Saturation gain-length product during short-wavelength plasma lasing Appl. Phys. Lett. 101, 081105 (2012) Laser induced avalanche ionization in gases or gas mixtures with resonantly enhanced multiphoton ionization or femtosecond laser pulse pre-ionization Phys. Plasmas 19, 083508 (2012) A new scheme for stigmatic x-ray imaging with large magnification Rev. Sci. Instrum. 83, 10E527 (2012) Additional information on J. Appl. Phys.Generation of a high amplitude shock wave by laser plasma in a water confinement regime has been investigated for an incident 25-30 ns/40 J/ϭ1.064 m pulsed laser beam. Experimental measurements of temporal and spatial profiles of induced shock waves for this regime of laser shock processing of materials were performed using a velocimetry interferometer system for any reflector system. Above a 10 GW/cm 2 laser intensity threshold, a saturation of the peak pressure is shown to occur while the pressure pulse duration is reduced by parasitic plasma occurring in the confining water. The observation of the interaction zone with a fast camera system shows that this breakdown plasma, which mainly occurs at the very surface of the water rather than within the water volume, limits the efficiency of the process. This plasma absorbs the incident laser energy, and the power density reaching the target gradually decreases with increasing power densities while the shock-wave duration is correspondingly reduced. Both pressure measurements and plasma observations allow explaining the current limit of high amplitude shock-waves generation by laser plasma in the water-confinement mode and open new research areas for the understanding of breakdown plasma effects at the surface of the confining water. © 1997 American Institute of Physics. ͓S0021-8979͑97͒03618-9͔

The first part of this article presents a review of the main process parameters controlling pressure generation in a confined mode. The effect of laser intensity, target material, laser pulse duration, and laser wavelength are, therefore, discussed. An optimized process can then be defined. The second part of this article deals with the surface modifications induced by laser-shock processing. The generation of residual compressive stresses is then highlighted. Finally, in the third part, the interest of laser-shock processing is discussed for several typical applications. A conclusion will present the future trends of this technique.

The generation of high-intensity shock waves by laser plasma in the water-confinement regime has been investigated at 1.064, 0.532, and 0.355 μm laser wavelengths. Experimental characterizations of pressures induced by laser plasma have been performed with a velocimetry interferometer for any reflector. For each incident laser wavelength, above a laser power density threshold, maximum pressure levels saturate and the pressure durations are reduced due to parasitic plasma occurring in water. However, it is shown that this threshold is lower at the 0.532 and 0.355 μm wavelengths than at the 1.064 μm wavelength. The generation of the parasitic plasma in water is easier with a short wavelength because it would be dominated by multiphotoionization mechanisms. Below the saturation pressure threshold, the pressure levels are significantly higher at the 0.532 and 0.355 μm wavelengths than at the 1.064 μm wavelength. Unlike the detrimental effect of short laser wavelengths on water breakdown plasma, the confined laser interaction is shown to be more efficient in ultraviolet than in infrared laser irradiation.

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Please cite this article as: Gattacceca, J., Lamali, A., Rochette, P., Boustie, M., Berthe, L., The effects of explosive-driven shocks on the natural remanent magnetization and the magnetic properties of rocks,