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1.
在日本东京大学CRIB次级束装置上,用长气体靶开展了22Na+α共振散射的厚靶实验研究。针对长气体靶实验中的两体运动学重构问题,提出了一套包括构建空间复杂几何关系、计算能量损失以及反应运动学的逐事件分析方法;对22Na+α共振散射的实验数据进行了重构分析,得到了Ec.m.=4.2~5.4 Me V区间22Na(α,α)的激发函数,从实验的激发函数中观测到了复合核26Al 5个较为明显的共振峰。鉴于26Alα共振态的衰变模式比较复杂,本工作发现的26Al新共振态的能级性质有待进一步的理论分析。  相似文献   
2.
Angular distributions of the ^7Li(^6Li, ^6Li)^7Li elastic scattering and the ^7Li(^6Li, ^7Lig.s.)^6Li, ^7Li(^6Li, ^7Li0.48)^6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of ^6Li + ^7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation (DWBA) analysis, spectroscopic factors of ^7Li =^6Li n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in ^7Li, respectively. Using the spectroscopic factors, the cross sections of the ^6 Li(n, γ0,1)^7 Li direct neutron capture reactions and the astrophysical ^6Li(n, γ)^7 Li reaction rates are derived.  相似文献   
3.
在研究容错图像编码算法的基础上,针对图像压缩编码中复杂度较大和将图像分成多个小块而带来的图像重建中有分块痕迹等问题,在子带位平面编码(SBC)算法中加入了与图像无关的率失真优化编码并采用虚拟分块的方法,对SBC算法进行了改进,实验结果表明,在相同压缩倍数和相同误码率情况下,本算法与传统的图像压缩算法重建图像的峰值信噪比提高了1.0~1.5dB。  相似文献   
4.
长寿命放射性核素26Al是星际介质、$\gamma$射线天文学和太阳系形成研究中最重要的核素之一。最可能合成26Al的三种天体场所都与25Mg(${\rm p},\,{\rm{\gamma }}$)26Al反应相关,因此精确测量其近阈能级的共振强度和天体物理反应率对人们认识宇宙26Al的来源具有重要意义。本文回顾了25Mg(${\rm p},\,{\rm{\gamma }}$)26Al反应的实验研究方法和最新研究进展,特别是介绍了我国对该反应的间接测量实验以及直接实验测量计划。当前的间接测量结果提升了25Mg(${\rm p},\,{\rm{\gamma }}$)26Al天体物理反应率的精度,也可以帮助我们估算直接测量的产额,并优化深地直接测量的实验设计。高能点的直接测量结果与国际上其它实验结果在误差范围内符合很好,表明本项目研制的探测装置工作状态良好,能够胜任锦屏深地核天体物理实验研究。  相似文献   
5.
北京放射性离子束装置(Beijing Radioactive Ion-beam Facility,BRIF)是基于在线同位素分离器技术的国家大科学平台。在BRIF装置上利用100 MeV的质子束轰击较厚的反应靶产生放射性核素;反应产物经离子源电离和在线分离,在线同位素分离段可引出100~300 keV的放射性核束,质量分辨率达20 000。在基金委科学仪器基础研究专项的支持下,建成了多用途的衰变实验终端,包括束流传输管道、通用靶室、带电粒子和γ探测器、集成电子学和数据获取系统等。利用100 MeV的质子束轰击MgO厚靶产生了流强高达1×105 pps的20Na放射性核束。通过高效率地同时测量β,γ和α,第一次直接观测到20Na非常稀有的β-γ-α衰变模式。Beijing Radioactive Ion-beam Facility(BRIF) has been commissioned as the national Radioactive Ion Beam(RIB) facility based on the Isotope Separator On Line(ISOL) technique since 2016. At BRIF, the radioactive nuclides are produced by the proton beam of 100 MeV bombarding a thick-target, the reaction products diffusing out of the target are ionized by an ion source and delivered to the online mass separator. In addition to the post-accelerated radioactive ion beams, BRIF can provide low-energy ISOL beams of 100 to 300 keV with a mass resolution of 20 000. A general-purpose decay station has been built including the ISOL beam transport line, a conventional reaction chamber, charge-particle and γ detectors with integrated electronics and data acquisition system. An intense 20Na ISOL beam up to 1×105 pps was produced by using the 100 MeV proton beam bombarding a MgO thick target. With high-efficiency measurements of β, γ and α simultaneously, very rare β-γ-α decay mode in 20Na has been directly observed for the first time in the present work.  相似文献   
6.
