Investigation of scattering processes in a laser plasma

Spectral-time resolved measurements were taken of scattered laser radiation at various angles, and at the fundamental and the second harmonic frequencies. Investigations were carried out for radiation from a single-frequency neodymium laser at normal and oblique incidence on plane targets. Three basic processes which determine the scattering at the basic frequency were identified: (1) classical scattering of the plasma at a critical density, (2) reradiation of Langmuir waves, and (3) stimulated Brillouin scattering. Conclusions are presented concerning plasma corona dynamics at a power density of greater than 10 to the 14th W/sq cm. Initially (at 1-2 ns), the scale of the inhomogeneity is sufficiently large in the critical density region, and plasma flow velocity is relatively low. As time passes, the corona changes, and plasma flow velocity is relatively low. As time passes, the corona changes, and plasma flow velocity increases to M greater than 3, the concentration being equal to approximately (0.3-0.1) times the critical concentration; it is also probable that the inhomogeneity scale decreases in the critical density region.