Studies of Exotic Nuclei with the MoNA LISA Neutron Detectors

中密歇根大学的一名教员和他的本科生合作建造、组装和测试了价值100万美元的模块化中子阵列（MoNA），该阵列于2004年完成。随后，该合作获得了130万美元的NSF拨款，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）与扫荡磁体一起使用。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轻的、富含中子的原子核。这是非常弱束缚的核物质的领域，在那里已经观察到迷人的新现象，如光晕或壳结构的剧烈变化。MoNA LISA和Sweeper探测系统非常适合通过研究其基态和低激发态的性质来探索近滴线核的内在结构。它还将提供位于滴注线和滴注线以外的原子核中刚好高于粒子发射阈值的低洼共振的信息。最后，探测器被设计成这样一种方式，它们可以很容易地测量中子的巧合，这样发射的中子之间的相关性也可以被详细地研究。MoNA的合作是一个独特的情况，与任何其他合作或研究小组在国家科学实验室提出的实验都大不相同。具体来说，它首次允许以本科院校为主的教授和他们的本科生参与到顶级研究仪器的建设中来。该集团已经应对了从建筑向生产转型的挑战。我们建立了一个独特的分析方案，允许本科生参与MoNA实验的运行、还原和分析。因此，112名本科生有机会参与最前沿的核物理实验。此外，中密歇根大学积极致力于让高中生和他们的老师接触实验核物理，甚至把MoNA带给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.