2014年 第31卷 第4期
密度依赖的对称能作为核物质状态方程的同位旋相关部分，是当前核物理和天体物理两个领域共同关注的重要热点问题之一。人们在实验和理论两方面对此进行了大量的探索，然而由于问题的困难性，对其研究尚未达成共识。目前，研究对称能的方法有很多，其中包括微观和唯像核多体理论、重离子碰撞、原子核的巨共振等。近年来，低密对称能的研究已经取得了重要进展。本文综述了利用有限核的信息来约束核物质对称能的密度依赖性方面的研究工作，这一研究途径尽可能地降低了理论分析的模型依赖性。研究表明，208Pb 对称能(系数) asym(A) 等于参考密度ρA = 0.55ρ0 处的核物质对称能(系数)。这个关系将有限核与核物质的对称能联系了起来，借此可以探究亚饱和密度核物质对称能的密度依赖性，因此核心目标是准确确定208Pb 对称能(系数)。我们通过重核β- 衰变能和质量差来提取208Pb 对称能(系数)，进而约束亚饱和密度下核物质对称能的密度依赖行为。Nuclear symmetry energy characterizing the isospin dependent part of equation of state, is a hot topic in nuclear physics and astrophysics. Although many theoretical and experimental efforts have been performed, due to its difficulty, this problem remains unsolved. There are many approaches to deal with this issue, including nuclear many-body theories, heavy ion reactions, and nuclear giant resonances. Recently,significant progress has been made in constraining the density dependence of the symmetry energy around the saturation density. We explore the symmetry energy around the saturation density with the help of the properties of finite nuclei to reduce the uncertainty as far as possible. It is found that the symmetry energy (coefficient) of 208Pb equals that of nuclear matter at reference density ρA = 0.55ρ0 . This relation links the symmetry energy of the nuclear matter and the one of finite nuclei, with the help of which one can explore the density dependence of the symmetry energy. Thus, the central issue is to obtain the symmetry energy (coefficient) of 208Pb. We exacted it with the experimental 8722;-decay energies of heavy nuclei and with nuclear mass differences, and then to constrain the density dependent symmetry energy at subsaturation density.
提出了一种新的用于壳模型截断计算的基矢空间的构建方法，即关联基的方法。关联基是利用壳模型中每个粒子数分布下哈密顿量的本征态作为基矢。在此基矢之上，可以很自然地通过考虑能量相对较低的关联基矢进行相应的截断计算。当所有的关联基矢都被考虑时，计算结果回到一般jj耦合给出的结果。最后，对关联基下壳模型的计算与标准的壳模型计算进行了比较，计算结果表明，关联基下壳模型能量和波函数有着良好的收敛性，同时表明关联基计算的有效性。We present a new basis selection algorithm for truncated shell model calculations. In this method the basis is taken as the correlated eigenvectors of the Hamiltonian in each shell-model partition. A truncation scheme is established by naturally taking the low-lying correlated basis vectors in the different partitions, which is equivalent to the j-j coupling scheme of the shell model when all correlated basis vectors are considered. The calculations are compared with standard shell model calculations. The convergence properties of the correlated basis method are also discussed. The calculation results show that one can get both good convergence of energies and wave functions, which indicate the effectiveness of correlated basis shell-model calculation.
天体环境下的核反应速率是各种关于天体核合成理论模型所需的输入量，对于了解天体核合成过程，以及宇宙的演化很重要。但是在天体温度下，核反应是在很低的能量上发生的。由于库仑位垒的作用，反应截面非常低，直接测量很难进行。通过测量合适的三体反应截面，特洛伊木马方法提供了一种提取感兴趣的低能两体反应截面的方法；而且，采用一系列近似可得到便于计算的理论公式。本文介绍特洛伊木马方法的原理及其在天体核反应中的应用。The nuclear reaction rates in the astrophysical environment are indispensable input parameters in different astrophysics theories, and play important roles in understanding the astrophysical nuclear synthesis and the evolution of the universe. However，at the astrophysical temperature, the nuclear reactions proceed at very low energies. Due to the Coulumb barrier the reaction cross sections are very small, so that the direct measurement is almost impossible. The Trojin horse theory provides a useful method to measure indirectly the low energy two body cross sections by measuring the suitable three body reactions. Some approximations are applied in the theory to get convenient formula. This paper introduces the Trojin horse theory and its application in astrophysics nuclear reactions.
