中、重质量区新核素的合成

论述了远离稳定线核素合成的科学意义,总结了有关新核素合成研究的国内外概况以及中、重质量区远离稳定线核素的主要产生机制．给出了我国合成的一些新核素的半衰期,并与理论预言值进行了比较．简略地叙述了核反应产物的传输、分离以及新核素的鉴别方法.The importance of synthesis of new nuclei far from stability is concisely recounted. The prograsses on synthesis of the new nuclides and the main methods used for producing new nuclei far from stability in the intermediate and heavy mass region is summarized. The half lives of some new nuclides synthesized in china are compared with those calculated based on the gross theory and the microscopic theory. Some examples for transport and chemical separation of the nuclear reaction products...     

An Experimental Study of In-Situ Phase Fraction in Jet Pump Using Electrical Resistance Tomography Technique

We perform the experiments to investigate in-situ phase fraction in a jet pump using the electrical resistance tomography （ERT） technique. A new jet pump with ERT sensors is designed to measure in-situ phase fraction and flow regime. The study is based on laboratory experiments that are carried out on a 50-mm vertical flow rig for various gas and liquid phase superficial velocities. The different flow patterns of gas liquid in the jet pump and vertical pipe are studied using the ERT technique. The results suggest that the ERT system can be used to successfully produce images of gas-liquid flow patterns with frames rates of 58 fps and the in-situ phase fraction with frame rates of 5 fps can be obtained. The visualizations of a rapid mixing process in the throat of a jet pump obtained in this work provide a reliable basis for theoretical study and optimal design of jet pumps.     

Performance test of the low-pressure thin window multi-wire chamber

A flow gas low-pressure multi-wire proportional chamber(LPMWPC)with an active area of 180 mm×80 mm has been developed for the flying time test of the recoil nuclei on super heavy nuclear experiments.The LPMWPC detector can be operated in single as well as double step operational modes.In the case of double step operational mode with a high gas amplification factor,signals fromα-particles reside well above the electronic noise.The gas leakage rate and time resolution obtained from theα239Pu source are shown and discussed at the condition of 3 mbar Isobutane gas.It was shown that the time resolution was better than 2.9 ns at the best work condition,and the detecting efciency was larger than 98%at the low energyαparticles.So the LPMWPC is fit to measure the flying time in the super heavy nuclear fragments experiment.     

Outline of the progress in the study of radioactive nuclear physics and super-heavy nuclei

We briefly introduce the current status and progress in the field of radioactive ion beam physics and the study of super-heavy nuclei. Some important problems and research directions are outlined, such as the sub-barrier fusion reaction, the direct reaction at Fermi energy and high energies, the property of nuclei at drip-lines, new magic numbers and new collective motion modes for unstable nuclei     

β~--Decay Half-Lives for Waiting Point Nuclei Around N=126

We have systematically analyzed the experimental β--decay half-lives of waiting point heavy nuclei around neutron number N = 126. A new set of parameters for the exponential formula of β~--decay half-lives is proposed. The forbidden transition effects are included in the new set of parameters self-consistently. Theoretical β~--decay half-lives of nuclei around N = 126 are compared with recent theoretical results and experimental data. It is found that the new theoretical results are in better agreement with experimental data. The unknown β~--decay half-lives of some nuclei in this region are predicted for studies on nuclear structure far from stability and the nucleosynthesis in stars.     

Pro duction of Exotic Nuclei in Low-Energy Multi-Nucleon Transfer Reactions

Multinucleon transfer processes in low-energy heavy ion collisions open a new field of research in nuclear physics, namely, production and studying properties of heavy neutron rich nuclei. This not-yet-explored area of the nuclear map is extremely important for understanding the astrophysical nucleosynthesis and the origin of heavy elements. Beams of very heavy U-like ions are needed to produce new long-living isotopes of transfermium and superheavy elements located very close to the island of stability.The calculated cross sections are high enough to perform the experiments at available accelerators.Beams of medium-mass ions (such as 136Xe, 192Os, 198Pt) can be used for the production of neutron rich nuclei located along the neutron closed shell N = 126 (the last waiting point) having the largest impact on the astrophysical r-process. The Low-energy multinucleon transfer reactions is a very efficient tool also for the production and spectroscopic study of light exotic nuclei. The corresponding cross sections are 2 or 3 orders of magnitude larger as compared with high energy fragmentation reactions.     

