RUI: Shell Structure and Collective Excitations in Exotic Nuclei

该项目吸引了乌尔西诺学院的本科生参与实验核结构研究。该项目是与佛罗里达州立大学（FSU）和劳伦斯伯克利国家实验室（LBNL）的同事正在进行的合作的一部分。乌尔西诺学院核结构小组将通过在FRIB和FSU的实验工作，有助于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来支持核结构界。该项目将通过在乌尔西诺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。本科生参与者将在课堂外应用他们的物理学知识，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操作，并在Ursinus学院夏季研究员研讨会和美国物理学会/核物理部会议上展示他们的工作。该项目包括两个独立的实验计划和一个探测器模拟工作。首先，在Ca-48以下的N=28同位素中驱动结构变化的机制，包括Z=14处N=28壳层的侵蚀，是一个非常感兴趣的话题，该小组建议在FRIB用逆运动学质子散射和库仑激发测量Si-42。所提出的Si-42的测量将扩展中子和质子对N=28的同位素中的第一个2+激发的相对贡献的经验图像，直到Z=14，其中N=28壳层崩溃。第二，第一个2+状态能量的系统学表明，N=32的子壳层间隙随着中子数的增加而减小，并且在Ca同位素以上完全消失。该小组建议继续他们正在进行的研究，通过在FSU对N=28 Cr-52靶进行中子转移测量来关闭N=32亚壳层。最后，该项目将支持继续开发GRETA伽马射线跟踪阵列的模拟。这项工作对核科学界很重要，至少有两个原因。首先，模拟是实验设计的核心工具，需要在FRIB的实验规划和建议。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。该奖项反映了NSF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 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.