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2014年  第31卷  第3期

专栏-中能重离子碰撞及其交叉学科科研会(精选)
超重核性质与合成机制的理论研究
李璐璐, 吕炳楠, 王楠, 温凯, 夏铖君, 张振华, 赵杰, 赵恩广, 周善贵
2014, 31(3): 253-272. doi: 10.11804/NuclPhysRev.31.03.253
摘要:
探索原子核的电荷与质量极限,合成长寿命超重核是当前原子核物理研究的重要前沿问题之一。本文综述了我们近几年在超重原子核结构性质与合成机制方面取得的理论研究进展。在结构性质方面,利用处理对关联的粒子数守恒方法,基于推转壳模型,系统研究了锕系核与超镄核低激发谱,发展了多维形状约束的协变密度泛函理论并用于研究锕系核势能面和裂变位垒以及N = 150 同中子素中的非轴对称八极关联等。在超重核合成机制方面,系统研究了利用重离子熔合反应合成超重核的三步过程,包括俘获过程----提出了一个位垒穿透概率新公式、熔合过程----提出了一个基于动力学形变势能面的双核模型、存活过程----系统研究了激发态超重复合核存活概率等。系统研究了合成超重核的热熔合反应,得到的熔合蒸发截面与实验符合,并预言了合成119 和120 号超重元素的生成截面。
The exploration of charge and mass limits of atomic nuclei and the synthesis of long-lived or stable superheavy nuclei (SHN) are on the frontier of modern nuclear physics. Recent theoretical progresses made by us on the study of structure and synthesis mechanism of SHN are reviewed. The study of structure properties includes a systematic study of low-lying spectra of actinide and transfermium nuclei by using a cranked shell model with the pairing treated by a particle number conserving method (PNC-CSM), the study of potential energy surfaces and fission barriers of actinide nuclei and non-axial octupole correlations in N = 150 isotones by using newly-developed multi-dimensional constraint covariant density functional theories (MDCCDFT).The study of the synthesis mechanism of SHN is carried out by examining in details of the three steps in producing SHN via heavy-ion fusion reactions: i) For the capture process, a new barrier penetration formula is proposed for potential barriers containing a long-range Coulomb interaction; ii) For the fusion process, a dinuclear system model with a dynamical potential energy surface (the DNS-DynPES model) is developed; and iii) For the survival process, a systematic study of the survival probability against fission in the 1n-channel of SHN with 100 6 Z 6 134 is made and it is found that the survival probability in the 1n-channel is mainly determined by the nuclear shell effects. By using the DNS-DynPES model, hot fusion reactions for synthesizing SHN with charge numbers Z =112s120 are studied. The calculated evaporation residue cross sections are in good agreement with available data and predictions are made for synthesizing SHN with Z=119 and 120.
对称能研究进展(英文)
陈列文
2014, 31(3): 273-284. doi: 10.11804/NuclPhysRev.31.03.273
摘要:
总结了目前基于分析地面实验室以及天文观测数据所得到的关于核物质对称能密度相关性的约束。结果表明,在核物质饱和密度ρ0处,关于对称能的大小Esym(ρ0) 及其密度梯度参数L 的不同具体约束强烈地依赖于不同的实验数据或理论方法。另一方面,所有存在的约束都和Esym(ρ0) = (32.5±2.5) MeV 以及L=(55±25) MeV一致。如何确定核物质对称能的高密行为仍然是一个挑战。We summarize the current available constraints on the density dependence of the symmetry energy obtained from terrestrial laboratory measurements and astrophysical observations. While the magnitude Esym(ρ0) and density slope L of the symmetry energy at saturation density ρ0 can vary largely depending on the data or analysis methods, all the available constraints are in agreement with Esym(ρ0) =(32.5±2.5) MeV and L=(55±25) MeV. The determination of the high density behaviors of the symmetry energy remains a big challenge.
对称能密度依赖的输运理论模型研究中的一些问题的讨论
李祝霞
2014, 31(3): 285-290. doi: 10.11804/NuclPhysRev.31.03.285
摘要:
本文非常简要地介绍了目前通过重离子碰撞中的对称能敏感观测量获取对称能密度依赖的研究现状,讨论了在输运理论模型计算中可能引起计算结果的不确定性的几个问题。特别与目前广泛采用的输运理论模型计算相关的3 个方面的问题,即对称势动量依赖项和中子、质子有效质量劈裂;不同电荷态Δ产生的阈能和相关截面的介质修正;输运理论模型中的多体关联和涨落等的处理等问题。
This article briefly discusses the deviations appeared in the constraints on the density dependence of the symmetry energy obtained from the sensitive observables in the heavy ion collisions. The problems which possibly influence the constraints obtained from the comparison between the transport model calculations and experimental measurement of isospin sensitive observables are discussed. The three problems: (1) The momentum dependent part of symmetry potential and the neutron, proton effective mass splitting, (2) The isospin dependence of the medium correction of the thresholds and cross sections for different charged Δ production, (3) Many-body correlation and fluctuation treatment in transport model and other things in the transport model codes are discussed in more detail for the reference of the colleagues with common interest in nuclear community.
