EXPERIMENTAL STUDY ON THE HEAVY ELEMENT SYNTHESIS AT THE SUPERNOVA EXPLOSION

超新星爆炸重元素合成的实验研究

• 批准号: 15340085
• 负责人: MIYATAKE Hiroari
• 金额: $ 10.69万
• 依托单位: High energy Accelerator Research Organization (2004)The High Energy Accelerator Research Organization (2003)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15340085/
• 关键词: nuclear astrophysics; radioactive nuclear beams; nuclear physics; rapid neutron capture process; neutron-rich nuclei; laser ion-source; nuclear spin-polarizatinn; スピン偏極; г-過程

In this project, we studied seed-nuclei creation process prior to the possible rapid neutron capture at the moment of the type II supernova explosion his process has been believed to occur from proton and neutron, which create heavy elements in the seed region consisting of iron and nickel isotopes thorough nuclear reactions like (alpha, n) and (n, gamma). So far, time dependence of relevant element abundance in this process has been estimated by a large nuclear reaction network code based on the predicted reaction rates of the statistical model. However, the statistical prediction in dais light nuclear region keeps little confidence for its predictability due to the small level densities. Therefore a direct measurement of astrophysical reaction rate becomes issue to further quantitative investigation of the above synthesis senarios.We have measured systematically the (alpha, n) reaction cross sections by using light neutron rich radioactive nuclear beams and efficient detector system, which makes it possible to measure excitation functions exclusively in fine broad energy region. In this project, we observed 8^Li,^<12>B, and ^<16>N (alpha, n) reaction cross sections. The obtained excitation function of the ^8Li experiment has 10 times higher statistics and deduced reaction rates are about a half values compared to the previous ones. This indicates that the ^8Li(alpha, n) reaction rate as well as resultant neutron number density should be suppressed in the element synthesis senarios so that mass abundance pattern of the r-process will be changed.As a part of this project, we have also proceeded to study technical aspects of a laser ion-source and a new nuclear-spectroscopy with spun-polarized radioactive nuclei, which are important developments for further astrophysical studies at a new radioactive nuclear beam facility constructing at JAERI.

在本项目中，我们研究了在II型超新星爆炸瞬间可能发生的快中子捕获之前的种子核生成过程，该过程被认为是由质子和中子产生的，质子和中子通过（α, n）和（n, γ）等核反应在种子区产生由铁和镍同位素组成的重元素。到目前为止，该过程中相关元素丰度的时间依赖性已由大型核反应网络代码根据统计模型预测的反应速率估计出来。然而，由于能级密度小，轻核区的统计预测对其可预测性缺乏信心。因此，直接测量天体物理反应速率成为进一步定量研究上述合成情景的问题。我们利用富轻中子放射性核束和高效探测系统系统地测量了（α, n）反应截面，使精细宽能区激发函数的测量成为可能。在这个项目中，我们观察到8^Li，^<12>B和^<16>N （α， N）反应截面。得到的^8Li实验的激发函数统计量提高了10倍，推导出的反应速率约为以前的一半。这表明在元素合成过程中，应该抑制^8Li（α, n）反应速率和生成的中子数密度，从而改变r过程的质量丰度模式。作为该项目的一部分，我们还着手研究激光离子源的技术方面和具有自旋极化放射性核的新核谱，这是在JAERI建设的新放射性核束设施中进一步进行天体物理研究的重要进展。

项目成果

A detection system for astrophysical reaction-rate measurement with low-intensity radioactive nuclear beam

低强度放射性核束天体物理反应速率测量探测系统

• 期刊: Nucl. Instrum. Meth. (to be published)
• 作者: M.Wakasugi;T.Suda;Y.Yano;T.Hashimoto et al.
• 通讯作者: T.Hashimoto et al.

Study of astrophysical (α,n) and (p,n) reactions on light neutron-rich nuclei by means of low-energy RNB

利用低能RNB研究轻中子富核的天体物理(α,n)和(p,n)反应

• 期刊: CP 704, 453, 2003, AIP. Proc. Tours Symp. Nucl. Phys.V,Aug. 26-29, 2003,Tours, FRANCE
• 作者: I.Sugai;Y.Takeda;et al.;K.Saigo et al.;H.Ishiyama et al.
• 通讯作者: H.Ishiyama et al.

Spectroscopic study of 11Be through β-delayed neutron- and γ-decays of spin-polarized 11Li

通过自旋极化 11Li 的 β 延迟中子和 γ 衰变对 11Be 进行光谱研究

• 发表时间: 2004
• 期刊: Nuclear Physics A 738
• 作者: H.Miura;T.Nakamoto;H.Hirayama et al.
• 通讯作者: H.Hirayama et al.

H.Hashimoto et al.: "A detector system for astrophysical reaction-rate measurement with low-intensity radioactive nuclear beam"Nuclear Instrument and Methods in Physics Research. (発表予定).

H. Hashimoto 等人：“用低强度放射性核束测量天体物理反应速率的探测器系统”，物理研究中的核仪器和方法（待提交）。

Structure of 11Be studied in β-delayed neutron- and γ-decay from polarized 11Li

在极化 11Li 的 β 延迟中子和 γ 衰变中研究 11Be 的结构

• 发表时间: 2004
• 期刊: Nucl. Phys. A746
• 作者: A.Odahara;et al.;Y Hirayama et al.
• 通讯作者: Y Hirayama et al.