Thomson Scattering in Inertial Confinement Fusion Research

Thomson scattering with a short-wavelength probe laser has been developed into a standard diagnostic of high-density inertial confinement fusion plasmas that are produced with high energy lasers. A the Nova laser facility, we have applied Thomson scattering to investigate fundamental properties of ion acoustic or electron plasma (Langmuir) waves such as their dispersion and diagnostic value in two-ion species plasmas as well as their saturation and decay. Moreover, we have used Thomson scattering in a large number of studies that require accurate characterization of plasma conditions to benchmark radiation hydrodynamic calculations and to test kinetics modelling. In particular, the implementation of an ultraviolet probe laser that operates at 263 nm (4ω) has allowed us to accurately measure the electron and ion temperature in high-density gas-filled hohlraums and to investigate scalings to high gas fill densities characterizing the low-Z gas plasma as well as the high-Z wall plasma. These measurements have provided us with a unique data set that we use for comparisons with integrated radiation-hydrodynamic modelling using the code LASNEX. This code is presently being applied o design fusion targets for the National Ignition Facility. The Thomson scattering experiments show the existence of electron temperature gradients in the gas plasma that are well modelled when including a self-consistent calculation of magnetic fields. Furthermore, the temperature data have been applied to test kinetics calculations of x-ray spectra observed from these hohlraum plasmas.