Primakoff 效应具有独特的动力学筛选条件，是研究原子核和粒子物理的强大的实验工具。未来电子-离子对撞机(EIC) 机器具有质心能量高、亮度高、动力学范围广、本底低、探测器探测效率高以及碰撞离子种类丰富等优点。这将为我们开启一扇通往Primakoff 物理研究的新时代的大门。在EIC 机器上开展Primakoff 物理实验可以严格检验量子色动力学的基本对称性，研究强子的电弱相互作用性质，并探索超出标准模型的新物理。Primakoff 效应实验是EIC 物理研究的又一亮点。The Primakoff effect is a powerful experimental tool in the nuclear and particle physics, as it has excellent kinematic filters. The future electron-ion collider (EIC) facility has a lot of advantages, such as high center-of-mass energy, high luminosity, broad kinematic range, low background, high particle detection efficiency and various ion species. It will open a door for new era of the Primakoff experiments to test fundamental QCD symmetries, to study the electro-weak properties of hadron and to search for new physics beyond the standard model. The Primakoff experiment is another highlight of the EIC machine.
高能重离子碰撞产生的带电粒子由两部分组成：一部分来源于碰撞产生的高温高密度物质，另一部分是带头粒子。假设高温高密度物质按照由演化过程主导的流体力学的规律膨胀并冻析为带电粒子，带头粒子来源于参与者且具有大致相同的能量。基于该假设，得到了高能重离子碰撞带电粒子的赝快度分布，并与BNL-RHIC 上的PHOBOS 合作组在(sNN)1/2 = 62.4 与200 GeV 的Cu-Cu 碰撞中给出的实验结果相比较，理论与实验测量符合得很好。The charged particles resulting in high energy heavy ion collisions consist of two parts: One is from the hot and dense matter produced in collisions. The other is the leading particles. We suppose that the hot and dense matter expands and freezes out into the charged particles according to the evolution-dominated hydrodynamics, and the leading particles are from participants with approximately the same energy. On the basis of this assumption, we get the pseudorapidity distributions of the charged particles produced in high energy heavy ion collisions, and make a comparison with the experimental data presented by PHOBOS Collaboration at BNL-RHIC in Cu-Cu collisions at (sNN)1/2= 62.4 and 200 GeV. The theoretical predictions are in good accordance with experimental measurements.
高通量μ子源是国际上μ子科学研究的重要条件。在中国散裂中子源的高能质子应用区中，运用蒙特卡罗工具Geant4 和G4beamline 软件设计了使用内靶超导螺线管俘获高通量表面μ子的束线。与传统的分离靶和基于四极磁铁的收集系统相比，大孔径超导螺线管可以将收集效率提高两个量级。通过对不同靶材的粒子产率进行分析得出石墨是最佳靶材，然后比较俘获螺线管与束流的不同偏转角度下收集的表面的产率，提出了合理的较高产率的俘获和输运螺线管的设计方案，并与常规磁铁方案比较，最终在衰变螺线管端口的表面μ 通量高达108/s。High intense muons are required by many applications in muon science. A large acceptance channel for surface muons was designed at China Spallation Neutron Source (CSNS) using a superconducting solenoid and an internal target, which can provide a large solid angle to collect intense surface muons. Compared to conventional separate target and collection system based on quadrupole magnets, a superconducting solenoid with large aperture can collect two orders larger of surface muons. This device was simulated by Geant4 and G4beamline. By analyzing the surface muon production ratio produced by the process that protons bombard four different materials, we chose the graphite as the target material. Then comparing the intensity of surface muon by different angles between the axis of the capture solenoids and the proton beam line, we proposed the capture and transport solenoid system with higher muon production ratio. Finally, the yield of surface muon at the exit of decay solenoid can be up to 108/s.