低SIS 能区重离子碰撞过程的系统性研究
李庆峰, 王永佳, 郭琛琛, 李祝霞
2014, 31(3): 291-305. doi: 10.11804/NuclPhysRev.31.03.291
摘要:
在极端相对论量子分子动力学(UrQMD) 模型中加入势能密度泛函形式的势修正、核子-核子弹性散射截面的更细致的介质修正以及碎片重构模式中的同位旋效应后,重点研究低SIS 能区(约40~400 MeV/u) 重离子碰撞的动力学过程。在较系统地研究此能区重离子碰撞后的轻碎片产生及集体流后,重点研究对高密区对称能密度依赖敏感的观测量。发现:(1) 质量对称的Sn 系列同位素反应系统,其中子平衡能的系统N=Z 分布能敏感探测对称能密度依赖;(2) 横速度/动量分布的中子和质子及氢同位素的椭圆流比vn2 =vp;H2 敏感依赖于对称能。经采用多组核物质标量不可压缩系数K0 值差别很小、对称能斜率参数L 值相差较大的Skyrme 势参数计算并对FOPI/LAND 相应数据做χ2 分析后抽取的L值为(89±45)MeV。After inserting the Skyrme potential energy density functional for potential update, more detailed medium modifications for nucleon-nucleon elastic cross sections, and the isospin effect for cluster recognition into the Ultra-relativistic Quantum Molecular Dynamics (UrQMD), the dynamic process of heavy ion collisions (HICs) at low SIS energies (about 40s400 MeV/u) is primarily studied. And, after systematically studying the emission and collective flows of light clusters from HICs in such beam energy region, the sensitive observables especially to the density dependent symmetry energy at supra-normal densities are focused. It is found that: (1)the initial neutron/proton ratio dependence of the balance energy of neutrons from mass-symmetric Sn isotopes can be taken as a useful probe to constrain the stiffness of the nuclear symmetry energy; (2) the transverse velocity/momentum dependence of the elliptic flow ratio of neutrons and protons or hydrogen isotopes (vn 2 =vp;H2 )is also sensitive to symmetry energy. The 2 analysis from the difference bet e the theoretical (taking Skyrme potential parametrizations with incompressibility K0 being almost same but the slope parameter L of symmetry energy being largely different) and experimental (taking FOPI/LAND data) vn 2 =vH2 values determines the value of L to be (89±45) MeV within in a χ2 uncertainty.
中能重离子碰撞中的自旋效应(英文)
徐骏, 李宝安, 夏银, 沈文庆
2014, 31(3): 306-314. doi: 10.11804/NuclPhysRev.31.03.306
摘要:
详细介绍并深化了在IBUU输运模型中引入核子的自旋轨道相互作用及其自旋自由度来研究重离子反应的工作。虽然自旋相关的平均场势中时间反演对称项与时间反演不对称项的贡献相反,但依然观察到体系存在局域自旋极化。发现最终的结果由时间反演不对称项决定,可以利用重离子碰撞中自旋向上核子与自旋向下核子的横向差分流来研究介质中自旋轨道相互作用的性质,包括其强度、密度依赖性和同位旋依赖,而且即使在小体系下该差分流依然不失为自旋轨道相互作用的良好探针。In this paper, we report and extend our recent work where the nucleon spin-orbit interaction and its spin degree of freedom were introduced explicitly for the first time in the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model for heavy-ion reactions. Despite of the significant cancellation of the time-even and time-odd spin-related mean-field potentials from the spin-orbit interaction,an appreciable local spin polarization is observed in heavy-ion collisions at intermediate energies because
of the dominating role of the time-odd terms. It is also found that the spin up-down differential transverse flow in heavy-ion collisions is a useful probe of the strength, density dependence, and isospin dependence of the in-medium spin-orbit interaction, and its magnitude is still considerable even at smaller systems.
