丰中子和丰质子奇特核低位激发态寿命测量

寿命测量是一种高精细核谱学技术，测量结果为奇特核结构提供了最直接的证据。在过去的100年，尽管寿命测量有了长足的进展，但却存在两个重大缺陷。首先，研究对象局限于稳定及部分丰质子核。其次，测量了大量长和短寿命激发态，对于中等寿命的测量则相对困难。本项目利用次级束二次反应后处于低位激发态的丰质子和丰中子核快速冲出；对于次级束产额不足而无法充分产生的能级，将采用主束碎裂直接布居。只有中等寿命激发态在靶后小范围探测区域内退激特征γ射线。利用8台高颗粒度的Clover探测器测量此γ射线多普勒展宽形成的峰形。应用大型叠层闪烁体对散射产物进行测量。在粒子-γ符合识别目标核的特征γ射线后，拟合γ射线峰形获取目标能级的寿命。通过测量的寿命，确定球形单粒子或集体振动和形变的集体转动属性以及镜像核的镜像对称。最终认识壳结构和演化以及核力在背后扮演的角色，理解单粒子如何协同发展成集体运动，探索同位旋对称和破缺。

Lifetime measurement is a kind of high precision nuclear spectroscopy technique. The measured lifetime provides the direct proof on exotic nuclear structure. During the pasr 100 years, considerable progress has been made in lifetme measurement. However, two important problems have not been completely solved so far. First，the study territory is limited to the stable or partial proton-rich nuclei. Second, it is problematic for the medium-lifetime measurement. This project will utilize the high velocity of proton- and neutron-rich nuclei in low-lying states produced by the secondary reactions induced by the radioactive beams. For the insufficient radioactive beams, we will adopt the fragmentation reactions of primary beams to directly populate the aimed low-lying states. The emitted γ rays after target from the low-lying states with medium lifetimes will be detected by eight Clover detectors, while the phoswich detectors will detect the scattered particles. After identifying the characteristic γ rays by particle-γ coincidences, we will fit the peak shapes of γ rays and obtain the lifetimes of aimed levels. Single-particle or collective properties can be determined from the measured lifetimes. Finally, we wish to comprehend the shell structure and evolution driven by the nuclear force, understand the collectivity created by the single-particle conspiracy and explore the isospin symmetry and breaking.