~2H(~6He,~7Li)n反应角分布和~7Li的质子谱因子

在中国原子能科学研究院HI-13串列加速器次级束流线上,使用6He次级束首次测量了质心系能量为9.1 MeV的2H(6He,7Li)n反应角分布,并用扭曲波波恩近似(DWBA)进行理论分析,导出了7Li的质子谱因子为0.40±0.02。     

用屏栅电离室测量~6Li(n,t)~4He反应微分截面

用屏栅电离室对 3.6 7MeV与 4 .4 2MeV中子6Li(n ,t) 4He反应微分截面进行了测量。利用氘气体靶通过D(d ,n) 3 He反应产生中子 ,用BF3 和液闪探测器 (NE2 13)进行相对中子通量监测 ,绝对中子通量用2 3 8U(n ,f)与H(n ,p)反应来刻度。测量结果表明 ,氚的质心系微分截面在中子能量为 3.6 7MeV时很接近 90°对称 ,而到 4 .4 2MeV时则明显前倾     

~(14)N(~7Li,~6He)~(15)O和~(14)N(~7Li,~6Li)~(15)N反应的测量

正H是宇宙中丰度最高的元素,H燃烧反应是恒星重要的能量来源。H燃烧有p-p链和CNO循环两种方式。而~(14)N(p,γ)~(15)O是CNO1循环中最慢的核过程,它控制着整个CNO循环的进程,从而影响对球状星团年龄的判断。球状星团年龄与由哈勃常数确定的宇宙年龄之间的矛盾尚待解决。     

利用(~7Li,~6Li)反应测量~(15)N(n,γ)~(16)N天体物理反应率

用Q3D磁谱仪测量了15N(7Li,6Li)16N布居16N基态和前三个激发态的角分布。通过对实验数据的扭曲波玻恩近似(Distorted wave Born approximation,DWBA)分析,导出这些态的谱因子和渐进归一化系数(Asymptotic normalization coefficient,ANC),进而用新的谱因子得到15N(n,γ)16N的天体物理反应率。结果表明,尽管15N为中子满壳核,但16N中转移中子处于2s1/2轨道的两个能级并不是很好的单粒子能级,与壳模型的理论预言结论相反。     

~(25)Mg(~7Li,~6He)~(26)Al反应角分布的测量

正为研究~(25)Mg(p,γ)~(26)Al反应的58keV共振,在串列加速器Q3D磁谱仪上利用31.5 MeV的7Li束流分别轰击~(25)MgO靶、~(24)MgO靶和~(12)C靶,对~(25)Mg(~7Li,~6 He)~(26)Al反应布居6.364激发态的角分布进行了测量。反应生成的~6He离子经磁谱仪的分离聚焦后,在焦平面上由二维位置灵敏硅探测器阵列进行收集和鉴别。探测器阵列由6块X4型探测器组成,沿水平方向依次安装在精度为μm量级的二维平移台上,每块探测器有效探测面为75mm×48mm,探测器之间相距55mm,相同     

利用~4He(~(13)C,n)~(16)O和~1H(~7Li,n)~7Be反应作中子源的建议

本刊试办“学术争鸣”专栏,提倡在学术上解放思想,名抒已见,勇于争鸣,探索和认识客观世界的规律。本专栏拟刊登原子能科学技术领域内新提出的或有争议的各种学术见解、观点、建议等,欢迎读者来稿,或对所发表的文章展开讨论。     

Determination of the Astrophysically Relevant ~6Li(n,γ)~7Li Cross Sections from the ~7Li(~6Li,~7Li)~6Li Elastic-Transfer Reaction

Angular distributions for the ~7(Li)(~6(Li),~7(Li))~6(Li) Li elastic-transfer reaction have been measured with the Q3D magnetic spectrograph at the HI-13 tandem accelerator of Beijing, China. The neutron spectroscopic factors of 7Li are derived by comparing the calculated differential cross sections, which are obtained through the distorted-wave Born approximation (DWBA) calculation, to the experimental data. And these spectroscopic factors are then used to deduce the direct capture cross sections in 6Li(n,γ)7 Li at energies of astrophysical relevance.     

6Li(n,t)4He反应微分截面的实验测量

用屏栅电离室对1．85和2．67MeV中子^6Li(n,t)^4He反应的微分截面及截面进行了测量。使用氚固体靶通过T(p,n)^3He反应产生中子,利用BF3长中子管进行相对中子通量监测,绝对中子通量则用^238U(n,f)反应来刻度。测量结果与已有数据进行了比较。     

Differential Cross Section Measurement for the ~6Li(n,t)~4He Reaction

The differential cross sections and integrated cross sections of the 6Li(n,t)4He reaction were measured at 1.85 and 2.67 MeV by using a gridded ionization chamber. Neutrons were produced through the T(p,n)3He reaction. The absolute neutron flux was determined through the 238U(n,f) reaction. Present results are compared with existing data.     