本文着重论述了中国科学院近代物理研究所目前正在研制的三大磁体工程，它们包括重离子治癌工程(HIMM)，强流重离子加速器(HIAF) 工程，以及加速器驱动次临界系统(ADS)。在HIMM工程中的常规磁体建设中，着重介绍了联合运用钝化槽与活极头两项技术改善磁场品质的设计方法，并且运用Opera-3D 设计软件，对该类高场常规磁体进行了数值分析，进一步地测量了该磁体磁场分布情况，相关的测量结果与数值模拟结果吻合良好。而对于正在处于预研阶段的HIAF 工程中的快脉冲超导二极磁体，讨论了超导磁体的前期设计与结构优化技术，包括CACC超导线缆的结构设计，80 K冷屏与线圈盒结构的优化，力-磁耦合结构计算方法等。而在嬗变核废料处理的C-ADS 注入器II中，核心部件是具有高磁场(高达7s8 T) 的多层复合超导螺线管磁体结构，介绍了其在励磁和失超过程中相关磁学和力学多场实验测试工作。这些相关的设计和测量技术将为中国科学院近代物理研究所自主研制的磁体工程的物理和结构设计提供方法和指导。High- eld conventional magnets and superconducting magnets for three new projects, which can include Heavy Ion Medical Machine (HIMM), High Intensity heavy ion Accelerator Facility (HIAF), and Accelerator Driven sub-critical System (ADS) project, are under construction or design at Institute of Modern Physics (IMP). In conventional magnet of HIMM, air trim slot and removable pole were used jointly for improving the conventional magnets' quality. The measurements of the magnetic eld distribution in the median plane of the working area have been carried out. Results from Opera-3D simulation show good agreement with the measurement data. For superconducting dipole coil prototype in HIAF Project, which is in design phase, the R&D of cable-around-conduit conductor, 80 K thermal shield , the coil case and a smart coupled mechanical analysis method were described. And for SC solenoid magnet of C-ADS Injector-II, which is in test phase, magnetic eld and strain measurement technology at IMP were introduced during excitation and quench. The present results and methods
may provide some basis experiences on the construction of the magnet at IMP.
超导直线加速器腔体几何β选取是否合适，直接影响到所需要的腔体类型(腔型) 和腔体的总量，进而影响加速器的造价。采用线性近似的物理模型，并结合粒子群优化算法，开发出一套用来选择腔体几何 的程序。将之运用到中国加速器驱动次临界系统(C-ADS) 质子直线加速器的设计中，得出一组最合适的βg 和对应的物理设计方案。与现有的设计方案相比，新的设计方案的腔型个数少一个，而腔体总数基本不变，具有一定优势，同时也验证了本模型及优化算法的正确性。The βg of cavity in superconducting linac will determine how many cavities and cavity-types will be used in a project, and then it will affect to the total costs. In this paper, to get the most suitable βg of cavity,a linear approximation model has been proposed and a code has been developed combined with the algorithm of the particle swarm optimization(PSO). Then it was been examined in the project of China Accelerator Driven sub-critical System(C-ADS). Finally it was passed and got a set of the most suitableβg and the corresponding physical design. The new design has certain advantages over the existing design for the number of cavity type has been reduced while the total number of cavities was not increased.
超导离子源(SECRAL) 的超导磁铁电源的控制非常重要。为防止超导磁铁的失超，需要对超导磁铁电源采用恰当的策略进行控制。在SECRAL 系统中，4 台电源分别为4 个超导线圈独立供电，供电的电流大小不同，电流上升和下降的速率也不同。4 个线圈的电流不平衡，将导致整个超导磁铁失超，所以超导线圈的电流上升和下降过程必须协同完成。为了提升磁铁电源的安全性和稳定性，设计并实现了一个远程控制系统。在硬件方面使用串口通讯服务器实现TCP/IP 网络通讯与RS232 串行通讯间的协议转换。软件使用VC++ 直接对串口编程完成。该系统能够自动完成4 台电源的同步操作，简化了超导离子源SECRAL的调试过程，提高了操作过程中的安全性。The control of the superconducting magnet power supply (SMPS) is very important for Superconducting Electron Cyclotron Resonance Ion source with Advanced design in Lanzhou(SECRAL). In order to improve the safety and the reliability of the SMPS, a remote control system was designed and implemented.There are four power supplies needed to be controlled with suitable strategy to avoid the quench of the superconducting magnet. These four power supplies are used to supply four superconducting solenoids. Because the value and the changing rates of the current for these four solenoids are different, the power supplies must be operated synchronously to keep the current of the solenoids balanced. In this paper, we provide a detailed description for the control strategy of the four power supplies and the architecture of the hardware and the software. A serial switch is used for protocol conversion between TCP/IP and RS232 in firmware. And the software is implemented using VC++. The system can operate the four power supplies automatically after it is triggered. With the help of the control system, operation of the SMPS gets easier and safer.
