Fiber-coupled laser-driven flyer plates experiments

Abstract

A system for the launch of hypervelocity flyer plates is developed, characterized and applied. Laser-driven flyers are launched from substrate backed aluminum-alumina- aluminum sandwiched films. A laser-induced plasma is used to drive flyers with a thicknesses of a 5.5 m and a diameter of less than 1 mm, and typically, the flyer plates can achieve velocities of a few kilometers per second. These flyer plates have several applications ranging from micrometeorite simulation to laser ignition. The flyer plates considered here have three layers: an ablation layer for forming plasma; an insulating layer; and a final thicker layer for forming the final flyer plate. The optical fiber delivery system determines the spatial profile of the laser spot and power capacity. A technique and procedure for coupling high power laser pulse into optical fiber is developed. The surface finish of the fiber is found to be a critical factor. This fiber optic system is successfully used to launch flyer plates. Measurements of the flyer performance including the mean velocities and planarity are made by an optical time-of-arrival (TOA) technique with using an optical fiber array probe. The flyer shows a good planarity and achieves an average velocity of 1.7 km/s. The relationship between flyer velocity and incident laser pulse energy is investigated.