中能重离子碰撞中参与者区域的粘滞系数与熵密度之比(英文)
马余刚, 周铖龙, 方德清
2014, 31(3): 315-325. doi: 10.11804/NuclPhysRev.31.03.315
摘要:
在同位旋依赖的量子分子动力学(IQMD) 和Boltzmann-Uehling-Uhlenbeck(BUU) 的框架下研究了重离子碰撞过程中核物质的剪切粘滞系数与熵密度的比值。用不同的方法提取了剪切粘滞系数(η)、熵密度(s) 和其他相关的物理量。随着碰撞能量的增加,粘滞系数和熵密度的比值在BUU 模型中逐渐趋于一个饱和值而在IQMD模型中出现了一个极小值,认为这个局域的最小值或饱和值对应于中能重离子碰撞中发生的核物质液气相变现象。The ratio of shear viscosity (η) to entropy density (s) of nuclear fireball created in the central region of intermediate-energy heavy-ion collisions has been investigated within two transport models, namely the Boltzmann-Uehling-Uhlenbeck (BUU) model and the isospin-dependent quantum molecular dynamics (IQMD) model. Different methods are used to calculate η and s. With the collisionenergy increasing, the η/s displays a saturation value or a local minimum value at a certain beam energy.We argue that the saturation or minimum point corresponds to an occurrence of nuclear liquid gas phase
transition.
中能重离子碰撞中K介子产生动力学研究(英文)
冯兆庆
2014, 31(3): 326-332. doi: 10.11804/NuclPhysRev.31.03.326
摘要:
基于兰州量子分子动力学(LQMD) 模型研究了阈能附近K介子(K0 和K+) 产生动力学机制。LQMD模型能够较好地描述中能重离子碰撞中K介子产额分布。通过拟合K介子动能谱分布,计算中采用了排斥的K-核子相互作用势。该光学势增强了高动量K介子产生,而降低了K介子总产额。结合实验数据比较,在高密区域给出了较软的对称核物质状态方程。对称能的软硬对K0/K+ 比值起着重要作用,特别是在阈下区域。而K介子光学势对K0/K+ 比值激发函数影响不明显。Dynamics of kaons (K0 and K+) produced in nuclear reactions near threshold energies has been investigated within the Lanzhou quantum molecular dynamics (LQMD) transport model.The production yields are consistent with the available experimental data. A repulsive kaon-nucleon potential is implemented in the model through fitting the kinetic energy spectra of inclusive cross sections in heavy-ion collisions, which enhances the energetic kaon emission squeezed out in the reaction zone and reduces the total kaon yields. The comparison to the available data supports a soft equation of state in the density region of 2 ~3ρ0 for isospin symmetric nuclear matter. It is found that the stiffness of nuclear symmetry energy plays a significant role on the isospin ratio with decreasing the incident energy, in particularly in the domain of subthreshold energies.
非核子自由度物质的对称能(英文)
蒋维洲, 杨荣瑶, 张东睿
2014, 31(3): 333-338. doi: 10.11804/NuclPhysRev.31.03.333
摘要:
通常人们在有限核与核子物质中研究对称能,而本工作利用相对论平均场模型研究包含超子和夸克自由度物质的对称能。发现了含超子和夸克自由度物质中对称能的表观软化,并用相对论模型对此做了阐述。该软化现象提示由重离子碰撞产生的含非核子自由度致密物质的对称能提取将有待细致的甄别。While the nuclear symmetry energy is usually studied in nite nuclei and nucleonic matter,we study the symmetry energy in relativistic mean- eld models with the inclusion of the hyperon and quark degrees of freedom at high densities. Apparent softening of the symmetry energy with the inclusion of hyperon and quark degrees of freedom is found and demonstrated in the relativistic mean-eld model. This softening would have associations with the symmetry energy extraction which needs detailed discriminations in dense matter with the admixture of new degrees of freedom created by heavy-ion collisions.
原子核质量中的奇偶性
赵玉民
2014, 31(3): 339-343. doi: 10.11804/NuclPhysRev.31.03.339
摘要:
原子核质量的描述和预言是原子核结构理论中的基础问题之一。相邻原子核质量存在奇偶性,这些奇偶性对于构造局域质量关系和研究核子对力相互作用有参考意义。本文回顾了我们在近年来注意到的相邻原子核质量之间的奇偶性方面研究的主要结果,包括最后一个质子与中子相互作用[标记为δV1p-1n] 的奇偶性及其起源δV1p-1n 奇偶性导致的Garvey-Kelson 质量关系的奇偶性、单核子分离能与原子核的质子和中子数奇偶相关性等。The description of nuclear masses is one fundamental issue in nuclear structure theory. A number of odd-even staggerings of masses have been observed in double differences of neighboring nuclei. These oddeven staggerings are very useful to study local mass relations and nucleon-pair correlations. In this paper we discuss the odd-even features that we discerned in recent years, such as the odd-even staggering of the interaction between the last proton and the last neutron (denoted by δV1p-1n), the odd-even feature of the Garvey-Kelson mass relations, the odd-even feature of one-nucleon separation energies, and so on, exhibited in masses of neighboring nuclei and related quantities.
