大径厚比光学元件低应力夹持多因素耦合作用机理及实验研究

Clamping in low stress of optical elements with high radius-thickness ratio is one of the key technologies which restrict the efficiency and energy-output of ICF equipment in China. This paper studies microscopic characteristics of contact area, and develops a theoretical model of multiscale contact based on residual stress and crack as well as micro-defects in interface/sub-surface; Meanwhile, we analyse influencing factors of residual stress and crack & micro-defects of interface between crystal and crystal frame parts, and study its influence to contact force and contact property; A mathematical model is established based on deformation of crystal frame parts in residual stress; Accordingly, it enhances secular stability of the accuracy of crystal frame parts; Combining with experiment and texting technology, an interactional mechanism between KDP crystal and crystal frame is researched based on micro-topography in interface, and analyse influence factors of the surface accuracy of crystal in partial contact; Dynamic performance of clamping system and dynamic interactional mechanism between KDP crystal and crystal frame are also researched, analyse influence factors of the surface accuracy of crystal in dynamic stress coupling; Combining with FEA technology, design principles of clamping and evaluation criterion of surface error of crystal surface are developed, and sum up a design theory of clamping in low stress of optical elements with high radius-thickness ratio. It's a significant technology for the clamping in low stress of optical elements as well as the development and application of surface contact theory.

大径厚比光学元件的低应力夹持技术是制约我国惯性约束核聚（ICF）装置输出能量和运行效率提高的关键技术之一。本项目对接触表面微观特性进行研究，建立基于接触表面/亚表面残余应力、裂纹及微观缺陷的多尺度接触理论模型，分析晶体和晶体框接触时残余应力、裂纹及微观缺陷的相互影响规律，及其对接触力和接触特性的影响规律；结合实验和测试技术，研究基于接触区域微观形貌的KDP晶体与晶体框之间相互作用机理，分析局部接触状态下晶体面形精度的影响规律；研究夹持系统动态特性及KDP晶体与晶体框动态相互作用机理，分析动态条件下应力耦合作用机理对KDP晶体面形精度的影响规律；结合有限元分析技术，归纳夹持支撑设计原则和晶体表面面形误差评价标准，建立大径厚比光学元件低应力夹持的设计理论。这对于光学元件低应力夹持技术和表面接触理论的发展和应用均具有重要意义。

本项目针对大径厚比KDP晶体的低应力夹持技术展开研究，有效提高了惯性约束核聚变终端光学组件的输出能量和运行效率，在晶体和晶体框加工表面质量、晶体与晶体框接触特性、晶体夹持方案以及夹持系统的动静态特性等方面取得了新的进展和突破。系统研究了晶体框低应力超精密加工工艺及加工表面完整性，确定了保证晶体框平面度和粗糙度的加工工艺，建立了加工表面残余应力预测模型和有限元分析模型以及晶体框表面粗糙度回归模型，并在此基础之上建立了晶体和晶体框多尺度接触模型。同时还进行了晶体加工实验，晶体表面粗糙度可以达到2.19nm，表面波纹度小于10nm，满足惯性约束激光核聚变系统的使用要求；深入研究了晶体和晶体框之间的相互作用机理，揭示了晶体与晶体框局部接触变形机理，得到了接触面粗糙度和平面度对晶体应力和变形的影响规律，进而确定了谐波转换效率的关键影响因素，并阐述了晶体变形和应力的表征方法。系统研究了夹持系统的动态特性，揭示了晶体与晶体框动态作用机理，得到了冲击条件下晶体夹持应力和面形精度的变化规律以及激光冲击对谐波转换效率的影响规律；系统研究了大径厚比KDP晶体低应力夹持方案，建立了晶体夹持变形的理论预测模型以及谐波转换效率与晶体力学参数的数学模型，得到了夹持参数和晶体应力参数对谐波转换效率的影响规律，确定了全周长夹持和力矩夹持方案。通过本项目的研究，获得了晶体夹持面形精度优于3λ（1.854μm）和平面度优于5μm 的晶体框，研究成果很好的应用于惯性约束核聚变终端光学组件系统中。