Effect of Material Properties and Mass of Pusher Layer on an Implosion Process for Multilayer Fuel Pellet During Heavy-Ion Inertial Fusion

In this study, we investigated the effects of pusher layer density and mass on fuel density, areal density, implosion velocity, and fuel ion temperature in an implosion process for a multilayered-structure target pellet in heavy-ion inertial fusion with a direct-indirect mixture mode. A dense material outside the fuel layer was proposed to suppress preheating due to radiation transport in the radial direction for implosion robustness. In this study, we investigated aluminum (Al) as a lower-density material and lead (Pb) as a higher-density material for the pusher layer placed outside the fuel layer. The implosion process was modeled as 1D spherical coordinate radiative hydrodynamics, with a numerical calculation code developed for the Lagrangian system. The compression ratio and areal density of the Pb pusher are higher than those of the Al pusher, while the implosion velocity of the Al pusher exceeds that of the Pb pusher. Although the implosion velocity of the Pb pusher was lower for the same pusher mass, the implosion parameters obtained were higher for the Pb pusher. The fuel isentrope parameter was successfully maintained at a small value in the Pb pusher. Moreover, the increase in fuel isentrope parameter caused by the increased pusher mass was insignificant. The results suggest that the pusher density and mass are critical parameters for obtaining sufficient fusion output.