用He 离子诱导的裂变激发函数探测核摩擦强度(英文)
叶巍
2014, 31(3): 344-349. doi: 10.11804/NuclPhysRev.31.03.344
摘要:
随机模型被用于分析3He+197Au,3He+208Pb 和3He186W反应测量的裂变激发函数。提取的鞍点前摩擦强度约为4x1021 s-1。揭示了能级密度参数的大小在约束核摩擦强度中的作用。计算表明,高激发条件能能显著增强裂变截面对核耗散的敏感性。The stochastic approach to ssion is employed to analyze measured ssion excitation functions in the reactions 3He+197Au, 3He+208Pb and 3He+186W. A pre-saddle friction strength of about 4 x 1021 s-1is extracted by comparing theoretical calculations with experimental data. The important role of level-density parameters in accurately determining the strength of nuclear friction is revealed.It is further shown that high-energy conditions can enhance the sensitivity of ssion cross sections to nuclear dissipation.
重离子碰撞中熔合位垒的研究
祝龙, 苏军, 谢文杰, 郭琛琛, 张冬红, 张丰收
2014, 31(3): 350-358. doi: 10.11804/NuclPhysRev.31.03.350
摘要:
熔合位垒的研究对熔合反应以及超重核合成有重要的意义。在改进的同位旋相关的量子分子动力学(ImIQMD) 模型框架下,提取了熔合反应体系40Ca+40Ca,48Ca+208Pb,48Ca+204Pb 和16O +154Sm的熔合位垒。研究了壳修正能对熔合位垒的影响、动力学位垒的能量依赖性、同位旋效应以及形变核的方向效应。计算发现壳修正能降低了熔合反应的位垒。在研究动力学位垒的能量依赖性时,发现位垒高度和位垒半径表现出相反的能量依赖行为。在动力学反应中,当两个核距离接近时,缺中子体系的库仑势同样表现出一定的能量依赖性。对于丰中子体系,由于中子屏蔽作用,库仑势基本没有能量依赖性。Study of fusion barrier is very important for people to better understand fusion reactions. In this paper the Improved Isospin-dependent Quantum Molecular Dynamics(ImIQMD) model is introduced firstly.Then the shell correction effects, energy dependence, isospin effects and orientation effects of fusion barrier are studied. The fusion barriers for the fusion reactions 40Ca+40Ca, 48Ca+208Pb, 48Ca+204Pb and 16O+154Sm are extracted. The negative shell correction energies lower potential barriers of a certain reaction. A complex phenomenon of energy dependence is observed. It is also found that incident energy dependence of the barrier radius and barrier height shows opposite behaviors. The Coulomb potential shows weak energy dependence when distance of two colliding nuclei is lower than the touching distance. The isospin effects of the potential barrier are investigated. The orientation effects of the potential barrier are also discussed for the system 16O+154Sm.
软物态方程支持大质量中子星机制概述
文德华, 荆珍珍
2014, 31(3): 359-365. doi: 10.11804/NuclPhysRev.31.03.359
摘要:
重离子碰撞实验分析及相关理论研究认为高密度非对称核物质可能具有较软的物态方程;在约2~3 倍饱和核密度下超子等奇异物质的出现也可能会使物态方程变软。然而,软物态方程却无法支持大质量中子星。脉冲星PSR J1614-2230 具有大质量(1.97±0.04)M 的观测发现使这一矛盾变得尤为突出。为了解决该矛盾,人们提出了各种可能的物理机制:包括考虑修正的引力理论、修改描述高密度物质物态的理论模型等。在概述和讨论这些能使软物态方程支持大质量中子星的可能物理机制的基础上,还计算和讨论了强电场、强磁场对中子星最大质量的影响,发现强电磁场可以有效地增大中子星的最大质量。The analysis of the laboratory data from the heavy-ion collisions and the correlated theoretical research prefer a soft equation of state (EOS) for the unsymmetric dense matters; and the presence of hyperons at density exceeding 2~3 times of normal nuclear density 0 also may soften the EOS of the dense matters.But a soft EOS cannot support a massive neutron star. After the observation of pulsar PSR J1614-2230 with a mass of (1.97±0.04) M, we have to face this intractable contradiction. In order to solve this contradiction,people have proposed several possible mechanisms, including the modified gravity theory, the modified models for the description of the dense matters and so on. This paper has reviewed these mechanisms. In addition, we also calculated and discussed the effect of the strong electromagnetic field on the maximum mass of the neutron stars. It is found that the strong electromagnetic field can increase the maximum mass of the neutron stars efficaciously.
