80MeV/u 20Ne轰击9Be碎裂产物反应总截面的测量

介绍了用透射法测量中能区²⁰Ne打⁹Be靶碎裂产生的次级束与Si靶作用的核反应总截面的方法,以及实验的探测器布局、实验过程和实验结果.并对理论上预言有奇异结构的核¹²N,¹⁷Ne和¹⁷F的实验结果与其相邻核进行了比较.     

12N直接碎裂反应研究

描述了在兰州放射性束流线(RIBLL)上用78.6MeV/u的¹⁴N束流轰击Be靶产生出34.9MeV/u的¹²N次级束流. 利用¹²N轰击Si靶作为次级靶, 利用直接碎裂反应测量它的反应总截面. 利用理论模型进行了计算, 理论计算和实验结果符合的很好. 发现¹²N的质子密度分布相对于中子而言, 有一个很大的弥散.     

奇异核的实验研究

总结了兰州放射性束实验小组在兰州放射性次级束流线上近几年来利用产生的放射性束流,轰击Si或C等靶子,测量它的反应总截面.并利用经验公式将这些结果归一到相同的能量和靶子,与其相邻的核相比较,发现了⁹C,¹¹Be,¹⁴Be,⁸B,¹⁴B 和¹²N等核素的反应总截面值有奇异增大的现象.利用微观的Glauber模型进行了计算,对有奇异结构的核采用核芯加价核子的密度分布形式,理论计算和实验结果符合得很好,可以给出奇异核的弥散的密度分布.     

294MeV 20Ne+159Tb反应中出射α粒子的研究

在294MeV Ne束轰击Tb靶的反应中,用ΔE-E望远镜测量了10°—150°发射的α粒子能谱,并用运动源模型拟合了所得的实验能谱,得到与前角度源、中等速度源、熔合蒸发源的有关参数.计算谱很好地复现了实验能谱的形状、峰位信数值,角分布也得到极好的模拟.实验所得的发射α粒子截面为3300mb,运动源模型计算值为3700mb.     

利用GEANT4和TALYS研究中子与铁作用的次级中子双微分截面

铁的次级中子双微分截面对核装置的设计、运行与维护具有重要作用。相关实验数据缺乏,且评价数据不完善,需要使用可靠的核理论模型进行计算。本工作利用GEANT4程序结合不同的中子评价数据计算了8.17, 11.5, 14.1和18 MeV等入射能量下中子轰击薄铁靶不同出射角度的次级中子双微分截面;同时利用TALYS程序和GEANT4程序结合BIC、BERT和INCLXX模型计算了25.7, 65, 100和150 MeV等入射能量下中子轰击薄铁靶不同出射角度的次级中子双微分截面,并与实验数据进行对比。研究表明,在20 MeV以下能区,ENDF/B-VIII.0库的计算结果与实验数据符合较好,BROND-3.1、CENDL-3.1、JENDL-4.0u和JEFF-3.3库的计算结果与实验数据存在差异。在20~150 MeV能区,GEANT4程序的BERT模型和TALYS程序的计算结果与实验数据符合较好,INCLXX模型和BIC模型的计算结果与实验数据存在分歧。整体来看,需要对铁的中子评价数据和核反应理论模型做进一步研究。     

200A GeV硫核及其重碎片与铜核作用的电荷改变总截面的测量

测量了200A GeV的³²S及其碎片P,Si,Al,Mg,Na和Ne与Cu靶作用的电荷改变总截面.观察到次级碎片的电荷改变总截面比相同电荷的初级粒子的要高.导出的电磁散裂截面与弹丸电荷的平方成比例,与理论预言一致.     

丰质子核反应中轻带电粒子发射的同位旋效应

采用同位旋相关的Boltzmann—Langevin方程计算了核素^12-15N和^17-20Ne反应中轻带电粒子发射的同位旋效应。^12-15N与^28Si靶的反应结果显示轻带电粒子的产生截面有明显的同位旋效应,^12N的轻带电粒子产生截面突然增大,与实验得出的结论相同,由此检验了所采用的计算方法的可行性。同时还计算了^17-20Ne与^9Be靶的反应,发现^17Ne的轻带电粒子产生截面也是突然增大,并且其质子分布有较大的弥散,据此认为^17Ne可能具有晕结构。 Within the Boltzmann-Langevin equation, the isospin effects on the production cross sections of light charged particles （LCP） in the reaction of proton rich nuclei were studied. We have calculated the LCP productio n cross sections of the reaction ^12-15N ＋ ^28Si at 55 MeV/u and ^17-20Ne ＋ ^9Be at 60 MeV/u. The LCP production cross sections of ^12N increase abnormally in comparison with those of ^13-15N. The result accorded with experimental one. It also happened to ^17-20Ne. It suggests that ^17Ne is probably a proton halo nucleus.     

