基于微结构靶材的激光X射线源光子产额优化

In order to satisfy the diagnosing demands for x-ray source with high flux of material structure and property studying under extreme conditions, the photon yield of x-ray source generated from ultra-short and ultra-intense laser interaction with metal target should be further improved and optimized. As the first step of this process, the absorptance of target to incident laser is one of the most important factors. In this project, the improvement of photon yield of x-ray source with small point spot size would be achieved via the employing of femtosecond laser fabricated high absorptance microstructure targets on metal copper surface. The following two goals would be achieved when this project is finished: firstly, the progressive evolution mechanism of laser fabricated microstructures and the physical mechanism of absorptance improving would be explained respectively, and the key experiment parameters for fabricating microstructures would be decided; secondly, the physical model and experiment system for laser interaction with structured target for x-ray source would be established respectively, and the key experiment parameters for generation of high photon yield x-ray source would be decided. This work would be an alternative choice for diagnosing source of material researching under extreme conditions.

为满足极端条件下材料结构和性质的研究对高通量X射线源的需求，超短超强激光驱动金属靶材产生的X射线辐射源在光子产额方面尚需优化。作为激光驱动靶材产生X射线源的第一步，靶材对激光的吸收率是影响光子产额的关键因素。本项目拟借助飞秒激光加工技术在金属铜表面构造微结构，最大限度地提升激光能量的吸收效率，在保证小点源尺寸的前提下实现X射线源光子产额的优化。通过本项目研究，实现两个目标：（1）揭示飞秒激光构造微结构的演化规律及其对吸收光谱的调控机制，掌握构造高吸收微结构靶材的关键参数；（2）建立超短超强激光驱动金属微结构靶材产生X射线源的物理模型和实验系统，揭示微结构类型对光子产额的调控规律，掌握获取高光子产额X射线源的关键参数，从而为极端条件下材料结构和性质的研究提供性能稳定的诊断源。

本项目围绕“微结构靶材实现激光X射线源光子产额优化”的研究目标，开展了飞秒激光加工金属Cu微结构靶材和激光驱动金属微结构靶材产生X射线源两个方面的实验研究，取得的主要研究进展有：1）基于“集成化/一体化控制”的思路，研发了飞秒激光加工控制软件，为加工实验效率的提升奠定了重要基础；2）基于运动补偿的思路，提出了焦平面实时校正的新方法，实现了低反射且分布均匀的金属微结构靶材加工，获得了微结构演化的规律及其对反射光谱的调控规律，掌握了飞秒激光加工低反射且分布均匀微结构靶材的关键参数；3）基于“集成化/一体化控制”的思路，研发了超短超强激光X射线实验真空光路调控软件，为实验效率的提升奠定了重要基础；4）基于超短超强激光X射线实验光路系统，获得了激光驱动微结构靶材产生的X射线源能谱曲线及光子产额。从微结构的特征尺寸和化学成分两个方面，分析了未能实现光子产额优化的物理原因，为今后激光X射线源光子产额的的优化提供了借鉴；5）提出了一种紧凑型大量程电子磁谱仪的研制方案，为激光X射线源实验提供了必要的超热电子能谱测量设备。