极化电子源的原理及实验研究

简单介绍了极化电子束的获得,即极化电子源,讨论了对电子束极化度的测量,极化电子与原子散射,以及极化电子束在固物理、生物物理、核物理与粒子物理中的应用． The getting of polarized electrons was briefly introduced, that is the source of polarized electrons. The measurement of polarization in future, the application of polarized electrons in atomic and molecular physics, condensed physics, biological physics, nuclear and particle physics were discussed.     

低能实验核物理及其应用

简要地介绍了北京大学技术物理系和重离子物理研究所近年来在低能实验核物理及其应用方面的部分研究工作.Some recent studies on the low energy experimental nuclear physics and its applications at the Department of Technicsal Physics and the Institute of Heavy Ion Physics of Peking University are beiefly introduced in this paper.     

Quark Energy Loss and Shadowing in Nuclear Drell-Yan Process

The energy loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Dre11-Yan process. By means of three kinds of quark energy loss parameterizations given in literature and the nuclear parton distribution extracted only with lepton-nucleus deep inelastic scattering experimental data, measured Dre11-Yan production cross sections are analyzed for 800 GeV proton incident on a variety of nuclear targets from FNAL E866. It is shown that our results with considering the energy loss effect are much different from those of the FNAL E866, who analyzes the experimental data with the nuclear parton distribution functions obtained by using the deep inelastic IA collisions and pA nuclear Drell-Yan data. Considering the existence of energy loss effect in Drell-Yan lepton pairs production, we suggest that the extraction of nuclear parton distribution functions shoul““““d not include Dre11-Yan experimental data.     

Comparison between the time-integrated spectrum and the peak time spectrum of gamma-ray bursts and possible implications

The mono-frequency peak luminosity and the corresponding photon energy of the time-integrated(Ls p,Es p)and peak time(Lt p,Et p)νfνspectra were derived for a sample of 38 redshift-known Fermi GRBs by fitting the spectra with the Band function.It was found that Et pis generally consistent with Es p,and Lt pis averagely three times larger than Ls p.The slope of the Lt p-Et prelation was consistent with that of the Ls p-Es prelation.The photon indices in the peak time spectrum,particularly,the index of the low energy end was,were statistically larger than that in the time-integrated spectrum.These results indicate that Ls pand Es pare dominated by Lt pand Et p,respectively.The difference of the spectral indices between the time-integrated and peak time spectra may be because of the overlap effect of a series of time-resolved spectra within a GRB.Our simulations,which were based on the observed spectral evolution and correlation between the energy flux and the peak energy within individual GRBs support our speculations.The Lt p-Et prelation may be less contaminated by the overlap effect,and it would may be an intrinsic feature of radiation physics.     

爆发性核合成与核结构

讨论了天体物理环境中爆发性核合成及其与核结构的紧密关系.用反射不对称壳模型计算了远离稳定线丰中子核148Ba的低能八极转动带,结果与实验很好符合.展示了其应用于不稳定核低能态计算的有效性 ,以及在核天体物理研究中的应用前景.The explosive nucleosynthesis in the astrophysical environment and its close link to nuclear structure are discussed. The low lying octupole bands for neutron rich nucleus 148 Ba far from the stability line have been calculated by the reflection asymmetric shell model and the results are in good agreement with the experimental data, presenting the capability of the model for calculations of the low lying states of unstable nuclei as well as the foreground of application in nuclear astrophysics.     

Specific heat and related thermophysical properties of liquid Fe-Cu-Mo alloy

The specific heat and related thermophysical properties of liquid Fe77.5Cu13Mo9.5 monotectic alloy were investigated by an electromagnetic levitation drop calorimeter over a wide temperature range from 1482 to 1818 K. A maximum undercooling of 221 K (0.13 Tm) was achieved and the specific heat was determined as 44.71 J·mol-1·K-1. The excess specific heat, enthalpy change, entropy change and Gibbs free energy difference of this alloy were calculated on the basis of experimental results. It was found that the calculated results by traditional estimating methods can only describe the solidification process under low undercooling conditions. Only the experimental results can reflect the reality under high undercooling conditions. Meanwhile, the thermal diffusivity, thermal conductivity, and sound speed were derived from the present experimental results. Furthermore, the solidified microstructural morphology was examined, which consists of (Fe) and (Cu) phases. The calculated interface energy was applied to exploring the correlation between competitive nucleation and solidification microstructure within monotectic alloy.     

