Experimental study of shock wave discontinuities and interactions with laser induced plasmas

Summary form only given. The transmission of shock waves through weakly ionized reducing plasmas with gradients in the plasma electron density, the neutral particles density and the gas temperature is of interest in several scientific and applied problems. We report the initial measurements and analysis of Nd:YAG 1064 nm laser induced plasmas in air and the generated shockwave discontinuity analysis and its interaction with decaying plasma. The plasma is generated by focusing 1st harmonic 1064 nm Nd:YAG 450mJ, 45 MW high power IR laser radiation on to a 30 micron spot size that can produce a maximum laser intensity of >;10¹³ W/cm² well above the threshold flux for air ionization. Optical laser shadowgraphy diagnostic is currently setup to study the spatial and temporal evolution of the laser focused plasma and shock waves using the second harmonic laser beam at 532 nm and using high speed 2 ns gated ICCD. The plasma temperatures can be measured by measuring the velocity of the shock wave front [1]. The laser induced plasmas and concurrent shockwaves and their interactions at various configurations are studied. Two-wavelength laser interferometry diagnostic technique is being developed to study the density decay of the plasma. These optical diagnostics are used to study the propagation of a shock wave through weakly ionized laser induced plasma at various gradients of the plasma evolution such as growing and decaying phases.