2014年 第31卷 第2期
核子及其激发态性质研究一直是中高能核物理的一个重要研究领域。然而，到目前为止，对核子及其激发态内部结构的了解还处在初级阶段。首先介绍了核子及其激发态研究现状，指出了三夸克模型在描述核子特别是核子激发态内部结构方面存在很大的缺陷。为解决传统三夸克模型的不足，有一种新的观点认为虽然独立的五夸克态不存在，但是核子及其共振态中存在可观的五夸克激发。这种五夸克图像提供了一个描述核子内部结构的新见解，给出了与经典三夸克图像相当不同的核子激发态谱预言，还有待实验检验。目前国内外正在论证的电子–离子对撞机(EIC) 将是研究核子结构下一代最重要的加速器装置，被视为“超级电子显微镜”。由于EIC 有较高的能量和亮度，特别是低本底等优势，可以开展核子及其激发态性质的研究以及新强子态研究。The study of the properties of the nucleon and nucleon resonances is an important field in the high and intermediate energy nuclear physics, however, until now, our understanding about the structure of the nucleon and nucleon resonances is still in its infancy. We give a brief review on the current researches of the nucleon and nucleon resonances, and point out that the classical quark model can not successfully describe the structure of the nucleon and nucleon resonances. For doing this, a new idea claims that although the five-quark state does not exist, but, there could be significant five-quark components in the nucleon and nucleon resonances.This five-quark configure gives different predictions for the nucleon resonances which will be tested by the future experiments. Now, the proposed Electron-Ion Collider (EIC) will be the most important accelerator installation for studying the nucleon structure, and it is called ”super-electronic-microscope”. Because of the high energy and luminosity, and also low background, we can study the properties of the nucleon and nucleon resonances and new hadron states on EIC.
对150 AMeV 4He，290 AMeV 12C，400 AMeV 12C，400 AMeV 20Ne 及500 AMeV 56Fe 诱发乳胶不同靶核反应靶核碎片多重数分布及关联进行了研究。结果表明，黑径迹粒子、灰径迹粒子及重电离粒子平均多重数随靶核大小的增加而增加，不同靶核碎片多重数之间存在线性关联。这些实验结果均可以依据核-核碰撞几何模型及级联蒸发模型来解释。The multiplicity distributions and correlations of target fragments produced in 150 AMeV 150 AMeV 4He，290 AMeV 12C，400 AMeV 12C，400 AMeV 20Ne and 500 AMeV 56Fe induced different emulsion target interactions are investigated. It is found that the averaged multiplicity of grey track particle,black track particle and heavily ionized track particle increase with the increase of target size.There is a linear correlation between the multiplicity of different target fragments. The experimental results can be well explained based on the geometrical picture and the cascade evaporation model of nucleus-nucleus interactions.
利用同位旋相关的量子分子动力学模型模拟了40Ca+40Ca，50Ca+40Ca，64Cu+64Cu 和197Au+197Au 等多个碰撞系统中快度轻碎片集体流标度的性质。发现，中能区不同碰撞系统横向动量相关的椭圆流存在对碎片核子数的标度，且存在v4=v 22 标度，对不同碎片该比值都近似为常数0.5。同时探讨了碰撞能量、碰撞参数、核状态方程对标度律的影响，发现这些标度行为不敏感于以上物理量，可能是核碎片形成机制(组合机制) 的必然结果。The properties of light particles’ collective flows from 40Ca+40Ca, 50Ca+40Ca, 64Cu+64Cu and 197Au+197Au systems are simulated by Isospin-dependent Quantum Molecular Dynamics model. Transverse momentum dependent elliptic flows from different systems are found to be scaled by nucleon numbers of fragment in intermediate energy, and v4=v 22 scaling is also found and nearly to be a constant 0.5 for different light fragments.These scaling behaviors are investigated for different collision energies, impact parameters, nuclear equation of states and found insensitive to the above physical quantities, which may be the result of coalescence mechanism that describes the formation of fragments.
计算了相对论重离子碰撞中轻矢量介子(ρ，ω和Φ) 的光生过程。基于窄-宽近似，严格推导了相对论重离子碰撞中ρ，ω和Φ半弹性和非弹性光生过程的遍举和单举横截面。从数值结果可以看出对于p-p 碰撞，光生过程的贡献是不重要的，但是对于pT >2.5 GeV Au-Au 碰撞和pT >3 GeV Pb-Pb 碰撞，轻矢量介子光生过程的贡献是明显的。We calculate the photoproduction processes of light vector meson(ρ, ω and Φ) in heavy ion collisions. Based on the narrow-width approximation, we rigorously derive the exclusive and inclusive cross sections of ρ, ω and Φ produced by the semielastic and inelastic photoproduction processes in relativistic heavy ion collisions. The numerical results indicate that contribution of photoproduction processes of light vector meson is not prominent for p-p collisions, but thecontribution becomes evident for pT >2.5 GeV in Au-Au collisions and pT >3 GeV in Pb-Pb collisions.
