Fokker-Planck simulations for core heating in subignition cone-guiding fast ignition targets

On the basis of two-dimensional coupled relativistic Fokker-Planck and fluid simulations, the core heating by fast electron beam in subignition cone-guiding fast ignition targets is investigated. It was found that the magnetic field due to the thermoelectric current reduces the beam pinching due to the resistive magnetic field. Compared with the carbon-deuterium fuel used in the early phase of Fast Ignition Realization Experiment, phase-I, the core heating of deuterium-tritium (DT) fuel used in the later phase is less effective. One reason is the slower temperature relaxation between bulk electron and ion for the DT case, which is previously reported by Johzaki et al. [Phys. Plasmas 15, 062702 (2008)]. In addition, in the lower-Z DT case, the pinching effects by the resistive magnetic field are weaker due to smaller resistivity; the optical thickness for fast electron beam is smaller, which leads to further reduction in core heating efficiency. It was also found that the fast electron beam quality deteriorates during the transport in the only 10 μm thickness high-Z (e.g., Au and Cu) cone tip because of the collisional scattering and drag. As the result, the core heating efficiency considerably goes down compared to the case neglecting the transport in the cone tip.