强激光间接驱动材料动态破碎过程的实验技术研究

强激光驱动加载已成为冲击波作用下材料动态破碎过程研究的一种有效手段.采用间接驱动方式,设计合适的腔型进行物理实验研究,可实现更大且更均匀的冲击加载一维区.采用数值模拟和物理实验方法,研究强激光间接驱动材料动态破碎过程的实验技术.首先,利用IRAD程序设计适用于开展动态破碎过程研究的半柱腔,其直径为2 mm、腔长为2 mm;进而通过物理实验获得此腔型下多个激光能量点、脉宽2 ns和3 ns条件下辐射峰值温度和波形;最后,利用流体模拟方法给出多种辐射波形下的冲击加载波形.利用高能X射线成像和光子多普勒干涉仪诊断给出间接驱动加载下层裂过程的物理图像和速度历史.经分析发现,间接驱动的加载一维区达到2 mm,平面性优于5%,能有效地开展相关物理实验研究.研究结果为新型柱腔设计、冲击加载技术及动态破碎过程研究提供了重要的研究基础.

Experimental technique for dynamic fragmentation of materials via indirect drive by high-intensity laser

High intensity laser is an efficient method for shock generator to study the dynamic fragmentation of materials,in which the direct drive is widely utilized.The continuum phase plate is used for smoothing the focal spot of the laser,but the loading region is usually smaller than the designed value.In this work,we study an experimental technique for investigating the dynamic fragmentation of metal via indirectly driving a highintensity laser.Firstly,the radiation distributions on the sample for four different hohlraums each with a diameter of 2 mm but different length are simulated via the IRAD software,in which the proper hohlraum with a diameter of 2 mm and a height of 2 mm is selected for the experiments.Secondly,the peak temperatures and radiation waves under different laser energy and pulse durations are measured.The peak temperature decreases simultaneously as the laser energy decreases.In addition,the loading shock waves under a peak temperature of140 e V and different radiation waves are estimated via the hydrodynamic simulation.It is revealed that a peak pressure of several tens of gigapascals is acquired and the peak pressure is greatly increased when the 10μm CH layer is placed on the sample.In the end,the dynamic fragmentation process via indirect drive is investigated by using the high energy X-ray radiography and photonic Doppler velocimetry.The radiograph is a snapshot at600 ns and shows a typical result of the spall process.The first layer is measured to be 0.06 mm thick and 0.3 mm away from the unperturbed free surface.It is also exhibited that the hohlraum is expanded to a large extent but is not broken up.The jump-up velocity and time of spall are measured to be 0.65 km/s and 131 ns,respectively.The average velocity of the first layer is estimated to be(0.63±0.1)km/s,obtained via the distance of 0.3 mm divided by the time difference of 469 ns(600 ns minus 131 ns).The one-dimensional loading region is 2 mm,and the flatness is better than 5%.This work provides a reference for designing new hohlraum,shock wave loading technique and dynamic fragmentation process.