Precise measurement of magnetic moment of short-lived β-emitting nuclei ~(12)B (I~π=1~+,T_(1/2)=20.18 ms)

1 Introduction The production of nuclear spin polarization and the maintenance of the nuclear po-larization in a stopper are the essential requirement for the measurement of nuclear magnetic and electric quadrupole moments of the b-emitting nuclei by the ?NMR and b-NQR (b-ray detected Nuclear Magnetic Resonance and b-ray detected Nuclear Quad-rupole Resonance) technique. This requirement can be realized by the selection tech-nique of the incident particle energy of the nuclear reaction th…     

The generation of a hyperchaotic system based on a three-dimensional autonomous chaotic system

This paper reports a new four-dimensional hyperchaotic system obtained by adding a controller to a three-dimensional autonomous chaotic system. The new system has two parameters, and each equation of the system has one quadratic cross-product term. Some basic properties of the new system are analysed. The different dynamic behaviours of the new system are studied when the system parameter $a$ or $b$ is varied. The system is hyperchaotic in several different regions of the parameter $b$. Especially, the two positive Lyapunov exponents are both larger, and the hyperchaotic region is also larger when this system is hyperchaotic in the case of varying $a$. The hyperchaotic system is analysed by Lyapunov-exponents spectrum, bifurcation diagrams and Poincar\'{e} sections.     

山东大学(威海)开展的核物理研究

综述了山东大学威海校区原子核物理研究团队在原子核精细谱学、核天体物理、探测器研制和高能核物理等方向开展的研究工作及最新进展;尤其重点介绍了$A\sim 110$核区原子核的形状共存和带交叉延迟,“订书机”和“雨伞”模式转动带,碳氮氧循环过程中关键核反应的测量进展,中子星参数化的状态方程及双中子星并合引力波研究,带电粒子探测器的设计与制作,相对论重离子碰撞物理中量子输运理论和高阶反常输运等研究工作,并展望了下一步的工作重点。     

Experiments with intense secondary beams of radioactive ions

Electromagnetic mass separation applied on-line to accelerators and nuclear reactors is now a standard technique for producing preselected isotopic beams (A, Z selection) of nuclear reaction products. The development, performance and anatomy of a large on-line isotope separator facility, the CERN-ISOLDE, is discussed. As a result of recent technical developments it is now possible to study individual nuclei of about 40 elements, in many cases out to where the limits of nucleon binding are approached and half-lives become as short as 10 ms. It is shown that the nuclear reaction processes induced with the high-intensity several hundred MeV proton beam can provide secondary radioactive beams in almost all regions of the nuclidic chart with intensities which are not matched by any other method. The intense beams of 10⁸–10¹¹ atoms/s have opened up a number of new experimental possibilities like laser spectroscopy on radioactive atoms, radioactive targets for nuclear reaction spectroscopy, and precision X-ray shift measurements.     

Determining the potential based on Rutherford backscattering data and electron screening in nuclear fusion reactions

A technique for determining the interaction potentials of He⁺–W, Ta systems on the basis of experimental data on the Rutherford backscattering of accelerated particles at an angle of 165° is proposed. This method provides an opportunity to extend the range of short distances within which the experimentally determined potential is known to 0.005 au and calculate corrections for electron screening relevant to the measurement of cross sections of the d + d nuclear fusion reaction. These corrections agree closely with the experimental data.     

加速器质谱在核科学研究中的应用进展

加速器质谱(AMS) 由于其极高的测量灵敏度而广泛应用于核科学、生命科学、地球科学、环境科学和考古学等研究领域,同时,AMS还可以用来分析样品中的微量核素,是核科学领域的重要研究工具。目前,AMS研究的最新领域是U和Pu 等锕系元素的测量,在核保障、核监测及核试验沉降物示踪大气输运和表面沉积物的迁移等研究中也显示出了较大潜力。综述了AMS在核科学研究中的应用及研究现状,主要包括AMS在放射性核素半衰期的测定、核反应截面的测量等方面的研究进展。Accelerator mass spectrometry (AMS) is a promising method to provide extreme sensitivity measurements of the production yields of long-lived radioisotopes, which cannot be detected by other methods. AMS technique plays an important role in the research of nuclear physics, as well as the application field of AMS covered nuclear science and technology, life science, earth science, environmental science, archaeology etc. The newest AMS field is that of actinide, particularly U and Pu, isotopic assay with expanding applications in nuclear safeguards and monitoring, and as a modern bomb-fallout tracer for atmospheric transport and surface sediment movement. This paper reviews the applications of AMS in the research of nuclear energy and nuclear security including the research of half life of radionuclides, cross section of nuclear reaction.     