太阳中微子问题研究进展

系统评述了国际上对太阳中微子研究的进展 ,说明了核物理实验对研究太阳中微子问题作出的贡献 ,对未来的中微子实验作了展望.The comparison between experimental results and theoretical predictions has yielded the solar neutrino problem. Over the years, the large communities of astrophysics and of nuclear physics took enormous efforts in solving this problem. The current progress on the study of solar neutrino problem is reviewed. Nuclear physics can make a significant contribution to this problem. The importance of the nuclear physics experiment is introduced. To minimize the uncertainties of neutrino detection has led to new...     

Acoustic response characteristics of unsaturated porous media

By employing the plane wave analysis method, the dispersion equations associated with compressional and shear waves using Santos’s three-phase poroelastic theory were driven. Considering the reservoir pressure, the high frequency corrections and the coupling drag of two fluids in pores, the influences of frequency and gas saturation on the phase velocities and the inverse quality factors of four body waves predicted by Santos’s theory were discussed in detail. The theoretical velocities of the fast compressional and shear waves were compared with the results of the low and high frequency experiments from open publications, respectively. The results showed that they are in good agreement in the low frequency case rather than in the high frequency case. In the latter case, several popular poroelastic models were considered and compared with the experimental data. In the models, the results of White’s theory fit the experimental data, but the parameter b in White’s model has a significant impact on the results. Under the framework of the linear viscoelasticity theory, the attenuation mechanism of Santos’s model was extended, and the comparisons between the experimental and theoretical results were also made with respect to attenuation. For the case of water saturation less than 90%, the extended model makes good predictions of the inverse quality factor of shear wave. There is a significant difference between the experimental and theoretical results for the compressional wave, but the difference can be explained by the experimental data available.     

Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra.     

Synthesis of ^197Os

An isotope at a particular region in the chart of nuclides can be produced with a certain type ot nuclear reactions and experimental approaches. The (n, 2p) reaction is one of useful techniques for producing heavy neutron-rich nuclei in region not accessible from fission. In the present experiment, ^197Os was produced by using ^198Pt(n, 2p)^197Os reaction.     

136Xe+198Pt多核子转移反应机制的理论研究

如何生成丰中子重核是目前原子核物理领域的热点问题之一,多核子转移反应是生成丰中子重核的一种可行途径.本工作采用时间相关的Hartree-Fock(TDHF)方法研究了136Xe+198Pt在Ec.m.=645 MeV的多核子转移反应.对动力学过程中的核子转移、能量耗散、形变核的朝向效应等进行了细致的分析,并结合统计衰变...     

星际26Al核合成的研究进展

介绍了星际 26Al衰变所发射1 809 keV γ射线的最新空间探测结果， 综述了目前关于星际 26Al起源的各种天体模型的研究进展。最后， 简要阐述了14N(p,γ)15O反应截面的最新测量结果及其对 26Al起源研究的影响， 探讨了一种星际 26Al合成的可能新途径。The recently detection outcome about interstellar 26Al is introduced, as well as the investigation progresses of interstellar 26Al nucleosynthesis in all models are reviewed. Finally, the new nuclear physics experimental results for the14N(p,γ)15O reaction effect on sources of interstellar 26Al and an alternative new way for nucleosynthesis 26Al in SNIa are discussed.     

核能和物理学

本文分别讨论了实现裂变和聚变核能的利用与物理学各学科（核物理、中子物理、等离子体物理、磁流体力学、材料物理、热物理、剂量防护、堆物理）研究工作的相互促进关系。     

Radioactive nuclear beams: Present and future

Some results of investigations into a new nuclear-physics field associated with the production of radioactive nuclear beams and physical studies with these beams are presented. The most recent results obtained by studying the structure of nuclei and reaction mechanisms with radioactive nuclear beams are surveyed. Data obtained in Dubna at the DRIBs accelerator complex are presented along with allied results from other research centers. In this connection, existing experimental data on light loosely bound exotic nuclei are discussed. The parameters of DRIBs3, which is a new accelerator complex, are presented, and the physics research program that will be implemented with the aid of new setups, including a high-resolution magnetic analyzer (MAVR) and a 4π neutron detector (TETRA), is described. A collaboration in the realms of employing radioactive nuclear beams at the DRIBs complex together with other accelerator complexes [SPIRAL2 (France), RIKEN (Japan), FAIR (Germany), and RIBF (CIIIA)] on the basis of employing new highly efficient experimental facilities has already led to the discovery of new phenomena in nuclear physics and will make it possible to study in the future new regions of nuclear matter in extreme states.     

