Implosion and heating experiments of fast ignition targets for FIREX-1 project

Implosion and heating experiments of Fast Ignition (FI) targets for FIREX-1 project have been performed with Gekko-XII and PW/LFEX lasers at the Institute of Laser Engineering, Osaka University. Typical FI target has a hollow cone for guiding the short-pulse heating laser beam at the time of the maximum compression. The cone is mounted so as to in one-side penetrate the shell target. Detailed implosion hydrodynamics, FI heating and core plasma formation of plastic (CD) shell target with gold cone have been clarified by observing those with fast imaging x-ray spectroscopy and neutron diagnostics. A new Multi-channel Multi-Imaging X-Ray Streak Camera (McMIXS) was developed for observation of time-resolved two-dimensional x-ray images and time-resolved two dimensional temperature distributions. Also, a monochromatic x-ray imager coupled with 2D-SIXS (Two-Dimensional Sampling Image X-ray Streak camera) was developed for time resolved x-ray line-emission imaging. With these instruments, one can observe heating properties of the imploded core such as spatial distribution of the heated region and its temporal evolution. Synchronization of the heating beam injection to the implosion dynamics has been monitored with an x-ray framing camera. It was found that the shape of the core is neither spherical nor uniform mainly because of the existence of the cone and moving toward the tip of the cone and interacting with it. Experimental results are compared with two-dimensional hydrodynamic simulations. Target design taking into account of these phenomena is quite important because such core movement and jet formation can affect the condition of the cone. (author)