加速膛对激光驱动飞片速度及形貌的影响规律

为揭示加速膛对激光驱动飞片速度及形貌的影响规律,采用光子多普勒测速(PDV)技术、阴影成像技术和显微分析方法研究了厚度20μm单层Al飞片在不同加速膛孔径和长度下的速度和形貌演化历程。结果表明,加速膛孔径与Al飞片被激光烧蚀的孔径大小相当时,即孔径在800μm时飞片可获得3100 m·s^-1的最大速度;加速膛孔径大于800μm时对飞片无法起到有效约束作用,飞片速度有所下降,其中加速膛孔径为1500μm时飞片速度最小,为2700 m·s^-1;加速膛孔径为600μm小于激光烧蚀孔径时,造成周围部分能量的浪费,飞片速度也偏低,为2900 m·s^-1。固定加速膛孔径为1000μm,长度在200~700μm时,飞片速度随加速膛长度增加而明显降低,并且Al飞片在飞出加速膛后均破裂成碎片状并迅速向周围扩散,无法保持完整,飞片碎片总体向外扩散速度随加速膛长度的增加而降低,与PDV获得的飞片速度规律基本一致。

Influence of Barrel Parameters on Velocity and Morphology of Laser-driven Flyer

In order to obtain the influence of barrel parameters on the laser-driven flyer velocity and morphology,the velocities and evolution process of laser-driven Al flyers confined by steel barrels with various diameters and lengths were investigated using Photonic Doppler Velocimetry(PDV)and Shadowgraph technique.The maximum velocity of 3100 m·s^-1 can be obtained when the diameter of the barrel was 800μm,which is equal to the size of the Al flyer ablated by laser.When the diameter of the barrel was larger than 800μm,it can not restrain the flyer effectively,and the velocity of the flyer decreased,which led to the lowest velocity of 2700 m·s^-1 with the barrel’s diameter of 1500μm.When the diameter of the barrel was 600μm,the energy around the flyer was wasted and the velocity of the flyer decreased to 2900 m·s^-1.The results also showed that flyer velocity decreased with the increase of the barrel length.Shadowgraph results showed that the Al flyer was fragmented and splashed around after it got away from the barrel exit,indicating that it was difficult for a 20μm Al foil to maintain integral and planar when ablated by a pulsed laser.