高耦合效率及对称性的黑腔构型柔性设计方法与实验研究

High-temperature and high-quality X-ray source generated from the warmed wall of hohlraum by incident lasers is an important means to conduct research on hydrodynamics, high-pressure equations of state, radiation transport, and atomic parameter under extreme conditions, which is very meaningful for high energy density physics such as controlled nuclear fusion or astrophysics. Such X-ray radiation and ablation is also utilized to drive the implosion of centrally located capsule in laser indirectly driven Inertial Confinement Fusion (ICF). In such ICF, the hohlraum is usually modelled with simple conical curves such as lines, ellipses, parabolas, or circles, which leads to only a few design parameters allowed for shape optimization, and difficulty in further improving its performance such efficiency and radiation symmetry. A novel representation approach, Non-uniform rational B-spline is proposed to represent the shape of hohlraum in this project, which can be used to uniformly and flexibly represent all the hohlraums for radiation computation, by modifying its control points and their weights. In addition, such flexible representation enables it possible to obtain an optimal shape over a large design domain for the holhraum with more uniform radiation and higher driven temperature on the capsule. Finally, hohlraum physical experiments on Shenguang III laser facility will be carried out to validate their performances including driven temperature and radiation symmetry, and then correct their design for the ICF research. Such approach has significant research and engineering meaning for its much generic representation property, since it can break the limit of current conical curve representation, and substantially expand the design domain to enable obtaining an optimal target for any laser facility.

利用激光注入黑腔被腔壁吸收转换而产生的X射线辐射源是进行流体动力学、高压状态方程、辐射输运及极端条件下原子参数等研究的重要手段，对受控核聚变、天体物理等高能量密度物理研究领域具有重要意义。激光间接驱动惯性约束聚变（ICF），也采用这种X射线辐射烧蚀驱动聚变靶丸内爆，实现中心点火。传统ICF黑腔均采用简单圆锥曲线构造，如直线、椭圆、抛物线及圆弧等，过于局限，设计自由度少，限制黑腔效率和品质的进一步提高。本申请拟采用非均匀有理B样条方法，通过调节控制点和权重，实现现有各种黑腔构型的统一柔性表示及辐射场计算，且可在更大优化空间寻找可能更为优化的腔形，使辐射场更均匀且靶丸表面驱动温度更高。在神光III激光装置上，开展有针对性的验证实验，检验这种设计的效果，并通过实验结果修正设计。该方法突破了传统黑腔构型采用圆锥曲线描述形式的局限性，更具一般性，拓展了优化设计域，可得到不同激光装置的最优黑腔构型。

黑腔几何构型设计是惯性约束聚变中十分重要的研究课题，它与激光与靶的耦合效率、辐射驱动对称性和等离子体填充效应等问题密切相关，直接关系到点火的成败并涉及耗资数十亿美元的驱动激光排布与装置结构。在ICF黑腔设计中，需要给出黑腔的形状、尺寸和激光注入孔个数的最佳设计。基于非均匀有理B样条函数表示理论，项目组提出柔性黑腔设计方法，突破以前黑腔外形轮廓只能采用圆锥曲线的局限性，实现现有腔型的统一表示和集中优化分析，研制出黑腔构型柔性设计软件IRAD3D，具备腔靶三维建模、激光排布设计及腔型优化分析等功能，已广泛应用于神光系列实验设计和分析。借助IRAD3D，优化设计出耦合效率高、对称性好的多种新型高效黑腔，并得到国内某大型激光装置的实验验证，可为ICF点火靶新型黑腔的设计提供重要参考。