Velocity Measurements of Laser Driven Flyers Backed by High Impedance Windows

摘要

Because of possible applications to inertial confinement fusion, the response of free-standing foils to laser intensity levels of 10 exp 3 to 10 exp 6 GW/cm exp 2 has been well characterized. Our interest is in characterizing the response of free-standing and backed foils at much lower intensities, i.e., in the region of 1 to 20 GW/cm exp 2 , and using these flyers to initiate insensitive secondary high explosives. The output of a 3.5-J Nd:glass laser with a 16 ns pulse was used to drive 1.5-mm-diameter aluminum (Al) flyers. The velocities of both free-standing flyers and flyers backed on the driven side by windows of water, fused silica, or sapphire were measured using ORVIS (Optically Recording Velocity Interferometer System). Intensities were on the order of 10 GW/cm exp 2 and velocities as high as 5 km/s were measured for 13- mu m/thick, Al flyers. Velocity and acceleration were observed to vary only slightly with the shock impedance of the window. Preliminary measurements indicate that PETN (pentaerythritol tetranitrate) at a density of 1.4 grams/cm exp 3 , and HNS-FP (hexanitrostilbene-fine particle) at a density of 1.6 grams/cm exp 3 , can be promptly detonated by 66- mu m-thick, Al flyers impacting at a velocity of near 2.5 km/s. (ERA citation 10:041004)