研究了对BC501A 液体闪烁体对 射线的光输出响应特性。实验上利用 放射源(60Co，137Cs) 测量了不同光电倍增管高压下，尺寸为Φ5.08 cm x5.08 cm 的BC501A 液体闪烁体探测器的脉冲幅度谱。利用Geant4 软件进行模拟，计算结果与实验数据很好地符合，得到了能量分辨函数及能量刻度曲线。利用Geant4 研究了BC501A 的脉冲幅度谱的康普顿边缘Ec、康普顿峰Emax 及康普顿半高点E1=2 与能量分辨率的关系。同时模拟结果显示，随射线能量(0.2~0.3 MeV) 的增加，康普顿边缘位置Nc=Nmax 从0.8 至0.7 线性减少。The light output response of BC501A liquid scintillator to -rays has been studied. The pulseheightspectra of BC501A (Φ5.08 cm x 5.08 cm) for different PMT high voltages have been measured using 137Cs, 60Co γ-ray sources. The Geant4 simulated pulse-height spectra showed a good agreement with experimental data. The energy resolution functions and energy calibration curves have been obtained by comparing measured light output distribution with simulated one. The position of the Compton edge relative to the position of the maximum and the half height of the spectra has also been studied using Geant4 in detail. The value of Nc/Nmax at the position of Compton edge decreases from 0.8 to 0.7 with the increase of incident -rays energy (0.2~0.3
描述了为兰州重离子加速器冷却储存环(HIRFL-CSR) 外靶实验系统硅微条阵列探测器而设计的前端电子学模块。该模块采用专用ASIC 芯片，可以处理96 路能量信号。对前端电子学模块的性能进行了测试，结果表明，该模块在0.1~0.7 V范围内的积分非线性好于0.3%；其电子学分辨好于0.45%，最大串扰小于10%；通道一致性测试结果好于1.3%；在室温下连续工作24 h 后，零点峰位最大漂移为1.48 mV。The silicon strip array detector is one of external target facility subsystems in the Cooling Storage Ring on the Heavy Ion Research Facility at Lanzhou (HIRFL-CSR). Using the ASICs, the front-end electronics module has been developed for the silicon strip array detectors and can implement measurement of energy of 96 channels. The performance of the front-end electronics module has been tested. The energy linearity of the front-end electronics module is better than 0.3% for the dynamic range of 0.1 ~ 0.7 V. The energy resolution is better than 0.45%. The maximum channel crosstalk is better than 10%. The channel consistency is better than 1.3%. After continuously working for 24 h at room temperature, the maximum drift of the zero-peak is 1.48 mV.
蒙特卡罗模拟是放射性测井一种重要的数值模拟方法，利用通用程序MCNP可方便地建立各种地层模型，为放射性测井研究提供了简便有效的方法。借助于蒙特卡罗方法建立随钻条件下地层模型，正演模拟随钻方位伽马成像特征。结果表明，随钻方位伽马成像图呈现正弦线特征，利用成像图可准确反演井眼相对倾角和放射性地层厚度；井眼相对倾角越大，放射性地层厚度越厚，成像图的正弦线高度值及在井轴方向上的展布高度值越大；井眼尺寸对利用成像图求取井眼相对倾角没有影响，但对计算放射性地层厚度有影响，仪器偏心对利用成像图求取井眼相对倾角和放射性地层厚度都有较大影响，若伽马计数满足测井计数统计性，可忽略井眼流体对成像图的影响。Monte Carlo simulation is one of the most important numerical simulation methods in nuclear logging. Formation models can be conveniently built with MCNP code, which provides a simple and effective approach for fundamental study of nuclear logging. Monte Carlo method is employed to set up formation models under logging while drilling condition, and the characteristic of azimuthal gamma imaging is simulated. The results present that the azimuthal gamma imaging shows a sinusoidal curve features. The imaging can be used to accurately calculate the relative dip angle of borehole and thickness of radioactive formation. The larger relative dip angle of borehole and the thicker radioactive formation lead to the larger height of the sinusoidal curve in the imaging. The borehole size has no affect for the calculation of the relative dip angle, but largely affects the determination of formation thickness. The standoff of logging tool has great influence for the calculation of the relative dip angle and formation thickness. If the gamma ray counts meet the demand of counting statistics in nuclear logging, the effect of borehole fluid on the imaging can be ignored.
