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

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组成部分。它们是如何在大爆炸之后形成的，它们现在又是如何相互作用来改变它们的基本元素性质的？是否存在由非常奇特的原子核组成的新形式的物质？我们如何制造和研究这些物质？为此，该小组将在核科学方面开发特殊的新技术，并培训未来的科学家来帮助回答其中的一些问题。一个重要的培训组成部分将是继续在密歇根州新布法罗高中对教师和学生进行已经建立并非常成功的推广，该推广已经向这些学生介绍了有趣、重要和令人兴奋的科学职业。这项研究开发和使用的技术将应用于其他重要领域，例如国土安全（核恐怖主义）、核废料的安全储存和监测以及核医学（包括放射治疗）方面的应用。后者包括一种与本研究直接相关的新模式：离子束的产生和成像，以治疗特定形式的癌症肿瘤。在该小组过去的研究项目中接受培训的研究生和其他人员中，近50%目前正在从事核安全或核医学方面的职业，预计由于目前的资助，这种情况将继续下去。拟议的项目将涉及利用稳定和短寿命放射性核束研究核反应，以及开发仪器、技术和设备以促进此类研究。这包括使用由密歇根大学和诺特丹大学联合开发的TwinSol低能放射性离子束设备。具体实验将着重研究在核稳定极限附近的富含中子和质子的核的结构和反应机制，以阐明在稳定性极限弱束缚系统中出现的奇异“核晕”结构对库仑势垒附近的聚变、转移、非弹性激发和破裂概率的影响。这里特别感兴趣的是与连续统之间和连续统内部的高阶耦合对各种反应机制的影响，因为接近连续统是弱束缚系统的特征定义特征。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，利用一个原型主动目标时间投影室（at - tpc）。一个相关的项目将使用最近在国家科学实验室的再加速束设施（ReA3）上服役的完整的at - tpc。此外，在UM研究小组及其同事的主要指导下，UM- und合作将继续推进氘化闪烁体的先进开发和应用，用于涉及中子的核测量。这将包括（d,n）和（3He,n）反应的选择测量，包括稳定和不稳定光束，特别是天体物理学中感兴趣的7Be（d,n）。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，因此当与适合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的核天体物理小组一起进行此类实验，特别是几个关键的（A,n）测量。该小组最近开发的独特中子探测器阵列在核科学以及国土安全和核不扩散方面具有广泛应用的潜力。与过去一样，拟议的工作将涉及新大和澳大的研究生和本科生，以及位于这两所大学附近的几所主要本科学院的教职员工和学生。因此，拟议研究的高技术性质将大大有助于培训具有技术知识的工作人员。

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.