Thomson scattering from laser plasmas

Thomson scattering has recently been introduced as a fundamental diagnostic of plasma conditions and basic physical processes in dense, inertial confi nement fusion plasmas. Experiments at the Nova laser facility [E. M. Campbe ll et al., Laser Part. Beams 9, 209 (1991)] have demonstrated accurate temp orally and spatially resolved characterization of densities, electron tempe ratures, and average ionization levels by simultaneously observing Thomson scattered light from ion acoustic and electron plasma (Langmuir) fluctuatio ns. In addition, observations of fast and slow ion acoustic waves in two-io n species plasmas have also allowed an independent measurement of the ion t emperature. These results have motivated the application of Thomson scatter ing in closed-geometry inertial confinement fusion hohlraums to benchmark i ntegrated radiation-hydrodynamic modeling of fusion plasmas. For this purpo se a high energy 4 omega probe laser was implemented recently allowing ultr aviolet Thomson scattering at various locations in high-density gas-filled hohlraum plasmas. In particular, the observation of steep electron temperat ure gradients indicates that electron thermal transport is inhibited in the se gas-filled hohlraums. Hydrodynamic calculations which include an exact t reatment of large-scale magnetic fields are in agreement with these finding s. Moreover, the Thomson scattering data clearly indicate axial stagnation in these hohlraums by showing a fast rise of the ion temperature. Its timin g is in good agreement with calculations indicating that the stagnating pla sma will not deteriorate the implosion of the fusion capsules in ignition e xperiments. [S1070-664X(99)96305-X].