Mass dependence of critical parameter and multiplicity of intermediate mass fragments in heavy ion reaction

The mass dependence of critical parameters for the liquid-gas phase transition and multiplicity of intermediate mass fragment in the heavy ion reaction is qualitatively explored under the framework of lattice gas model.Some results are compared with experimental data.

Predicting ^(28)Si projectile fragmentation cross sections with Bayesian neural network method

This study utilizes the Bayesian neural network(BNN)method in machine learning to learn and predict the cross-sectional data of ^(28)Si projectile fragmentation for different targets at different energies and to quantify the uncertainty.The detailed modeling process of the BNN is presented,and its prediction results are compared with those of the Cummings,Nilsen,EPAX2,EPAX3,and FRACS models and experimental measurement values.The results reveal that,compared with other models,the BNN method achieves the smallest root-mean-square error(RMSE)and the highest agreement with the experimental values.Only the BNN method and FRACS model show a significant odd-even staggering effect;however,the results of the BNN method are closer to the experimental values.Furthermore,the BNN method is the only model capable of reproducing data features with low cross-section values at Z=9,and the average ratio of the predicted to experimental values of the BNN is close to 1.0.These results indicate that the BNN method can accurately reproduce and predict the fragment production cross sections of ^(28)Si projectile fragmentation and demonstrate its ability to capture key data characteristics.

Isospin dependence of projectile fragmentation and neutron-skin thickness of neutron-rich nuclei

By investigating the cross section distributions of fragments produced in the 140 A MeV 40,48Ca＋9Be and 1 A GeV 124,136Xe＋Pb reactions, the isospin dependence of projectile fragmentation in fragment production is studied. In the framework of the statistical abrasion-ablation model, the 1 A GeV 136Xe＋ 208Pb reaction is calculated. By adjusting the diffuseness parameter in neutron density distribution of 136Xe, we find the isospin dependence of projectile fragmentation in fragment production is sensitive to the neutron-skin thickness of the projectile nucleus.

Projectile fragment emission in the fragmentation of 56Fe on Al,C,and CH2 targets

The emission angle distribution of projectile fragments(PFs)and the temperature of PF emission sources for fragmentation of 56Fe on polyethylene,carbon,and aluminum targets at the highest energy of 497 A MeV are investigated on the basis of corrected data,using a CR-39 plastic nuclear track detector.It is found that the average emission angle of PFs increases with the decrease in PF charge for the same target,and no obvious dependence of angular distribution on the mass of the target nucleus is found for the same PF.The cumulative squared transverse momentum distribution of PFs can be well represented by a single Rayleigh distribution.The temperature of PF emission sources is extracted from the distribution,and it is about 1.0-8.0 MeV and does not depend on the mass of the target for PFs with charges of 9≤Z≤25.

Isoscaling of projectile-like fragments

In this paper, the isotopic and isotonic distributions of projectile fragmentation products have been simulated by a modified statistical abrasion-ablation model and the isoscaling behaviour of projectile-like fragments has been discussed. The isoscaling parameters α and β have been extracted respectively, for hot fragments before evaporation and cold fragments after evaporation. It looks that the evaporation has stronger effect on α than β. For cold fragments, a monotonic increase of α and ｜β｜ with the increase of Z and N is observed. The relation between isoscaling parameter and the change of isospin content is discussed.

Fragmentation in ^16 O-emulsion interactions at 3.7 A GeV

The topology of ^16 O fragmentation at 3.7 A GeV in reactions with emulsion nuclei is presented. The multiplicity distributions of projectile fragments, charged secondaries and their dependences on the projectile residues are discussed.

Isoscaling properties for neutron-rich fragments in highly asymmetric heavy ion collision systems

Traditionally,isoscaling has been interpreted and applied within the framework of the grand canonical ensemble,based on the assumption that fragment production occurs following the attainment of a statistical equilibrium state.However,the influence of the symmetry energy can lead to differences in the neutron and density distribution in neutron-rich nuclei.This in turn may impact the iso scaling parameters(usually denoted byαandβ).We examine the isoscaling properties for neutron-rich fragments produced in highly asymmetric systems on inverse kinematics,namely^(40,48)Ca and ^(58,64)Ni+^(9)Be at 140 MeV per nucleon.We evaluate α and β values and sort them as a function of the neutron excess I≡N-Z.The significant differences in a extracted from fragments within different ranges of I emphasize the importance of understanding the dependence of isoscaling parameters on fragments generated in various collision regions.Furthermore,the|β(N)|/α(Z)value for a specific fragment in small size and highly iso spin asymmetry systems can serve as a probe to detect the variations in neutron density and proton density in different regions of the nucleus and indicate the limitations of theoretical models in investigating these issues.