为了对兰州彭宁离子阱LPT 内的离子运动进行偶极和四极共振激发，采用变压器原理，设计制作了两套分相器： 一套工作频率为200 kHz~4 MHz，适用于四极激发模式；另一套工作频率为1700 ~ 1750 Hz，适用于偶极激发模式。详细测试了它们在空载和负载情况下的幅频曲线与相频曲线。测试结果表明：RF分相偏置电路的输出幅度与相位均达到了设计要求。In order to excite the ions in the Lanzhou Penning Trap (LPT), two sets of RF phase splitters by using the principle of transformer have been developed, one of which is applied for the quadruple excitation and works at a frequency of 200 kHz ~ 4 MHz and the other is for the dipole excitation and works at a frequency of 1700 ~ 1750 Hz. Their amplitude-frequency and phase-frequency characteristic curves in the condition of without-load and with-load have been tested in detail. The results showed that the amplitudes and the phases
of both RF phase splitters have met their design requirements.
FinFET 器件比主流CMOS 技术表现出更多优势，如快速、高集成度、低功耗、多功能性和强扩展性，基于ISE TCAD，考虑迁移率、量子效应、载流子重组、辐射效应等的影响，建立了一种纳米FinFET 器件SEE 的3D 仿真模型。分析了工艺掺杂浓度、栅压、粒子能量、寄生电容及技术节点等对单粒子瞬态电流的影响，并探讨了其影响机制。基于此分析，找到了一些潜在的工艺加固技术，如降低源极掺杂浓度、增加漏极和衬底的掺杂浓度、减少粒子能量、降低栅压、优化寄生电容等。FinFET presents more advantages than current bulk CMOS technologies, such as high speed, high density, lower power, more functionality and high scalability. A 3D single event effect model of nano-scale FinFET is simulated by using ISE TCAD. The considered physical models include mobility model, quantum effect model, recombination model and radiation effect model. The effects of the doping concentration, gate voltage, ion energy, parasitic capacitor, and technologies nodes on single event transient current in FinFET are analyzed. The possible mechanisms behind these effects are also presented. The results indicate some potential hardened technologies. It includes decreasing source doping concentration, increasing drain and substrate doping concentration, reducing ion energy,upgrading gate voltage (Vg) and optimizing parasitic capacitor.
单粒子效应(SEE) 加速器地面模拟需要离子束具有较好的均匀度，针对回旋加速器单粒子效应模拟的束流特点，建立了一套以位置灵敏平行板雪崩探测器(Parallel Plate Avalanche Counter，PPAC) 为基础的均匀度探测系统并完成了带束测试，对它的结构、工作原理、均匀度获得方法及带束测试结果进行描述。为验证PPAC 测量结果准确性，在带束测试过程中，前方同时放置PET膜测量穿过PPAC 探测器的粒子分布，与离子径迹测量结果对比，给出PPAC的均匀度的测量误差在5% 之内。探测器具有50 mmx 50 mm的灵敏面积和小于1 mm的位置分辨，符合单粒子效应实验对束流均匀度测量的要求。The homogeneity of beam is an important physical parameter in the ground-test accelerator of single event effects (SEEs), it can affect the SEEs evaluation accuracy. Nuclear track detector cannot get the beam profile promptly. A uniformity measurement system based on the Position sensitive parallel plate avalanche detector (PPAC) was built to fulfil the homogeneity analysis in real time during the SEE test. Here its construction and principle, the method of analysis and the result of beam test are described. To validate the result of PPAC, a PET film was synchronously irradiated before the PPAC. In comparison with the obtained results of PET films observation, the uniformity value from the PPAC has an estimated maximum error of 5%.The PPAC has about 1 mm position resolution and 50 mm x 50 mm sensitive area. Which can satisfy the
requirement of uniformity analysis on SEEs test by accelerator irradiation.
