Studies of Exotic Nuclei with the MoNA LISA Neutron Detectors

中央密歇根大学的一名教员和他的本科生是建造、组装和测试价值100万美元的模块化中子阵列(MONA)的合作者，该阵列于2004年完成。随后，该合作获得了美国国家科学基金会130万美元的赠款，用于建造大型多机构闪烁体阵列(LISA)。蒙娜丽莎中子探测器串联在国家超导回旋加速器实验室(NSCL)与扫描磁铁一起使用。《蒙娜丽莎》的主要目的是提取中子非束缚核的质量和非束缚态的激发能。要解决的物理问题是位于滴线附近甚至更远的非常轻的、非常富含中子的原子核。这是非常弱束缚核子物质的领域，在那里已经观察到了令人着迷的新现象，例如光晕或壳层结构的剧烈变化。Mona Lisa和Sweeper探测系统非常适合于通过研究近滴线核的基态和低激发态的性质来探索其内在结构。它还将提供有关位于滴线及更远的原子核中粒子发射阈值上方的低激发共振的信息。最后，探测器的设计方式是，它们可以很容易地以符合的方式测量中子，从而也可以详细地研究发射的中子之间的关联。MONA的合作处于一个独特的情况下，这与任何其他在NSCL提出实验的合作或研究小组截然不同。具体地说，它首先允许以本科生为主的机构的教授及其本科生参与顶级研究工具的建设。该集团已经应对了从建设向生产转型的挑战。我们已经建立了一个独特的分析方案，允许本科生项目参与MONA实验的运行、减少和分析。因此，112名本科生有机会参与尖端核物理实验。此外，中央密歇根大学积极努力让高中生和他们的老师接触实验核物理，甚至把莫纳带给了密歇根州的立法者和他们的工作人员。

A faculty member and his undergraduates at Central Michigan University were collaborators in the construction, assembly, and testing of the one million dollar Modular Neutron Array (MoNA) which was completed in 2004. Subsequently, the collaboration received a $1.3 Million NSF grant to construct the Large multi-Institutional Scintillator Array (LISA). The MoNA LISA neutron detector tandem is used with the Sweeper magnet at the National Superconducting Cyclotron Laboratory (NSCL). The main purpose of MoNA LISA is to extract masses of neutron-unbound nuclei and excitation energies of unbound states. The physics to be addressed is that of light, very neutron-rich nuclei located in the direct vicinity of the drip line or even beyond. This is the domain of very weakly bound nucleonic matter where fascinating new phenomena have already been observed, such as halos or drastic changes in shell structure. The MoNA LISA and Sweeper detection system is ideally suited to explore the intrinsic structure of near drip line nuclei by studying the properties of their ground and low excited states. It will also provide information about low-lying resonances located just above the particle emission threshold in nuclei at the drip line and beyond. Finally, the detectors are designed in such a way that they can readily measure neutrons in coincidence so that correlations between emitted neutrons can be investigatedin detail as well.The MoNA collaboration is in a unique situation that is quite different from any other collaboration or research group proposing experiments at the NSCL. Specifically it first allowed professors from predominantly undergraduate institutions and their undergraduate students to participate in the construction of a top-level research instrument. The group has answered the challenge to transform from construction to production. We have built a unique analysis scheme that allows the undergraduate programs to be involved in the running, reduction, and analysis of MoNA experiments. As a result, 112 undergraduates have had the opportunity to participate in cutting-edge nuclear physics experiments. Additionally, Central Michigan University has aggressively worked to expose high school students and their teachers to experimental nuclear physics, and has even brought MoNA to Michigan state legislators and their staffs.