纳秒激光冲击加载的全过程诊断

 与传统的冲击加载方式相比，激光驱动试样具有微尺寸（直径小于1 mm，厚度约10 μm）、超短作用过程（纳秒量级）等特点，但其速度变化历史的实时诊断颇为困难，因此发展适用于激光驱动的高时空分辨率的实时测试技术是十分重要和有价值的。采用桌面式脉冲Nd:YAG激光器作为加载平台，发展了激光加载下的小焦点多普勒光纤探针测量系统（焦斑直径约200 μm，时间分辨力约50 ps），成功实现了从激光脉冲驱动微尺寸飞片飞行直至撞击Z-切石英试样的全过程实时诊断。实验结果显示，将6 μm 厚Al箔飞片驱动至2.48 km/s时，撞击Z-切石英试样的粒子速度为1.27 km/s，与Hugoniot理论计算结果相符，表明该测试技术是可靠、有效的；多层薄膜靶结构设计（基底/烧蚀层/硅油/Al箔）可提升激光与靶物质的能量耦合效率，使飞片保持更好的宏观完整性。为开展超短脉冲激光加载下材料动态特性研究提供了一种有效的技术途径。

An Integrated Velocity Profile Measurement from Nanosecond Pulse Laser-Driven Mini-Flyer to Shocked Sample

It is very important to develop a high time and space resolved velocity diagnostic technique for laser-driven shock wave experiments.However,it is still a difficult problem because of the limited size of laser-launched mini-flyer and ultra-short loading time in shocked sample.Thus,a micro focus Doppler pins system with time resolution of 50 ps and spatial resolution of 200 mm has been developed in our nanosecond laser-driven shock wave experiments,to perform an integrated velocity profile measurement from laser driven mini-flyer to impacted sample.The measured particle velocity of Z-cut quartz sample is 1.27 km/s while the impact velocity of 6 μm-thick Al foil flyer is 2.48 km/s,which is in agreement with the calculated Hugoniot results.This validates our technique.Using our technique,the experimental results for three different types of mini-flyers show that the "substrate/deposit layer/silicone oil/Al foil flyer" structure has higher laser energy coupling efficiency and better integrity.This is valuable for designing a laser-driven shock wave experimental assembly.These results indicate that our technique is a viable approach for studying dynamics of laser-driven shock wave in materials.