丰中子C同位素的实验研究
Experimental Study of Neutron-rich C isotopes
摘要
\justifying 我们在兰州放射性束流线开展了丰中子C同位素在$^{12}$C上的(准)弹性散射实验。初级束采用69.7MeV/u的$^{18}$O.入射的$^{18}$O与初级靶（$^{9}$Be）碰撞后碎裂,产生了包含α,$^{6,7}$Li,直到丰中子C和丰中子O同位素在内的20多种核素。我们在次级靶前采用磁刚度加降能片的方法对产生的放射性核素进行选择。在次级靶前采用ΔE-TOF方法对进行粒子鉴别,次级靶后采用由双面位置硅条探测器(DSSD)和CsI(Tl)闪烁晶体阵列组成的望远镜系统进行鉴别散射粒子,这样不但出射粒子的种类、能量和出射角度都可以获得。通过将实验得到的弹性散射截面与卢瑟福散射截面相比,最终得到了丰中子C同位素在$^{12}$C靶上的弹性散射角分布。利用光学模型和耦合道模型方法分析$^{16,17,18}$C在$^{12}$C靶上的弹性散射角分布,通过使用Woods-Saxon型的光学势对实验结果进行理论分析,很好地复现了实验数据,并得到相应的光学势参数。计算结果表明,$^{16,17,18}$C的弹性散射与 $^{11,12,13}$C 核的相比并不具有明显增强的吸收,具备出现核虹现象的条件。Abstract
\justifying We performed (quasi-)elastic scattering experiments of neutron-rich C isotopes on $^{12}$C. The primary beam was $^{18}$O with 69.7MeV/u. The Incident $^{18}$O breakup after bombarding with a primary target ($^{9}$Be). Then nearly 20 nuclides, including α, 6,7Li , up to neutron-rich C and O isotopes, were produced. We selected the produced nuclides with Bρ + degrader method before the secondary target. The particle identification was performed using ΔE-TOF method. A telescope system consisting of a double-sided silicon strip detector (DSSD) and a CsI(Tl) scintillation crystal array was used after the secondary target to identify the scattered particles. The particles were identified, and also the particles energy and emitting angle were also measured. By comparing the experimentally obtained elastic scattering cross section with the Rutherford scattering cross section, we finally obtained the $^{16,17,18}$C elastic scattering angle distribution on $^{12}$C target. The distribution of the elastic scattering angle of $^{16,17,18}$C on the $^{12}$C target is analyzed by using the optical model and coupled-channel model method. The experimental data are well reproduced by using the Woods-Saxon type optical potential for the theoretical analysis of the experimental results, and the corresponding optical potential parameters are obtained. The calculated results show that the elastic scattering of $^{16,17,18}$C does not have significantly enhanced absorption compared with that of $^{11,12,13}$C nuclei, and the conditions for the appearance of the nucleus rainbow phenomenon are present. 
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