HTR-PM中燃耗测量方法研究和测量系统原型研制
闫威华, 张立国, 张钊, 肖志刚
2014, 31(3): 366-373. doi: 10.11804/NuclPhysRev.31.03.366
摘要:
作为球床模块式反应堆中燃料元件循环的重要组成部分,燃耗测量系统必须对连续排出堆芯的燃料球进行非破坏性在线测量,以确定是作为乏燃料球退出循环,还是将其返回堆芯。137Cs 的活度和燃耗值存在很好的单调对应关系,因此在高温气冷堆(HTR-PM) 核电站示范工程中将利用高纯锗探测器测量燃料球中137Cs 的活度,进而根据燃耗计算曲线确定其燃耗值。通过实验以及基于Geant4 的蒙特卡罗全模拟,利用效率传递方法准确得到了系统刻度的修正因子。同时发展了快速自动的谱寻峰和峰面积分析程序用于双源实验和MCNP模拟的 谱分析,结果表明,尽管有干扰峰的影响,该系统预计对137Cs 的活度测量相对不确定度依然可以控制在3.0% 以内。在以上工作基础上成功研制并测试了一套全尺寸的燃耗测量系统原型。In a pebble-bed core which employs the multi-pass scheme, it is mandatory to determine the burnup of each pebble after the pebble has been extracted from the core in order to determine whether its design burnup has been reached or whether it has to be reinserted into the core again. The burnup of the fuel pebbles can be determined by measuring the activity of 137Cs with an HPGe detector because of their good correspondence, which is independent of the irradiation history in the core. Based on experiments and Geant4 simulation, the correction factor between the fuel and calibration source was derived by using the efficiency transfer method. By optimizing spectrum analysis algorithm and parameters, the relative standard deviation of the 137Cs activity can be still controlled below 3.0% despite of the presence of interfering peaks. On the foundation of the simulation and experiment research, a complete solution for burnup measurement system in HTR-PM is provided.
加速器
162.5 MHz高频数字低电平控制监控系统设计与实现
张瑞锋, 王贤武, 许哲, 仪孝平
2014, 31(3): 374-378. doi: 10.11804/NuclPhysRev.31.03.374
摘要:
中国科学院近代物理研究所自主研发的ADS 162.5 MHz 高频低电平控制采用数字化技术实现,控制环路的参数设置、开闭环操作以及状态监测都通过监控系统实现。该系统基于以太网通讯,采用轻量化客户端-服务器端的工作方式,运行在上位机的客户端程序发送指令数据包,运行在高频数字低电平系统的服务器端响应指令,完成参数监测与控制。系统首先以Atera 公司Stratix III 系列现场可编程门阵列(FPGA) 开发板为基础,构建以Nios II 处理器和三速以太网接口为核心的服务器端硬件系统;其次基于Micro C/OS II 实时操作系统和轻量级TCP/IP 协议栈,设计服务器端软件系统;最后利用MFC 设计运行于上位机的客户端界面程序。经过长时间测试运行,该监控系统运行稳定可靠,TCP发送和接收吞吐率达到11.931 038 Mbps 和8.117 624 Mbps。162.5 MHz high-frequency low-level control system self-developed by Institute of Modern Physics for ADS project took digital technology. All parameters' reading & writing,including loop parameter setting,open& close-loop operation, and condition monitoring, were achieved through the monitoring system. The system used lightweight client-server working mode that client running in the PC sent command data, server running on high-frequency digital low level system responded instructions to complete parameter monitoring and control. The system consisted of three parts. Firstly, server hardware system was constructed based on Atera Stratix III family of eld-programmable gate array (FPGA) development board. Secondly,the server software system was designed based on Micro C/OS II real-time operating systems and lightweight TCP / IP protocol stack, and nally a client PC program was designed based on MFC. After a long test, it was indicated that the monitoring system works properly and stably. TCP sends and receives throughput reached 11.931 038 Mbps and 8.117 624 Mbps.
兰州重离子加速器储存环引出切割磁铁电源数字化升级
赵江, 原振栋, 陈又新, 黄玉珍, 张华剑, 吴凤军, 高大庆
2014, 31(3): 379-384. doi: 10.11804/NuclPhysRev.31.03.379
摘要:
介绍了兰州重离子加速器储存环(HIRFL-CSR) 引出切割磁铁电源的工作原理及进行数字化升级方案。采用了基于FPGA(Field Programmable Gate Array) 的可编程片上系统(SOPC)、NIOSII 的软件架构及硬件描述语言编写的多环调节算法,探讨了在FPGA 上实现加速器电源控制算法的一些关键问题。对引出切割磁铁电源进行数字化升级后,HIRFL-CSR的主环束流引出过程更加可靠,同时提高了实验终端束斑位置的稳定性。本工作为HIRFL-CSR 磁铁电源的全面数字化及重离子治癌数字电源的研发提供了重要的技术参考。This paper introduces the working principle of the power supplies for the septum magnets in HIRFL-CSR and presents a feasible scheme of digitalizing these power supplies. The scheme employed the SOPC (system-on-a-programmable-chip) technology based on FPGA, the software framework of NIOSII and the polycyclic adjustment algorithm realized by the hardware description language. Then, several key problems that could be encountered in realizing the power supply control algorithm on FPGA were discussed. After the power supplies were upgraded, the beam of HIRFL-CSR was extracted more reliably and the stability of beam spot position at the experimental terminals has been obviously improved. This work would provide a valuable reference for the engineers of digitalizing other magnetic power supplies in HIRFL-CSR and of developing magnetic power supplies for heavy ion cancer therapy.
