The target performance of laser direct-drive inertial confinement fusion (ICF) can be limited by the development of hydrodynamic instabilities resulting from the nonhomegeneous laser absorption at the target surface, i.e., the laser imprint on the ablator. To understand and describe the formation of these instabilities, the early ablator evolution during the laser irradiation should be considered. In this work, an improved modeling of the solid-to-plasma transition of a polystyrene ablator for laser direct-drive ICF is proposed. This model is devoted to be implemented in hydrocodes dedicated to ICF which generally assume an initial plasma state. The present approach consists of the two-temperature model coupled to the electron, ion and neutral dynamics including the chemical fragmentation of polystyrene. The solid-to-plasma transition is shown to significantly influence the temporal evolution of both free electron density and temperatures, which can lead to different shock formation and propagation compared with an initial plasma state. The influence of the solid-to-plasma transition on the shock dynamics is evidenced by considering the scaling law of the pressure with respect to the laser intensity. The ablator transition is shown to modify the scaling law exponent compared with an initial plasma state.

中文翻译：

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用于激光直接驱动惯性约束聚变水码的聚苯乙烯烧蚀器的固体到等离子体转变的改进建模

激光直接驱动惯性约束聚变 (ICF) 的目标性能可能会受到由目标表面的非均匀激光吸收（即烧蚀器上的激光印记）导致的流体动力学不稳定性的发展的限制。为了理解和描述这些不稳定性的形成，应该考虑激光照射期间的早期烧蚀器演变。在这项工作中，提出了用于激光直接驱动 ICF 的聚苯乙烯烧蚀器的固体到等离子体转变的改进建模。该模型致力于在专用于 ICF 的水代码中实现，这些水代码通常假定初始等离子体状态。本方法包括与电子、离子和中性动力学耦合的双温度模型，包括聚苯乙烯的化学碎裂。固体到等离子体的转变显着影响自由电子密度和温度的时间演变，与初始等离子体状态相比，这可能导致不同的冲击形成和传播。通过考虑压力相对于激光强度的标度定律，可以证明固体到等离子体转变对冲击动力学的影响。与初始等离子体状态相比，消融器转变显示出修改标度律指数。通过考虑压力相对于激光强度的标度定律，可以证明固体到等离子体转变对冲击动力学的影响。与初始等离子体状态相比，消融器转变显示出修改标度律指数。通过考虑压力相对于激光强度的标度定律，可以证明固体到等离子体转变对冲击动力学的影响。与初始等离子体状态相比，消融器转变显示出修改标度律指数。