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Laser Produced Hemispherical Shock Waves

An experimental study of laser induced hemispherical shock waves has been carried out. A Q-switched ruby laser was focused on aluminum or carbon targets and the plasma produced expanded into an ambient atmosphere of argon or helium. Trajectories of the primary and secondary shock waves were determined for initial pressures from 0.05 to 5 torr. Spherical blast wave theory was found to apply for radii greater than the mass length, (M/p0), where M is the plasma mass and p0 the background gas density. The results are compared with previous numerical solutions, and several rules for secondary shock wave behavior are stated.