Start-Up Imprinting and Shock Dynamics in Laser-Target Interaction
NAVAL RESEARCH LAB WASHINGTON DC CENTER FOR COMPUTATIONAL PHYSICS DEVELOPMENTS
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Improved uniformity of the laser for-al spot profile is a necessary criterion for the success of high intensity laser fusion and to improve the quality of data from moderate intensity laser driven shock experiments in solids. Recently developed laser smoothing techniques rely on both temporal smoothing and thermal smoothing to produce uniform ablation pressures on the target surface. Thermal smoothing is not effective during the low intensity portion of a laser pulse and the resultant shock structure mirrors the residual laser nonuniformities. The impact of the first nonuniform shock can be diminished by using foam layers, a precursor flash, shallow angles of incidence, and by adiabatically compressing the target with a temporally long, slowly rising laser pulse.
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