Collaborative Research: Nuclear Reaction and Structure Studies with Radioactive and Stable Beams

这项由该奖项资助的研究旨在促进对原子核的更好理解，原子核是宇宙中所有正常物质的基本构件。它们是如何在大爆炸之后形成的，它们现在是如何相互作用来改变它们的基本元素性质的？有没有由非常奇异的原子核组成的新形式的物质？我们如何制造和研究这些？为此，该小组将开发核科学方面的特殊新技术，并培训能够帮助回答其中一些问题的未来科学家。一个重要的培训部分将是密歇根州新布法罗高中向教职员工和学生提供的成熟和非常成功的外联活动的继续，该活动向这些学生介绍了有趣、重要和令人兴奋的科学职业。这项研究中开发和使用的技术将在其他重要领域得到应用，如国土安全(核恐怖主义)、核废料的安全储存和监测，以及包括放射治疗在内的核医学应用。后者包括一种与这项研究直接相关的新模式：用于治疗特定形式癌症肿瘤的离子束的产生和成像。在该集团过去的研究项目中，近50%的研究生和其他人员目前正在从事核安全或核医学方面的职业生涯，预计由于目前的授权，这种情况将继续下去。拟议的项目将涉及利用稳定的和短寿命的放射性核束研究核反应，以及开发促进此类研究的仪器、技术和仪器。这包括使用圣母大学正在运行的TwinSol低能放射性离子束设施，该设施由密歇根大学(UM)和圣母大学联合开发。具体的实验将着重于研究核稳定极限附近富中子和质子核的结构和反应机制，以阐明在稳定极限下弱束缚系统出现的奇异“核晕”结构对库仑势垒附近的聚变、转移、非弹性激发和解体几率的影响。这里特别令人感兴趣的是，由于接近连续统是弱束缚系统的特征定义特征，所以到连续统和在连续统内的更高阶耦合对各种反应机制的影响。这些研究将在TwinSol与国家超导回旋加速器实验室(NSCL)的一个小组合作进行，利用一个原型有源-目标时间投影室(AT-TPC)。一个相关的计划将使用最近在NSCL的再加速束流设施(ReA3)上投入使用的完整AT-TPC。此外，在密歇根州立大学研究小组及其同事的主要指导下，密歇根州立大学与联合国环境规划署的合作将继续推进用于涉及中子的核测量的氢化闪烁体的开发和应用。这将包括对涉及稳定和不稳定光束的(d，n)和(3He，n)反应的选定测量，特别是对天体物理学中感兴趣的7Be(d，n)的测量。由于这些探测器允许在没有中子飞行时间的情况下进行中子光谱和截面测量，因此当与适用于核天体物理测量的高强度、低能量、非脉冲加速器一起使用时，它们具有特别的优势。后者包括最近在ND安装的新的5 mV加速器，我们将与ND的核天体物理学小组一起进行这些实验，特别是几个关键的(A，n)测量。该小组最近开发的独特的中子探测器阵列在核科学以及国土安全和核不扩散方面都具有广泛应用的潜力。与过去一样，拟议的工作将涉及来自ND和UM的研究生和本科生，以及来自这些大学附近几所主要是本科生的学校的教职员工和学生。因此，拟议研究的高技术性将大大有助于培训一支精通技术的工作队伍。

The research funded by this award is designed to promote a better understanding of atomic nuclei, the basic building blocks of all normal matter in the Universe. How did they form following the Big Bang, and how do they now interact to change their basic elemental nature? Are there new forms of matter made up from very exotic types of atomic nuclei and how might we make and study these? To this end the group will develop special new techniques in nuclear science, as well as train future scientists that can help answer some of these questions. One important training component will be a continuation of the well-established and highly successful outreach to faculty and students at New Buffalo High School in Michigan that has introduced these students to interesting, important, and exciting careers in the sciences. The technology developed and used in this research will have applications in other important areas, such as homeland security (nuclear terrorism), the safe storage and monitoring of nuclear wastes, and applications in nuclear medicine, including radiation therapy. The latter includes a new modality directly related to this research: the production and imaging of ion beams to treat particular forms of cancer tumors. Nearly 50% of graduate students and other personnel trained in the group's past research projects are currently pursuing careers in nuclear security or nuclear medicine, and it is anticipated that this will continue as a result of the present grant.The proposed project will involve the study of nuclear reactions utilizing stable as well as short-lived radioactive nuclear beams, together with the development of instrumentation, techniques, and apparatus to facilitate such studies. This includes use of the TwinSol low-energy radioactive ion-beam facility in operation at the University of Notre Dame (ND), developed jointly by the University of Michigan (UM) and ND. Specific experiments will emphasize the investigation of the structure and reaction mechanisms of neutron- and proton-rich nuclei near the limits of nuclear stability to elucidate the effect that the exotic "nuclear halo" structure, which appears for weakly-bound systems at the limits of stability, has on fusion, transfer, inelastic excitation, and breakup probabilities near the Coulomb barrier. Of particular interest here is the influence that higher-order couplings to and within the continuum have on the various reaction mechanisms, since proximity to the continuum is the characteristic defining feature of weakly-bound systems. These studies will be carried out at TwinSol in collaboration with a group from the National Superconducting Cyclotron Laboratory (NSCL), utilizing a prototype active-target time-projection chamber (AT-TPC). A related program will use the full AT-TPC recently commissioned at the reaccelerated beam facility (ReA3) at NSCL. In addition, the UM-UND collaboration, under the primary direction of the UM research group and their colleagues, will continue advanced development and application of deuterated scintillators for nuclear measurements involving neutrons. This will include selected measurements of (d,n) and (3He,n) reactions involving both stable and unstable beams, and in particular 7Be(d,n) which is of interest in astrophysics. Since these detectors permit neutron spectroscopy and cross section measurements without neutron time-of-flight, they have a particular advantage when used with the high-intensity, low-energy, non-pulsed accelerators suitable for nuclear astrophysics measurements. The latter includes the new 5 MV accelerator recently installed at ND and we will pursue such experiments, and in particular several key (A,n) measurements, together with the nuclear astrophysics group at ND. The unique neutron detector array the group has recently developed has potential for wide-spread applications both in nuclear science as well as in homeland-security and nuclear non-proliferation. As in the past, the proposed work will involve graduate and undergraduate students from ND and UM, together with faculty members and students from several primarily undergraduate schools located in close proximity to these universities. The highly-technical nature of the proposed research will thus contribute significantly to the training of a technically-literate work force.