424 / 2019-03-01 00:19:32

Three-dimensional simulation of hohlraum targets

Inertial fusion; computational fluid dynamics;

全体主题 > Laser and Particle Beam Fusion

Several aspects of three-dimensional numerical simulation of holhraum targets are discussed. Advances in the modeling of such targets by the three-dimensional hydrodynamics code MULTI-3D are presented. Special emphasis has been placed on the transfer of energy between different parts of the target by thermal X-rays. To solve this problem, the well proved algorithm for axisymmetric two-dimensional configurations used in the code MULTI-2D is extended to 3D and to multigroup transport. This algorithm goes beyond the diffusion approximation, and can be used in both optically thin and optically thick regimes. It does not require the resolution of the large systems of linear equations that usually appears in implicit discretizations. Instead, the SSI (Symmetric Semi-Implicit) method is used to guarantee unconditional numerical stability. The energy transfer algorithm has to be coupled with MULTI-3D staggered Lagrangian hydrodynamics for unstructured meshes. Hohlraum targets are complex structures whose geometry evolves with time (capsule implosion, plasma filling, hole closure, etc). Due to the subsequent large grid distortion, Lagrangian methods cannot be directly applied to such configurations. To change the grid at specific moments (remapping) or continuously (ALE; Arbitrary Lagrangian-Eulerian methods) a second-order algorithm for generic staggered grids has been developed.