Ultracold Neutral Plasmas as High Energy Density Plasma Simulators

该项目将推进对剧烈碰撞期间离子温度如何变化的基本理解。在美国和其他地方已经建造了非常强大的激光器来制造小型的，可控的核反应。这些激光被紧紧聚焦，将原子加热到数百万度的温度，迫使它们猛烈碰撞。准确理解这一过程是如何工作的，对于优化激光驱动核反应的未来实验至关重要。该项目将在一个实验中以慢动作再现剧烈的离子碰撞，在这个实验中，离子运动可以被极其精确地测量。与理论专家合作，结果将用于验证计算机模拟。反过来，这些模拟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。在激光驱动的高能量密度（HED）实验中产生的等离子体变化迅速。等离子体是在激光能量加热和压缩低温固体氘氚燃料靶时形成的。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，这使得对快速变化的环境的计算机模拟变得复杂。在这种HED等离子体中，电子和离子温度和密度的实验测量也是具有挑战性的，这是由于将测量的量转换为基本等离子体性质所需的剧烈物理条件和密集建模。通过适当的温度和密度标度，本研究项目将探索这些难以建模和难以测量的情况下的碰撞动力学。该项目将研究强耦合等离子体制度中的能量传递，辐射加热和热弛豫，在初始密度和温度范围内以及几种不同的几何形状。第一个任务将是测量双组分超冷中性等离子体中的动量传递和碰撞加热。 第二项任务的目标是测量磁化和未磁化超冷中性等离子体中的电子-离子能量弛豫。 该奖项反映了NSF的法定使命，并通过使用基金会的智力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.