基于Dyson-Schwinger 方程(DSEs) 所确定的夸克传播子和算符成积展开(OPE)，在彩虹近似下，预言了QCD真空中非定域夸克真空凝聚的结构。这种结构由夸克自能函数Af 和Bf 决定，通过数值求解DSEs 就可以得到这些自能函数。但是，直接数值求解DSEs 方程非常复杂，这里采用Roberts 和Williams 提出的参数化方法，用参数化的夸克传播函数fv (p2) 和fs (p2) 计算夸克自能函数。同时，也计算了定域的夸克真空凝聚值，夸克胶子混合的真空凝聚值，以及夸克的虚度。理论预言和计算结果均与标准QCD求和定则、格点QCD和瞬子模型的理论结果大致相符。和这些模型的结果相比，参数化方法得到的轻夸克(u, d, s)的定域真空凝聚偏大，这主要是由于模型依赖导致的。与u, d 夸克相比，s 夸克的真空凝聚比较大，这是因为s 夸克自身质量较大的缘故。当然，Roberts-Williams 参数化的夸克传播子只是一个经验公式，只能近似描述夸克的传播。Based on the Dyson-Schwinger Equations (DSEs) with the rainbow truncation, and Operator Product Expansion, the structure of nonlocal quark vacuum condensate in QCD, described by quark self-energy functions Af and Bf given usually by the solutions of the DSEs of quark propagator,is predicted numerically. We also calculate the local quark vacuum condensate, quark-gluon mixed local vacuum condensate, and quark virtuality. The self-energy functions Af and Bf are given by the parameterized quark propagator functions fv(p2) and fs (p2) of Roberts and Williams, instead of the numerical solutions of the DSEs. Our calculated results are in reasonable agreement with those of QCD sum rules, Lattice QCD calculations, and instanton model predictions, although the resulting local quark vacuum condensate for light quarks, u, d, s, are a little bit larger than those of the above theoretical predictions. We think the differences are caused by model dependence. The larger of strange quark vacuum condensate than u, d quark is due to the s quark mass which is more larger than u, d quark masses. Of course, the Roberts-Williams parameterized quark propagator is an empirical formulism, which approximately describes quark propagation.
利用压控振荡器锁相环路(VCO-PLL) 锁定超导射频谐振腔体的本征频率，使腔体稳定谐振。在原理验证阶段，利用NI-Labview 对实验原理做了仿真。得到的仿真结果显示，环路增益选取的不同会直接影响整个系统的锁定状态。在实验测试阶段，根据原理和仿真结果搭建了相应的实验平台，从而得到环路锁定的测试结果。最后在低温超导态测试阶段，用经过验证的实验平台对IMP-HWR010 超导腔体进行了频率锁定测试，并得到了腔体频率随氦压变化的实际测量结果，df/dp 约为0.73 Hz/Pa。The main issue of this paper is to introduce the application of phase lock loop (PLL) in superconducting RF technology. The voltage-controlled oscillator phase lock loop (VCO-PLL) can be used for locking the eigen frequency of the superconducting cavity. It can keep superconducting cavity resonant stably. In thispaper, the principle of the cavity locking by the VCO-PLL is verified by a simulation, which is done by using NI-Labview software. The simulation result shows that the different gain of the PLL system can impact the locking situation of the whole system. In the test stage, the locking test plant is set up and passed validation. Finally, at the low temperature test stage, the frequency of the IMP-HWR010 superconducting cavity is locked by the test plant. The frequency change with helium pressure of the cavity is about 0.73 Hz/Pa.
