Plasma Physics and Controlled Fusion ( IF 2.2 ) Pub Date : 2021-03-31 , DOI: 10.1088/1361-6587/abe353 J L Milovich , O S Jones , R L Berger , G E Kemp , J S Oakdale , J Biener , M A Belyaev , D A Mariscal , S Langer , P A Sterne , S Sepke , M Stadermann
The interaction of laser radiation with foams of various porosities and low densities has been the subject of several numerical and experimental studies (Nicola et al 2012 Phys. Plasmas 19 113105; Perez et al 2014 Phys. Plasmas 21 023102). In all cases, the modeling of low-Z under-dense foams as uniform gases of equivalent average density using standard radiation-hydrodynamics codes has resulted in heat-front velocities that are considerably faster than those observed experimentally. It has been theoretically conjectured that this difference may be attributed to the breakdown of the foam’s morphology, leading to a dynamics of filament expansion where the ion and electron energy partitions are significantly different from those calculated using the uniform gas model. We found that 3D computer simulations employing a disconnected representation of the foam’s microstructure which allowed for the dynamics of foam element heating, expansion, and stagnation largely supported the theoretical picture. Simulations using this model for laser experiments on under-dense 2 mg cc−1 SiO2 aerogel foams (Mariscal et al 2021 Phys. Plasmas 28 013106) reproduced the experimental data fairly well. We used the validated model in simulations of low-density structured foam-like materials (produced via additive manufacturing) with a variety of morphologies. We found that the log-pile configurations were consistent with the analytical propagation model of Gus’kov et al (2011 Phys. Plasmas 18 103114). Further validation of the model was obtained by simulating experiments performed at the Jupiter Laser Facility using the log-pile and octet-truss foam morphologies. Simulations of the foam–laser interaction using a wave propagation code showed that the microstructure was able to enhance stimulated Brillouin scattering (SBS) by concentrating the light energy into density holes. In turn, this promotes laser filamentation, reducing SBS and bringing the predicted values closer to the experimental data.
中文翻译:
激光辐射与增材制造泡沫相互作用的模拟研究
激光辐射与各种孔隙率和低密度泡沫的相互作用已成为多项数值和实验研究的主题(Nicola等人2012 Phys. Plasmas 19 113105;Perez等人2014 Phys. Plasmas 21023102)。在所有情况下,使用标准辐射流体动力学代码将低 Z 低密度泡沫建模为具有等效平均密度的均匀气体,导致热前速度比实验观察到的速度快得多。理论上推测,这种差异可能归因于泡沫形态的破坏,导致长丝膨胀的动力学,其中离子和电子能量分配与使用均匀气体模型计算的那些明显不同。我们发现 3D 计算机模拟采用了泡沫微观结构的不连续表示,允许泡沫元件加热、膨胀和停滞的动力学在很大程度上支持理论图景。使用此模型进行低密度 2 mg cc 激光实验的模拟-1 SiO 2气凝胶泡沫(Mariscal et al 2021 Phys. Plasmas 28 013106)相当好地再现了实验数据。我们在具有各种形态的低密度结构泡沫状材料(通过增材制造生产)的模拟中使用了经过验证的模型。我们发现对数桩配置与 Gus'kov等人(2011 Phys. Plasmas 18)的分析传播模型一致103114)。模型的进一步验证是通过模拟在木星激光设施使用原木桩和八角形桁架泡沫形态进行的实验获得的。使用波传播代码对泡沫-激光相互作用的模拟表明,微结构能够通过将光能集中到密度孔中来增强受激布里渊散射 (SBS)。反过来,这会促进激光成丝,减少 SBS 并使预测值更接近实验数据。