Helium production from ^84Kr- and ^197Au-emulsion interactions at high energies

The properties of the relativistic helium fragments produced in interactions of ^84Kr at 1.8 A GeV and ^197Au at 10.7 A GeV in emulsion are investigated. The experimental results are compared with those obtained from various projectiles with emulsion collisions at different energies. It is found that the multiplicity distribution of helium projectile fragments （HPFs） is well described by the Koba-Nielsen Olesen （KNO） scaling presentation. The second Mueller moment f2 of the HPF multiplicity distribution is independent of the projectile energy for the same projectile, but it is dependent on the projectile mass number. The value of f2 increases with the increase of projectile mass number Ap. The negative value of f2, when Ap 〈 69, means that the emission of HPFs is anticorrelated, but positive value of f2, when Ap 〉 69, refers to that the emission of HPFs is correlated. The non-zero f2 moment in this experiment implies the strong correlation existing between the HPFs.

Projectile fragment emission in the fragmentation of ^(56)Fe on C,Al and CH_2 targets at 471 A MeV

The emission angle and the transverse momentum distributions of projectile fragments produced in the fragmentation of 56Fe on CHs, C and A1 targets at 471 A MeV are measured. It is found that for the same target, the average value and width of the angular distribution decrease with an increase of the projectile fragment charge; for the same projectile fragment, the average value of the distribution increases and the width of the distribution decreases with increasing the target charge number. The transverse momentum distribution of a projectile fragment can be explained by a single Gaussian distribution and the averaged transverse momentum per nucleon decreases with the increase of the charge of projectile fragment. The cumulated squared transverse momentum distribution of a projectile fragment can be explained well by a single Rayleigh distribution. The temperature parameter of the emission source of the projectile fragment, calculated from the cumulated squared transverse momentum distribution, decreases with the increase of the size of the projectile fragment.

30MeV/u^(40)Ar+^(159)Tb反应中用于中等质量碎片测量的BGO阵列探测器

报道３０ＭｅＶ小４０Ａｒ＋１５９Ｔｂ反应中用于中等质量碎片（Ｚ≥３）测量的△Ｅ（Ｓｉ）＋Ｅ（ＢＧＯ）望远镜阵列的测试结果，实验表明该探测器阵列对中等质量碎片有较好的粒子鉴别能力。

10.7 AGeV ^(197)Au诱发乳胶核反应α射弹碎片分布

对10.7 AGeV 197Au诱发乳胶核反应α射弹碎片产生的分截面进行研究。讨论了197Au核碎裂产生α多重碎片的产生率,并与其它能区的相应实验结果进行了比较。实验结果表明,α射弹碎片多重数分布服从KNO标度无关性。

中能重离子反应

本文讨论了中能重离子碰撞反应机制特点,评述近年来中能重离子碰撞中所发现的主要现象和理论研究,并着重介绍了BUU理论及其应用。

放射性次级束流分离器的分离性能

放射性次级束流分离器(HFRS)是强流重离子加速器装置(HIAF)上开展放射性次级物理研究的重要装置。HFRS是飞行时间型(PF)碎片分离器,具有大磁刚度、大接受度、大孔径磁铁以及高动量分辨的特点。HFRS采用Bρ-ΔE-Bρ方法纯化弹核碎裂或裂变反应产生的放射性核素,是开展高精度储存环内实验及环外实验研究的重要工具。主要介绍HFRS分离纯化奇异核的能力,采用MOCADI程序模拟单降能器与双降能器下典型弹核碎裂反应和裂变反应中粒子的鉴别和纯化。模拟结果表明:HFRS具有很好的消色散和聚焦特性,对于弹核碎裂反应中轻核的分离采用单降能器系统即可得到很好的纯化效果;而弹核碎裂反应中重核的分离则需采用双降能器系统才可得到很好的纯化效果;对于裂变反应,由于裂变反应的能散较大,则在采用双降能器系统时也仅仅能得到一定的纯化效果。