针对加速器驱动次临界系统(ADS) 注入器Ⅱ对超导磁铁电源系统的要求，设计了一款主要由光纤模块、数模转换器(DAC) 和模数转换器(ADC) 相关电路组成的高稳定度的超导磁铁电源控制器。提出了一种基于数字电位器(DCP) 与现场可编程门阵列(FPGA) 所组成的DAC，该DAC可实现高稳定度的超导磁铁电源的控制，电源电流值通过该DAC 给定，其电压给定输出稳定度优于2x105，完全满足超导磁铁电源系统5x105量级的稳定度要求。最后给出了系统的实际测试数据，验证了设计的合理性和使用的可靠性。According to the requirements of ADS project for superconducting magnet power supply system,a controller with high stability for superconducting magnet power supply system is designed, and it mainly consists of optical ber module, digital to analog converter (DAC) and analog to digital converter (ADC) circuit. The DAC based on digitally controlled potentiometer (DCP) and eld rogrammable gate array (FPGA) can achieve high stability control of superconducting magnet power supply, and the value of current can be given by the DAC. The output stability of this DAC can be more than 2x105, which can fully meet the requirement of 5x105 for superconducting magnet power supply. The test data of the system is given, which veri ed the rationality and reliability of this design.
为获取ADS 工程中四翼型RFQ加速器在设计、调谐和运行等方面的经验，设计和建造了一台一米长四翼型RFQ加速器。该RFQ的设计频率为162.5 MHz，但是测量结果显示即使没有调谐器时，腔体的频率也为163.7 MHz。为降低腔体频率，使用四线模型理论进行了分析并重新设计了腔体的端板。使用了二极模稳定杆来加大四极频率与相邻二极频率的间隔。最终测量结果显示，在腔体电压分布没有大的波动的情况下腔体频率达到了设计频率。同时，腔体Q值降低了1%，这就要求需要更多的功率注入腔体。使用水对二极模稳定杆进行了冷却，以便腔体能够稳定工作。In order to get experiences of design, tuning and running of a four-vane RFQ for theChina ADS project, a one-meter four-vane RFQ was designed and fabricated. The quadruple frequency of the RFQ was designed to be 162.5 MHz (operating frequency), but the measured frequency after fabrication was 163.7 MHz even without tuners in the cavity. To reduce the frequency the four-wire line model theory was used, and the endplates were redesigned. Dipole mode stabilizer rods were employed to expand the span of the quadruple frequency and the adjacent dipole frequency. As a result, the quadruple frequency was altered to the operating frequency without rippling voltage distribution along the RFQ severely. Meanwhile, the Q value was reduced by 1%, which means more RF power was required to be fed into the RFQ. The dipole mode stabilizer rods were cooled by water to make the RFQ work stably.
由于低能带电粒子核反应截面直接测量遇到的库仑位垒和电子屏蔽势的困难，基于准自由反应机制的特洛伊木马方法得到特别关注。利用Geant4 模拟的结果，与在中国原子能研究院串列加速器上通过三体反应9Be+2H->8Be+2H+n 对两体反应9Be+1H->8Be+2H 的反应截面做的间接测量实验数据进行了比较，这是Geant4 模拟在特洛伊木马方法中的首次应用。通过对模拟数据研究，提高了对实验数据的理解，也检验了模拟系统的可靠性，对今后的实验设计和改进提供了有益的意见。Due to the difficulties of the Coulomb barrier and electron screening potential in directly measuring the cross sections of nuclear reaction for low-energy charged particle, Trojan-horse method based onquasi-free reaction was paidspecialattention. For the first time the Geant4 simulation is used for the indirect measurement of Trojan-horse method in the indirect measurment of two-body reaction 9Be+1H->8Be+2H by three-body reaction 9Be+2H->8Be+2H+n in Tandem accelerator of China Institute of Atomic Energy. The stability and reliability of the simulation system are examined by comparing the experimental data and simulated results, the simulation can provide useful comments for the design and improvements of future experiments.
中国科学院近代物理研究所材料研究中心开展了对静态随机存储器(Static Random Access Memory，SRAM)单粒子效应(Single Event Effects，SEEs) 的深入研究。材料中心目前拥有的两套SRAM单粒子检测系统各自具有一定的局限性，所以又提出了一种改进的SRAM SEE检测方法，并研制了相关电路。该检测系统在兰州重离子研究装置(HIRFL) 提供的束流辐射终端上进行了多次实验，获得了一批实验数据。其中包括129Xe 束流辐照条件下，对65 nm SRAM单粒子翻转的研究；12C束流辐照条件下，对65，130 和150 nm商用错误纠正编码加固SRAM SEE 的研究；129Xe 束流辐照条件下，对普通商用SRAM 单粒子锁定的研究等。实验验证了该检测系统的有效性和可靠性，为开展SRAMSEE 的研究提供了重要的检测平台，并为以后开展更复杂器件SEE 的研究提供了实验经验和技术基础。The material research center in Institute of Modern Physics, Chinese Academy of Sciences (IMP,CAS) have made a fruitful achievements in the research of single event effects(SEEs) occurring in static random access memory (SRAM). However, there are some drawbacks exist in the two systems of detecting SEE owning by the material research center. Therefore, an improved method of detecting SEE is proposed, and the method functionality is implemented in a circuit. Further, a sequence of experiments are carried out in the beam radiation terminal of the Heavy Ion Facility in Lanzhou (HIRFL), and a bunch of experimental data are collected. The irradiation tests were carried out using 129Xe for the SEE research of 65 nm SRAMs; Using 12C for the SEE research of the 65, 130 and 150 nm SRAMs with ECC module; Using 129Xe for the SEL research of the common commercial SRAMs and so on. These experiments provide a statistical evidence of the effectiveness and robustness of the improved system. It is believed that the proposed system will be beneficial for detecting SEE in diverse settings, and it could be taken advantage of as a platform for future research on SEE tests in more intricate devices.