基于箍缩装置的高能量密度物理实验研究进展

基于脉冲功率技术的箍缩装置能够在cm空间尺度和百ns时间尺度产生极端的高温、高压、高密度以及强辐射环境。中物院流体物理研究所在已建成的10 MA级的大型箍缩装置上开展多种负载构型的高能量密度物理实验研究。利用Z箍缩动态黑腔创造出了惯性约束聚变研究所需的高温辐射场;研究了金属箔套筒和固体套筒的内爆动力学特性;利用中低Z材料内爆获得了可观的K壳层线辐射并用于X射线热-力学效应实验研究;磁驱动准等熵加载和冲击加载为材料动态特性研究提供了新的实验能力;采用环形二极管和反射三极管技术的轫致辐射源获得了高剂量（率）的X射线和γ射线;利用磁驱动的径向金属箔模拟了天体物理中恒星射流的形成及其辐射的产生。此外,还介绍了利用反场构型磁化靶聚变装置开展的预加热磁化等离子体靶形成等实验结果。     

厚靶低中能9Be(d,xn)反应加速器中子源特性研究

利用PHITS程序评价计算了厚靶9Be(d, xn)反应加速器中子源的能谱和角分布数据，重点讨论了JQMD、INCL和INCL/DWBA三种核反应物理模型计算厚靶9Be(d, xn)反应中子辐射场分布的适用性。研究结果显示，基于INCL/DWBA耦合模型的PHITS程序计算所得到的厚靶9Be(d, xn)反应中子能谱和角分布数据能够较好地与实验数据符合，可以为厚靶9Be(d, xn)反应中子源特性研究及应用提供较为准确的中子辐射场数据。此外，设计了水冷大面积旋转铍靶的方案，并在5~25 MeV/5 mA入射氘能量下条件下，开展了靶面温度模拟研究，结果显示，靶面最高温度可控制在100 oC以下。     

基于Bagging 算法的神经网络在粒子鉴别中的应用

分析了神经网络方法和bagging 算法在实验高能物理和核物理数据分析中的应用现状。分别对神经网络方法和bagging 算法的基本原理进行了介绍。以蒙特卡罗产生器产生的夸克胶子喷注样本为例,详细讨论了神经网络方法以及bagging 算法与神经网络结合对粒子鉴别中信号和背景区分问题的应用过程,并对结果进行了讨论和分析。实验结果表明,应用bagging 算法后,神经网络能够较大幅度地提高实验高能物理和核物理数据分析中粒子鉴别的精度,以及能够得到较高的信噪比。The paper presents the application of neural network and bagging algorithm in experimental high-energy physics and nuclear physics data analysis. Paper also introduces the basic principles of neural network method and bagging algorithm. We use the data samples of quark-gluon jets, which are generated by Monte Carlo generator, to solve the problem of discriminating signal events and background events by the combined algorithm of bagging algorithm and neural network. Experimental results show that, to apply bagging algorithm, neural networks can greatly improve the accuracy of the identification of particles in the experiments of high energy physics and nuclear physical data analysis,and also obtains a larger SNR (Signal to Noise Ratio).     

核反应实验数据库(EXFOR)

核反应实验数据库(EXFOR)及其检索系统提供了丰富的中低能核反应物理信息和数据,已经成为国际上最全面的核反应实验数据汇编.目前,由国际原子能机构核数据科(IAEA/NDS)协调管理,国际核反应数据中心协作网(NRDC)13个成员进行全球性合作,旨在协调国际范围内核反应实验数据的收集、编纂和传播.中国核数据中心(CND...     

On nuclear states of [`(K)] \bar K mesons

The search for nuclear states of $ \bar K $ \bar K mesons poses interesting problems for the nuclear and low energy hadron physics: the behavior of tightly bound nuclear systems with strongly correlated impurities, the new kind of binding mechanisms and the extension of effective low energy theories to the strange sector. These problems are briefly presented and a method of variational calculation of the binding energies is discussed.