RUI: Shell Structure and Collective Excitations in Exotic Nuclei

这个项目邀请乌尔辛斯学院的本科生进行实验性的核结构研究。该项目是与稀有同位素束设施(FRIB)、佛罗里达州立大学(FSU)和劳伦斯伯克利国家实验室(LBNL)的同事们正在进行的合作的一部分。乌尔辛斯学院核结构小组将通过FRIB和FSU的实验工作，帮助理解单粒子和集体激发的系统演化。该小组还将通过继续开发在FRIB广泛使用的GRETA伽马射线跟踪阵列的模拟，为核结构界提供支持。该项目将通过在乌尔辛斯学院校园内保持积极的核结构研究计划，为STEM工作人员的培训做出贡献。本科生学员将在课堂之外应用他们的物理知识，获得数据采集、分析和模拟方面的实用技能，观察和参与核加速器设施的运行，并在乌尔辛斯学院夏季研究员研讨会和美国物理学会/核物理系会议上展示他们的工作。该项目包括两个独立的实验项目和一个探测器模拟工作。首先，推动Ca-48以下N=28同位素结构变化的机制(S)，包括在Z=14处N=28壳层的侵蚀，是该小组建议在FRIB上通过对Si-42的逆运动学质子散射和库仑激发测量来解决的一个非常感兴趣的话题。所提出的对Si-42的测量将把N=28同位素中中子和质子对第一个2+激发的相对贡献的经验图扩展到Z=14，此时N=28壳层坍塌。第二，对前2+态能量的系统学研究表明，N=32亚壳层能隙随着Ca同位素以上中子数的增加而减小，而在Fe同位素上则完全消失。该小组建议通过对FSU的N=28Cr-52靶进行中子转移测量，继续他们正在进行的关于关闭N=32亚壳的调查。最后，该项目将支持继续开发格雷塔伽马射线跟踪阵列的模拟。这项工作对核科学界来说很重要，至少有两个原因。首先，模拟是实验设计的中心工具，在FRIB的实验计划和建议中是必需的。其次，由于许多实验技术的复杂性，需要精确的模拟来从原始数据中提取实验结果。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project engages Ursinus College undergraduates in experimental nuclear structure research. The project is part of an ongoing collaboration with colleagues at the Facility for Rare Isotope Beams (FRIB), Florida State University (FSU), and the Lawrence Berkeley National Laboratory (LBNL). The Ursinus College Nuclear Structure Group will contribute to the understanding of the systematic evolution of single-particle and collective excitations through experimental work at FRIB and FSU. The group will also support the nuclear structure community through the continuing development of simulations of the GRETA gamma-ray tracking array used extensively at FRIB. The project will contribute to the training of the STEM work force by maintaining an active research program in nuclear structure on the Ursinus College campus. Undergraduate participants will apply their knowledge of physics outside the classroom, gain practical skills in data acquisition, analysis, and simulation, observe and participate in the operation of nuclear accelerator facilities and present their work at the Ursinus College Summer Fellows Symposium and at American Physical Society/Division of Nuclear Physics meetings.The project consists of two independent experimental programs and a detector simulation effort. First, the mechanism(s) driving changes in structure in the N=28 isotones below Ca-48, including the erosion of the N=28 shell at Z=14 is a topic of great interest which the group proposes to address at FRIB with inverse-kinematics proton scattering and Coulomb excitation measurements of Si-42. The proposed measurements of Si-42 will extend the empirical picture of the relative contributions of neutrons and protons to first 2+ excitations in the N=28 isotones down to Z=14, where the N=28 shell collapses. Second, the systematics of first 2+ state energies suggest that the N=32 subshell gap decreases with increasing neutron number above the Ca isotopes and vanishes entirely in the Fe isotopes. The group proposes to continue their ongoing investigation of the closing of the N=32 subshell through a neutron-transfer measurement to an N=28 Cr-52 target at FSU. Finally, the project will support the continuing development of simulations of the GRETA gamma-ray tracking array. This work is an important to the nuclear science community for at least two reasons. First, simulations are a central tool in experimental design, needed for the planning and proposal of experiments at FRIB. Second, due to the complexity of many experimental techniques, accurate simulations are needed to extract experimental results from raw data.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.