Poissonian Reducibility and Thermal Scaling in Nuclear Dissociation

The emission of clusters in the nuclear dissociation was investigated within the framework of isospin dependent lattice gas model.As observed in the recent experimental data,it was found that the emission probability of individual cluster is Poissonian and thermal scaling was observed in the linear Arrhenius plots made from the average multiplicity of each cluster as a function of the inverse temperature.The‘emission barriers’were extracted from the slopes of the Arrhenius plots and mainly depends on the surface energy of the cluster.

Measurements of Total Reaction Cross Section for Light Nuclei and Evidence for the Anomalous Nuclear Structure in ^(15)C

Measurements of the total reaction cross section for^(12-16)C,^(14-17)N and^(16-18)O on carbon target at intermediate energies were performed on RIBLL of HIRFL.A larger enhancement ofσR for^(15)C was observed than that for its neighbors.The analysis of these data indicates possible existence of an anomalous nuclear structure in^(15)C.A new quantity was suggested as the criterion to distinguish anomalous structure nuclei from normal nuclei.

Study on Excitation Function and Isospin Dependencies of Total Reaction Cross Section via the Boltzmann-Uehling-Uhlenbeck Model

The excitation function and isospin dependencies ofσR have been investigated by using the Boltzmann-Uehling-Uhlenbeck(BUU)model with a square-type density distribution.When the width parameter of the square distribution is obtained by fittingσR at relativistic energies,the BUU-model can reproduce the experimental data at intermediate energies better than Glauber model.The systematical underestimation ofσR at intermediate energy by Glauber model was removed out now by BUU calculation framework.It is also found thatσR is sensitive to nuclear equation of state andσin-NN medium.The difference factor d defined in text is sensitive to the nuclear structure such as neutron halo and neutron skin,etc.

剂量增强效应的蒙特卡罗模拟及实验研究

当X射线入射不同材料组成的界面时,在低Z材料的一侧将产生剂量增强,介绍了剂量增强效应的基本原理,并采用MCNP5构建三维铅铝屏蔽盒模型,计算了不同能量的X射线透过铅与铝产生的次级电子能谱以及穿过屏蔽盒后的金硅界面剂量深度分布.模拟计算表明,能量低于300 keV的X射线穿过铅铝屏蔽盒后的次级电子通量明显降低,剂量增强效应几乎可以忽略,界面硅一侧剂量均匀分布,并且实验结果与计算结果几乎吻合.

重离子碰撞中QCD物质整体极化的实验测量

高能重离子碰撞中Λ超子和φ, K*0矢量介子的整体极化的实验数据证实了夸克物质整体极化的新现象,引起了研究人员的广泛关注,成为高能核物理前沿新的热点研究方向.本文主要从实验测量上回顾整体极化研究,着重阐述相对论重离子对撞机(RHIC)上的螺旋径迹探测器(STAR)合作组在不同对撞能量点开展的Λ超子和φ, K*0介子的整体极化测量结果,并拓展到含有多个奇异夸克粒子Ξ,Ω的整体极化测量和Λ沿着束流方向的局域极化研究.本文也将简单点评大型强子对撞机(LHC)能区和HADES实验低能区的测量结果,并对这些实验结果给出的物理信息进行简单描述.

微通道反应器内CO2传质反应行为研究

以水平放置圆形截面的微通道反应器,进行K2CO3-CO2两相流传质实验。研究气速、液速、管径以及反应时间对微通道中瞬时吸收速率及气液两相传质的影响。实验结果表明:雷诺数Re与流动状态关系与传统理论类似;微通道中气液两相传质系数在0.1-6s^-1之间,K La随液体表观速率的增大而增大;随气体表观速率的增大而减小,属于液膜控制反应;随通道尺寸的增大,传质系数减小;瞬时吸收速率随时间先增大后减小并趋于平稳。

Effects of Neutron Skin Thickness in Peripheral Nuclear Reactions

Effects of neutron skin thickness in peripheral nuclear collisions are investigated using the statistical abrasion ablation (SAA) model. The reaction cross section, neutron (proton) removal cross section, one-neutron (proton) removal cross section as well as their ratios for nuclei with different neutron skin thickness are studied. It is demonstrated that there are good linear correlations between these observables and the neutron skin thickness for neutron-rich nuclei. The ratio between the (one-)neutron and proton removal cross section is found to be the most sensitive observable of neutron skin thickness. Analysis shows that the relative increase of this ratio could be used to determine the neutron skin size in neutron-rich nuclei.