使用中国原子能科学研究院HI-13 串列加速器产生的32S 离子轰击BOPET 薄膜，薄膜在空气中陈化3 个月后在专用装置中使用NaOH 溶液蚀刻制备核孔膜，研究NaOH 溶液浓度、蚀刻温度对微孔孔形的影响。在不同温度和蚀刻液浓度条件下，蚀刻出微孔孔径为0.2 至0.93μm的亚微米核孔膜，计算其微孔锥角，得出微孔锥角随着蚀刻温度、蚀刻液浓度和微孔孔径的变化趋势。研究表明，采用低浓度、高温度的NaOH 溶液蚀刻有利于减小微孔锥角，有利于制备较小孔径的核孔膜。如选用0.5 mol/L 的NaOH 溶液浓度，在蚀刻温度为90 ℃的条件下蚀刻，此时蚀刻时间小于2 h，既可以得到高质量微孔膜也有利于提高生产效率。The PET membranes are irradiated by 32S ions. The 32S ions were produced by the HI-13 tandem accelerator in China Institute of Atomic Energy. The membranes used for the experiment have been aged in air for three months. The PET membranes are etched in the particular device. Sodium hydroxide solution is used as etchant. The effects of different concentration of sodium hydroxide solution and etching temperature on the pore shape have been studied. The pores have a diameter of 0.2~ 0.93 μm respectively in different membranes and the taper angle have been calculated. The pore diameter, etchant concentration and etching temperature respectively as a function of the taper angle under different etching conditions are displayed. The experiment result showed that low concentrations of sodium hydroxide solution with high temperature make the pore taper angle and pore size relatively smaller and the pore more close to a cylinder which enables us to conclude the proper etching condition for producing. Meanwhile, Pore taper angle was relatively minimal on 0.5 mol/L sodium hydroxide solution, at 90 ℃ with etching time in 2 hours.
重离子束放疗可有效杀死肿瘤细胞。研究表明：重离子束能引起癌细胞的基因异常，引发基因组不稳定性。BTG1作为一个重要的G0/G1 期相关蛋白，具有强烈的抗细胞增殖能力。以碳离子辐射为手段，通过蛋白质印迹杂交技术发现：人肾癌786-O 细胞中BTG1 能够对重离子辐射应激产生应答。同时，荧光定量PCR结果显示碳离子辐照后，BTG1转录本与microRNA-19b 的表达水平呈负相关变化。瞬时转染microRNA-19b 类似物于人肾癌786-O 细胞中，能够抑制由碳离子辐射引起的BTG1 蛋白上调，并增加细胞的微核发生率。因此microRNA-19b 能够通过抑制BTG1 的表达，增加重离子辐射诱导的细胞基因组不稳定性。Heavy ion radiotherapy is a curative treatment for human malignancies and offers hopeful prospects for the treatment of cancer. Recent studies demonstrate that heavy ion irradiation leads to not only cell killing but also genomic instability. Expression of BTG1 inhibits the proliferation of cells and plays important roles in the progress from G0/G1 to S phase in cell cycle. In this study, we found that BTG1 was inducible in human renal cancer 786-O cells in the presence of carbon ion irradiation. Meanwhile, the results of qRT-PCR analyses displayed an inverse relationship between expression of BTG1 and microRNA-19b at different times. The up-regulation of BTG1, which was induced by carbon ion irradiation, was inhibited by microRNA-19b mimic transfected into 786-O cells. Subsequently, down-regulation of BTG1 increased the number of micronuclei in bi-nucleated cell of 786-O cells. Thus, we speculate that microRNA-19b leads to enhancement of heavy ion irradiation induced genomic instability by inhibiting the expression of BTG1 gene.
实验研究了300 和600 keV 的O7+ 离子与宏观玻璃管内壁的相互作用，利用位置灵敏法拉第筒测量了传输离子的偏转角和传输效率随倾斜角的变化关系，观察到偏转角不等于倾斜角的不完全导向现象。实验结果证实，高能入射离子在玻璃管内壁产生的沉积电势相对于入射离子动能横向分量较小，难以使传输离子沿着玻璃管的轴向出射，从而发生不完全导向现象；并且，入射离子的能量越高，导向效应越不明显。Transmissions of 300 and 600 keV O7+ ions through a single glass macrocapillary were investigated.The transmitted fraction and the deflection angle for various tilt angles were measured using the Distribution Sensitive Faraday Cup. The results show the incomplete guiding that the deflection angle is not equal to the tilt angle. The incomplete guiding results from that the potential established by the deposited charge is not strong enough in contrast to the high transverse velocity of the ions and it leads to the ions deviating from the capillary axis exiting out. The higher incident energy, the weaker guiding effect.
