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Study of structure of unstable nuclei with the new method of beta-delayed spectroscopy

β延迟光谱新方法研究不稳定核结构

基本信息

批准号：
17540256
负责人：
SHIMODA Tadashi
金额：
$ 2.24万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17540256/
关键词：
beta decay spin polarization beta-delayed decay states in the daughter nucleus spin-parity neutron-rich nuclei magic number 娘核の準位ベータ遅発中性子崩壊中性子散乱

项目摘要

A new method in beta-delayed decay spectroscopy has been successfully applied to investigate the exotic structure of 11Be. The essential feature of the present method is a use of spin-polarized radioactive nucleus. The beta-decay asymmetry enables us to assign the spin-parity of the beta-decay daughter state. Firm spin-parity assignments have been made for seven states in 11Be, and their detailed decay paths have also been determined. From these evidences it was found that various types of cluster states co exist in 11Be.In the last two years we have focused on the low energy neutron data analysis. In the beta-delayed neutron decay of 11Be →10Be + n there must be at least two decay paths associated with very low energy neutron emission. We used five 6Li-doped glass scintillators to detect the neutrons with energies of less than 200 keV. In order to assess the effects of the neutron scattering, prior to the detection, by material of the experimental apparatus, Monte Carlo simulations based on the neutron transport code MCNP have been performed. The experimental neutron spectra have been carefully analyzed by the help of the simulated neutron response function. Two neutron peaks with the kinetic energies of 16 keV and 72 keV were successfully assigned and the two neutron decay paths and intensities have been determined for the first time.It was planned to apply the presently established method to the structure studies of the very neutron-rich Mg isotopes. The feasibility has been investigated in detail. A proposal for the experiment at TRIUMF, Canada has been finished. The proposal was recommended as the experiment with high priority by the experiment evaluation committee. The experiment will be performed in 2007.

β延迟衰变光谱的新方法已成功应用于研究 11Be 的奇异结构。本方法的基本特征是使用自旋极化放射性核。 β 衰变不对称性使我们能够分配 β 衰变子态的自旋宇称。已经对 11Be 中的七个态进行了严格的自旋宇称分配，并且还确定了它们的详细衰变路径。通过这些证据发现11Be中多种类型的团簇态共存。近两年我们主要致力于低能中子数据分析。在 11Be →10Be + n 的 β 延迟中子衰变中，必须至少有两条与极低能量中子发射相关的衰变路径。我们使用五个 6Li 掺杂玻璃闪烁体来探测能量小于 200 keV 的中子。为了评估中子散射的影响，在检测之前，通过实验装置的材料，进行了基于中子输运代码MCNP的蒙特卡罗模拟。借助于模拟中子响应函数，对实验中子能谱进行了仔细分析。成功分配了动能分别为16 keV和72 keV的两个中子峰，并首次确定了两个中子衰变路径和强度。计划将目前建立的方法应用于高中子镁同位素的结构研究。可行性已进行了详细调查。加拿大 TRIUMF 的实验提案已经完成。该提案被实验评估委员会推荐为高度优先实验。该实验将于2007年进行。