University of Rochester Laboratory for Laser Energetics, Rochester 14623, New York, USA.
Lawrence Livermore National Laboratory, Livermore 94550, California, USA.
Phys Rev Lett. 2023 Apr 7;130(14):145103. doi: 10.1103/PhysRevLett.130.145103.
Inverse bremsstrahlung absorption was measured based on transmission through a finite-length plasma that was thoroughly characterized using spatially resolved Thomson scattering. Expected absorption was then calculated using the diagnosed plasma conditions while varying the absorption model components. To match data, it is necessary to account for (i) the Langdon effect; (ii) laser-frequency (rather than plasma-frequency) dependence in the Coulomb logarithm, as is typical of bremsstrahlung theories but not transport theories; and (iii) a correction due to ion screening. Radiation-hydrodynamic simulations of inertial confinement fusion implosions have to date used a Coulomb logarithm from the transport literature and no screening correction. We anticipate that updating the model for collisional absorption will substantially revise our understanding of laser-target coupling for such implosions.
基于通过经过充分特征描述的有限长等离子体的透射，测量了逆韧致辐射吸收，该等离子体使用空间分辨 Thomson 散射进行了充分的特征描述。然后，使用诊断的等离子体条件来计算预期的吸收，同时改变吸收模型组件。为了匹配数据，有必要考虑 (i) Langdon 效应；(ii) 在库仑对数中，激光频率（而不是等离子体频率）的依赖性，这是韧致辐射理论的典型特征，但不是输运理论的特征；以及 (iii) 离子屏蔽引起的修正。惯性约束聚变内爆的辐射流体动力学模拟迄今为止使用了输运文献中的库仑对数，并且没有屏蔽修正。我们预计，为碰撞吸收更新模型将大大改变我们对这种内爆的激光-靶耦合的理解。
