The increase in entropy from the physical mixing of two adjacent materials in inertial confinement fusion (ICF) implosions and gas-filled hohlraums is analytically assessed. An idealized model of entropy generation from the mixing of identical ideal-gas particles across a material interface in the presence of pressure and temperature gradients is applied. Physically, mix-driven entropy generation refers to the work done by the gases in expanding into a larger common volume from atomic mixing under the condition of no internal energy change, or work needed to restore the initial unmixed state. The effect of a mix-generated entropy increase is analytically shown to lead to less compression of the composite ICF fluid under adiabatic conditions. The amount of entropy generation is estimated to be ∼10 J for a Rayleigh–Taylor-induced micrometer-scale annular mixing layer between the solid deuterium–tritium fuel and (undoped) high-density carbon pusher of an imploding capsule at the National Ignition Facility (NIF). This level of entropy generation is consistent with lower-than-expected fuel compressions measured on the NIF [Hurricane et al., Phys. Plasmas 26, 052704 (2019)]. The degree of entropy increase from mixing of high-Z hohlraum wall material and low-Z, moderate- to high-density gas fills is estimated to lead to ∼100 kJ of heat generation for NIF-scale experiments [Moody et al., Phys. Plasmas 21, 056317 (2014)]. This value represents a significant fraction of the inferred missing x-ray drive energy based on observed delays in capsule implosion times compared with mainline simulations [Jones et al., Phys. Plasmas 19, 056315 (2012)].

中文翻译：

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惯性约束聚变间接驱动目标中流体动力混合的熵产生

分析评估了惯性约束聚变 (ICF) 内爆和充气空腔中两种相邻材料的物理混合引起的熵增加。应用了在存在压力和温度梯度的情况下通过材料界面混合相同的理想气体粒子产生熵的理想模型。在物理上，混合驱动的熵生成是指气体在没有内能变化的情况下从原子混合膨胀到更大的公共体积所做的功，或恢复初始未混合状态所需的功。分析表明，混合生成的熵增加的影响导致在绝热条件下复合 ICF 流体的压缩较少。对于瑞利-泰勒诱导的微米级环形混合层，在国家点火装置的固体氘-氚燃料和（未掺杂的）高密度碳推进器之间的熵产生量估计为~10 J (NIF)。这种熵产生水平与在 NIF [Hurricane等。，物理。血浆26 , 052704 (2019)]。据估计，高Z空腔壁材料和低Z中到高密度气体填充的混合导致的熵增加程度导致 NIF 规模实验产生约 100 kJ 的热量 [Moody等人。，物理。血浆21 , 056317 (2014)]。与主线模拟相比，该值代表了基于观察到的胶囊内爆时间延迟而推断出的缺失 X 射线驱动能量的很大一部分 [Jones et al. ，物理。血浆19 , 056315 (2012)]。