弱束缚弹核7Li+96Zr系统在近库伦势垒的熔合反应研究

The fusion reaction induced by weakly bound projectile is one of interesting topics in recent years. It is experimentally observed that the complete fusion cross section is suppressed around the coulomb barrier. Furthermore in 6Li induced fusion reaction, the suppression factor does not be consistent in light target mass region with heavy mass region. It needs more experiments of different weakly bound projectile induced reactions on medium mass targets to answer how the target mass affect. In this project, the fusion cross section of 7Li+96Zr system is to be measured by applying gamma spectroscopy and beam intensity detection. Through characteristic gamma, the residues originating from different reaction channels can be identified. This information is useful for studying the role of different cluster structures of 7Li in the dynamic of reaction mechansim and for extracting the excitation functions of complete and incomplete fusions. The suppression factor for 7Li+96Zr system can be obtain by comparing the experimental dates with theoretical values. The results will check the existing factor on heavy target nuclei and try to answer the effect of target mass on the complete fusion suppression.

弱束缚弹核重离子熔合反应是近年来核反应研究的热点课题之一。实验上观察到，弱束缚弹核体系在近库伦势垒的全熔合反应截面存在压低现象。而6Li体系的垒上全熔合反应截面压低系数在重靶核区与中重靶核区不一致。对于这一现象，需要不同弱束缚弹核体系更多中重靶核的熔合反应截面测量数据予以验证。本项目将应用伽马谱学方法，结合束流测量，开展7Li+96Zr熔合反应截面的测量工作。通过特征伽马射线鉴别，确定各种反应产物，研究7Li中不同集团参与熔合反应的行为，并给出该系统完全熔合与非完全熔合反应道的激发函数。根据实验激发函数与理论计算的对比结果，确定该系统垒上全熔合截面的压低系数，并与现有重靶核体系比较，探讨7Li弹核体系中靶核质量与原子序数对垒上全熔合截面压低效应的影响。

弱束缚弹核重离子熔合反应是近年来核反应研究的热点课题之一。实验上观察到，弱束缚弹核体系在近库伦势垒的全熔合反应截面存在压低现象。本项目利用在束谱学与离线衰变谱学的方法，测量了7Li + 96Zr系统在近库伦位垒能区14至30MeV能量范围的熔合反应截面。实验中，通过测量不同反应产物退激发射的特征伽马射线，提取了完全熔合反应，非完全熔合反应氚核俘获、α粒子俘获反应以及核子转移反应的产额。测量结果表明，在垒上能区完全熔合反应占主导，而随着入射粒子能量的降低，核子的转移反应在垒下成为重离子反应的主要机制。基于实验测量结果，7Li + 96Zr系统垒上完全熔合压低约40%，而氚核的俘获反应是该系统产生α粒子的主要生成机制。该过程生成了α原子核总数的约60%的粒子。