丰中子奇异核17B的实验研究

在兰州重离子加速器国家实验室(HIRFL)放射性次级束流线(RIBLL)上,用束流透射法测量了丰中子奇异核¹⁷B与C靶反应的总截面.假定¹⁷B具有¹⁵B(核芯)＋2n结构,采用Gauss＋HO形式的密度分布和零力程Glauber模型进行计算的结果可以很好地拟合实验数据,并得出¹⁷B的密度分布有一个很大的弥散,表明¹⁷B是双中子晕核. 关键词： 丰中子奇异核 反应总截面 Glauber模型 密度分布     

200AGeV硫核及其重碎片与铜核作用的电荷改变总截面的测量

测量了200AGeV的~(32)S及其碎片P,si,Al,Mg,Na和Ne与Cu靶作用的电荷改变总截面。观察到次级碎片的电荷改变总截面比相同电荷的初级粒子的要高。导出的电磁散裂截面与弹丸电荷的平方成比例,与理论预言一致。     

0.4—3.0Mev质子引起的Ta,Au和Bi的L壳X射线研究

以(?).4—3.0Mev质子轰击Ta,Au和Bi薄靶,测得其L—X射线产生截面.求出了比值L_α/L_(?),L_α/L_β和L_α/L(?).将得到的截面及L-X射线强度比与ECPSSR理论计算值作了比较.     

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/cm2 12C target. The data analysis is under procedure and the primary results are provided.     

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.     

17F和18Ne与质子的弹性散射角分布

采用逆运动学方法对放射性核束¹⁷F和¹⁸Ne与质子进行弹性散射实验,得到了实验测量微分截面.用较准确描述放射性核素性质的CH89参数化的光学势为初始光学势,用扭曲波玻恩近似的理论计算程序DWUCK4和自动参数搜索程序ABOD对实验数据进行光学势参数理论拟合,得到了与实验数据相符合的光学势参数.将得到的光学势参数进行分析,得到了17F和18Ne实势相互作用均方根半径分别为3.239fm和3.317fm.     

Experimental investigation on divertor tungsten sputtering with neon seeding in ELMy H-mode plasma in EAST tokamak

Neon (Ne) seeding is used to cool the edge plasma by radiation to protect the divertor tungsten (W) target in the Experimental Advanced Superconducting Tokamak (EAST). The W sputtering in the outer divertor target with Ne seeding is assessed by the divertor visible spectroscopy system. It is observed that the W sputtering flux initially increases with Ne concentration in the divertor despite the decreasing plasma temperature. After reaching a maximum around 25 eV, the W sputtering rate starts to decrease, presenting a suppression effect. The effect on the divertor W sputtering flux and yield due to the competition between the increase of the Ne concentration and the decrease of the plasma temperature is discussed. The results show that enough Ne seeding is essential to effectively reduce the electron temperature and thus to suppress W sputtering. Moreover, ELM suppression is observed when Ne and W impurities enter the core plasma, which could be correlated to the enhanced turbulence transport in the pedestal.     

Angular Distribution of Elastic Scattering of 17F and 18Ne on Proton

Under reverse kinematics, elastic scattering of ¹⁷F and ¹⁸Ne on proton is studied. The experimental differential cross sections were measured. A kind of global optical potential with the CH89 parameters is used to describe the radioactive nucleus as an initial optical potential parameters. The experimental differential cross section data are analyzed by using the theoretical calculation code DWUCK4 with the distorted wave Born approximation and parameter search subroutine ABOD which automatically searches the suitable parameters. Then the optical potential parameters of scattering ¹⁷F and ¹⁸Ne on proton are obtained. From the analyses of the optimized parameters, the real central potential mean square radii of ¹⁷F and ¹⁸Ne, 3.239fm and 3.317fm are deduced, respectively.     

A study of three-nucleon transfer reactions on 17O

The reactions ¹⁷O(¹¹B, ⁸Li)²⁰Ne, ¹⁷O(¹²C, ⁹Be)²⁰Ne and ¹⁷O(¹³C, ¹⁰B)²⁰F have been studied using beams of 115 MeV ¹¹B and ¹²C and 105 MeV ¹³C incident on a gas target. Shell-model calculations have been performed for ²⁰Ne and ²⁰F, for comparison with the experimental data. It is found that the data can be interpreted using the shell model spectroscopic factors and a semi-classical reaction theory. We justify the use of the latter by applying it to the cases of three-nucleon transfer on ¹⁶O. Spin assignments are suggested for previously unidentified states in ²⁰F.     

Calculation of electron wave functions and refractive index of Ne

The radial wave functions of inner electron shell and outer electron shell of a Ne atom were obtained by the approximate analytical method and tested by calculating the ground state energy of the Ne atom. The equivalent volume of electron cloud and the refractive index of Ne were calculated. The calculated refractive index agrees well with the experimental result. Relationship between the refractive index and the wave function of Ne was discovered. Supported by the New Star Program of Beijing Science and Technology, China (Grant No. 952870400), the Beijing Municipal Commission of Education, and the Excellent Young Teachers Program of Ministry of Education, China     

Experimental evidence of (2)He decay from (18)Ne excited states

Two-proton decay from (18)Ne excited states has been studied by complete kinematical reconstruction of the decay products. The (18)Ne nucleus has been produced as a radioactive beam by (20)Ne primary projectile fragmentation at 45 AMeV incident energy on a Be target. The (18)Ne at 33 AMeV incident energy has been excited via Coulomb excitation on a (nat)Pb target. The obtained results unambiguously show that the 6.15 MeV (18)Ne state two-proton decay proceeds through a (2)He diproton resonance (31%) and democratic or virtual sequential decay (69%). The quoted branching ratio has been deduced from relative angle and momentum correlations of the emitted proton pairs.