Diffusion of external magnetic fields into the cone-in-shell target in the fast ignition

We simulated the diffusion of externally applied magnetic fields into cone-in-shell target in the fast ignition. In this ignition scheme, the externally magnetic fields up to kilo-Tesla is used to guide fast electrons to the high-dense imploded core, and understanding diffusion of the magnetic field is one of the key issues for increasing the coupling efficiency from the heating laser to the imploded core plasma. In order to study the profile of the magnetic field, we have developed 2D cylindrical Maxwell equation solver with Ohm’s law, and carried out simulations of diffusion of externally applied magnetic fields into a cone-in-shell target. Also, we estimated the conductivity of the cone and shell target based on the assumption of Saha-ionization equilibrium. We present our results of temporal evolution of the magnetic field and its diffusion into the cone and shell target. We also show that the target is heated by the eddy current. Because of the temperature dependence of the conductivity, the magnetic fields diffuse into the material with varying conductivity. Consequently, the magnetic fields into the cone-in-shell target depend on the temporal profile of the magnetic fields as well as the electrical and thermal properties of the material.