ADS注入器II 热冲击损伤研究(英文)
贺守波, 何源, 王志军, 杨阳阳, 张生虎, 赵红卫
2014, 31(3): 385-390. doi: 10.11804/NuclPhysRev.31.03.385
摘要:
由于束流脉冲无法控制而引起直线加速器的热冲击损伤是造成加速器无法完成聚束及偏转的主要因素,而对热冲击进行定量的热应力评估可以有效地避免RFQ、超导腔以及其他加速元件等加速器设备的损伤,这在研制强流直线加速器的过程中至关重要。本研究引用一种新颖的计算方法定量分析整个注入器的热冲击损伤并明确了三种不同材料高纯铌、无氧铜和不锈钢对应的加速器件的热冲击的特征。基于有限元方法对瞬态热应力进行分析,得出三种不同材料对应的加速器件在入射角度为90 度时的温度分析结果。对于所研制的注入能量低于10 MeV的强流直线加速器来讲,得到可允许的入射时间为20 µs。Because of injecting an out-of-control beam pulse, thermal shock damage to the accelerator may well cause a failure of focusing and steering elements. In order to prevent RFQ accelerator,superconducting cavities and other accelerator components from thermal damage, t is essential to conduct a quantitative evaluation of the thermal stresses induced in the material during the thermal shock. The present study in this paper proposed a novel method to evaluate the thermal stresses quantitatively, which can clarify the characteristics of thermal shock of several materials, such as OFHC, SUS304 and Niobium. Transitional thermal stress is investigated by three dimensional nite element method (FEM) to obtain the temperature distribution for three materials at the beam incident angle of 90°. Finally the simulation results prove that the machine protect system response time meets the requirement when the allowable injection time is de ned as 20 μs.
核技术
氚分析的β衰变诱发X射线谱技术研究进展(英文)
毛莉, 陈浩, 孙洪伟, 安竹, 邬琦琦
2014, 31(3): 391-400. doi: 10.11804/NuclPhysRev.31.03.391
摘要(1364) PDF (7KB)(321)
摘要:
介绍了氚分析的 衰变诱发X射线谱( BIXS) 方法的发展历程和研究现状。叙述了刻度曲线法、解析方法和蒙特卡罗模拟结合Tikhonov 正则法等三种不同解谱技术的BIXS 方法的特点,重点介绍了课题组近年来开展的研究工作和取得的进展,包括蒙特卡罗模拟和Tikhonov 正则法的引入,氚β衰变内韧致辐射、样品表面粗糙度、氚含量以及实验装置几何参数误差对分析结果影响的研究和应用等,同时也提出了BIXS 方法需进一步开展的研究工作。 This paper presents the status and recent progress on -decay induced X-ray spectroscopy (BIXS) for tritium measurements. The development history of BIXS method and its applications on tritium analysis are introduced, and at the same time the characteristics of three kinds of BIXS methods, i:e. calibration curve method, analytical method and Monte Carlo simulations combined with Tikhonov regularization method are also introduced. The recent studies on the BIXS method performed in our group, including the incorporation of Monte Carlo simulation and regularization method, effects of internal bremsstrahlung of tritium -decay, sample surface roughness, tritium content and geometrical parameter’s uncertainty of experimental setup in BIXS method, and the application are mainly presented. Finally, the general comments on the further improvements of the BIXS method are given.
