全国中学生物理竞赛与国际奥林匹克物理竞赛

全国中学生物理竞赛与国际奥林匹克物理竞赛都是由中国科协领导,中国物理学会主办的重要物理教育工作．自20世纪80年代中期兴办以来,物理竞赛受到国家和地方的科协与物理学会的高度重视和支持,全国各省、市大批物理工作者长期为此无私奉献、精心耕耘,形成了一整套严格的规范和很高的社会声誉,大大促进了中学生学习物理的积极性,     

Experimental study of the elastic scattering of ~(10)Be on ~(208)Pb at the energy of around three times the Coulomb barrier

Elastic scattering of 10Be on a 208Pb target was measured at ELab=127 MeV,which corresponds to three times the Coulomb barrier.The secondary 10Be beam was produced at the Radioactive Ion Beam Line in Lanzhou of the Heavy-Ion Research Facility in Lanzhou.The angular distribution of elastic scattering in the 10 Be+208Pb system shows a typical Fresnel diffraction peak.Optical model analysis of the angular distribution was performed using the Woods-Saxon,double-folding and global potentials.With the global potential,different density distributions were used.The results indicate that different density distributions for the projectile induce distinct effects in the angular distribution.     

Resistive plate chambers for muon detection at LHC

One resistive plate chamber made of Chinese materials and one Italian resistive plate chamber have been tested in the Gamma Irradiation Facility (GIF) at CERN on a high intensity muon beam together with a¹³⁷Cs source to give a uniform photon background, and simulating conditions close to those expected for an LHC muon detector. The results are analyzed. Good space and time resolutions are obtained which satisfy the future CMS experiment requirements. The detection efficiency is different between two RPCs against a high irradiation background. The reason is discussed.     

Systematic analysis of fusion barrier heights and positions for proton projectiles using the single folding model

The nuclear potentials between protons and different target nuclei are calculated by using the single folding model with the density-dependent nucleon-nucleon interaction.The fusion barrier heights and positions for proton projectiles fusing with different target nuclei with masses from 51 amu to 139 amu are systematically shown,with charge numbers and root-mean-square radii of the interacting nuclei.The parameterized formulas for the fusion barrier height and position are obtained for proton projectile fusing with the different nuclei.The calculated results of parameterized formulas are compared to empirical values,as well as those of the proximity potential and AkyüzWinther(AW) potential.It is shown that the calculated results agree perfectly with theirs.The parameterized formulas can reproduce the exact barrier heights and positions for proton fusion systems.     

Effects of relativistic kinematics in heavy ion elastic scattering

Relativistic corrections to the reaction kinematic parameters were made for elastic scattering of ⁶Li, ¹²C and ⁴⁰Ar from ⁴⁰Ca, ⁹⁰Zr and ²⁰⁸Pb targets at incident energies between 20 and 100 MeV/nucleon. The results of optical model calculations show that the effects of such corrections are important when describing the angular distributions of elastic scattering cross sections for heavy ion scattering at incident energies as low as around 40 MeV/nucleon. The effects on the total reaction cross sections on the other hand, were found to be small within the energy range studied when the optical model potential is fixed.     

A sub-millimeter spatial resolution achieved by a large sized glass RPC

Three large sized glass resistive plate chambers (RPCs) are built and applied to measure the spatial resolution of the detector. The readout strips are collected to a LC delay-line and the time difference is used to determine the position. Cosmic rays are triggered by a set of two scintillation counters and the coincidently measured positions from the three RPCs are used to deduce the position uncertainty. In average a spatial resolution of 0.90 mm (FWHM) is obtained for a single RPC, with a good uniformity across the detection area. This result suggests that large sized glass RPC operating in the avalanche mode is a promising candidate for the muon tomography detection system.     

通过破裂反应研究轻丰中子核的集团结构

概括介绍了关于轻丰中子同位素链集团结构的理论模型和通过破裂反应研究该结构的实验方法、 实验装置及物理分析。 The theoretical models of the cluster structures of the light neutron rich nuclei as well as the corresponding physical mechanism and experimental approaches by breakup reaction have been introduced, which may serve as references for possible experimental studies of the cluster structure of light neutron rich nuclei.      

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/cm^{2 12}C target. The data analysis is under procedure and the primary results are provided.     

垒下16O+232Th裂变碎片角关联模拟

使用Monte-Carlo模拟计算了垒下¹⁶O+²³²Th系统转移裂变和复合核裂变碎片角分布及角关联.转移过程、熔合过程和裂变过程分别用半经典模型、耦合道模型及鞍点过渡态统计模型进行模拟.考虑了各物理量分布产生的运动学效应及裂前中子发射和裂后碎片粒子蒸发对碎片角分布及角关联的影响.模拟结果和实验测量的分布相一致.使用折叠角技术借助Monte-Carlo模拟区分转移裂变和复合核裂变是可能的.考虑了转移裂变和裂前中子发射的影响,复合核裂变碎片角分布各向异性异常仍然存在.