Ultracold Neutral Plasmas as High Energy Density Plasma Simulators

这个项目将推进对剧烈碰撞中离子温度变化的基本理解。在美国和其他地方已经建造了非常强大的激光器来产生小的、可控的核反应。这些激光被紧密聚焦，将原子加热到数百万度的温度，并迫使它们猛烈碰撞。准确理解这一过程是如何工作的，对于优化未来激光驱动核反应的实验至关重要。这个项目将在一个实验中以慢动作重现剧烈的离子碰撞，在这个实验中，离子运动可以以极高的精度测量。在与理论专家的合作下，研究结果将用于验证计算机模拟。这些模拟，反过来，可以更有信心地应用于更高温度的激光驱动实验。除了这一重要的科学贡献之外，该项目还将允许本科生和研究生参与等离子体科学领域的前沿研究。激光驱动高能量密度实验产生的等离子体变化很快。等离子体是由包覆的低温固体氘氚燃料靶在激光能量的加热和压缩下形成的。等离子体温度从接近绝对零度上升到数百万度，密度上升到固态密度以上。在整个过程中对碰撞进行建模需要许多不同的近似，使计算机模拟快速变化的环境变得复杂。在这样的等离子体中，电子和离子温度和密度的实验测量也具有挑战性，因为剧烈的物理条件和将测量量转换为基本等离子体特性所需的密集建模。通过适当的温度和密度缩放，该研究项目将在一些难以建模和难以测量的情况下探索碰撞动力学。该项目将在一系列初始密度和温度以及几种不同几何形状下，研究强耦合等离子体状态下的能量传递、辐射加热和热松弛。第一个任务将是测量双种超冷中性等离子体中的动量传递和碰撞加热。第二项任务将是测量磁化和未磁化的超冷中性等离子体中的电子-离子能量弛豫。研究生和本科生将被招募和训练来进行实验。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will advance fundamental understanding of how ion temperatures change during violent collisions. Extremely powerful lasers have been built in the US and elsewhere to create small, controlled nuclear reactions. These lasers are tightly focused to heat atoms to temperatures of millions of degrees and force them to collide violently. Understanding exactly how this process works is critical for optimizing future experiments in laser-driven nuclear reactions. This project will reproduce violent ion collisions in slow-motion in an experiment where the ion motion can be measured with extreme precision. In collaboration with theory specialists, the results will be used to validate computer simulations. These simulations, in turn, can then be applied to higher temperature laser-driven experiments with greater confidence. In addition to this important scientific contribution, this project will allow undergraduate and graduate students to participate in cutting-edge research in the field of plasma science.The plasma generated in laser-driven high energy density (HED) experiments changes rapidly. The plasma is formed when a coated cryogenic solid deuterium-tritium fuel target is heated and compressed by laser energy. The plasma temperature rises from nearly absolute zero to millions of degrees and the density rises above solid-state density. Modeling collisions throughout this process requires many different approximations, complicating computer simulations of the rapidly changing environment. Experimental measurements of the electron and ion temperature and density are also challenging in such HED plasmas, due to both the violent physical conditions and the intensive modeling required to convert measured quantities into basic plasma properties. With appropriate temperature- and density-scaling, this research project will probe collision dynamics in some of these difficult-to-model and difficult-to-measure circumstances. The project will study energy transfer, radiative heating, and thermal relaxation in the strongly-coupled-plasma regime, over a range of initial densities and temperatures and for a few different geometries. The first task will be to measure momentum transfer and collisional heating in a dual-species ultracold neutral plasma. The second task will be aimed at measuring electron-ion energy relaxation in magnetized and unmagnetized ultracold neutral plasmas. ​Graduate and undergraduate students will be recruited and trained to work on the experiments.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.