Nonlinear Plasma Dynamics at High Intensity Laser Interaction

Some aspects of progress in laser fusion are briefly reviewed which indicate that experiments are on the threshold of entering a regime where nonlinear dynamics will become important. Recent studies of the general nonlinear force that include additional nonponderomotive terms are reviewed. Computer calculations that provide a detailed knowledge of the transfer of optical energy into a plasma corona by nonlinear forces are then described. Two key regimes are observed: 1) early production of fast moving cold blocks of plasma followed by 2) a decay of the corona where the plasma velocity obeys a Kortweg-de-Vries equation. This soliton decay corresponds to a fast thermalization of laser radiation in the corona at perpendicular incidence, i.e., without asymmetries of laser incidence as in the case of resonance absorption or striated motion. This permits a short pulse high intensity irradiation to achieve conditions equivalent to an ideal gasdynamic ablation compression.