Measurements of Total Reaction Cross Sections for Exotic Nuclei Close to the Proton Drip-line at Intermediate Energies and Observation of a Proton Halo in ^(27)P

Measurements of total reaction cross sections(σR)for some proton-rich nuclei(N=11-15 isotones)on carbon target at intermediate energies have been performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou.A large enhancement ofσR for ^(27)P has been observed than for its neighbors.Evidence for a proton halo in ^(27)P has been revealed in the Glauber analysis of the total reaction cross sections in terms of the difference factor d.

Re-examination of Finite-Size Effects in Isobaric Yield Ratios Using a Statistical Abrasion-Ablation Model

The"finite-size"effects in the isobaric yield ratio(IYR),which are shown in the standard grand-canonical and canonical statistical ensembles(SGC/CSE)method,are claimed to prevent the actual values of physical parameters from being obtained.The conclusion of SGC/CSE may be questionable for neutron-rich nucleus-induced reactions.To investigate whether the IYR has finite-size effects,we re-examine the IYR for the mirror nuclei[IYR(m)]using a modified statistical abrasion-ablation(SAA)model.It is found that when the projectile is not so neutron-rich,the IYR(m)depends on the isospin of the projectile,but size dependence can not be excluded.In reactions induced by the very neutron-rich projectiles,contrary results to those of the SGC/CSE models are obtained,i.e.,the dependence of the IYR(m)on the size and the isospin of the projectile is weakened and disappears in both the SAA and experimental results.

The influence of Multi-Step Sequential Decay on Isoscaling and Fragment Isospin Distribution in GEMINI Simulation

Extensive calculations on isoscaling behavior with the sequential-decay model GEMINI are performed for the mediate-heavy nuclei in the mass range A=110 and at excitation energies of up to 3 MeV per nucleon.Isoscaling can still be observed after entire−step decays are considered for the light products as in the only first-step decay process case.Comparison between the products after the first-step decay and the ones after entire-step decay demonstrates that multi-step secondary sequential decay strongly influences the isoscaling parametersα,βas well as the fragment isospin distribution.After entire−step decays,the isoscaling parametersαandβare decreased and the fragment isospin distribution can better reproduce the isospin distribution shape as the experimental data.

Directed and Elliptic Flows in ^(112)Sn+^(112)Sn Collisions

The directed and elliptic flow in collisions of ^(112)Sn+^(112)Sn at energies from 35 to 90 MeV/nucleon are studied in an isospin-dependent quantum molecule dynamics model.With increasing incident energy,the directed flow rises from negative to positive.Its magnitude depends on the nuclear equation of state(EOS).However,the elliptic flow decreases with increasing incident energy and its magnitude is not very sensible to EOS.Systematic studies of the impact parameter dependence and the cluster mass dependence are also performed.The study of directed flow at intermediate energies thus provides a means of extracting the information on the nuclear equation of state.

Total Reaction Cross Section Measurements at Intermediate Energy for the Proton Halo Candidate ^(23)Al and Its Neighbours

Total reaction cross sections σR for some proton-rich isotones (N = 10) near ^(23)Al on a carbon target have been measured at intermediate energies in the experiment performed at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. The Z-dependence of σR shows a remarkable enhancement for ^(23)Al relative to its neighbours. The difference factor d has been deduced from the measured σR by using the Glauber or Boltzmann-Uehling-Uhlenbeck models. From the above analysis, a possible one-proton halo structure is suggested for ^(23)Al.

Production of Light Nuclei from ^(36)Ar and ^(40)Ar Fragmentation at About 60 MeV/Nucleon

Fragments produced in the reactions of 69 MeV/nucleon ^(36)Ar and ^(55)MeV/nucleon ^(40)Ar on a Be target have been measured experimentally.The isotopic distributions from fragmentation reaction for both projectiles are reproduced by using a modified statistical abrasion-ablation model.Strong isospin effect exhibits in the isotopic distributions produced in ^(36)Ar and ^(40)Ar fragmentation.Experimental evidence is seen for the disappearance of the isospin effect in fragmentation reaction.