Calculation of depth-dose distribution of intermediate energy heavy-ion beams

Based on the characteristics of the interactions between intermediate energy heavy-ion beam and target matter, a method to calculate the depth-dose distribution of heavy-ion beams with intermediate energy (10-100 MeV/u) is presented. By comparing high energy beams where projectile fragmentation is overwhelming with low energies where energy straggling is the sole factor instead, a crescent energy spread with increasing depth and a simple fragmentation assumption were included for the depth-dose calculation of the intermediate energy beam. Relative depth-dose curves of carbon and oxygen ion beams with intermediate energies were computed according to the method here. Comparisons between the calculated relative doses and measurements are shown. The calculated Bragg curves, especially the upstream and downstream Bragg peaks, agree with the measured data. Differences between the two results appear only around the peak regions because of the limitations of the calculation and experimental conditions, but the

10.7 A GeV^(197)Au-Em作用电荷为3≤Z≤9的射弹碎片研究

对10.7 A GeV197Au-Em作用电荷为3≤Z≤9的射弹碎片的整体特征进行了研究.实验结果显示其约化自由程与距扫描起点距离D无关,电荷为3≤Z≤9的射弹碎片平均自由程不存在反常现象.这一结论可以通过I.Otterlund等人提出的检验方法和F-检验得到进一步证实.

10.7AGeV^(197)Au诱发乳胶核反应射弹碎片平均自由程研究

本文对10.7 AGeV197Au诱发乳胶核反应射弹碎片平均自由程进行了研究,结果表明射弹碎片的平均自由程在实验误差范围内与距射弹作用点的距离D无关,射弹碎片的平均自由程不存在反常现象.对于α射弹碎片平均自由程,实验发现在实验误差范围内与距射弹作用点的距离D、碰撞参数b、射弹α碎片多重数无明显的依赖关系,以上结论也可以通过I Otterlund等人提出的检验方法得到进一步证实.

736 AMeV^(28)Si与C靶作用弹核碎片发射角研究

利用CR-39探测器、HSP-1000高速成像显微镜和PitFit径迹分析软件研究了中高能^(28)Si与C靶反应产生的弹核碎片角分布。通过束流照射、化学蚀刻以及径迹重建等实验过程,首次给出了能量为736 AMeV^(28)Si与C靶反应弹核碎片发射角分布的实验结果,并与能量在800和775 AMeV下^(28)Si与C靶反应产生的弹核碎片发射角分布进行比较。结果表明,弹核碎片发射角分布的平均值和宽度大于^(28)Si束流粒子散射角分布的平均值和宽度;大多数弹核碎片发射角小于2.0度,很少有发射角大于2.0度;不同电荷数Z的弹核碎片发射角平均值范围在1.0度以内,其角分布平均值和宽度随碎片电荷数Z的增加总体呈现减小的趋势。

一套用于重离子耗散反应测量的电离室望远镜(英文)

重离子耗散反应需要鉴别产物的电荷数Z ,为此 ,研制了一套ΔE E望远镜 .ΔE由两个串接在一起的气体电离室ΔE1和ΔE2 组成 ,位置灵敏硅半导体测量粒子的剩余能量E .被探测粒子的轨迹与电离室的电场方向平行 .该望远镜具有很低的能量探测阈 ,较小的外尺寸和强的抗电磁干扰能力 .重离子耗散反应19F +2 7Al产物的激发函数实验测量表明 ,该望远镜的电荷分辨Z/ΔZ约为 30 .

用修正的擦碎模型研究碎裂反应的同位素分布

对统计擦碎模型(SAA)的计算方法进行修正和优化,并引入参数化的介质中核子-核子碰撞截面和核物质密度分布弥散度,可很好符合从中能到高能下碎裂反应产生同位素分布的实验截面,并能计算和拟合远离峰位、很低截面的同位素分布.

晕核反应机制与内部结构之间的关系

在对中子晕核和质子晕核反应机制研究的基础上,经仔细分析和对比,进一步展现晕核反应机制和它的内部结构之间存在着内在的关系．计算结果分析表明,由于所选中子晕核11Li的结构比质子晕核23Al的结构更加松散,故与23Al比较,11Li更易碎裂,因而导致碎片多重性明显增加．同时由于11Li 的松散结构导致两体碰撞过程的减弱,因而导致动量耗散的减弱,故与23Al对比,将引起原子核阻止明显减少．