Shock waves from a water-confined laser-generated plasma

Abstract

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

Generation of controlled delaminations in composites using symmetrical laser shock configuration

“…In order to drive significant shock pressure, water confinement is generally used. The confinement slows down the plasma expansion and results in an increased ablation pressure (from 5 to 10 times higher compared to the direct irradiation) and a longer shock duration (from 2 to approximately 3 times longer) [23,24]. Furthermore, a sacrificial layer can be interposed between the target surface and the confining medium in order to absorb the plasma induced thermal effects.…”

Shock pressure induced by glass-confined laser shock peening: Experiments, modeling and simulation

“…The fraction of the internal energy converted to the thermal energy is a and typically is 0.25. 7,8 The incident laser power density is I 0 ðtÞ, and R C and R P are the laser reflection coefficients of the confined overlay's surfaces as shown in Fig. 4.…”

“…26 A quartz crystal transducer is not suitable in LSP because of high amplitude and nanosecond duration of the shock pressure in LSP. 8 The PVDF is unlikely to work on nanosecond shock measurement because of the limitation of the gauge thickness and impedance mismatch effect. Moreover, it is difficult to calibrate, and the noise signal is difficult to eliminate.…”

“…Some analytical models of shock pressure for LSP were developed. 7,8,[14][15][16][17][18][19][20][21][22] However, in the previous models, the dynamic effect of the material system was simplified as constant reduced shock impedance. As a result, the dynamic response of the material was not fully considered and a more realistic pressure model is demanded.…”

“…[1][2][3][4][5][6] Through the interaction of a pulsed high-intensity laser beam and an energy absorption layer on the metallic target surface, a shock wave with a high amplitude can be generated and propagates into the target. 2,[7][8][9][10][11][12][13] If the amplitude of the shock wave exceeds the Hugoniot elastic limit (HEL) of the target material, plastic deformation occurs and residual compressive stresses are induced near the surface, which results in the enhancement of fatigue life.…”