给出了径向和轴向倒料行波堆堆芯的详细设计，通过燃耗计算软件MCORE对两种堆芯进行了分析计算。对于轴向行波堆，得到了稳定的核子密度分布和功率分布，并模拟出增殖-燃耗波。稳态时，keff 为1.065，波速约为5.0 cm/a，燃耗深度达到400.0 MWD/kg-HM。对于径向倒料行波堆，采用由外向内的倒料方案，经过一定倒料周期后功率分布趋于稳定。研究发现，渐进稳态keff 随倒料周期的增加呈抛物线变化，燃耗深度随倒料周期的增加线性增大。以最低功率峰为依据，确定倒料周期450 d为最佳倒料周期。此时，渐进稳态keff为1.020，平均燃耗达到156.0 MWD/kg-HM。Radial and axial fuel shuffling Traveling Wave Reactor (TWR)core were designed in detail, and burn-up calculation code MCORE was used to perform calculation and analysis. For the axial core, stable nuclide densities and power distribution were obtained, and the breeding-burning wave was simulated. For steady state, keff is 1.065, the drift speed is about 5.0 cm/a, and the burn-up is up to 400.0 MWD/kg-HM. For the 8 adial core, the fuel is shuffled from outside in, and the power distribution becomes stable after several shuffling steps. The results show that, asymptotic keff parabolically varies with the shuffling period, while the burn-up increases linearly with the shuffling period. To reduce the power peak, shuffling period 450 d is recognized as the best design. Asymptotic keff is 1.020, and the average burn-up is up to 156.0 MWD/kg-HM.
采用国际开源程序包Geant4，构建高能质子束轰击加速器驱动次临界系统(ADS) 散裂靶的物理模型，模拟计算质子轰击液态金属铅、铅-铋合金和汞靶的泄漏中子谱分布，以及计算不同能量质子对应的铅靶泄漏中子产额和轴向积分分布，获得1 GeV 质子对应的铅圆柱靶优化参数，考虑入射质子的利用率和整个堆芯的体积质量，优化靶半径范围为16 ~ 24 cm，靶高为100 cm，相关研究结果可为(ADS) 散裂靶的物理和工程设计提供理论依据。We use Geant4 toolkit to model high-energy proton irradiating spallation target in an Accelerator-Driven sub-critical System (ADS). The simulated neutron leakage spectrum resulting from proton bombarding liquid metal targets of lead, lead-bismuth eutectic, and hydrargyrum are obtained. The neutron leakage yields from lead target and their axial integrated distributions are calculated with different incident proton energies.Considering the incident proton efficiency and the whole size and mass of the reactor core, the optimized target radius and target height are suggested to be a range of 16~ 24 cm and 100 cm, respectively, which is helpful for the physical and engineering design of the ADS spallation target.
由于加速器驱动次临界堆存在外中子源，堆芯结构复杂，中子注量的各向异性严重，所以相关燃耗计算在次临界系统设计中起着重要作用。为实现次临界系统的燃耗计算，结合粒子输运程序MCNP 处理复杂几何和燃耗程序LITAC 处理核素全面的特点，开发了接口程序MCADS耦合MCNP 和LITAC。然后选取IAEA-ADS 基准题对耦合程序进行了验证计算。结果表明，燃耗、外源强度、空泡效应、初始功率分布等方面的计算结果和其他国家的计算结果相比有很好的一致性，证实了MCADS在次临界模式计算中的可靠性。Burnup analysis plays an important role in the design of ADS since subcritical reactor has complex geometry structure as well as anisotropic ux distribution caused by external source. In order to simulate burnup, a Monte-Carlo Activation and Depletion Code System (MCADS) has been developed combining advantages of MCNP in complex geometry neutron transport calculation with LITAC in fast and precise inventory calculation. Then, IAEA ADS-Benchmark (stage1) is worked out, verifying that the code can be used to deal with subcritical reactor with an external source. Also, burnup, source evolution, void reactivity, initial spatial power density distribution are gured out with the code, showing good agreement with results from other countries.