Enhancing the integrity of the laser-driven flyer with modified surface microstructure

Abstract

Laser-driven flyer has attracted considerable attention and made significant progress in both military and civil applications. However, most flyer layers are made of aluminum, which make them susceptible to damage from deformation during both the formation and acceleration processes. Herein, an improved process was designed to prepare flyers with surfaces featuring numerous independent columnar crystals. The attractive forces between surface atoms cause the material to contract inward, resulting in overall compressive stress. The compressive residual stress enhances the closure force of microcracks and hinders crack propagation. Velocity and integrity of the flyer were tested using the photonic Doppler velocimetry system, ultrahigh-speed camera, and schlieren photography, with the flyers being driven by 32 mJ of laser energy. Flyers with a thickness of 2.5 μm maintain good integrity at a displacement of 0.06 mm. An intact flyer provides axial confinement to the plasma, which causes the formation of an empty zone and a distinct spherical shock wave at the exit of the acceleration chamber. In contrast, a flyer without a surface featuring numerous columnar crystals may break apart at the central region during the generation and acceleration process. Moreover, flyers with compressive stress can be accelerated to speeds of up to 3 km/s, which is significantly faster than the speed of the flyers without surfaces featuring numerous columnar crystals (less than 2 km/s).