多个Sn同位素位于慢速中子俘获(s-)过程路径上,其中子谱因子可用于计算ASn(n,γ) A+1Sn直接辐射俘获的天体物理反应率,并可研究Sn同位素对s-过程核合成的贡献。本工作在中国原子能科学研究院HI-13串列加速器Q3D磁谱仪上,对实验室系下8°~66°范围内的122,124Sn(d,p)和(p,d)单中子转移反应角分布进行了测量。利用DWBA理论计算了转移反应角分布,并提取了122-125Sn的基态以及123,125Sn第一激发态的中子谱因子。其中,122Sn和124Sn的基态中子谱因子是首次从实验上获得。由于本工作成功鉴别开了123,125Sn的基态和第一激发态的效应,因此给出的谱因子比前人的结果更可信。Several Tin isotopes are on the path of slow neutron capture (s-) process, and the direct components of (n, γ) reactions can be derived from their neutron spectroscopic factors. In the present work, the angular distributions of 122,124Sn(p, d) and (d, p) reactions are obtained using the high-precision Q3D magnetic spectrograph in Beijing HI-13 tandem accelerator in China Institute of Atomic Energy. The distorted-wave Born approximation (DWBA) calculations are performed to extract the neutron spectroscopic factors of the ground state of 122-125Sn and the first excited state of 123,125Sn. The neutron spectroscopic factors of the ground state of 122Sn and 124Sn are firstly obtained in this work. As the events of the ground state and first excited state of 123,125Sn can be distinguished clearly by our experiment, the neutron spectroscopic factories of 123,125Sn are more reliable.  相似文献   
7.
弹性共振散射反应的厚靶实验设计   总被引:1,自引:0,他引:1  
为了开展次级束引起的弹性共振散射反应的厚靶实验, 在北京HI-13串列加速器的次级放射性核束装置上建立了一套包含飞行时间和大面积双面硅微条探测器的探测系统, 并用57.0MeV 17F次级束轰击7.66mg/cm2的(CH2)n靶对17F+p弹性共振散射反应进行了试测量.  相似文献   
8.
曾晟  F.Raiola  B.Burchard  C.Rolfs  连刚 《中国物理 C》2005,29(12):1131-1135
为了揭示低能带电粒子核反应中电子屏蔽效应与温度之间的关系, 在德国鲁尔大学实验室的100kV加速器上系统测量了T=200\textcelsius时元素周期表中第三、四族以及镧系元素氘化靶中d(d,p)t反应的电子屏蔽效应. 由于氘在介质中的溶度(介质对氘的吸附能力)随温度升高而迅速下降, 该温度下金属表面不能形成氘化物, 导致金属性增强, 因而观测到了比常温下更显著的电子屏蔽效应. 这一测量结果可以用德拜模型来解释. 为了进一步验证德拜模型, 还测量了不同温度下氘化Co和Pt靶中d(d,p)t反应的电子屏蔽效应, 得到了电子屏蔽效应和温度 相关性的曲线. 实验结果与德拜模型的预言相符.  相似文献   
9.
The angular distribution of the ^2H(^8Li, ^9Be)n (ground state) reaction, important to primordial nucleosynthesis in the inhomogeneous model, has been measured at E = 8.1 MeV using a secondary ^8Li beam. Cross section of this reaction was determined to be 9.0 4±3.4 mb. According to the cross section, the astrophysical S-factor was calculated to be 272 4±103 keV b. It is shown that ^2H(8^Li, ^9Be)n (ground state) reaction is important for creating 9Be, but less important for destroying aLl in primordial nucleosynthesis.  相似文献   
10.
慢速中子俘获过程(s过程)是合成比铁重元素的重要途径之一。22Ne(α,n)25Mg反应是大质量AGB星中s过程主要的中子源,其中的22Ne主要通过14N(α,γ)18F(β+)18O(α,γ)22Ne反应链合成。该反应链中关键反应18O(α,γ)22Ne在天体物理感兴趣能区的截面非常低,其天体反应率主要来自于22Ne α分离阈附近低能共振态的贡献,但目前相关能级的共振参数严重缺失。在HI-13串列加速器的Q3D磁谱仪上,通过测量18O(6Li,d)22Ne反应的角分布,利用DWBA分析确定了22Ne分离阈附近共振能级Eα=470 keV的自旋宇称为0+,为后续计算18O(α,γ)22Ne的天体反应率打下了基础。About a half of the abundances of elements heavier than iron comes from the so-called slowneutron capture process (s-process) in Asymptotic Giant Branch (AGB) stars, with the 22Ne(α, n)25Mg reaction as one of the main neutron sources. In the beginning phase of AGB thermal pulse, 22Ne is produced by the 14N(α, γ)18F(β+)18O(α, γ)22Ne reaction sequence, in which the 18O(α, γ)22Ne reaction plays a key role. While the reaction rate of the 18O(α, γ)22Ne is mainly affected by several resonant states lying closely to the α threshold in 22Ne, up to now, the relevant 22Ne parameters are fragmentary in the energy region corresponding to the typical temperatures of s-process. The direct measurement of the 18O(α, γ)22Ne reaction rate is extremely difficult due to the very low cross section. In this work, we investigated the 22Ne resonant states via the 18O(6Li, d)22Ne reaction at the Beijing HI-13 tandem accelerator of China Institute of Atomic Energy. Based on the DWBA analysis, preliminary results showed that the spin-parity of 22Ne Eα=470 keV resonant states was assigned as 0+, which would make contributions to subsequent calculation for the reaction rate of the 18O(α, γ)22Ne.  相似文献   
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