中能中子与58Ni反应的理论计算

在中子与⁵⁸Ni反应的总截面、去弹性散射截面和弹性散射角分布的实验数据基础上, 获得了入射中子能量从0.825—150MeV的一组普适的中子与⁵⁸Ni反应的光学模型势参数. 利用光学模型、宽度涨落修正的Hauser-Feshbach理论、预平衡反应的激子模型和核内级联模型的中能核反应计算程序MEND, 计算了中子与⁵⁸Ni反应的所有截面、角分布和能谱, 并将理论计算结果与实验数据和评价数据进行了分析比较.     

Light Particle and Complex Fragments Emission from 12C Induced Reactions on 58Ni,64Ni at E/A=46.2MeV

Energy spectra of light charged particles and complex fragments emitted in the interaction of 46.2MeV/u ¹²C with different target ⁵⁸Ni,⁶⁴Ni,¹²C,¹⁹⁷Au and ²⁰⁹Bi have been measured by telescopes,consisting of CsI(Tl) and surface barrier detector stacks.These telescopes for light charged particles and complex fragments have good energy resolution and mass identification.The inclusive data have been analysed within a moving source parametrization.The complex fragment yields from different targets have been compared at several angles.The systematic variation of deduced isotope yields ratios with different reaction systems is used to detemine the N/Z degree of freedom equilibration of the system achieved.     

Radial Expansion Flow in Reactions of 40Ca+58Fe and 40Ca+58Ni

By means of using an isospin-dependent Boltzmann-Langevin equation which includes isospin-dependent symmetry energy, Coulomb energy, isospin-dependent nucleon-nucleon cross sections, Pauli blocking, and initialization, the radial expansion flow of reaction systems ⁴⁰Ca+⁵⁸Ni and ⁴⁰Ca+⁵⁸Fe at 53, 100, 150, and 200 MeV/u in the central collisions were studied. It has shown that the more neutron rich system exhibits smaller radial expansion flow. It was found that the neutron rich system had smaller threshold energy which may provide a new method to determine the isospin dependent nuclear equation of state from calculated result and linear fitting result.     

DETERMINATION OF THE AVERAGE NEUTRON ENERGY USING CROSS SECTION RATIO OF 58Ni(n,p)58m+gCo and 58Ni(n,2n)57Ni REACTIONS

The method of determination for average neutron energy from D-T reaction by using two silicon semiconductor detectors and the cross section ratios of ⁵⁸Ni(n,p)^58m+gCo and ⁵⁸Ni(n,2n)⁵⁷Ni reactions is described.The plot of the cross section ratio against the neutron energy has been obtained.The results have been compared with existing data.     

Element Distributions of Intermediate Mass Fragments Emitted in 30 MeV/u 40Ar+58,64Ni and 115In Reactions

The element distribuhons of intermediate mass fragments (IMF) emitted over an angular region of 5°—140° have been measured in the reachons of 30MeV/u ⁴⁰Ar+^58,64Ni and ¹¹⁵In. Within 20°—80° range the IMFs with Z=3-24 were observed. The IMF production cross section changes smoothly with its charge number,and the element distribuhon changes continuously when the IMF charge number increases across the charge number of the projectile. There is no strong dependence of the element distribution on the charge number of the projectile in this angular region.The transition nature of the reaction mechanism in the intermediate energy region and the power law of the IMF element distribution,as well as the dependence of element distributions on the threshold of the detectors were discussed.     

20 MeV以下65Cu(n,p)65Ni 反应截面及其协方差数据的评价

为满足核工程对核数据的需求,对20 MeV以下65Cu(n, p)65Ni 反应截面的实验数据进行了分析和评价,包括实验数据的收集、修正、选取、归一、误差调整和数据处理,在分析实验误差特别是关联误差的基础上构造了每家数据的协方差矩阵,最后利用样条拟合程序SPCC给出了评价截面数据和实验数据的协方差矩阵。评价不仅考虑了实验数据的误差,还考虑了数据间的相关性。To meet the needs for nuclear data engineering, the experimental data of the 65Cu(n, p)65Ni cross section below 20 MeV were analyzed and evaluated.The evaluation procedure includes the experimental data collection, correction, selection, normalization, error adjustment and data processing, especially the covariance matrix for each experimental data is constructed with the information on experimental errors and correlation errors. The evaluation cross section data and the corresponding covariance matrices were given using the spline fitting procedure SPCC. The evaluation work was done with the consideration of not only the experimental errors but also the correlation of data.     