THE SUMMARY OF EVALUATIONS OF ~1H,~4He,~6Li,~7Li,~9Be,~(14)N,~(16)O AND MO FOR CENDL-2

The evaluations of neutron nuclear data of ~1H,~4He,~6Li,~7Li,~9Be,~(14)N~(16)O and Mo were completed by various evaluators for CENDL-1 before 1985.Due to the conditions at that time,these evaluated data sets are not complete     

1―2MeV能区~6Li(n,t)~4He反应微分截面与截面的实验测量

利用屏栅电离室对1.05、1.54及2.25MeV中子6Li(n,t)4He反应的微分截面与截面进行了实验测量。采用氚固体靶的T(p,n)3He反应产生准单能中子,用相对效率已知的BF3长中子管和238U裂变片相结合来测定绝对中子通量。将测量结果与已有数据进行了比较,1―2MeV能区6Li(n,t)4He反应截面的分歧在一定程度上得到了澄清。     

~8Li(n,γ)~9Li的天体物理反应率

近年来,8Li(n,γ)9Li反应在二类超新星及大爆炸核合成中具有重要意义,引起了众多核天体物理学家的兴趣。在二类超新星核合成中,4He(t,γ)7Li(n,γ)8Li(α,n)11B反应链被认为是形成γ射线的过程种子核的关键反应之一。然而在核合成过程中,该反应链将受到8Li(n,γ)?9Li反应的影响     

Neutron Data Evaluation for ~7Li(n,n’t)~4He Reaction

For the cross section of ~7Li(n,n't)α reaction higher accuracy is requires.In recent ten years a lot of experimental data were carried out by many laboratories.The values of recent measured cross section for ~7Li(n,n't)α reaction aresmaller than the old ones,and differences exist in E_n>8MeV.In fact it isshown by benchmark testing results that the old ones are too large.     

闪烁谱仪测量~6Li,~7Li(d,n)中子能谱方法

本文扼要介绍了应用芪晶体反冲质子积分法测量快中子能谱的原理、方法和实验技术。还给出了当氘核能量为3.7和5.03兆电子伏时,~6Li,~7Li(d,n)反应的中子能谱测量方法、数据处理以及误差分析。     

T(d,n)~4He反应中子角分布

用反冲质子望远镜测量了T(d,n)~4He反应中子角分布,E_d=1,1.5和2 MeV,角度范田0—150°。实验结果用最小二乘法按照勒让德(Legendre)多项式拟合,误差为±2.6%,并与国外结果进行了比较。     

单质子转移反应~(208)Pb(~7Li,~6He)~(209)Bi在深垒能区的测量

正由于受放射性束流强度和品质的限制,很难通过直接的弹性散射测量来抽取晕核体系的光学势。因此,采用转移反应作为间接的方法研究晕核体系的光学势。为能在深垒能区进一步研究晕核~6 He体系光学势的性质,在垒下能区测量了单质子转移反应~(208)Pb(~7Li,~6He)~(209)Bi的角分布,通过拟合实验数据以期抽取出射道晕核~6 He+~(209)Bi体系的光学势。实验在中国原子能科学研究院的HI-13串列加速器上完成,束流7Li的能量分别为E_(lab)(~7Li)=21.20、24.30、25.67和28.55 MeV,束流强度约     

Cross Section Measurement of ~2H(~8Li, ~9Li)~1H Reaction for Astrophysics Interesting

The standard model (SM) is know to produce fairly good agreement with primordial abundances ofnuclides up to mass 7 amu, and to produce very tiny abundances of the high-mass elements due primarilyto the lack of stable particles at 5 and 8 amu. The recently developed inhomogeneous models (IMs)predict that short-lived isotopes are created which allow for more reaction pathways, such as     

The Astrophysical ~8Li(n,γ)~9Li Reaction Rate

The 8Li(n, γ)9Li reaction has attracted much attention in the recent years because of its importance in astrophysics. Nucleosynthesis of light nuclides is impeded by the gap at mass number A=8, where no stable nuclei exist. In the explosive neutron-rich …     

快中子与~6Li,~7Li的三体反应

用载锂乳胶对14—18兆电子伏中子与~6Li,~7Li的三体反应——~6Li(n,nd)α与~7Li(n,nt)α作了“运动学完全”的测量。由此得到次级中子能谱以及通过~6Li第一激发态与~7Li第二激发态的非弹性散射中子的角分布。观察到中子与锂核内α集团的准自由散射。用“平面波冲量近似”得到了Li核表面α集团的动量分布,间接地证明了~6Li核中氘集团有收缩效应。