Probing Nuclear Structure with Fast Neutrons

原子核由质子和中子组成，形状各异。一些核是球形的，而另一些核是非球形的（类似于洋葱、西葫芦或梨）；每种元素的每种同位素的原子核形状都是独一无二的。因为我们不能拍摄原子核的普通照片来研究它的形状和结构，所以必须采用其他方法。通过肯塔基大学粒子加速器的反应，产生中子，然后从原子核散射出去。在这个过程中，原子核获得并随后释放出可以被探测到的能量。这些信息被用来推断原子核的形状，并了解原子核中的中子和质子是如何影响它的性质的。该研究项目的毕业生将获得粒子加速器操作、核科学仪器、辐射探测和数据采集系统的实践经验，并成为训练有素的核科学家，能够为我们的国家需求做出重要贡献。肯塔基大学加速器实验室的基础广泛的研究项目包括几个前沿领域的研究：与中微子双β衰变相关的核结构；经历形状转变的核；变形结构与形态共存；核结构的贡献支持对基本对称性的研究。在本研究中，快中子的非弹性散射被用于检测低能集体核激发，并获得非激发态的能级寿命和跃迁多极混合比等其他反应无法获得的信息。稳定核的详细研究补充了在极端温度和角动量条件下或远离稳定区域研究核结构所取得的进展。实验室的实验创新，例如测量重核寿命的能力的发展，在这项研究中发挥了关键作用。这些进步，加上这个实验室生产高质量、时间束的单能中子的独特能力，探测了重要问题，并为我们的核结构知识做出了有意义的贡献。

Atomic nuclei are composed of protons and neutrons and exhibit a variety of shapes. Some nuclei are spherical, while others have non-spherical shapes (similar to an onion, a zucchini, or a pear); the shape of the nucleus is unique for each isotope of each element. Because we cannot take an ordinary photograph of the nucleus to investigate its shape and structure, other methods must be employed. Through reactions at the University of Kentucky particle accelerator, neutrons are produced and then scattered from the nucleus. In the process, the nucleus gains and subsequently releases energy that can be detected. This information is used to deduce the shape of the nucleus and to gain an understanding of how the neutrons and protons in the nucleus contribute to its properties. Graduates of this research program receive hands-on experience with particle accelerator operation, nuclear science instrumentation, radiation detection, and data acquisition systems, and emerge as well-trained nuclear scientists who are capable of important contributions to our national needs. The broad-based research program at the University of Kentucky Accelerator Laboratory includes studies in several forefront areas: nuclear structure relevant to neutrinoless double-beta decay; nuclei undergoing shape transitions; deformed structures and shape coexistence; nuclear structure contributions in support of searches for fundamental symmetries. In this research, the inelastic scattering of fast neutrons is used to examine low-energy collective nuclear excitations and to obtain information, e.g., level lifetimes and transition multipole mixing ratios for non-yrast states, which is inaccessible with other reactions. Detailed investigations of stable nuclei complement advances in nuclear structure achieved by studying nuclei at extreme conditions of temperature and angular momentum or in regions far from stability. Experimental innovations in the laboratory, e.g., the development of capabilities for measuring lifetimes in heavy nuclei, have played a key role in this research. These advances, coupled with the unique capabilities of this laboratory for the production of high-quality, time-bunched monoenergetic neutrons, probe important questions and make meaningful contributions to our knowledge of nuclear structure.