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.     

Quasi-Elastic Scattering of 16C from 12C at 47.5 MeV/Nucleon

Differential cross sections for the quasi-elastic scattering of^16 C at 47.5 MeV/nucleon from ^12 C target are measured.Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.     

Calculation and Analysis of Neutron-Induced Reactions on 58Ni Below 150MeV

Based on the experimental data of the total, the nonelastic and the elastic cross sections and the elastic scattering angular distributions for n+⁵⁸Ni reactions, a set of parameters for a neutron optical model potential is obtained in the incident neutron energy region from 0.8—150MeV. Then reaction cross sections, angular distributions, energy spectra, gamma-ray production cross sections and gamma-ray production energy spectra are calculated in terms of the optical model, the distorted wave Born approximation theory, the Hauser-Feshbach theory, the exciton model and the cascade mechanism inside nuclear. The results are analyzed and compared with the existing experimental data and other evaluated data from ENBF/B-6. They are in agreement with each other within error bars.     

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.     

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.     

46.7MeV/u12C引起的弹核碎裂及轻带电粒子关联

我们在HIRFL提供的46.7MeV/u的~(12)C离子轰击~(58)Ni、~(115)In和~(197)Au靶所引起的核反应中研究了弹核碎裂与转移反应的竞争,分别提取了对应于弹核碎裂和转移反应的类弹碎片的约化动量宽度,从粒子发射不稳定态的相对布居得到了不同反应系统的核温度参数。 The projectile fragmentation and its competition with the transfer reactions have beenstudied in the reactions induced by 46.7 MeV/u ~(12)C ion on the ~(58)Ni, ~(115)In and ~(197)Au targets. Thereduced momentum distribution widths of the projectile-like fragments for projectile fragmentationand transfer reactions were extracted from the experimental data respectively. The nuclear temperatureperameters were obtained from the relative populations of the unstable particle emission ...     

ANALYSIS FOR ENERGY SPECTRA OF LIGHT PARTICLES EMITTED FROM 12C+64Ni REACTION

Some experimental results measured for light emission particles with Z≤2 from ¹²C+⁶⁴Ni reaction at E(¹²C)=69, 56MeV are reported. A comparison between moving source model calculation and proton's spectra have been performed. Extracted parameters of the source with faster velocity are agreement with the systematic values found before. The composite particle energy spectra of α, ³He and D were analyzed by coalescence model.     

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.     

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.     

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.     

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.     

Simulation of 200–400 Me V/u ~(12)C+~(12)C elastic scattering on SHARAQ spectrometer

In order to further obtain the information of three-body force(TBF) from 200–400 Me V/u12C+12C elastic scattering, we plan to perform this experiment on a SHARAQ spectrometer. Based on the experimental condition of the Radioactive Ion Beam Factory(RIBF)-SHARAQ facility, a simulation is given to find a compromise between the better energy and angular resolutions, and higher yield by optimizing the target thickness, beam transport mode, beam intensity and angular step. From the simulation, we found that the beam quality mainly limits the improvements of energy and angular resolutions. A beam tracking system as well as a lateral and angular dispersionmatching technique are adopted to reduce the influence of beam quality. According to the two angular settings of SHARAQ as well as the expected cross sections on the basis of the theoretical model, the energy and angular resolutions, and statistical accuracy are estimated.     

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.     

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.     

Origins of the Forward Emission of Complex Fragments for 40Ar+159Tb Reaction at 30MeV/u

Light charged particles and complex fragments have been measured at forward angles in coincidence with two fission fragments for ⁴⁰Ar+¹⁵⁹Tb reaction at 25MeV/u. These three-body coincident events were sorted as a function of the impact parameter using linear momentum transfer and total transverse momenta methods. Equilibrium statistical emissions of complex fragments from quasi-target residues accompanied by non-equilibrium mid-rapidity components were found to dominate in central collisions, while projectile fragmentations were found to dominate in peripheral collision. Three components of complex-fragments from quasi-target, quasi-projectile and mid-rapidity soures were found in mid-central collision.     

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...     

Population of Unstable Nuclides and Nuclear Temperature Extraction in 46.7MeV/u 12C Induced Reaction

The experiment results of unstable nucliaes decay by using the light charged particle correlation function obtained in ¹²C 46.7MeV/u+⁵⁸Ni experiment are reported.Under the assumption of statistical equilibrium,the nuclear temperatures are extracted,and the influence of the reaction mechanism on the nuclear temperature are also investigated.     

Study of Production of Secondary Beams from 95MeV/u 12C Projectile

A systematic study about the production of secondary beams in 95MeV/u ¹²C+Be,Cu and An targets was performed by using the GANIL doubly achromatic spectrometer LISE.The maximum values of the secondary beam production calculated by programs LISE and INTENSITY are in agreement with the experimental results for the secondary beams near the β stability line.However,the calculations are larger than the experimental results for the secondary beams far from the β stability line.The optimum target thickness for the production of secondary beams corresponds to about 30% beam energy loss in the target.Beryllium target was found to offer higher production for all the secondary beams than copper and gold targets.     

Optical Potential Parameters for Halo Nucleus System ^6He＋^12C from Transfer Reaction ^11B（^7Li, ^6He）^12C

The optical potential parameters for the halo nucleus system ^6He＋^12C are extracted from fits to the measured angular distributions of ^11B（^7Li, ^6He）12C reaction at energies of 18.3 and 28.3MeV with distorted-wave Born approximation analysis. The characters of the obtained optical potentiM parameters are basically consistent with the results extracted from the fits to the elastic-scattering angular distributions in the literature.     

Time Scsle for Emission of Intermediate Mass Fragments in E/A=30MeV 40Ar+natAg Reaction

Fragment-fragment conelation functions have been measured in E/A=30 MeV ⁴⁰Ar+^natAg reaction via the technique of intensity interferometry. Emission times of intermediate mass fragments have been extracted from reduced velocity correlation functions by using the threebody trajectory model. The average emission time of intermediate mass fragments varies with the energy of fragments. It decreases from about 300fm/c for low energy fragments to about 80fm/c for energetic fragments. After subtmcting the contribution of projectile-like fragments, average emission times of mid-rapidity fragments are of the order of 250fm/c for this reaction.It indicates that intermediate mass fragments emitted in this reaction mainly come from sequential binary decays.