High-resolution inelastic x-ray scattering in warm dense matter

热致密物质中的高分辨率非弹性 X 射线散射

• 批准号: 493108501
• 负责人: Professor Dr. Ronald Redmer
• 金额: --
• 依托单位: European X-Ray Free-Electron Laser Facility (XFEL)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/493108501?language=en
• 关键词: resolution; inelastic; ray; scattering; warm

The project aims at determining low-frequency structural dynamics in warm dense matter by highly resolved inelastic x-ray scattering. We jointly develop (a) the experimental platform at the High-Energy Density instrument at the European XFEL GmbH in Schenefeld (EuXFEL) and (b) the required theoretical framework by using density functional theory molecular dynamics simulations (DFT-MD) at the U Rostock. We treat Al and Fe in this project. The behavior of both materials under extreme conditions is of high interest but specific for our purposes. First, we investigate the simple metal Al which is experimentally and theoretically well manageable so that many data on the structural, thermodynamic, transport an optcial properties exist both for the solid and liquid state. This data set will be extended to the warm dense matter region in this project. Based on this benchmark study for Al we will treat Fe under such extreme conditions which are relevant for geophysics (solid inner and liquid outer core of Earth) as well as forplanetary physics (super-Earths). Warm dense matter is characterized by temperatures of few eV, high densities (condensed matter and beyond) and pressures (several Mbar). Such plasma parameters are generated by, e.g., irradiating the target with intense optical laser pulses for which the DiPOLE-100X laser will be availbale at EuXFEL (< 100 J, < 15 ns) from 2022 onwards. These highly transient excited states will then be probed by bright, ultrashort pulses with few meV spectra bandwidth from the EuXFEL. Since the experiments will allow for repetition rates of several Hz, the quality of the expected data goes far beyond current capabilities so that new insight in the structure and dynamics of warm dense matter, in particular of Al and Fe, will be gained. Simultaneously, the x-ray spectra will be determined by calculating the dynamic structure factor of warm dense matter (Al and Fe) by using DFT-MD simulations. Comparing the experimental data with a generalized hydrodynamic model finally allows us for the first time to directly extract the ion temperature, sound speed, thermal conductivity and viscosity for the extreme conditions of warm dense matter. In particular, the results for Fe will be essential for geophysics and planetary physics and will allow new insight in processes in the solid inner and liquid outer core of Earth. Furthermore, the new data will also allow to benchmark current models for the interior structure and evolution of super-Earths, besides mini-Neptunes the most abundant class of exoplanets.

该项目旨在通过高分辨非弹性x射线散射确定热致密物质的低频结构动力学。我们共同开发了(a)在Schenefeld欧洲XFEL有限公司的高能密度仪器上的实验平台（EuXFEL）和(b)在U Rostock使用密度泛函理论分子动力学模拟（DFT-MD）所需的理论框架。我们在这个项目中处理Al和Fe。这两种材料在极端条件下的行为是我们非常感兴趣的，但对我们的目的来说是特殊的。首先，我们研究了简单的金属Al，它在实验和理论上都很好地管理，因此固态和液态都存在许多关于结构、热力学、输运和光学性质的数据。该数据集将在本项目中扩展到热致密物质区域。基于对Al的基准研究，我们将在与地球物理学（地球的固体内核和液体外核）以及行星物理学（超级地球）相关的极端条件下处理Fe。热致密物质的特点是温度低至几电子伏，密度高（凝聚态物质及以上），压力大（几毫巴）。这些等离子体参数是通过，例如，用强光激光脉冲照射目标产生的，从2022年起，di极点- 100x激光器将在EuXFEL （< 100 J, < 15 ns）上可用。这些高度瞬态激发态将被来自EuXFEL的明亮的超短脉冲探测，这些脉冲的光谱带宽只有很少的meV。由于实验将允许几赫兹的重复率，预期数据的质量将远远超出当前的能力，因此将获得对热致密物质，特别是Al和Fe的结构和动力学的新见解。同时，通过DFT-MD模拟计算热致密物质（Al和Fe）的动态结构因子来确定x射线能谱。将实验数据与广义流体力学模型进行比较，使我们首次可以直接提取热致密物质极端条件下的离子温度、声速、导热系数和粘度。特别是，铁的结果将对地球物理学和行星物理学至关重要，并将使人们对地球固体内核和液体外核的过程有新的认识。此外，新的数据还将允许对超级地球的内部结构和演化的现有模型进行基准测试，除了迷你海王星（数量最多的系外行星）。