质子滴线核8B的实验研究进展

质子滴线核8B的最后一个质子的分离能只有0.137 5 MeV，被认为是最有可能具有质子晕结构的候选核之一，对其反应机制和奇特结构的研究吸引了人们的关注。针对8B的奇特结构和反应机制研究是一个非常有趣的课题，研究人员在包括反应截面、碎裂产物动量分布宽度、电四极矩、熔合截面及弹性散射等方面开展了大量的工作。但是8B的研究至今仍不够充分，需要从理论和实验上对其进行更深入的研究。     

Investigation of the near-threshold cluster resonance in ~(14)C

An experiment for p(~(14)C,~(14)C~*→~(10)Be+α)p inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 Me V/u.A series of~(14)C excited states,including a new one at 18.3(1)Me V,were observed which decay to various states of the final nucleus of~(10)Be.A specially designed telescope system,installed around zero degrees,played an essential role in detecting the resonant states near theα-separation threshold.A state at 14.1(1)Me V is clearly identified,being consistent with the predicted band-head of the molecular rotational band characterized by theπ-bond linear chain configuration.Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools.     

20Mgβ衰变谱学与15O(α,γ)19Ne反应(英文)

15O（α，γ）19Ne（p，γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径，相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息，并构建了完整的衰变纲图，还进行了19Ne 4 033 keV共振态衰变性质的探索，获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性，为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质，有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.     

Performance of a double sided silicon strip detector as a transmission detector for heavy ions

The performance of a double sided silicon strip detector （DSSSD）, which is used for the position and energy detection of heavy ions, is reported. The analysis shows that although the incomplete charge collection （ICC） and charge sharing （CS） effects of the DSSSD give rise to a loss of energy resolution, the position information is recorded without ambiguity. Representations of ICC/CS events in the energy spectra are shown and their origins are confirmed by correlation analysis of the spectra from both the junction side and ohmic side of the DSSSD.     

CsI（Tl）+Si-APD探测器的性能测试

介绍了Si-APD的工作原理并对Si-APD中的暗电流进行了理论分析。基于RIBLL上产生的放射性核束流，使用CsI（Tl）+Si-APD探测器对中能重离子进行了能量测试。测试结果显示，CsI（Tl）+Si-APD探测器测量20 MeV/u的重离子时，可得到3%的能量分辨；同时还发现Si-APD中的暗电流大小以及入射粒子的能量大小都会对探测器的能量分辨产生影响。In this paper, the working principle of Si-APD was introduced and the dark current of Si-APD was analyzed theoretically. The intermediate energy heavy ions, which are produced on the RIBLL(Radioactive Ion Beam Line in Lanzhou), were measured with CsI(Tl)+Si-APD detector. The energy resolution of CsI(Tl)+Si-APD detector is about 3% for heavy ions with energy around 20 MeV/u. It is also found that the energy resolution of detector can be in uenced by the dark current of Si-APD and the energy of incident particles.     

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。     

Performance of a double sided silicon strip detector as a transmission detector for heavy ions

The performance of a double sided silicon strip detector (DSSSD), which is used for the position and energy detection of heavy ions, is reported. The analysis shows that although the incomplete charge collection (ICC) and charge sharing (CS) effects of the DSSSD give rise to a loss of energy resolution, the position information is recorded without ambiguity. Representations of ICC/CS events in the energy spectra are shown and their origins are confirmed by correlation analysis of the spectra from both the junction side and ohmic side of the DSSSD.     

Proton and Two-proton Emissions from Proton-rich Nuclei with 10≦Z≦20

Proton (p) and two-proton (2p) emissions from the proton-rich nuclei with 10≦Z≦20 have been explored by the in-fight decay and implantation decay methods, respectively, in a series of experiments at the HIRFL-RIBLL facility. The in-flight 2p emissions from the excited states of 28,29S /26,27P and 17;18Ne were studied by complete-kinematics measurements. Mechanisms of 2p decay and related p-p correlations have been explored. Obvious 2p correlated emissions have been observed in the cases of 28,29S but not in 27,28P, indicating the 2p halo plays an important role in the diproton emission. In the 17;18Ne cases, a small 2p opening angles were deduced by the HBT analyses, implying the BCS-BEC crossover may occur in the dilute nuclear matter. Moreover, 27S/26P/25Si, 22Si/20Mg, 23Si/22Al/21Mg, 24Si/23Al, and 36;37Ca were implanted in a thin double-sided-silicon-strip detector and their -delayed p and 2p decays have been measured by a surrounding silicon detector array under the continuous-beam mode. Important information on the nuclear spectroscopy, such as energy, lifetime, branching-ratio, and so on, has been extracted, which helps us to understand the nuclear structures of proton-rich exotic nuclei close to the drip-line.     

17F + p 厚靶实验对18Ne共振态性质的研究

实验通过17F+p共振弹性散射研究了复合核18Ne激发态中与天体核反应14O(α, p)17F相关的共振态性质。利用兰州放射性束流线(RIBLL)对弹核碎裂反应产生的放射性束17F进行了分离和提纯。经过降能后,能量为4.22 AMeV 的17F束流轰击在T2终端的厚氢靶(CH₂)_n上。　两套∆E-E Si探测器望远镜放置在两个不同的探测角度θ_lab≈2.3°和14°上,对反冲质子的角度和能量进行了测量。实验观测到了复合核18Ne的几条质子共振能级。通过R-Matrix理论程序对激发函数进行拟合,得到了共振态的能量、 自旋、 宇称和衰变宽度等共振参数。Resonant properties in18Ne relevant to the stellar reaction of 14O(α, p)17F have been investigated through a resonant elastic scattering of 17F+p. The 17F RI beam was produced via a projectile fragmentation reaction, and subsequently separated and purified by Radioactive Ion beam Line in Lanzhou(RIBLL). After a series of energy degradation,a 4.22 AMeV 17F beam bombarded a thick(CH₂)_ntarget at T2 terminal. Energy and angle of the recoiled protons were measured by two sets of ∆E-E silicon telescope at θ_lab≈2.3°,14° respectively. Several resonances in 18Ne were observed,and their resonant parametersincluding energy,spin parity and decay width have been determined by an R-Matrix analysis of the experimental excitation function.