采用双脉冲方法，研究了日本滨松光子学株式会社R3809U-52 型MCP-PMT 对于半宽为20ns和100 ns 两种脉冲宽度下的线性输出性能，阳极输出线性电流分别为150 mA 和25 mA；经过分析，提供了将该型MCP-PMT 用于百纳秒宽度范围内脉冲测量的线性电流动态范围递推公式，拓宽了其参数范围。The double pulse method was applied to study the pulse linear current property of R3809U-52 type MCP-PMT (micro-channel plate photo-multiplier tube) from amamatsu Photonics Co.Ltd. When the FWHM of pulse are 20 and 100 ns, the pulse linear currents are 150 and 25 mA, respectively. According to the experiments results, we deduced the functions of pluses' FWHM lower than 100 ns with linear current, which extends the range of parameters available.
利用Lomb-Scargle 傅里叶变换法和统计折叠周期分析法，对2009 年8 月到2011 年10 月期间西藏羊八井国际宇宙线站的ARGO实验大厅内的氡浓度监测数据进行研究。结果表明，实验大厅内的氡浓度具有1 日和半日周期变化规律，其中以1 日周期变化为主。在1 d 中氡浓度的平均值为(567.2±1.1)Bq/m3，变化幅度为(79.0±1.4) Bq/m3，北京时间约11:20 时达到最大，北京时间约23:20 达到最小。分析还表明，在一年中月平均浓度的最小值出现在6 月份，而较大值出现在下半年的某些月份，每月的日变化幅度和浓度最大时的时间多变。这些结果对环境氡的浓度变化规律及其相关理论模型研究具有重要的意义，同时对西藏地区居住环境监测评价提供了重要的参考。Using the Lomb-Scargle period grams and temporal variation folded into one period for statistical analysis, the radon concentration in the ARGO-YBJ experiment hall from Aug. 2009 through Apr. 2011 was investigated. Our results show that the radon concentration has main periods of half-day and 1-day with the period of 1 day being dominant. In one day the radon concentration reaches its peak at 11:20 (Beijing Time) and reaches the minimum at 23:20(Beijing Time). In one year, the radon concentration is lower in June, the monthly variation amplitudes and initial phases folded into one day are various. These results are of importance to the study of variation of radon concentration and theoretical models, and provide a good chance to estimate the living environment in Tibet.
在高放废物长期地质处置过程中，作为第一层工程屏障的固化体玻璃会受到持续的电子辐照，研究其电子辐照效应对高放废物的长期安全处置具有重要的意义。在透射电子显微镜(TEM) 上对硅酸盐玻璃样品进行原位电子辐照实验。在电子束的作用下，两种硼硅酸盐玻璃均很快发生相分离现象，这主要是由于电离作用导致Na 的迁移或逃逸引起网络体结构重组的结果。引入简单的结构模型解释了两种不同组分硼硅酸盐玻璃相分离的不同，结果表明，相分离的不同与玻璃组分中Na成分的多少密切相关。As the first layer of engineering barriers, glass will be irradiated by electron in the long-term disposal of high level radioactive waste (HLW). It is significant to study the electron irradiation effects of glass for the safe disposal of HLW. In this paper, the effects induced by electron irradiation were studied in situ by transmission electron microscope (TEM). Under electron beam, the phase separation occurred very soon in both glasses, which was correlated to the network relaxation processes as a consequence of diffusion and desorption of sodium species during electron irradiation. A simple structural model was introduced to explain the difference in separated phase in two different glasses, which indicates that the phase separation induced by electron irradiation is closely related to the sodium contents in the glass sample.
