Nuclear Structure and Nuclear Astrophysics

核天体物理学基本上就是恒星的物理学。恒星是如何形成的，它们是如何产生能量的，以及它们是如何结束的——有时是平静的，有时是灾难性的爆炸——是这个领域试图理解和提供答案的问题。这项工作的主要目的是试图了解核反应，核反应对恒星的能量产生和宇宙中观测到的大多数重元素的形成至关重要。我们将使用我们实验室和世界各地实验室中可用的粒子加速器，来研究对我们理解这些现象至关重要的特定核反应，特别是恒星环境中重元素的合成过程。在整体的方法中，我们将研究某些反应进行的速率以及这些速率对产生高质量原子核的影响，测量对这一过程至关重要的原子核的原子质量，研究这些反应的理论基础，并确定进一步研究的途径。我们还将研究核物质的体积特性，以便更好地了解中子星的形成以及在恒星存在的最后时刻发生超新星爆炸的概率。在这些研究的一种新方法中，我们将使用加速器质谱技术（以其在放射性碳测年中的应用而闻名）来识别发生在天体物理反应中的非常罕见的过程。这项工作的另一个方面是研究原子核量子运动的一些奇特方面。这些研究原子核“结构”的主要目的是了解原子核的组成部分——质子和中子——相互作用的基本方式，以及这些相互作用是如何导致观察到的核性质的。提出的若干核结构研究对构成本项目主体的天体物理现象有直接影响。拟议工作的一个非常重要的组成部分是培训年轻科学家。除了一些博士后之外，大量的研究生和本科生将参与这项工作。这些年轻的科学家将在未来几年形成训练有素的人才储备，不仅对美国在前沿科学技术领域的持续领导地位至关重要，而且对我们在国防和国土安全方面的努力也至关重要。

Nuclear Astrophysics is, basically, the physics of stars. How the stars form, how they generate the energy that powers them, and how they reach their end--sometimes quietly, at other times in cataclysmic explosions--are the questions this field seeks to understand and provide answers to. The primary aim of the proposed work is to attempt to understand the nuclear reactions that are critical to the energy generation in stars and to the formation of most of the heavy elements that are observed in the Universe. We will use the particle accelerators available in our laboratory, and at laboratories around the world, to investigate specific nuclear reactions that are critical to our understanding of these phenomena, in particular the process of synthesis of heavy elements in the stellar environment. In a holistic approach, we will look at the rate at which certain reactions proceed and the impact these rates have on the generation of higher mass nuclei, measure the atomic masses of the nuclei that are crucial to this process, investigate the theoretical underpinnings of these reactions, and identify avenues of further research. We will also study bulk properties of nuclear matter to better understand the formation of neutron stars and the probability of supernova explosions in the final moments of a star's existence. In a novel approach to these investigations, we will use the techniques of accelerator mass spectrometry (widely known for its use in radiocarbon dating) to identify very rare processes occurring in astrophysical reactions. Another aspect of this work is to investigate some exotic aspects of the quantal motion of the atomic nuclei. The primary aim of these investigations of the "structure" of the atomic nuclei is to understand the fundamental way in which the constituents of the atomic nucleus--the protons and neutrons--interact with each other, and how these interactions lead to the observed nuclear properties. A number of the proposed studies of nuclear structure have direct implications on the astrophysical phenomena the investigation of which constitute the main body of this project. A very important component of the proposed work is training of young scientists. A large number of graduate students and undergraduate students will be involved with this work, in addition to a few postdoctoral fellows. These young cientists will, in the future years, form the pool of highly-trained personnel, so crucial not only to the continuing leadership of the United States in frontier fields of science and technology, but also to our efforts in defense and homeland security.