CSR外靶实验终端中子流测量的模拟

随着兰州重离子加速器冷却储存环(HIRFL-CSR)外靶实验终端中子墙的建立, 为实验测量高能中子提供了机遇. 为确定CSR外靶实验终端对中子流测量的可行性, 基于BUU理论模型分别对对称系统(Ni+Ni, Pb+Pb)和非对称系统(Pb+Ni)进行了模拟计算, 发现当系统能量达到几百MeV/u时, 中子流信号相当明显, 并与碰撞参数有明显的依赖关系. 模拟结果表明, 在前角20°的覆盖范围内, 可以较好地实现中子流测量所需要的反应平面确定及碰撞参数选择. 对双击事件及其对中子流的影响进行了简单的讨论.     

Effects of Isospin Equilibrium on Cold Fusion of Superheavy Nuclei

The neutron flow model predicts that neutrons start to flow freely between the approaching nuclei ^58Fe and ^208 pb at s=3fm, a length in which the effective surfaces of these nuclei are 3 fm apart. As a result of neutron flow, the N/Z value rapidly reaches an equilibrium distribution. Meanwhile the system, originally in the fusion valley, is injected into the asymmetric fission valley. The dynamic process of the composite nucleus in the asymmetric fission valley is treated with a two-parameter Smoluchowski equation. It is shown that the probability to overcome the asymmetric fission barrier and to achieve compound nucleus configuration, hence the fusion cross section is obviously suppressed due to the effect of isospin equilibrium.