基于共轭梯度优化算法的BP神经网络在高能粒子鉴别等领域中的应用
王树旺, 路永钢, 陈旭荣
2014, 31(3): 401-406. doi: 10.11804/NuclPhysRev.31.03.401
摘要:
人工神经网络方法已被引入高能物理实验领域并被广泛地应用于夸克胶子喷注的鉴别、电子强子分辨、顶夸克和Higgs 粒子的寻找等等。本文采用了一种改良的共轭梯度优化算法并应用于高能物理实验中粒子的鉴别。在该应用中,此算法既能实现每步迭代时在搜索方向上获得最优步长,又能避免目标函数陷入局部收敛点,从而使目标函数快速收敛,提高了算法的有效性。分析结果表明,我们改进后的BP算法显著地提高了粒子物理数据分析中的粒子鉴别能力。Artificial neural network methods have been introduced in high energy physics experiments and have been widely applied to the identification of the quark-gluon injection, electronic hadron discrimination,top quark, and the Higgs particle searching and so on. This paper introduces a modified conjugate gradient optimization algorithm, which is applied to the identification of high-energy particles. In the application, the algorithm can obtain optimal step size in the search direction for minimizing the objective function, and can overcome the local vibration problem, so that the fast convergence of the objective function is obtained and the stability of the algorithm is improved. The analysis of experimental data shows that our new BP neural network algorithm can effectively improve the identification of particles in high energy physics.
一种折中的小波阈值方法对γ能谱平滑处理的研究
颜瑜成, 刘明哲, 刘福至
2014, 31(3): 407-410. doi: 10.11804/NuclPhysRev.31.03.407
摘要:
采用小波软、硬阈值函数折中后的小波阈值方法对天然放射性环境下 谱数据进行平滑处理。通过Matlab数据分析软件,分析对比了五种不同的平滑去噪方法:五点平滑法、傅里叶变换法、小波软阈值法、小波硬阈值法,以及折中的小波阈值方法。结果表明:折中的小波阈值方法在反映 能谱特征的峰本比和峰总比分别为7.160 9,0.394 5,平滑去噪效果要明显优于其他四种方法,能最大程度地保留原始信号特征,具有较高的应用价值。This work illustrated a wavelet threshold method by combining soft and hard threshold function of wavelet for energy spectrum under the natural radioactive condition as a kind of smooth processing. By using Matlab Program, we compared five different smooth de-noising methods including smoothing by five points, the Fourier transform method, soft and hard threshold method and average wavelet threshold method.We showed that the average wavelet threshold method can reflect the ratio of the peak and the peak-to-total ratio of characteristic peak of energy spectrum as 7.1609 and 0.394 5, respectively. Thus, this method is superior to the other four methods in de-nosing, and it is able to keep the original signal properties with the largest extent and has a high value of application.
交叉学科
12C6+离子辐照对苜蓿M1代低温胁迫存活率、过氧化氢酶及过氧化物酶活性的影响
王曙阳, 李景华, 姜伯玲, 哈荣华, 李腾腾, 余成群, 刘青芳, 李文建, 陈积红, 刘敬, 胡伟
2014, 31(3): 411-415. doi: 10.11804/NuclPhysRev.31.03.411
摘要:
研究了不同剂量12C6+离子辐照对中兰1 号、BC-04-477、塔城3 种苜蓿M1代个体在低温胁迫下存活率、过氧化氢酶(CAT) 及过氧化物酶(POD) 活性的影响。在辐照剂量为400 Gy 时,中兰1 号低温胁迫组存活率、CAT活性比未辐照的对照分别提高了33.3%,56.3%,POD活性与未辐照的对照无差异;在辐照剂量为400 Gy 时,BC-04-477 低温胁迫组存活率、CAT及POD 活性比未辐照的对照组分别提高了33.3%,69.2%,5.1%;塔城在辐照剂量为800 Gy时,低温胁迫组的存活率、CAT及POD活性比未辐照的对照组分别提高了25%,26%,22.8%。以上结果表明,12C6+离子辐照可以提高中兰1号、BC-04-477、塔城的低温环境的存活能力,提高苜蓿抗寒性能In this study, three kinds of alfalfa including Zhonglan 1, BC-04-477 and Ta Cheng were treated with different doses of 12C6+ (75 keV) heavy ion radiation, and then the influence of survival rate, catalase(CAT) and peroxidase(POD) activity of M1 with low temperature stress were tested. The results showed that under the condition of 400 Gy radiation dose , the survival rate and CAT activity of Zhonglan 1 under low temperature stress have increased by 33.3%, 56.3% respectively compared with those of the control group, while there was no difference in POD activity between those two groups. The survival rate, CAT and POD activity of BC-04-477 treated with low temperature have been improved by 33.3%, 69.2%, 5.1% respectively compared with those of the control group when the radiation dose was 400 Gy. Compared with those of the control group, the survival rate, CAT and POD activity of Ta Cheng under low temperature stress have been improved by 25%, 26%,22.8% respectively when the radiation dose was 800 Gy. These results indicate that the viability and the cold resistance ability of Zhong Lan 1, BC-04-477 and Ta Cheng can be improved by 12C6+ radiation.