Nuclear Zpif-Type Plots

Isospin dependent classical molecular dynamics model is used to investigate the nuclear disassembly of^(129)Xe.Zpif-type plot in the field of linguistics is tested for the rank-classified cluster arrangement from this nucleardisassembly.It is found that the average cluster charge(or mass)of rank n in the charge(or mass)list is exactlyinverse to its rank,i.e.there exists Zpif's law at the point of the liquid gas phase transition.This novel criterioncan be used to diagnose the nuclear liquid gas phase transition experimentally and theoretically.

Isospin Effect of Fragmentation Reaction on the Isotopic Distribution Producedin Intermediate Energy Heavy Ion Collisions

Fragments produced in the reaction of 60 MeV/n^(18)O on Be have been measured experimentally.The isotopic distribution of fragmentation reaction is well reproduced by a modified statistical abrasion-ablation model It is predicted that the isotopic distribution shifts toward the neutron rich side for neutron rich projectile,but this isospin effect decreases with the increase of the atomic number difference Z-Z_(A)and disappears at last,where Z and Z_(A)are atomic numbers of the isotopic distribution and the projectile respectively.

Detector Calibration by Monte Carlo Simulation Based on the Energy-Range Relationship of Energetic Ions

The experimental measurement of the total interaction cross sections of N,C,B,and Be isotopes on 12C target at medium energies is described.A new formula that gives a good description of the energy-range relationship of energetic ions over a wide energy range is presented.The energy calibration of detectors is made by a Monte Carlo simulation method based on this new formula.

Isospin Effects of Critical Behavior in Lattice Gas Model

Isospin effects of the critical phenomena were studied via Xe isotopes in the frame of the lattice gas model.All the critical temperatures for four Xe isotopes are close to 5.5 MeV at the same freeze-out density of about 0.39ρ0.The critical values of power law parameter of mass distribution,mean multiplicity of intermediate mass fragments,information entropy and Campi's second moment show minor dependence on the isospin at the critical point.

Study of Giant Dipole Resonance of Super Heavy Compound System

A microscopic semi-classical approach,i.e.,the linearized Vlasov equation with a collision term treated by the relaxation time approximation,is simply described and is used to investigate the giant dipole resonance(GDR)from hot super heavy compound system.The possibility of such GDRγrays emission is described also according to the fission delay.For Au+Au system(A=392)and Xe+U system(A=374),the temperature dependence of strength distribution of GDRγrays and the deformation effect on GDRγrays are discussed in framework of this approach.

淮海战役对新时代科协思想政治工作的教益与启示

党在不同历史时期,始终注重发挥思想政治工作的独特作用,将其作为带领人民追求国家独立、民族复兴、人民幸福的重要方面和有效手段。中国科协作为党和政府联系科技工作者的桥梁和纽带,肩负着汇聚科技人才和科技力量、凝聚科学价值和共识的重要使命,始终高度重视思想政治工作。回顾和总结淮海战役中充分的政治动员、强大的心理战攻势以及广泛的民众参与和解放区社会大支持等致胜因素,探究思想政治工作在其中的运用方式、典型经验和示范效应,对于新时代科协思想政治工作具有宝贵的借鉴价值和启示意义。

揭开中微子和反中微子的马约拉纳神秘面纱——无中微子双贝塔衰变低温晶体量热器实验

中微子可能的马约拉纳粒子属性超出了目前标准模型的范畴,是粒子物理与核物理研究领域最重要的科学问题之一。无中微子双贝塔衰变(0vββ)实验是能够确定中微子马约拉纳属性的唯一途径。0vββ的发现可以揭示中微子绝对质量、轻子数破缺、物质—反物质不对称等一系列自然奥秘,是当今粒子物理与核物理研究的前沿课题。在探索无中微子双贝塔衰变的可选择实验方案中,低温晶体量热器具有高能量分辨率、高运行稳定性和低辐射本底的技术优势,成为新一代0vββ实验最具竞争力的探测器技术之一。文章首先介绍无中微子双贝塔衰变的研究历史,之后介绍低温晶体量热器及其最先进的代表——CUORE实验,最后展望关于我国锦屏地下实验室开展低温晶体量热器0vββ实验研究的前景。