Diagnosing Astrophysical Plasmas Using Laser-Driven Nucleosynthesis in Far-From-Equilibrium Plasmas

本项目将利用超强激光研究高温致密等离子体中的聚变反应。我们周围所有常规物质的元素都是由轻元素融合而成的，从最轻的氢开始，依次变成更重的元素，如碳、氧、铝、铁和镍，这些元素是在恒星的核心合成的，比如太阳。氢原子聚变形成氦，两个氦原子聚变形成铍，等等。铜、银、金或铀等较重的元素是在大质量恒星燃烧的外壳和超新星爆炸中通过核合成形成的。在几乎所有情况下，这些核聚变过程都发生在高温、密集的等离子体环境中。到目前为止，使用加速器测量的核聚变反应还没有包括这些等离子体背景。这可能导致观测到的元素数量与天文测量推断的元素数量之间存在显著差异。这些差异也影响了我们对恒星及其演化的理解，以及在聚变技术中使用这些过程。通过使用超强激光，该项目将在高温致密等离子体中产生聚变反应，并测量聚变过程。在几万亿分之一秒的时间里，激光会产生10亿度的高温等离子体，并将原子加速到所需的能量，使它们发生聚变。通过测量不同的逃逸粒子，就有可能了解等离子体的条件以及它们如何影响聚变反应。这些数据可以用来改进核和恒星模型，提高我们对宇宙的理解，甚至可能有助于开发地球上的可控核聚变技术，提供无限的清洁能源。本项目计算和测量等离子体诱导的远平衡等离子体中轻核聚变反应的修正，目的是在受控的实验室条件下增加中子通量和反应速率。研究的主要反应，氘核-氘核聚变，被认为是激光驱动中子源的有希望的，并且已被证明在中子谱中携带有关等离子体的信息。该项目包括理论、计算和实验工作。理论工作将计算核反应速率的修正和等离子体条件下的观测值。数值模拟将比较激光和目标参数，以优化能量转移到氘核。模拟还将提供电子和氘核的分布，作为聚变截面及其等离子体相关修正的输入，以及反应体积和约束时间。实验计划从利用最近发展起来的中子和等离子体诊断技术改进德克萨斯petwat上的等离子体和中子测量开始。然后，该项目将通过逐步扩大到罗马尼亚的极光基础设施-核物理（ELI-NP）设施的实验来开辟新的领域。ELI-NP提供的广泛的光子和中子诊断套件将使精度和角度覆盖范围得到更大的提高，并可能允许搜索次级核反应。本项目将根据理论和仿真的进展对实验数据进行分析。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 study fusion reactions in a hot dense plasma by using ultraintense lasers. All elements of regular matter around us stem from fusing together light elements, starting with hydrogen as the lightest, into successively heavier elements, like carbon, oxygen, aluminum, iron, and nickel, which are synthesized in the cores of stars, like the sun. Hydrogen atoms fuse to form Helium, two helium atoms fuse to form beryllium, and so on. Heavier elements like copper, silver, gold, or uranium, are formed via nucleosynthesis within burning shells of massive stars and in supernova explosions. In almost every case, these nuclear fusion processes happen in a hot, dense plasma environment. Up to now, measurements of the nuclear fusion reactions using accelerators have not included these plasma backgrounds. This may have led to significant observed discrepancies between the expected amount of elements and those inferred from astronomical measurements. These discrepancies also influence our understanding of stars and their evolution as well as the use of these processes in fusion technologies. By using ultraintense lasers, this project will create fusion reactions in a hot dense plasma and measure the fusion processes. For a few trillionth of a second the laser will create a billion-degree hot plasma and accelerate atoms to the required energies to cause them to fuse. By measuring the different escaping particles, it is then possible to understand both the plasma conditions and how they influence the fusion reactions. This data can then be used to improve nuclear and stellar models and improve our understanding of the universe and maybe even help to develop controlled fusion technology here on earth, providing an infinite clean energy source.This project computes and measures plasma-induced corrections to fusion reactions between light nuclei in far-from-equilibrium plasmas with the aim of increasing neutron flux and reaction rate in controlled laboratory conditions. The primary reaction of study, deuteron-deuteron fusion, is known as promising for laser-driven neutron sources and has been shown to carry information about the plasma in the neutron spectrum. The project includes theoretical, computational and experimental efforts. The theory effort will compute corrections to nuclear reaction rates and observables from plasma conditions. Numerical simulations will compare laser and target parameters to optimize energy transfer to deuterons. Simulations will also provide the distribution of electrons and deuterons as inputs to the fusion cross sections and their plasma-dependent corrections, as well as reaction volume and confinement time. The experiment plan begins with improving plasma and neutron measurements at the Texas Petawatt using neutron and plasma diagnostics developed recently. The project will then break new ground by scaling up stepwise to experiments at the Extreme Light Infrastructure-Nuclear Physics (ELI-NP) facility in Romania. The extensive suite of photon and neutron diagnostics available at ELI-NP will enable greater improvements in precision and angular coverage and may allow searching for secondary nuclear reactions. The project will conclude with analysis of the experimental data in light of the theory and simulation progress.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.