Flyer acceleration by a high-power KrF laser with a long pulse duration

The experiments of flyer acceleration by the irradiation of a high power la ser are carried out using the ASHURA system at the Electrotechnical Laborat ory, in which the laser has a short wavelength (similar to 249 nm) and a lo ng pulse duration (similar to 30 ns). Three-layered targets (aluminum-polyi mide-tantalum) are irradiated. The laser ablates the aluminum and polyimide layers and the rear layer (tantalum) is accelerated as a flyer. It is sugg ested that the tantalum flyer is in a condensed state for the duration of f light. The flyer velocity estimated from the acceleration profile is at lea st 8 km/s. One-dimensional numerical simulation indicates that the terminal flyer velocity becomes higher than 15 km/s. The energy conversion from las er energy to flyer kinetic energy is more efficient than that in the previo us experiments using the three-layered targets with a longer wavelength and a shorter pulse duration (1-2 ns). Thus, it is found that a facility with a long pulse duration and a short wavelength is suitable for the realizatio n of a fast flyer keeping its state in a condensed phase. (C) 2000 American Institute of Physics. [S0021-8979(00)02517-2].