含氢类金刚石聚变靶丸壳层的表面粗糙度与结构控制机理研究

Laser inertial confinement fusion (ICF) is one of the main methods to realize fusion energy utilization, and an important research field of international power competition. The hydrogenated amorphous carbon (a-C:H) coatings have exceptional infrared transmittivity, which is benefit to infrared homogenization of deuterium tritium ice in fusion targets. Based on these advantages, a-C:H coating has become the most preferred target shell material in ICF targets design. In ICF experiment, rough surface of the shell will lead to the implosion failure since the surface roughness of the shell can seriously affect the fluid dynamics instability in the ICF implosion process. In this situation, there are rigorous requirements on the surface roughness of a-C:H targets, for example, when the wall thickness of targets exceeds 100 μm the surface roughness must lower than 20 nm. For this reason, we suggest to study the dynamic process of thick a-C:H coating in the process of degradation of mandrel, discover the affecting factors of surface roughness and the production mechanism of surface defects, and explore the surface deformation behavior during the degradation process. And then, it is possible to find the effective measures in controlling the surface roughness of a-C:H coatings and establish the corresponding relationship between the content of internal components H, sp2C, sp3C and infrared transmittivity of the coatings. Meanwhile, we can control the changes of internal structure during degradation to ensure that the coating remains in good infrared homogenization characteristics. The implementation of this project well be of great significance for the preparation of a-C:H targets meeting the requirements of ICF physical experiments.

激光惯性约束聚变（ICF）是实现聚变能源利用的主要方法之一，也是当前国际大国竞争的重要研究领域。含氢类金刚石（a-C:H）涂层，具有良好的红外透过性，能有效实现聚变靶丸中氘氚冰层的红外均化处理，是ICF靶丸设计中的首选壳层材料。由于壳层表面粗糙度会严重影响ICF内爆过程的流体力学不稳定性，进而导致点火失败。因此，ICF靶丸设计中对该壳层表面粗糙度提出了严苛要求（即厚度>100μm，Rq<20nm）。针对这一难题，本项目拟研究大厚度a-C:H涂层在降解过程中的动力学过程，分析降解过程对表面粗糙度的影响因素与表面缺陷的产生机理，探究大厚度涂层的表面变形行为，提出控制a-C:H涂层表面粗糙度的有效手段。同时，建立涂层内部组分H、sp2C、sp3C含量与红外透过性的对应关系，控制涂层内部结构变化，以确保涂层具有良好的红外均化特性。本项目的实施对制备出满足ICF实验需求的a-C:H靶丸具有重要意义。

本项目从热力学与动力学角度出发，采用FTIR、WLI、SEM等表征手段探索了大厚度a-C:H涂层在热降解过程中的动力学过程，研究了加热温度、保温时间以及升温速率对大厚度a-C:H涂层表面形貌与表面粗糙度等的影响机制，分析了热降解过程中表面形貌与表面颗粒尺寸的变化情况以及涂层表面颗粒之间的团聚现象随温度变化的演化轨迹，探究了a-C:H涂层表面皱缩与表面缺陷的形成机理。同时，针对大厚度的a-C:H涂层热降解前后的力学性能进行了表征，分析了降解过程中其硬度、弹性模量、微观应力等的变化规律，揭示了大厚度a-C:H涂层在降解过程中的表面变形行为与变形模式转变的作用机制。本项目也建立了涂层内部组分H、sp2C、sp3C等含量与涂层红外透过性的对应关系，揭示了不同温度分布对大厚度a-C:H涂层内部结构的影响，并提出了降解温度维持在300 ℃，升温速率0.2 ℃/min，保温24 h，是控制大厚度a-C:H涂层表面粗糙度与结构的最佳工艺参数。这将为制备出满足ICF物理实验需求的a-C:H靶丸具有重要理论和实践指导意义。