弹散破裂截面比方法与8B的晕结构

8B, with a proton separation energy of 0.1375 MeV, is a pronounced proton-halo nucleus. The reaction mechanism and structure of the weakly bound nucleus 8B have received much attention from both theoretical and experimental points of view. The experiment for breakup and elastic scattering cross sections of 8B on a 208Pb target at 21, 50 and 70 AMeV is planned to perform at RIBLL. New experimental data will be utilized to study the halo structure of 8B, and to examine and validate the ratio method recently proposed by theoreticians. This method suggests that the ratio between the angular distributions of breakup and elastic scattering cross sections of weakly bound nuclei are sensitive to the single-particle structure of the valence nucleon, and thus provides a new observable for the study of nuclear structure. The coupling effect of breakup channel on the elastic scattering channel with 8B as a function of incident energy will be studied at energies above the Coulomb barrier. . This work will also provide new experimental data for breakup and elastic scattering reactions of weakly bound nuclei on heavy targets at energies above the Coulomb barriers, which is very rare and far from being able to facilitate systematic studies. This work will be based on the facilities at the RIBLL.

本申请项目立足于兰州放射性束流线(RIBLL)，拟测量21、50和70 AMeV的8B在208Pb靶上的弹性散射和破裂产物的微分截面角分布，将首次从实验上验证新近理论上提出的“弹散破裂截面比”方法，检验该理论中绝热近似的适用条件及其低能修正的可靠性。利用“弹散破裂截面比”方法，把反应机制与核结构研究结合起来，在研究弱束缚核8B的弹性散射截面、破裂截面及其耦合道效应的同时，研究8B的晕结构。. “弹散破裂截面比”方法指出，弱束缚核的破裂反应截面与弹性散射截面的比值对其价核子的结构参数十分敏感，从而给出了用核反应研究弱束缚核单粒子结构的一个新方法，具有重要的学术意义。目前，弱束缚核在重靶上的弹性散射和破裂截面的实验数据多集中在库仑位垒附近能区，本课题研究将提供较高能区的实验数据，发挥RIBLL束流线的优势和特色。

为克服放射性束的品质差、束流强度低、束流时间紧缺等问题，也为了挑战更小截面的测量，我们研制了大面积像素硅探测器，为以后的实验研究奠定了基础。完成了丰质子核8B和9C弹性散射实验数据分析及文章撰写，并从理论上解释了丰质子核的耦合道效应很弱的原因是由于库仑势垒/离心势的存在。首次在兰州放射性束流线（RIBLL）上测量了四倍库仑势垒能区8B的破裂反应角分布，其破裂截面是丰中子核11Be的三分之一左右，这说明丰质子核相对更不容易发生破裂反应。首次给出了丰中子核11Be和丰质子核8B的破裂弹散比，11Be的比值明显大于8B的。