Pre-plasma effects on core heating and enhancing heating efficiency by extended double cone for FIREX

Abstract

The effect of pre-plasma on core heating in cone-guiding fast ignition is evaluated by two-dimensional particle-in-cell (PIC) and Fokker–Planck (FP) simulations. If the long-scale pre-plasma exists in the cone, the generated fast electron energy becomes too high for effective core heating. As a result, the energy coupling from laser to core η L→core is reduced by 80% compared with the case without a pre-plasma. Even for the case without a pre-plasma, η L→core obtained in the simulation is smaller than that required for 5 keV heating in FIREX-I. In order to enhance η L→core , we propose a new target design ‘extended double cone with short inner cone wall’ for fast electron guiding to imploded core and show sufficient improvement of heating efficiency using this new cone on the basis of PIC and FP hydro-simulations.