Laser-launched flyer plates for shock physics experiments

The TRIDENT laser was used to launch Cu, Ga, and NiTi flyers from poly(methylmethacrylate) (PMMA) substrates, coated with thin ( ∼ micron ) layers to absorb the laser energy, confine the plasma, and insulate the flyer. The laser pulse was ∼ 600 ns long, and the flyers were 50 to 250 μ m thick and 4 mm in diameter. With an energy of 10-20 J, speeds of several hundred meters per second were obtained. Simulations were performed of the flyer launch process, using different models. The simulations reproduced the magnitude of the flyer speed and qualitative variations with drive energy and design parameters, but systematically overpredicted the flyer speed. The most likely explanation is that some of the laser energy was deposited in the transparent substrate, reducing the amount available for acceleration. The deceleration of the flyer was measured on impact with a PMMA window. Given the equation of state and optical properties of PMMA, the deceleration allowed points to be deduced on the principal Hugoniot of Cu. The points deduced were in good agreement with the published equation of state for Cu, suggesting that there was no significant preheating of the flyer or other systematic effects which might reduce the accuracy of equation of state measurements.