甲基化抑制剂5-氮杂2′-脱氧胞苷对三维培养A549 细胞辐射敏感性的影响
潘冬, 陈亚雄, 薛刚, 李小满, 任振新, 杜亚蓉, 胡步荣
2014, 31(3): 416-422. doi: 10.11804/NuclPhysRev.31.03.416
摘要:
为探讨DNA去甲基化试剂5-氮杂-2′-脱氧胞苷(5-aza-2′-deoxycytidine,5-Aza-CdR) 对三维(3D)培养模式下的肺腺癌细胞A549 辐射敏感性的作用,开展了系列实验。使用不同浓度5-Aza-CdR 处理单层(2D)A549 细胞72 h 后,MTT法检测其对A549 细胞的增殖抑制作用。选取低浓度(2,5 μmol/L)5-Aza-CdR 预处理2D 和3D 培养的A549 细胞72 h,X射线分别辐照1,2,4,6 Gy,检测微核形成率和克隆存活。实验结果显示,不同浓度的5-Aza-CdR 均能抑制2D 的A549 细胞增殖,且呈剂量依赖性。5 μmol/L 药物预处理2D 与3D 细胞并联合辐照后诱导的细胞微核形成率均显著高于相应的对照组,并且细胞存活率显著降低。不过,较低浓度5-Aza-CdR(2μmol/L) 预处理的3D 培养A549 细胞4,6 Gy 辐照后微核数目较未用药处理组显著增加,克隆存活率较未用药组显著降低(P <0:05),而在2D 培养A549 细胞中未观测到上述现象。研究结果表明,5-Aza-CdR 能抑制A549 细胞增殖,3D 培养A549 细胞药物预处理更能增加其辐射敏感性。结果暗示,为减少对正常细胞的毒性作用,在临床放疗中,可低剂量使用5-Aza-CdR,实现肿瘤的有效靶向治疗。5-Aza-CdR is a specific inhibitor of DNMTs which could suppress tumor growth by demethylation of genomic DNA. There have only few studies thus far concerning it as radiosensitizers in three-dimensional (3D) cells. The principal aim of this study is to evaluate the effects of 5-Aza-CdR on the radiosensitivity of A549 cells in monolayer (2D) and 3D cultures in an attempt to find out a new combination treatments with radiotherapy. The cell proliferation was detected by MTT assay after pretreated with different doses of 5-Aza-CdR for 72 h. A549 cells were treated with or without 5-Aza-CdR (2, 5 μmol/L) for 72 h before be exposed to X-rays of 1, 2, 4, 6 Gy, respectively. The DNA damage was evaluated by micronucleus assay and clonogenic assays. Pretreatment with 5-Aza-CdR inhibited the A549 cell proliferation significantly. More micronucleus were observed after irradiation in 3D cells pretreated with 2 and 5 μmol/L concentration of drug than those without treatment. The survival fractions of cells pretreated by both 2 and 5 mol/L drug reduced significantly in 3D cultures after irradiation. These significances, however, were found in 2D cells pretreated by only 5 μmol/L drug. Our results suggest that 5-Aza-CdR can inhibit the A549 cells proliferation and apparently enhance the radiosensitivity of cells in 3D cultures. Using of the low dose 5-Aza-CdR in clinical radiotherapy may reduce side effects and enhance effectively the cancer target therapy.
GANRA-5对X射线和12C6+离子辐射防护作用研究
姜林, 裴海龙, 朱明月, 刘婷婷, 徐丹, 孙放, 张栩锐, 丁楠, 胡文涛, 王菊芳, 周光明
2014, 31(3): 423-427. doi: 10.11804/NuclPhysRev.31.03.423
摘要:
研究了一种新的恶唑酮类衍生物GANRA-5 对于人胚肺细胞MRC-5 的辐射防护作用。以MTT评价其对于细胞的毒性,以H2AX foci 形成法检测其对于辐照后细胞中双链断裂的影响,发现其对于受到X射线和12C6+离子照射的细胞具有较强的辐射防护作用,并进一步发现其能够显著清除辐照后细胞内的自由基。这些结果表明,GANRA-5 具有较低的细胞毒性,并能够通过清除自由基发挥较强的针对X射线和12C6+离子的辐射防护作用,有望开发为高效的辐射防护药物。The radio-protective effects on human embryonic lung fibroblast MRC-5 of an oxazolone derivative named GANRA-5 were studied. MTT test was used to evaluate the toxicity and H2AX foci assay was used to test the influence of GANRA-5 on the DSB (double-stranded break) formation after irradiation. It is found that GANRA-5 exhibited low toxicity and high radio-protective effects on MRC-5 cells against both X-ray and 12C6+ ion beam. It is also found that it can act as a scavenger of free radicals. These results suggest that GANRA-5 is a promising radioprotectant.