Beta-Decay Experiments along the R-Process Path

R 过程路径上的 Beta 衰变实验

• 批准号: 1714153
• 负责人: Alfredo Estrade
• 金额: $ 24万
• 依托单位: Central Michigan University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-15 至 2022-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1714153&HistoricalAwards=false
• 关键词: Beta; Decay; Experiments; along; Process

Most of the chemical elements in the universe have been produced by nuclear reactions in stars through a series of different nucleosynthesis processes. The basic features of most of these processes are well understood. However, one of the major open questions is the nature of the rapid neutron capture process (r-process), which is responsible for the synthesis of roughly half of the chemical elements heavier than iron, such as gold and uranium. Astronomical observations indicate that the r-process has been active since the early stages of galactic history, and takes place in explosive stellar environments, such as supernovae explosions or mergers between two neutron stars, but the details are not known. A major difficulty to understanding the r-process is that it involves unstable isotopes. The main activities supported by this award are a series of nuclear physics experiments to measure the radioactive decay properties of isotopes directly relevant to r-process studies. The experimental setup combines state-of-the-art radiation detectors for beta-decay measurements (BRIKEN), and unstable isotope beams at leading accelerator facilities in Japan (RIBF) and the US (NSCL). The nuclear data obtained in this experiments will allow for a more precise comparison between astronomical observations and astrophysical models for the r-process. Another objective of this proposal is to provide students, especially at the undergraduate level, with opportunities to become involved in research activities at the forefront of nuclear physics, and contribute to expanding the number of students pursuing scientific careers in the US. For this reason, the proposal includes research projects that will take place at the campus of Central Michigan University (CMU), such as the development of radiation detectors and computational work with astrophysical models of the r-process.The main scientific outcome of this award will be the measurement of beta-delayed neutron emission probabilities (Pn values) with the new BRIKEN detector setup at the Radioactive Ion Beam Factory in RIKEN, Japan. The BRIKEN setup consists of an active stopper detector for radioactive ion beams, surrounded by a high-efficiency neutron detector composed of He-3 proportional counters. The experiments currently planned will measure Pn values, as well as decay half-lives, for neutron-rich isotopes spanning the regions from the N=50 shell closure up to the rare-earth elements. These experiments will provide new nuclear data for r-process models in regions of the nuclear chart relevant to address important questions of r-process nucleosynthesis, such as the astrophysical conditions that lead to the formation of elements in the A=130 abundance peak. The award will also support the participation of CMU researchers in r-process experiments at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University. This includes a project to develop reaccelerated beams of heavy isotopes around the N=82 region, with the potential to open new opportunities for r-process measurements.

宇宙中的大多数化学元素都是由恒星中的核反应通过一系列不同的核合成过程产生的。大多数这些过程的基本特征已被很好地理解。然而，其中一个悬而未决的主要问题是快中子捕获过程（r-process）的性质，它负责合成大约一半比铁重的化学元素，如金和铀。天文观测表明，r-过程自银河系历史的早期阶段就一直活跃，并发生在爆炸性的恒星环境中，如超新星爆炸或两颗中子星之间的合并，但细节尚不清楚。理解r过程的一个主要困难是它涉及不稳定的同位素。该奖项支持的主要活动是一系列核物理实验，以测量与r过程研究直接相关的同位素的放射性衰变特性。实验装置结合了用于β衰变测量的最先进的辐射探测器（BRIKEN），以及日本（RIBF）和美国（NSCL）领先加速器设施的不稳定同位素光束。在这个实验中获得的核数据将允许在天文观测和天体物理模型之间进行更精确的比较。该提案的另一个目标是为学生，特别是本科生提供参与核物理前沿研究活动的机会，并为扩大在美国从事科学事业的学生人数做出贡献。出于这个原因，该提案包括将在中密歇根大学（CMU）校园进行的研究项目，例如辐射探测器的开发和r过程天体物理模型的计算工作。该奖项的主要科学成果将是利用位于日本理化学研究所放射性离子束工厂的新型BRIKEN探测器测量β -延迟中子发射概率（Pn值）。BRIKEN装置包括一个放射性离子束的主动阻挡探测器，周围是一个由He-3比例计数器组成的高效中子探测器。目前计划的实验将测量从N=50壳闭合到稀土元素的富中子同位素的Pn值以及衰变半衰期。这些实验将为核图中r过程模型提供新的核数据，以解决r过程核合成的重要问题，例如导致A=130丰度峰中元素形成的天体物理条件。该奖项还将支持CMU研究人员参与密歇根州立大学国家超导回旋加速器实验室（NSCL）的r-过程实验。这包括一个在N=82区域周围开发重同位素再加速束的项目，有可能为r过程测量开辟新的机会。

项目成果

The “Beta-Delayed Neutrons at RIKEN” Project (BRIKEN): Conquering the Most Exotic Beta-Delayed Neutron-Emitters

RIKEN 的“β 延迟中子”项目 (BRIKEN)：征服最奇特的 β 延迟中子发射体

• DOI: 10.1080/10619127.2018.1427937
• 发表时间: 2018
• 期刊: Nuclear Physics News
• 作者: Dillmann, Iris;Tarifeño-Saldivia, Ariel
• 通讯作者: Tarifeño-Saldivia, Ariel

The ORNL analysis technique for extracting β -delayed multi-neutron branching ratios with BRIKEN

用 BRIKEN 提取 β 延迟多中子支化比的 ORNL 分析技术

• DOI: 10.1016/j.nima.2018.09.121
• 发表时间: 2018
• 期刊: Detectors and Associated Equipment
• 作者: Rasco, B.C.;Brewer, N.T.;Yokoyama, R.;Grzywacz, R.;Rykaczewski, K.P.;Tolosa-Delgado, A.;Agramunt, J.;Taín, J.L.;Algora, A.;Hall, O.
• 通讯作者: Hall, O.

The BRIKEN Project: Extensive Measurements of $\beta $-delayed Neutron Emitters for the Astrophysical r Process

BRIKEN 项目：天体物理 r 过程中 $eta $ 延迟中子发射体的广泛测量

• DOI: 10.5506/aphyspolb.49.417
• 发表时间: 2018
• 期刊: Acta Physica Polonica B
• 影响因子: 0.5
• 作者: Tain, J.L.;Agramunt, J.;Ahn, D.S.;Algora, A.;Allmond, J.M.;Baba, H.;Bae, S.;Brewer, N.T.;Caballero Folch, R.;Calvino, F.
• 通讯作者: Calvino, F.

Strong one-neutron emission from two-neutron unbound states in β decays of the r -process nuclei Ga86,87

r 过程核 Ga86,87 β 衰变中两个中子未束缚态的强单中子发射

• DOI: 10.1103/physrevc.100.031302
• 发表时间: 2019
• 期刊: Physical Review C
• 影响因子: 3.1
• 作者: Yokoyama, R.;Grzywacz, R.;Rasco, B. C.;Brewer, N.;Rykaczewski, K. P.;Dillmann, I.;Tain, J. L.;Nishimura, S.;Ahn, D. S.;Algora, A.
• 通讯作者: Algora, A.