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

Abstract

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 lnterferometer 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 experimental proof of the flyer gesture and configuration. Thus, the acceleration and gesture investigation of aluminum flyer driven by laser plasma are studied on Xingguang-III laser 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, shadowgraph 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 20 μm and diameter of about 500 μm. The whole flyer remains the integrated shape after a great angle of rotation due to uneven plasma loading. The flight distance is about 400 μm, 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 .