圆晶体在6.4 keV能点处的能量分辨优于146 eV，获得了椭圆晶体中心位置处对于6.4 keV能量X射线的积分衍射效率。在大型激光装置均匀掺杂内爆混合实验中，通过条纹晶体谱仪获得了聚变区示踪元素Ar的时间分辨光谱信息，从中观测到电子温度先上升后下降、密度上升并保持的等离子体状态时间演化过程，同时获得了中子产额与靶丸内掺杂量之间的关系，显示出在靶丸内掺杂Ar元素且掺杂0.1%原子比的Xe元素时，聚变功率将迅速下降。