Science and Technology of Energetic Materials

Vol.66, No.2 (2005)


Blast wave characteristics under laser-driven in-tube accelerator operation conditions
Xilong Yu, Toshiro Ohtani, Sukyum Kim, Toshihiro Ogawa, In-Seuck Jeung, and Akihiro Sasoh


Laser-driven blast waves and associated flow dynamics in the impulse generation processes of the laser-driven in-tube accelerator are studied through Schlieren visualization and streak spectroscopy. Three monatomic species, argon, krypton and xenon, are examined as the working gas. The laser pulse (wavelength; 10.6 mm, duration; 3 ms) is emitted from a carbon dioxide TEA (Transversely-Excited Atmospheric) laser. Being influenced by laser energy absorption processes, the shape of the laser-generated plasma has an aspherical shape. The speed of evolution of the blast wave is basically in proportion to the speed of sound, thereby being consistent to the experimentally-measured impulse characteristics. However, at where the plasma-laser coupling is strong, the larger the atomic number the higher a local shock Mach number becomes. Electronic-excitation energy distribution of argon ion at the focal point that is measured through emission spectroscopy exhibits nonequilibrium profile during a laser pulse irradiation period, then asymptotically approaches to equilibrium corresponding to an electronic excitation temperature of the order of 3 eV. After the blast wave gets reflected against a parabolic wall, its interaction with the plasma causes interface instability.

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