温度相位匹配条件下大口径非线性晶体组件的热流固耦合作用机理研究

The rational thermal structure design is the key factor to determine the performance of large aperture nonlinear crystal under the condition of temperature phase matching. This proposal focuses on the phenomena of crystal clamping deformation and uneven temperature distribution in the design of large aperture nonlinear crystal modules in inertial confinement fusion devices. First of all, a multi-scale simulation and experimental method is used to study the dynamic evolution mechanism of gas flow field and temperature field in the final optical assembly under different heating modes and positions, and the influence rule on the temperature field of the crystal is also analyzed. Secondly, the heat transfer model between the crystal and the crystal frame based on the micromorphology of the contact region is established. The heat transfer characteristics and stress distribution between the crystal components in the thermal-fluid-structure coupling are studied. Furthermore, the clamping method of the crystal components under the thermal-fluid-structure coupling and the mechanical processing requirements of the crystal frame are put forward. Lastly, the method of tracing the source of dynamic error is put forward, and the cause of the reduction of frequency doubling conversion efficiency caused by coupling factors is traced. The mapping relationship between the frequency conversion efficiency and the coupling fields is revealed, and the weight of each coupling factor in the influence of the frequency doubling conversion efficiency is obtained, and the thermal structure design theory of the large diameter crystal assembly is perfected. The research results of the project have important theoretical and application value for solving the problem of thermal structure design of large aperture crystal components.

合理的热结构设计是决定温度相位匹配条件下大口径非线性晶体工作性能的关键。本项目针对惯性约束聚变装置中大口径非线性晶体组件在热结构设计时，热流固耦合作用造成的晶体夹持变形和温度分布不均的现象进行研究。首先，采用多尺度仿真与实验相结合的方法，研究不同加热方式和位姿条件对终端光学组件内气体的流场和温度场的影响规律，进而揭示晶体温度场的动态演变机理。其次，建立基于接触区域微观形貌的晶体与晶体框之间的传热模型，研究热流固耦合作用下晶体组件间的传热特性以及应力分布，提出晶体组件的夹持方法及晶体框的机械加工工艺要求。最后，提出动态误差溯源分析方法，对因耦合因素造成的倍频转换效率降低的原因进行溯源，揭示倍频转换效率与各耦合场之间的映射关系，获得各耦合因素在晶体倍频转换效率影响中所占的权重，完善大口径晶体组件的热结构设计理论。项目的研究成果对于解决大口径晶体组件热结构设计问题具有重要的理论和应用价值。

惯性约束聚变是我国中长期科学和技术发展规划的十六项重大专项之一。本项目针对惯性约束聚变装置中大口径非线性晶体组件在热结构设计时，热流固耦合作用造成的晶体夹持变形和温度分布不均的现象进行研究，探究热流固耦合作用对大口径晶体组件的影响规律，并提出合理的大口径非线性晶体热结构设计方案。项目中首先针对晶体与金属晶体框之间的传热机理不明进行研究，采用理论仿真与实验验证相结合的方法，得到加热温度、热流方向、加载应力和晶体切割方式对晶体与金属接触对间传热的影响；然后，根据晶体的加热机理，搭建不同形式的加热方案，揭示了采用热对流加热方案、热对流与热传导相结合的两种方案对晶体温度分布的影响规律，其中通过多尺度仿真方法得到密闭腔体内气体的流动规律，通过有限体积法和实验验证方法得到不同加热情况下的晶体温度分布规律；第三，采用有限体积法和实验验证相结合的方法得到不同动态气氛、装备工作位姿对晶体温度分布的影响，得到了各因素对晶体温度分布的影响权重；最后，根据所获得的传热机理，提出了一种大口径非线性晶体强化加热方案，该方案可将晶体温度快速稳定的达到预定工作状态；同时根据热流固耦合传热机理提出高斯温度分布时晶体的加热方法。该项目的研究成果已经成功应用于ICF装置中，实现了大口径晶体温度分布的高精度调控。