Study of the structure of borromean nucleus 17Ne

The ¹⁷Ne nucleus is a possible candidate with a two-proton borromean halo structure. Since the theoretical model is difficult to handle the three-body system, it is difficult to determine the two-proton halo structure in ¹⁷Ne. In the present research, we try to study the breakup reaction of ¹⁷Ne. For the Borromean nuclei, one-proton knockout results in an unstable nucleus which is decaying further by proton emission. This process will result in an angular correlation between the direction of the aligned recoiling unstable nucleus and its decay products. The angular correlations can give us information about the configuration of the valence proton in the ¹⁷Ne. Furthermore, theoretical calculations indicate that the momentum distributions of ¹⁶F c.m are sensitive to the structure of the halo in ¹⁷Ne. Thus the measurement of momentum distributions of ¹⁶F c.m may also give us conclusive information on the structure of ¹⁷Ne. The present experiment has been done at IMP in Lanzhou using the radioactive beam ¹⁷Ne at 30.8 MeV/u on a 43mg/cm^{2 12}C target. The data analysis is under procedure and the primary results are provided.     

Quasi-Elastic Scattering of 16C from 12C at 47.5 MeV/Nucleon

Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.     

核物理与核探测、核分析技术的应用

文章概要介绍了随着核物理研究发展起来的辐射和粒子探测的原理、方法和主要技术,举例介绍了相关核物理与核探测、核分析的典型技术及其在高精度测量和医学中的广泛应用,如活化分析技术、穆斯堡尔谱学、核磁共振技术、加速器质谱技术、核医学成像、同步辐射技术、中子散射分析、放射性示踪技术等等.     

RIBLL上的β+缓发粒子发射的在束测量

报道了在新建成的放射性次级束流线上完成的2 0 Na的 β+缓发α粒子发射2 0 Na—→β+　 　2 0　Ne →16 O +α的在束测量 .通过飞行时间和能损符合的方法实现2 0 Na次级束流的在束鉴别与调制 .在束和停束两个获取时段分别完成对次级束流和β+缓发粒子的记录 .利用脉冲发生器和记数器实现2 0 Na缓发粒子衰变半衰期的测量 .实验测量到2 0 Ne几个低能共振能级的衰变能量分别为 2 69,3 0 9,4 74 ,5 54MeV ,相对强度分别为 1 0 0 ,4 1 5,1 1 0 ,1 5 2 0 .测量到2 0 Na的β+缓发α衰变的半衰期为 (4 59± 7)ms,与现有的核数据基本上吻合 .     

晕核6He（25 MeV/u）的单、双中子转移截面测量

实验测量了25 MeV/u 的6He+9Be反应中的单、双中子转移微分截面. 利用反应耦合道模型初步分析了实验数据, 计算大体重现截面值. 转移反应对末态有相当的选择性, 并且双中子转移截面主要来自到基态的一步过程. 后角度截面的上升可能与连续态的耦合有关. Differential cross sections for quasi elastic scattering at forward angles and for 1n and 2n transfer reaction at backward angles induced by 6He at 25 MeV/u from 9Be target were measured. The experimental data were analyzed in the framework of the CRC model. The raise at backward angle of the 1n and 2n transfer cross section can not reproduced by the current calculation.     

用于HIRFL重离子治癌的PET成像实验研究与蒙特卡罗模拟

为了HIRFL重离子治癌的需要,使用两个位置灵敏闪烁体探测器组成了一个简单的PET成像系统.对PET成像进行了实验研究,实验测量得到了物体成像以及γ射线能谱,对于511keV全能峰处的能量分辨率为186%,峰总比为52.4%.采用GEANT3程序对该系统进行了模拟计算,并与实验进行比较,最后对该系统进行了优化设计     

低气压多丝正比室及其在放射性束流实验中的应用

介绍了为在放射性束流线上开展精确的散射和反应实验中,对入射束流的角度和有效数目等进行在线监测而设计制造的低气压多丝正比室.它透射性好,不干扰束流,并方便在真空环境中工作.测量表明,它的位置分辨率约0.5mm.对20—30MeV/u的低Z的放射性束流有着大于90%的位置探测效率,适用于中能次级束实验靶前的束流定位及在线监测,也可用在靶后测量出射带电粒子的角度.     

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.     

Measurement of the ~2H(~7Be,~6Li)~3He reaction rate and its contribution to the primordial lithium abundance

In the standard Big Bang nucleosynthesis(SBBN) model, the lithium puzzle has attracted intense interest over the past few decades, but still has not been solved. Conventionally, the approach is to include more reactions flowing into or out of lithium, and study the potential effects of those reactions which were not previously considered.~7Be(d,~3He)~6Li is a reaction that not only produces~6Li but also destroys~7Be, which decays to~7Li, thereby affecting~7Li indirectly. Therefore, this reaction could alleviate the lithium discrepancy if its reaction rate is sufficiently high.However, there is not much information available about the~7Be(d,~3He)~6Li reaction rate. In this work, the angular distributions of the~7Be(d,~3He)~6Li reaction are measured at the center of mass energies Ecm = 4.0 Me V and 6.~7Me V with secondary~7Be beams for the first time. The excitation function of the~7Be(d,~3He)~6Li reaction is first calculated with the computer code TALYS and then normalized to the experimental data, then its reaction rate is deduced. A SBBN network calculation is performed to investigate its influence on the~6Li and~7Li abundances. The results show that the~7Be(d,~3He)~6Li reaction has a minimal effect on~6Li and~7Li because of its small reaction rate. Therefore,the~7Be(d,~3He)~6Li reaction is ruled out by this experiment as a means of alleviating the lithium discrepancy.     

Characteristics of a 4-fold segmented clover detectore

Four high-purity germanium 4-fold segmented Clover detectors have been