用C语言编写的γ-电子级联过程的蒙特卡罗模拟程序GET

用C语言编写成γ-电子级联过程的蒙特卡罗模拟程序,可在IBM系列微机上运行。程序可实时显示粒子输运与反应的模拟物理过程,并可有选择地累积各种谱。结果以事件方式与谱方式记录,可进行数据再处理。目前适用γ能区为0.1~500MeV,可扩展至其他能区。程序可用于γ探测器研制、核辐射防护和核医学等领域。     

Covariant Non-Equilibrium Transport Theory Solutions for RHIC

New numerical solutions of 3+1D covariant kinetic theory are reported for nuclear collisions in the energy domain E_cm200 AGeV. They were obtained using the MPC 0.1.2 parton transport code employing high parton subdivision to retain Lorentz covariance. The solutions are compared to those of relativistic hydrodynamics employing Cooper–Frye isotherm freeze-out. The transport solutions follow a different dynamical path than hydrodynamics due to large dissipative effects when pQCD scattering rates and HIJING initial conditions are assumed. The transport freeze-out four-volume is sensitive to the reaction rates. The final transverse momentum distributions are found to deviate by up to an order of magnitude from those of Cooper–Frye frozen hydrodynamics.     

固体氧化物燃料电池模式阳极内传输与电化学反应耦合机理

模式电极因其结构可控、电化学/化学反应活性位和物质传输路径明确等优势,被广泛应用于固体氧化物燃料电池新型电极研究.现有研究多采用模式电极研究新材料电化学特性、表界面催化反应机理等,尚未涉及几何结构对其内部传输与电化学反应耦合机理的影响,限制了模式电极的应用.本文建立了固体氧化物燃料电池阳极内电荷传输与电化学反应过程的格子玻尔兹曼模拟方法,明确了控制电极过程的关键无量纲参数及其对电极性能的影响规律,研究了模式阳极几何结构的影响机理.根据电极性能对无量纲参数的敏感程度,绘制了指导模式阳极设计与运行的相图,指出相图过渡区(电极性能随操作参数显著变化区域)为进行反应机理研究的最佳操作参数取值范围.同时,研究发现模式阳极电子导体内电子的快速迁移虽不限制阳极性能,其几何结构显著影响过渡区范围;离子导体内离子迁移为影响阳极性能的限速步骤,但其几何结构几乎不影响过渡区范围.本文的数值方法与机理研究结果可为固体氧化物燃料电池模式电极的设计提供重要理论依据.     

Dense plasma effects on nuclear reaction rates

Plasma density effects can cause an exponential change in charged particle nuclear reaction rates important in stellar evolution. Reaction rates in dense plasma, with emphasis on quantum aspects, are examined here using path integral Monte Carlo calculations. Quantum mechanics causes a reduction in the many body enhancement of the reaction rate compared to the value for a classical system. This can be attributed to the "quantum smearing" of the short range Coulomb interaction resulting in reduced repulsion between the reacting pair and surrounding particles. Electron screening and ion exchange effects are also examined, with screening reducing and exchange slightly increasing the many body enhancement.     

核多体系统输运现象的微观理论

首先回顾了描写核多体系统输运现象的一些主要模型和方法,然后介绍了输运现象微观动力学基础研究上一些新的结果,强调了单粒子运动动力学特征在建立集体输运方程和理解超重核合成机制上的重要作用。能量耗散和熵产生的数值计算结果表明,集体运动耗散过程可分为退相干、弛豫和定态等3 个阶段,弛豫过程通常表现为非常复杂的反常扩散过程。在这些理论工作的基础上,提出了一种自洽地分离核多体系统集体和单粒子变量的可能途径。In this article, I provide a simple review on conventional methods and models on the transport phenomenon of nuclear many-body systems. By exploiting the basic idea of time-dependent projection operator, I recommend a novel method to derive the transport equation for collective motion which is embedded on the microscopic dynamics of timedependent single-particle motion. It is emphasized that the microscopic dynamics of single-particle motion should play an important role for understanding the dynamics of nuclear reaction and the synthesis mechanisms of new superheavy elements. The numerical results of energy dissipation and entropy production indicate that the collective motion passes through three stages, such as dephasing/decoherence, statistical relaxation and stationary state. The statistical relaxation is a complex anomalous diffusion process in general. With the aid of above analysis and results, a possible way to define the collective and single-particle variables for the realistic nuclear many-body systems is proposed.     

离子输运蒙特卡罗模拟的步长选取

介绍带电离子在物质中输运模拟的详细历史法,开发模拟程序ITR(ions transport and reaction),同时实现抽取离子飞行步长的基本方法和脉冲近似法,计算结果与CORTEO及TRIM程序的结果比较符合很好.讨论两种步长选取方法,对脉冲近似法的最大步长进行限制,分析CORTEO程序与TRIM程序计算结果差别的主要原因.ITR同时具有TRIM和CORTEO的优点,采用脉冲近似法减少需要计算的核碰撞次数,通过索引(Index)方法对散射角的计算进行加速,计算效率大幅提高.