预热影响柱收缩几何Rayleigh-Taylor不稳定性的特性研究

The convergent hydrodynamics instability exists in many fields, such as inertial confinement fusion (ICF), astrophysics and so on. In the indirect-driven implosion of ICF, multi-keV X-ray penetrates the ablation layer with low atomic number and causes preheating, resulting in the change of density distribution, Atwood number, acceleration and so on. Preheating leads the evolution of hydrodynamic instability in the cylindrical geometry to be much more complex than that in the plane geometry, because of its coupling with convergence effect by compressibility. The influence of preheating on hydrodynamics instability in the convergent geometry is rarely reported. This project aims to study the physical mechanism of the influence of preheating on the Rayleigh-Taylor (RT) instability in the cylindrical geometry by theoretical analysis and numerical simulation. By innovative preheating control method, the verification experiments of RT instability growth with different preheating are to be carried out in the cylindrical geometry. The results will be of great significance to optimize the ignition targets design in ICF by balancing the inhibition of instability growth and the low entropy compression of fuel, but also provide a new research tool for the supernova revolution and other astrophysical phenomena.

收缩几何流体力学不稳定性广泛存在于激光惯性约束聚变（ICF）、天体物理等诸多领域。在间接驱动ICF内爆过程中，数keV高能X射线易穿透低原子序数的烧蚀层而引起预热，导致密度分布、Atwood数、加速度等发生改变。在柱几何下，预热还将通过物质的可压缩度与几何效应相互耦合，引起比平面几何更加复杂的流体力学不稳定性演化。预热影响收缩几何流体力学不稳定性的特性是目前研究相对欠缺的关键科学问题。本项目拟通过理论和模拟方法，耦合高能量密度物理和流体力学研究，获得预热影响柱几何Rayleigh-Taylor（RT）不稳定性增长的基本规律和物理机制；拟基于神光系列激光装置创造的高能量密度条件，采用创新预热调控方法开展不同预热程度的柱几何RT不稳定性验证实验。本项目对ICF内爆靶丸优化设计以实现抑制不稳定性增长和燃料低熵增高压缩的平衡具有重要意义，也可为超新星爆发等天体物理现象提供新的研究手段。

预热影响收缩几何流体力学不稳定性的特性研究，对于ICF点火靶实验的优化控制和研究超新星爆发等天体物理现象具有重要意义。本项目基于大型激光装置，在平面几何下验证了峰值辐射温度≤250eV时100μm厚的CHBr（掺Br原子比3%）层可以有效阻挡金黑腔M带X射线对Al样品的预热、使其处于非熔化状态，相应的预热控制措施可服务于ICF和实验室天体物理实验研究中的预热屏蔽设计；在柱收缩几何下，通过在CH泡沫中增加CH柱芯并采用5.2keV和8.0keV两种不同能点的背光照相，较为完整地获取了Al样品内界面减速阶段的RT不稳定性增长数据，本方法已服务于高能量密度收缩几何内界面失稳混合的实验设计；对于柱收缩几何多层物质内爆时，通过MULTI一维辐射流体程序调整金黑腔内的M带份额，研究了不同预热程度下柱收缩几何Atwood数、加速度、密度梯度致稳等的变化，有助于理解多层物质收缩几何流体力学不稳定性增长的物理机制，促进ICF点火靶实验的优化控制和对超新星爆发等天体物理现象的新理解。