重离子实验结果表明，具有高线性能量转移(LET) 或大角度入射的快重离子导致静态随机存储器(SRAM) 中的多位翻转(MBU) 比例增大，甚至超过单位翻转比例。单个离子径迹中的电荷可以沿着径向扩散数个微米，被临近的灵敏区收集后引起MBU。器件灵敏区的各向异性空间布局与离子入射方向共同影响测试器件的MBU图形特征。位线接触点的纵向隔离导致横向型成为主要的两位翻转图形；“L”型和“田”型分别是主要的三位翻转和四位翻转图形。最后，对SRAM 抗MBU加固设计和实验验证方法进行了讨论。Heavy ion experimental results reveal that the ratio of multiple-bit upset (MBU) in static random access memory (SRAM) increases for ions with higher linear energy transfer (LET) value or at larger angle of incidence, even exceeds the ratio of single-bit upset. The diffusion distance of charges in single ion track can be several micrometers. The MBU patterns of device under test are influenced by both the anisotropic distribution of sensitive volumes and the track direction. Horizontal configuration turns out to be the predominant double-bit upset pattern due to the vertical isolation (bit-line contacts) of adjacent sensitive volumes. L-shaped and squareshaped configurations are the main triple-bit upset and quadruple-bit upset patterns, respectively. Finally,implications for MBU hardness strategies and evaluation methods are discussed.
综述了细胞衰老诱导因素和衰老细胞的特征，提出细胞衰老在癌症发生发展过程中具有双重作用效应。同时，以X 射线和12C6+离子束对黑色素瘤细胞系92-1 或人正常成纤维细胞系MRC5进行辐照，观察分析DNA损伤应答效应和细胞衰老诱导。实验结果表明，相对于X射线，12C6+离子束能导致DNA 团簇损伤，持续激活DNA 损伤应答，更容易诱导细胞衰老；12C6+离子束能同时诱导癌细胞和正常细胞衰老。这些实验结果暗示开展12C6+离子束诱导细胞衰老研究具有紧迫性。Cellular senescence played double roles in the genesis and development of cancer, which was put forward through reviewing the cases and characteristics of cellular senescence. In addition, human uveal melanoma cells and human fetal lung broblast (MRC5) cells were irradiated by X-rays or 12C6+ ion beam. DNA damage response (DDR) and cellular senescence were analyzed. The results showed that DDR was activated persistently by the unrepairable clustered DNA damage, which indicated that inducing same ratios of cellular senescence needed lower doses of 12C6+ ion beam than X-rays. Furthermore, both 92-1 cells and MRC5 cells treated by carbon ion beam underwent cellular senescence. These results pointed out the urgency to investigate the mechanism of cellular senescence induced by 12C6+ ion beam.
采用Geant4-DNA 低能物理模型研究了污染电子在细胞DNA水平上的物理作用和能量沉积。利用密度聚类算法分析了损伤产额分布；并结合皮肤细胞辐射敏感性参数和临床表征剂量，探讨了低能电子对皮肤细胞的损伤特征。模拟发现，产生的DSB 中约20% 是cDSB；DSB产额是SSB 的约4%；损伤聚类包含的SSB 一般6 3 个，20 keV 和100 keV 电子也可造成> 5 个SSB 的聚类损伤；晚反应、高 值的组织更应注意防护低能电子辐射；由于LQ 模型中剂量平方项的影响，cDSB 损伤致死系数ε随入射电子数目的增加而增大。当105 个电子入射时，ε 的数值可较单个电子增大3% s 15%。可通过调节直接电离损伤概率弥补间接损伤产额，研究细胞辐照损伤的内在机理。本工作建立的低能电子对细胞DNA的损伤模型及结果，可用于评价放疗中低能污染电子对皮肤细胞的损伤效应。The cell damage yield was simulated to investigate the micro-damage mechanism of the contaminative electron to the skin cell in external radiotherapy. The physical interaction and the energy deposited events of contaminative electrons in the cell DNA were modeled based on Geant4-DNA low energy physical model. The density-based cluster mining algorithm was used to analyze the micro-damage yield and obtain its detailed compositive information. By taking the irradiation sensitive parameter and the clinical feature dose threshold of the skin cell into consideration, the damage features of the low energy contaminative electron to the skin cell were studied. The DSB and SSB yield and ratio, the cluster size and the root mean square radius,the cell SF and the lethal coefficient ε of the complex cDSB were researched. The results show that there is about 20% cDSB in the DSB yield, the other is DSB. And the yield of DSB is about 4% of that of the SSB.Generally the cluster size includes less than 3 SSBs, in which 1 or 2 SSBs cluster size is more than 99%and >3 SSBs cluster size is less than 1%. However, for some very low energy electrons such as 20 keV and 100 keV,the cluster size can be more than 5 SSBs. The irradiation protection will be more crucial for the later response and the high tissue. The lethal coefficient " of the complex cDSB will increase with the incident electron number and the accumulative dose increasing for the dose square term in LQ model. If assuming α=0.3 Gy-1 and α/β =10 Gy, the " increment is less than 1% when the incident electron increases up to 103. However, the ε increment will increase 3% s 15% (e.g. 13.8% for 30 keV and 3.4% for 200 keV electrons) when the incident electron increases up to 105. The simulation of the direct physical damage of the cell can be adjusted by a probability parameter to offset the simulation of the indirect biochemical damage. Thus the micro-damage mechanism of the contaminative electron to the skin cell can be detected at a certain extent by Monte Carlo physical simulation. This damage model of the low energy electron to DNA and these simulated results could be used to evaluate the damage effect of the low energy contaminative electron to the skin cells in the external radiotherapy.
