RIBLL传输效率研究

利用实验测量和Monte Carlo模拟的方法,研究了RIBLL的传输效率。分析了影响传输效率的主要因素, 发现碎片的动量分布形式对传输效率的模拟结果有重要的影响。 另外通过比较, 发现大部分碎片传输效率的模拟结果稍大于实验测量结果, 两者最大相差约几十倍, 这可以帮助估算次级束流强度, 指导实验设计。 he transmission of RIBLL has been studied by experimental measurement and Monte Carlo simulation methods. The analysis of influence factors of the simulated transmission has been accomplished, and it was found that the momentum distribution of fragments is one of the most important factors influencing the simulation results. Furthermore, through comparing the measured and simulated results, it is found that the simulated result is larger than the measured transmission for most fragments and the maximal difference between them is about several tens of times. This simulation is a good theory tools for estimating the intensity of the secondary beam and designing the experiment in the future.     

中能8B和9C与Si反应总截面的测量

能量为75MeV/u的¹²C初级束轰击2mm厚的初级Be靶,并利用RIBLL从弹核碎片中分离出54.2MeV/u质子滴线核束8B和61.1MeV/u的⁹C,再轰击Si靶,用透射法测量了它们与Si的反应总截面σ_R.并应用Glauber模型进行理论计算,分析结果表明⁸B和⁹C都可能具有质子晕结构.     

放射性束弹性散射实验中的一种位置校准方法

在弹性散射实验中,探测器的位置校准是非常重要的。结合兰州放射性束流线(RIBLL)的实际情况,以低能轻炮弹在重靶上的弹性散射截面在前角区为卢瑟福散射的事实为依据,发展了一种简单而有效的位置校准方法。通过蒙特卡洛模拟来检测弹性散射角分布与不同方向上位置未校准时的依赖关系。该方法成功地应用在~7Be与重靶的弹性散射实验中,得到了正确的微分截面角分布。     

Measurement of the total reaction cross section for the mirror nuclei ^12N and ^12B

The mirror nuclei ^12N and ^12B are separated by the Radioactive Ion Beam Line in Lanzhou （RIBLL） at HIRFL from the breakup of 78.6 MeV/u 14N on a Be target. The total reaction cross-sections of ^12N at 34.9 MeV/u and ^12B at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming ^12N consists of a ^11C core plus one halo proton, the excitation function of ^12N and ^12B on a Si target and a C target were calculated with the Glanber model. It can fit the experimental data very well. The characteristic halo structure for ^12N was found with a large diffusion of the protons density distribution.     

Experimental Study on the Exotic Structure of ^12N in RIBLL

We measured the total reaction cross sections of 12N in Si at 36.2 MeV/u using Radioactive Ion Beam Line in Lanzhou （RIBLL） with a new method. The reaction target was installed at the intermediate focusing point T1 at RIBLL. This scheme allows us to identify particles before and after the reaction target unambiguously. The total reaction cross section （1760±78 mb） of ^12N in Si is obtained. Assuming that ^12N consists of a core ^11C plus one halo proton, the excitation function of 12N on the Si and C targets is calculated with the Glauber model and the Fermi-Fermi density distributions. It can fit the experimental data very well. A large diffusion of the protons density distribution supports the halo structure for ^12N.     

改进的Glauber模型对奇异核反应总截面数据的拟合

利用Glauber模型对奇异核的反应总截面进行计算时,对模型进行了有限程修正和库仑修正,并对奇异核输入的密度采用了核芯加价核子的形式,使得理论与实验在中高能下都得到了很好的符合.     

介质中的核子-孩子碰撞截面及其对原子核反应总截面的影响

给出了一个在较大能量范围内描述介质中核子－核子碰撞截面的计算公式，并结合微观修正的Ｇｌａｕｂｅｒ模型，研究了介质效应对原子核反应总截面的影响。     

Knockout reaction induced by ~6 He at 61.2 MeV/u

A knockout reaction induced by ⁶He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.     

重离子治癌终端的束流强度及剂量监测系统

 为实现重离子肿瘤治疗临床实验中对照射束流状态的实时监测,研制了束流强度及剂量监测系统,包括积分电离室、后续电流频率转换电路及LabVIEW数据获取处理三部分。利用闪烁体探测器和标准剂量计测试了系统的线性响应和得到剂量的准确性,结果表明：系统在束流临床照射流强范围内的线性响应好于90%,其实时反馈的临床照射剂量偏差小于5%。同时束流强度及剂量监测系统与安全控制系统相结合,保证束流照射状态满足临床照射的安全要求。     

6 MeV/u 的19F+27Al 反应碎片的发射机制

重离子核反应中的碎片发射机制是近年来人们十分关注的研究课题。利用ΔE-E 探测器,测量了~6 MeV/u 的19F+27Al 反应中核电荷数Z = 2 ~13 的出射碎片。对产物的能谱、角分布、激发函数及能量自关联函数的分析表明,出射产物主要来自弹靶核深部非弹性碰撞所形成的转动的双核系统。In recent years, extensive studies have been made to understand the fragment emission mechanisms in low energy light heavy-ion reactions. These fragments are found to be emitted from quasielastic/projectile breakup, deep-inelastic and fusion-fission processes. Fragments of Z = 2~13 induced by the collision of 19F+27Al have been measured by ΔE-E telescope. The analysis of the energy spectra, angular distributions, excitation functions and energy auto-correlation functions of these fragments shows that the emission of fragments is coming from a rotational dinuclear system formed in the dissipative collision of the projectile and target nuclei.