A novel approach to efficiently model 3-D laser plasma interactions at fluid scales is presented. This method, implemented in the IFRIIT propagation code developed at CELIA, relies on inverse ray tracing to compute laser fields at arbitrary locations in a plasma. This enables to describe the fields at high order in space compared to standard forward ray tracing approaches. In addition, inverse ray tracing enables the use of etalon integral methods to reconstruct caustic fields and greatly speeds up calculations of cross-beam energy transfer by decoupling the ray amplitude and ray phase calculations. A comparison of the inverse and forward methods for 3-D calculations of fields in presence or not of cross-beam energy transfer illustrates the significant advantages of the inverse method. Conversely, while the inverse method is well suited to most spherical plasma profiles, it currently cannot treat concave profiles or target holders. The coupling of IFRIIT with the 3-D ASTER radiative hydrodynamics code developed at the Laboratory for Laser Energetics is then presented. ASTER and IFRIIT resolve their respective equations on separate grids which communicate through interpolation. As such, IFRIIT uses a dedicated laser grid adapted to the computations at play, which also allows to use different parallelization methods for both codes: block decomposition for the hydrodynamics versus domain duplication for the laser. Applications to direct-drive implosions for inertial confinement fusion are presented, for which a geodesic icosahedron grid is implemented in IFRIIT. The performances of the ASTER/IFRIIT coupling are demonstrated by conducting simulations of cryogenic implosions performed on the OMEGA laser system, in presence of various sources of 3-D effects; laser port geometry, cross-beam energy transfer, beam imbalance and target mis-alignment. Comparison with neutron data, measured through bang-time, for a cryogenic implosion experiment shows an excellent agreement for the laser-plasma coupling.

提出了一种在流体尺度上有效模拟 3-D 激光等离子体相互作用的新方法。这种方法在 CELIA 开发的 IFRIIT 传播代码中实现，依靠逆光线追踪来计算等离子体中任意位置的激光场。与标准的前向光线追踪方法相比，这使得能够在空间中以高阶描述场。此外，逆射线追踪能够使用标准具积分方法来重建焦散场，并通过将射线幅度和射线相位计算解耦来大大加快横梁能量转移的计算。对存在或不存在横梁能量转移的场进行 3-D 计算的逆向和正向方法的比较说明了逆向方法的显着优势。反过来，虽然逆方法非常适合大多数球形等离子体轮廓，但它目前无法处理凹形轮廓或目标支架。然后介绍了 IFRIIT 与激光能量学实验室开发的 3-D ASTER 辐射流体动力学代码的耦合。ASTER 和 IFRIIT 在单独的网格上求解它们各自的方程，这些网格通过插值进行通信。因此，IFRIIT 使用了一个专门的激光网格来适应正在运行的计算，这也允许对两种代码使用不同的并行化方法：流体动力学的块分解与激光的域重复。介绍了用于惯性约束聚变的直接驱动内爆的应用，为此在 IFRIIT 中实现了测地线二十面体网格。ASTER/IFRIIT 耦合的性能通过在 OMEGA 激光系统上进行低温内爆模拟来证明，存在各种 3-D 效应源；激光端口几何形状、横梁能量转移、光束不平衡和目标未对准。与通过爆炸时间测量的低温内爆实验中子数据的比较表明，激光-等离子体耦合具有极好的一致性。