Stimulated Raman scattering in cannonball targets

Stimulated Raman scattering (SRS) in cannonball targets was experimentally investigated. Above the observed threshold laser intensity, the energy conversion to superhot electrons (E=100–800 keV) shows an increase of five orders of magnitude without saturation. Major differences in observing SRS from cannonball targets and directly driven targets lie in the background electron temperature and the electron plasma density where SRS occurs. A simple model calculation is presented and is compared with the data to infer coronal temperatures. The electron density ranges from 5×1019 to 3×1020 cm−3 and the coronal temperature is 0.2 keV for cannonball targets including cavity targets, while the density ranges from 3×1020 to 6×1020 cm−3 and the temperature is 1 keV for the directly driven target. The generation efficiency of SRS light is strongly correlated with superhot electron generation.