Investigations of Exotic Nuclei with Large Arrays

用大阵列研究奇异核

• 批准号: SAPIN-2016-00045
• 负责人: Andreoiu, Corina
• 金额: $ 1.82万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=616813
• 关键词: Investigations; Exotic; Nuclei; Large; Arrays

Almost every element on earth was formed at the core of a star. Nuclear reactions continually convert light elements into heavier ones, but the exact mechanism and astrophysical site where this takes place remain unclear. This situation arises because there are many ambiguities concerning the exact nature of the nuclear strong force, which is responsible for binding the protons and neutrons together at the centre of an atom. A primary goal of contemporary nuclear physics is to reveal a comprehensive unified description of this force so that we can understand the origin and evolution of all nuclear matter. The vast majority of elements existing on earth are stable nuclei, forming the so-called valley of nuclear stability. These stable nuclei are well described in the nuclear shell model developed by Nobel laureates M. Goppert-Mayers and J. H. Jensen in the late 1940s. This model has successfully explained many experimental observations, including the existence of the so-called magic numbers, a special set of proton and neutron numbers (2, 8, 20, 28, 82 and 126) that brings extra stability to nuclear matter, similar to the electron configurations of the noble gases in chemistry. For decades, the shell model has been the backbone to our understanding of nuclear structure. In recent years, experimental investigations of nuclei with larger numbers of neutrons compared to protons have revealed new magic numbers in these exotic nuclei. The challenge is to understand why exactly the magic numbers shift with different combinations of protons and neutrons, and to successfully predict whether other more exotic nuclei that might only exist for fractions of a second can be formed far from stability. The evolution of shell structure could lead to a new frontier of nuclear stability comprehension. In order to develop new models that will describe the structure of nuclear matter far from stability, the evolution of magic numbers, and the creation of elements in stars, scientists need detailed knowledge of nuclear masses, lifetimes, and decay probabilities. Experimental nuclear science, such as that described in this proposal, is responsible for the critical gathering of information for nuclei situated far from stability. In particular, the multitude of tin nuclei makes an excellent case study because they all have a magic number of 50 protons, and many tin isotopes exist far from stability with neutron numbers beyond the magic number of 82. The proposed experiments will take place mainly at TRIUMF in Vancouver, BC. Unstable nuclei are created on-site with the world’s largest cyclotron. These nuclei are then investigated with large state-of-the-art detectors that are able to observe the radiation emitted when the nuclei decay. The information extracted from these experiments provides clues into the nuclear matter and produces essential information for nuclear astrophysics about the creation of elements in the universe.

地球上几乎每个元素都是在恒星的核心上形成的。核反应不断地将光元素转化为较重的元素，但是发生这种情况的确切机制和天体物理部位尚不清楚。之所以出现这种情况，是因为有许多歧义涉及核强力的确切性质，核强力的确切性质是将质子和中子在原子中心结合在一起的原因。当代核物理学的主要目标是揭示对这项力量的全面统一描述，以便我们可以理解所有核物质的起源和进化。 地球上存在的绝大多数元素都是稳定的核，形成了所谓的核稳定谷。这些稳定的核在1940年代后期由诺贝尔奖获得者M. Goppert-Mayers和J. H. Jensen开发的核壳模型中得到很好的描述。该模型成功地解释了许多实验观察结果，包括存在所谓的魔法数，这是一组特殊的质子和中子数（2、8、20、28、82和126），这些数字与核物质具有额外的稳定性，类似于化学中贵族气体的电子构型。几十年来，壳模型一直是我们对核结构的理解的骨干。近年来，与质子相比，中性数量较大的核研究显示了这些异国情调的核数。面临的挑战是要了解为什么魔术数与质子和中子的不同组合的确切转移，并成功预测其他更奇特的核能是否仅在第二个部分而出现，而不是稳定性。壳结构的演变可能导致核稳定性理解的新边界。 为了开发新的模型，这些模型将描述核物质的结构远非稳定性，魔术数的演变以及恒星中元素的创造，科学家需要详细了解核质量，生命和衰减可能性。 实验性核科学，例如本提案中描述的核科学，是造成远非稳定性的核科学收集的重要收集。特别是，众多的锡核构成了一项出色的案例研究，因为它们都具有50个质子的魔术数，而且许多锡同位素远非稳定性，中子数超过82的中子数。拟议的实验将主要发生在BC的温哥华市的Triumf。不稳定的核是与世界上最大的回旋加成的现场创建的。然后对这些核进行研究，以大量的最新探测器能够观察到核衰减时发出的辐射。从这些实验中提取的信息为核物质提供了线索，并为核天体物理学产生有关宇宙中元素的基本信息。