The Angular Distributions of intermediate Mass Fragments Emittsd in 30 MeV/u 40Ar+58,64Ni and 115In Reactions

The angular distributions of intermediate mass fragments with Z=3-19 emitted in 30 MeV/u ⁴⁰Ar+^58,64Ni and ¹¹⁵In reactions over an angular range of 5°—140°have been measured.Exponential distribution function: dσ/dΩ=N·exp(-θ/a) was used tO fit the measured angular distributions.We have extracted the decay factor a that can be connected with the interaction time τ, and the factor N that is related to the intensity of the emission source.The relationships of a(Z) with Z and N(Z) with Z for different reaction systems and different angular ranges have been discussed. The dependence of angular distributions on isospin and the symmetry of reaction system have also been discussed.     

Study of the Reaction Mechanisms Induced by 16O on 64Ni at 96MeV

The angular distributions and Wilczynski plots of emitted fragments from He to O in reaction of ¹⁶O+⁶⁴Ni at 96MeV have been measured.The DIC cross section and intereaction time were obtained.DIC character of the reaction was discussed.The trace which shows that the emitted fragments of He and Li mainly come from the evaporation process of compound nuclei emerged.     

Angular and Z Distributions of the Fragments at Forward and Intermediate Angles in the Reaction of 25MeV/u 40Ar+115In,58Ni,27Al

The angular & Z distributions of foe fragments emitted in the forward and intermediary angles are measured at the reaction of 25 MeV/u ⁴⁰Ar+¹¹⁵In,⁵⁸Ni,²⁷Al. Their characteristics are investigated based on the model of Modified Qantum Molecular Dynamics (MQMD). Generally, the theoretical calculations are in good agreement with the experiment data. But in the forward angles the yield of the fragments is underestimated by MQMD model while in the case of the intermediate angle region, the calculation is higher than the experiment data in some degree for the fragments whose charge numbers are in the vicinity of the proiectile. The angular & charge distributions of the fragments are also compared with the statistical model of GEMINI. The results turn out to be that a small proportion of the statistical evaporation component exists in the forward angles while in the intermediate angle region, this component increases to some extent. However, its ratio is still small. It is found that the equilibrium evaporation component decreases gradually when the Z of the fragments becomes smaller.     

Elastic Transfer Reactions of 25MeV/u 6He on 9Be Target

Angular distributions for elastic transfer in the ⁶He+⁹Be system were measured at the incident ⁶He laboratory energy of E=150MeV. From a distorted-wave Born approximation (DWBA) analysis,³He spectroscopic amplitude in ⁹Be were extracted and compared with values obtained by shell model calculations. The result shows that the spectroscopic amplitude is much greater than 0.70.     

Phenomenological Study of 3He Photodisintegration up to 150MeV

A parametrization of ^3He（7,p）2H cross section data at laboratory photon energies between 9 and 150MeV iscarried out with a simple phenomenological function. The differential cross section data are normalized to the total cross-section values which are consistent with the measurement from monochromatic photon beams. The obtained results give a good representation of the experimental points.     

Model Calculation of n 6Li Reactions Below 20 MeV

Based on the unified Hauser-Feshbach and exciton model for light nuclei, the calculations of reaction cross sections and the double-differential cross sections for n 6Li are performed. Since all of the first-particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism must be taken into account. The fitting of the measured data indicates that the three-body break-up process needs to be involved, and the pre-equilibrium reaction mechanism dominates the reaction processes. In light nucleus reactions the recoil effect must be taken into account.``     

Developing AMS measurement of 59Ni at CIAE

Accelerator mass spectrometry (AMS) measurement of ⁵⁹Ni has been established at CIAE with the HI-13 tandem accelerator and the recently developed ΔE-Q3D detection system. ⁵⁹Ni standard and commercial NiO samples were measured to check the performance of the ΔE-Q3D detection system on ⁵⁹Ni isobar separation and suppression. An overall suppression factor of about 10⁷ for the interfering isobar ⁵⁹Co resulting in detection sensitivity as low as 3.8×10^-13 atomic ratio (⁵⁹Ni/Ni) has been obtained. Based on these techniques, the AMS measurement method of ⁵⁹Ni with high sensitivity is developed.     

Projectile Fragmentation in 46.7MeV/u 12C Induced Reactions

The projectile-like fragments emittd from 46.7MeV/u ¹²C induced reactions have been measured.The most probable energies of the PLFs due to the projectile fragmentation can be reproduced within the Abrasion picture.Their parallel momentum distribution widths are found to fulfill the Goldhaber relation and the extraced reduced parallel momentum distribution width σ₀ is 80±10MeV/c,which is close to the value obtained in the relativistic energy region.Futhermore,the values of σ₀ are the same for different reaction systems in our experiment.     

