双质子Borromean核17Ne的弹性散射研究

Unlike stable nuclei, the elastic scattering angular distributions of the weakly bound nuclei often exhibit suppressed Coulomb rainbows with different levels, due to the strong couplings between the elastic scattering and other direct reaction channels, e.g. breakup channel and transfer channel among others. Recent elastic scattering studies of 6He and 11Li suggest that the two-neutron Borromean configuration significantly affects these couplings. However, the effect from the two-proton Borromean configuration on the couplings is unclear yet, since elastic scattering data for two-proton Borromean nuclei near or above the Coulomb barrier is still scarce. .Thus, we propose to utilize the beams of the lightest Borromean nucleus 17Ne from HIRFL-RIBLL to impinge on the target of 208Pb, and measure the elastic scattering angular distribution of 17Ne for the first time. The effect from the two-proton Borromean configuration on the couplings will be investigated using the 3-body and 4-body continuum-discretised coupled channel calculations. This work will help to deepen the understanding on the exotic structure and reaction mechanism of the weakly bound nuclei.

性质不同于稳定核，弱束缚核的显著特征之一是弹性散射道与破裂、转移等直接反应道之间存在着强烈的耦合道效应。中子晕核6He和11Li的研究表明，双中子的Borromean结构特性对耦合道效应有显著影响。然而，目前丰质子弱束缚核的实验数据还非常缺乏，双质子Borromean核的结构特性对耦合道效应的影响也不清楚。.本申请项目立足于兰州大科学装置HIRFL-RIBLL，拟选取最轻的双质子Borromean核17Ne作为目标核，完成17Ne＋208Pb的弹性散射微分截面角分布的测量，通过三体和四体的耦合道计算，研究弱束缚核17Ne的双质子Borromean结构特性与耦合道效应的关联性。

弹性散射是研究弱束缚核的奇特结构和核反应机制的有效工具之一。本项目完成了17Ne轰击208Pb靶的弹性散射的实验准备，包括实验方案制定、探测器配套设施的机械设计、加工、安装和测试等。重点升级和改造了实验中所需的位置灵敏平行板雪崩计数器（PPAC）。改良了PPAC的电极结构，使其满足高计数率要求；优化读出电子学，实现信号的高增益、低噪声放大，使其稳定工作在106Hz环境下。建立完成了匹配升级后PPAC的高速数字化波形采样数据获取系统。使用高速采样数字化仪可对信号幅度小于20mV的信号进行定时分析，与传统的PPAC获取系统相比，探测效率提升4.3%。理论方面，利用建立的唯象模型无关方法分析放射性共轭双幻核56Ni的质子弹性散射数据，首次提取了弱束缚共轭双幻核56Ni的物质面密度分布，揭示了在π(f7/2)8ν(f7/2)8壳外加入两个中子后，π(f7/2)8ν(f7/2)8壳产生了剧烈的壳破裂现象。利用CDCC分析已测得的丰质子弱束缚核8B、9C在208Pb靶上的弹性散射角分布微分截面，理论上解释了丰质子弱束缚核耦合道效应很弱的原因是由于其的价核子具有库仑势垒所致。本项目对于研究丰质子弱束缚核素的奇异结构与反应机制有着重要意义。