Thomson Scattering Of Laser Plasmas In Relevance To Inertial Confinement Fusion

The field of laser-produced plasmas is rich in diverse applications, such as inertial confinement fusion (ICF), X-ray lasers and high energy density physics (HEDP). Detailed characterizations of plasmas parameters are essential to understand the physics of laser plasmas interactions, benchmark hydrodynamic simulations of laser fusion and study the electron thermal conduction. Especially, the electron thermal conduction play an important role in the ICF: it transports energy absorbed near the critical surface into the radiation conversion layers and therefore directly affects the ablation, the laser absorption and implosion dynamics.Thomson scattering (TS) has been introduced as a key diagnostic of plasmas conditions due to its ability to provide accurate temporal- and spatial- resolved information on densities, electron temperatures and average ionization levels. And therefore it can be used as an important experimental access to study the electron thermal conduction.Over the last yeas we have developed TS capability at Shenguang-II (SG-II) laser facility and have performed TS experiments with various kind of targets, such as Au disk, Au tile, empty Au hohlraum and gas-filled hohlraum. Especially, it is the first time that the TS spectrum of the empty Au hohlraum has been successfully obtained. Through these experiments, the TS technique has been proved to be a valuable tool in the SG-II experiments.From the experiments, we draw the following conclusions:1. With aid of a 263.3 nm probe beam, the TS spectrum of six locations away from the disk of 50μm to 300μm has been obtained equidistantly. Especially, the measurement of 50μm location proved that our TS diagnostic system has the superiority in applying in the high density plasmas.2. By fitting the experimental TS, the spatial profile of the charge-temperature product ZTe and the plasma flow Ui are obtained. All of the TS spectra become narrower with time, indicating the overall drop of plasma temperature as the high-Z plasmas blow off. Both the profiles of the electron temperature and the spectral asymmetry of the two ion-acoustic peaks show that the plasmas in the inner region(<150μm) are distinct from those in the outer region, which is out of the path of the heater beams (i.e. >150um). The temperature gradient is antiparallel to the target normal in the outer region, but it becomes parallel to the target normal in the inner region. The electron temperature profile in the inner region is qualitatively consistent with the theoretical prediction, indicating that the inner region in our experiment may belong to the radiation conversion layer.3. The asymmetry of the TS spectra is due to the relative drift between ion and electron driven by the heat flow carried by electrons, which provide a valuable access to study the...