RUI: Exploring the Origin of the Rarest Stable Isotopes via Photon-Induced Activation Studies at the Madison Accelerator Laboratory

RUI：通过麦迪逊加速器实验室的光子诱导激活研究探索最稀有的稳定同位素的起源

基本信息

批准号：
1913258
负责人：
Adriana Banu
金额：
$ 21.88万
依托单位：
James Madison University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1913258&HistoricalAwards=false
关键词：
RUI Exploring Origin Rarest Stable

项目摘要

The question of how nuclear reactions in stars and stellar explosions have forged the elements out of hydrogen and helium leftover from the Big Bang is a longstanding but timely research topic in nuclear astrophysics. There is a fairly complete understanding of the production of the elements up to iron by nuclear fusion reactions in stars but important details concerning the production of the elements beyond iron remain puzzling. The proposed research aims to advance fundamental knowledge on a forefront topic in nuclear astrophysics - the synthesis of elements beyond Fe and of the rarest stable isotopes naturally occurring on Earth. The astrophysical phenomenon responsible for this synthesis is termed the p-process. Though simulating the p-process nucleosynthesis on a computer is a daunting task, significant progress can be made by performing key measurements which constrain the models that are used to calculate the unknown stellar reaction rates. Moreover, the proposed research will create an rich research experience for undergraduates in an accelerator-based environment at the newly opened Madison Accelerator Laboratory (MAL). MAL is a unique bremsstrahlung facility on the campus of James Madison University. The students will have an excellent opportunity for hands-on participation in an accelerator-based environment and they will be able to participate in cutting-edge research in nuclear astrophysics. This experience is an important part of their training as future researchers and will provide them with skills necessary to pursue STEM careers in Industry, at National Laboratories and Universities.The focus of this proposal's research program is to determine experimentally the ground state reaction rates for eight photo-neutron reactions which are to be investigated by photon-induced activation at MAL. The eight photo-neutron reactions are: 64Zn(gamma,n)63Zn, 70Ge(gamm,n)69Ge,74Se(gamma,n)73Se, 78,80Kr(gamma,n)77,79Kr, 84,86Sr(gamma,n)83,85Sr and 90Zr(gaamma,n)89Zr. The eight proton-rich stable nuclei of interest belong to the region A 124 which is notoriously under produced by the current stellar evolution models. In the laboratory one only has access to target nuclei in the ground state and so the stellar photodisintegration reaction rates, dominated by excited state contributions at the high temperature regime of the p-process, cannot be directly constrained experimentally. With the experiments at MAL, we can instead provide nuclear science input (through inverse reaction kinematics) to constrain crucial parameters of the nuclear reaction models, i.e. gamma ray strength function especially relevant for photo-neutron reactions. Considering the very large number of nuclear reactions involved in the production of even a single p-nucleus, any new measurement of photodisintegration reactions relevant to the p-process path will put the nucleosynthesis calculations on a firmer foundation.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.

恒星和恒星爆炸中的核反应如何使大爆炸中的氢和氦剩饭剩余的元素是一个长期但及时的核天体物理学研究主题。恒星中的核融合反应对元素的产生有了相当完整的了解，但有关铁之外的元素产生的重要细节仍然令人困惑。拟议的研究旨在促进核天体物理学中最前沿的主题的基本知识 - FE以外的元素和地球上自然发生的最稀有稳定同位素的综合。负责该合成的天体物理现象称为P过程。尽管在计算机上模拟P过程是一项艰巨的任务，但可以通过执行关键测量值来限制用于计算未知恒星反应速率的模型来取得重大进展。此外，拟议的研究将在新开放的麦迪逊加速器实验室（MAL）的基于加速器的环境中为大学生创造丰富的研究经验。 Mal是詹姆斯·麦迪逊大学校园的独特Bremsstrahlung设施。学生将有一个很好的机会动手参加基于加速器的环境，他们将能够参与核天体物理学的尖端研究。作为未来研究人员，这种经验是他们培训的重要组成部分，并将为他们提供从事行业，国家实验室和大学的STEM职业所必需的技能。该提案研究计划的重点是通过实验确定八个照片中性反应的基态反应率，这些反应将通过MAL诱导的光子诱导的激活来调查。八个照片不合隆反应为：64Zn（伽玛，n）63zn，70ge（gamm，n）69GE，74SE（Gamma，n）73Se，78,80kr（Gamma，n）77,79kr，77,79kr，84,86Sr，84,86Sr（gamma，n）83,85,85sr和90zr（gamma n）890zr（gamma n）890zr（gamma n）。感兴趣的八个富含质子稳定的核属于该区域A 124，众所周知，当前恒星进化模型所产生的不足。在实验室中，只有在基态下才能访问目标核，因此在P过程的高温状态下，恒星的光构成反应速率不能直接受到实验来限制。通过MAL的实验，我们可以提供核科学输入（通过反应运动学）来限制核反应模型的关键参数，即伽玛射线强度函数，尤其与光 - 中子反应有关。考虑到即使是单个P核的生产中涉及的大量核反应，与P过程相关的光电整合反应的任何新测量都将使核合成的计算置于更牢固的基础上。该奖项反映了NSF的法定任务，并通过使用基金会的Merit进行评估，并通过评估了Crcriatia and crobia and Broadia and tocria and crowsia and tocria and tocria and tocria and tocria and tocria and tocria and tocria and tocria and tobleit和broaditia and broad and tobrit。