激光等离子体射流驱动亚毫米直径铝飞片及姿态诊断

Laser-plasma jet driven sub-millimeter diameter aluminum flyer and its gesture diagnosis

强激光烧蚀低密度有机材料形成等离子体射流碰撞,可以对材料进行准等熵加载,比激光冲击加载应变率低,相同压强下可以获得更高的压缩度和更低的温升,在状态方程、飞片加速等方面有很强的应用前景.在星光Ⅲ置上首次开展了等离子体射流驱动小尺寸铝飞片及姿态诊断联合实验.通过调控有机材料厚度和真空间隙长度,获得了厚度20μm、直径约400μm的铝飞片,飞片加速时间长达200 ns.基于ps拍瓦激光的高能X光背光照相结果显示铝飞片在飞行约400μm距离后仍然保持了很好的飞行姿态和完整性.

Laser-driven flyer has been studied for decades as it promises to possess many applications such as in measuring the equation of state(EOS)under ultrahigh pressure,investigating the material dynamic properties under high strain rate,simulating the high-speed impact for aircraft protection,and igniting explosives.However,the planarity and integrity of flyers are determined by indirect velocity Interferometer system for any reflector(VISAR)or witness slab results due to its high speed and small dimension.For further and wide applications,it is very important to obtain direct experirmental proof of the flyer gesture and configuration.Thus,the acceleration and gesture investigation of aluminum flyer driven by laser plasma are studied on Xingguang-Ⅲlaser facility.The X-ray radiography is achieved by a picosecond laser irradiating the copper wire target.The shadowgraph of flyer and plasma are realized by the incidence of a bunch of infrared laser through the flyer flight path.In additon,photon Doppler velocimetry is employed to measure the flyer velocity simultaneously.The radiography,sha.dowgraph and velocity of typical small aluminum flyer are obtained.By optimizing the thickness of both CH ablation layer and vacuum gap,the flyer is slowly accelerated via consecutive stress wave produced by plasma colliding.The aluminum flyer has a thickness of 20μm and diameter of about 500μm.The whole flyer remains the integrated shape after a great angle of rotation due to uneven plasma loading.The flight distance is about 400μm,giving an average velocity of 2.2 km/s.The planarity of the flyer is good except a little bend on the two sides due to side rarefaction of plasma.The study verifies that the laser plasma collision can generate a sub-millimeter-diameter metal flyer with integrated shape and a velocity of several kilo-meters per second,showing that it possesses the promising applications in measuring the EOS and igniting explosive.