丰中子p壳层原子核的产生截面测量

Projectile fragmentation is one of the most important methods for the production of exotic nuclei. It has been widely used to produce the radioactive nuclei far from β-stability line. Production of nuclei via fragmentation reactions and measurement of the production cross section are very crucial. An accurate database of production cross sections is essential for the development of reliable cross section models or empirical parametrizations, which play a crucial role in the design of the radioactive beam experiments. However, the production cross section for some light nuclei created via the fragmentation of light projectiles at relativistic energies is lacking. The validity of some widely-used empirical parametrizations (e.g., EPAX) needs further study when applying to the light nuclei. In this project, based on the heavy ion accelerator facility and the radioactive beam line RIBLL2 at IMP, the 18O at relativistic energies will be employed to bombard various targets. Some neutron-rich p-shell nuclei will be produced and their production cross sections will be measured. The energy dependence of the cross section and the influence of target material on the cross sections will be systematically investigated.

弹核碎裂反应是产生奇特原子核的最重要的方法之一，其已经被广泛地用于产生远离稳定线的放射性核素。利用碎裂反应产生原子核并测量其产生截面具有重要意义。高精度的产生截面数据对于构建和约束截面计算模型或经验公式起关键作用，而可靠的截面预言对于设计放射性束实验至关重要。目前，轻核区一些原子核在相对论能区的产生截面数据比较匮乏；常用的计算截面的经验公式（如EPAX）在轻核区是否有效仍有待进一步检验。基于近代物理研究所的重离子加速器装置和放射性束流线RIBLL2，本项目提议利用相对论能量的18O束流轰击不同种类的靶，产生一些丰中子p壳层原子核并测量其产生截面，系统研究截面随束流能量的变化和靶材料对截面的影响。

高精度的产生截面数据对于设计放射性束实验非常关键，同时对于约束截面模型或经验公式以及检验核反应理论也至关重要。在本项目的支持下，依托中国科学院近代物理研究所的重离子加速器装置HIRFL，利用260 MeV/nucleon的18O束流轰击C靶发生碎裂反应，测量了十几种p壳层原子核的产生截面，对于大部分核素，测得截面的相对误差小于30%。结合前人截面测量结果，系统考察了14-17N、12-15C和10-13B的产生截面随束流能量的变化。研究发现：对于N和B同位素，本工作测得的截面数据与前人在不同束流能量下测得的截面符合很好；而部分C同位素的截面似乎展现出对束流能量的依赖。同时，利用常用的截面理论模型和经验公式开展了计算，并将结果与实验数据进行了对比，检验了这些理论对所测截面预言的有效性。本项目为下一步测量丰中子sd壳原子核的产生截面奠定了坚实基础。