Model Calculation of n+6Li Reactions Below 20 MeV

Based on the unified Hauser-Feshbach and exciton model for light nuclei, the calculations of reaction cross sections and the double-differential cross sections for n+⁶Li are performed. Since all of the first-particle emissions are from the compound nucleus to the discrete levels, the angular momentum coupling effect in pre-equilibrium mechanism must be taken into account. The fitting of the measured data indicates that the three-body break-up process needs to be involved, and the pre-equilibrium reaction mechanism dominates the reaction processes. In light nucleus reactions the recoil effect must be taken into account.     

Isospin Effect on the Emission Mechanism of Hot Nuclei in 35MeV/u 40Ar +112Sn/124Sn Reactions

As an extension of radioactive ion beam physics, the research on isospin dependent properties of hot nuclei has increasingly attracted considerable interest. The isospin effect on the decay of hot nuclei in reactions 35MeV/u ⁴⁰Ar+¹¹²Sn/¹²⁴Sn has been investigared. It is concluded that due to Coulomb repulsion and instability, proton-rich hot nuclei probably emit prides such as a with high energy to increase their neutron-proton ratio. Moreover, the decay chain for those particles is seemingly long and the emission Probability is high. Thus, the conventional observations, for instance, the ‘slope temperature’ extracted from energy spectrum, may very appreciably with the measured particles.     

Neutrino Energy Loss by Electron Capture on Nucleus ^56Mn, ^56Fe, ^56Co and ^56Ni in Strong Electron Screening

Based on the p-f shell model, the neutrino energy loss rates for nucleus ^56Mn, ^56Fe, ^56Co and ^56Ni in the electron capture process are canvassed in and not in a strong electron screening. The results show that the neutrino energy loss rates for ^56Mn, ^56Fe, ^56Co and ^56Ni decrease about 15%, 10%, 60% and i order of magnitude correspondingly at the temperature T9 = 15 and even debase 2 orders of magnitude at the temperature T9 = 1.     

46.7MeV/u 12C轰击159Tb、197Au和209Bi的裂变测量及分析

用46.7MeV/u~(12)C轰击~(159)Tb、~(197)Au、~(209)Bi,测量关联裂片的速度和角度,研究了线性动量转移(LMT)、质量和出平面角分布,提取了核温度,应用级联两体统计衰变理论进行了拟合与解释,结果表明:在～50MeV/u入射能的中能重离子碰撞中,以非完全熔合方式形成了核温度高达4～5MeV的类复合核,其后通过裂变、蒸发级联统计两体衰变而退激。 The velocities and angles of fission partners emitted from reactions in ~(12)C+~(159)Tb, ~(197)Au,~(209)Bi systems with bombarding energy of 46.7MeV/u are measured. The linear momentum transferfrom projectile to target、mass and out-of-reaction plane angle distributions of fission fragments arestudied, and the temperatures of the target residues are extracted. These results have been explained by statistical binary decay model. It seems that the compound-likesystem with high temperature...     

Linear Momentum Transfer in the Reactions Induced by 50MeV/A12C Bombarding 209Bi and 197Au

The Distributions of the linear momentum transfer (LMT) in the reactions induced by 50MeV/u ¹²C with ²⁰⁹Bi and ¹⁹⁷Au were measured using fission fragment angular correlation technique.The most probable value of the linear momentum transfer per projectile,p^mp is dependent on the target.173MeV/c and 184MeV/c for ²⁰⁹Bi and ¹⁹⁷Au were obtained.In these distributions,there exists a small hump around 0.3 of LMT,which can probably be attributed to the alpha cluster transfer.     

Study of Two-Proton Interferometry in 46.7MeV/u 12C Induced Reactions

In this paper,the results of two-proton interferometry obtained in the experiment of 46.7 MeV/u ¹²C+⁵⁸Ni,¹¹⁵In,¹⁹⁷Au have been discussed. The influnce of nuclear force, Couloumb force and Fermi statistics on the correlation function is discussed also. The source radius parameters ro obtained from the experiment increase withincreasing of the target nuclei mass. In the experiment, the p-p correlation function seems to have a strong dependencs on the sum energy of two correlated protons. The ro parameter decreases with increasing of the sum energy, indicating that the high energy protons are mainly from the nonequilibrium emission process.