Direct Heating of Counter Imploded Core

Abstract

This study investigates the heating efficiency of the fast heating when the imploded core is directly illuminated with an ultraintense laser. Six counterbeams of the GEKKO XII (GXII) green laser at the Institute of Laser Engineering (ILE), Osaka University, of which the output was 1.6 kJ, imploded a spherical CD shell target of 500 μm in diameter and formed a dense core. DD-reacted protons and the x-ray core emissions showed a core density of 2.8 ~ 2.7 g/cm 3. The thermal neutron yields were used to estimate the core temperature determined as 850 eV. The core was then directly heated by a laser for fast-ignition experiments (LFEX), which is an extremely energetic ultrashort pulse laser at the ILE with its axis lying to the GXII bundle axis. The LFEX increased the core temperature to 890 eV, giving a heating efficiency of 1.3% for 261 J LFEX. The efficiency was compared to that from the uniformly imploded core, which was 4.8%.