Experimental confirmation of drive pressure boosting and smoothing for hybrid-drive inertial fusion at the 100-kJ laser facility

Abstract In laser-driven inertial fusion, drive pressure boosting and smoothing to suppress hydrodynamic instabilities are major challenge. A proposed hybrid-drive (HD) scheme of a coupling of the indirect-drive (ID) and direct-drive (DD) offers two new effects, ″bulldozer″ like and thermal smoothing, to boost and smooth the HD pressure far greater than the radiation ablation pressure to perform stable implosion and nonstagnation ignition. In this article, we report that such HD pressure was first verified experimentally by a planar ablator target in a semicylindrical hohlraum. Using laser energy of 43 kJ for ID and 3.6-4.0 kJ (intensity about 1.8×10 15 W⁄cm 2 ) for DD, the HD pressure measured by VISAR is about 3.5 times the radiation ablation pressure with measured radiation temperature 200 eV(peak) by FXRD. How the symmetric HD shock driven by the HD pressure catches up with and stops the asymmetric ID shock is observed as well. While total fractions for DD laser backscattering and hot electron energy about 4.5% and about 2%, respectively, both about one-third of the traditional DD for the same intensity, are measured.