激光辐照下熔石英表面损伤的原子模拟

Atomic simulation of surface damage of fused silica under laser irradiation

熔石英光学元件是惯性约束核聚变点火装置的核心部件,由于该装置严苛的点火条件对高功率激光的需求,熔石英光学元件在强激光下的损伤是制约点火装置运行的关键.因此,研究激光辐照下熔石英的表面损伤对惯性约束核聚变点火装置的研制至关重要.本文采用大规模非平衡分子动力学模拟方法和适用于动态过程的微结构分析技术,研究激光加载下熔石英表面的损伤过程,基于理论研究的高温等离子体火球模型模拟高温熔石英等离子体球对熔石英表面的破坏,通过跟踪局域结构、温度分布和表面形貌状态,分析影响熔石英表面损伤的因素.研究表明,高温熔石英球的尺寸、距表面的距离和温度都对熔石英表面的破坏具有重要的影响.本文可为认识激光辐照下熔石英中复杂的损伤过程提供指导.

Fused silica optical element is the core component of the inertial confinement nuclear fusion ignition device.Due to the requirement of ignition conditions of the device for high power laser,the damage to fused silica optical element under strong laser is the key to restricting the operation of the ignition device.Therefore,the study of the surface damage of fused silica irradiated by laser is crucial to the development of the ignition device for inertial confinement nuclear fusion.In this paper,large-scale non-equilibrium molecular dynamics simulation method and micro-structure analysis technology suitable for dynamic process are proposed to study the damage process of fused silica surface under laser loading.Based on the theoretical study of hightemperature plasma fireball model,the damage of high-temperature fused silica plasma ball to surface is simulated.By tracking the local structure,temperature distribution and surface morphology,the factors affecting the surface damage of fused silica are analyzed.Our research results show that the size,distance from the surface,and temperature of high-temperature fused silica balls have important effects on the surface damage.We find that there are two different damage modes under the combined effect of the above factors.One is related to a rapid damage process,generating U-shaped voids and no further obvious damages after the surface spraying,and the other is dependent of a slow damage process:continuously expanding and resulting in a larger damage area.The surface morphologies formed by these two damage modes are consistent with the two typical damage morphologies observed in the experiments.This research can provide a guidance for understanding the complex damage process in fused silica under laser irradiation.