Suppression of Instabilities and Stochastic Pulsation at Laser-Plasma Interaction by Beam Smoothing

Abstract

The key problem of direct drive laser fusion is the appearance of parametric instabilities, stochastic pulsation, self-focusing (filamentation) and other anomalies. During the long years studies, the empirical and intuitively developed methods for smoothing of the laser beam were rather successful but a transparent understanding of the physics has still to be found. The first theory how the instabilities are reduced by smoothing was given recently by using PIG simulation while the suppression of the 10-picosecond stochastic pulsation by broadband laser beams was analyzed by the genuine two fluid models. A synoptic evaluation of these results is presented here where the correlation between the instabilities with the pulsation is evident. This opens new ways for direct drive laser fusion with the fundamental red laser light avoiding expensive and because of crystal defects - unsolved problems with higher harmonic production.