以能量为1.5 MeV/u，剂量分别为500，750，1 000，1 250，1 500 Gy 的电子束对1，2，4，6，8 年等5 种年份浓香型白酒进行辐照处理；扫描各酒样200~400 nm波段的紫外光谱，根据紫外光谱图的差异，计算了280 ~ 300 nm 波段的光谱曲线相似度，分析光谱曲线变化规律。结果表明，对于前4种白酒，对照样与辐照样光谱曲线相似度值越小，催陈效果越好；白酒存放时间越久，酒体风格转向老熟所需剂量越小，越容易达到最佳催陈效果；对于8 年白酒，辐照剂量超过750 Gy 后，白酒体系动态平衡被打破，各单体物质增加，出现返生现象。因此，电子束辐照技术对低年份浓香型白酒催陈效果显著，是一种先进、高效的催陈方法。Electron beams were employed to irradiate liquor samples in various doses to study aging effects.Five samples which had been stored for 1, 2, 4, 6, 8 years were exposed to 500, 750, 1 000, 1 250, and 1 500 Gy doses of electron beams (1.5 MeV/u). After irradiation, liquor samples were scanned spectrophotometrically from 200 nm to 400 nm. According to the difference of the UV spectra, the spectral curve similarities from 280 nm to 300 nm and the change regulations were analyzed. The results showed that the less spectral curve similarities between control samples and irradiation samples were, the better the aging effects of liquor were;The longer the liquor were stored, the lower doses were required to reach the optimum aging effect. For eight year stored liquor, the dynamic balance of liquor system was broken and the monomer material increased when the doses were more than 750 Gy, which implied the retrogradation of liquor aging phenomena were clear. In conclusion, the electron beam irradiation has significant aging effect on short year Luzhou-flavor liquor and is an effective method for aging liquor.
在慢速高电荷态离子与氦原子碰撞的双电子转移过程中，借用虚态图像来描绘转移电子间的强关联特性；根据分子库仑过垒模型纳入反应Q值，定义势能参量! 来区分碰撞系统并度量双电子转移过程。对照之前的实验数据，清晰地显示当ω> 和ω>2 时，纯双电子俘获或自电离双俘获分别占优。澄清了碰撞系统的本质区别在于散射离子上两个转移电子的平均激发能和平均束缚能的相对比率。We borrow the concept of virtual state to characterize the strong interacting feature of the two transferred electrons in slow highly charged ions with helium collisions. Consequently, a potential parameter ! is de ned to distinguish the collision systems and to scale the double-electron transfer processes. The Q-value is taken into account according to the classical over-the-barrier model. Comparing with our previous experimental data, it is clearly shown that the true double capture or the autoionizing double capture dominates when ω>1 or ω> 2, respectively. We clarify that the distinction of the collision systems is essentially the ratio between the average excitation energy and the average binding energy of the two transferred electrons at the scattered ion.
实验测量了0.75 MeV 的O5+ 离子穿过一定长度不同原子数密度H2 靶后的电荷态分布；理论模拟了出射离子的平均电荷态以及达到平衡后的平均电荷态，得到了与实验吻合较好的结果。研究表明，随着靶原子数密度的增大，离子在碰撞过程中俘获电子的几率随之增加，平均电荷态降低；当靶原子数密度达到或超过1014 cm-3，入射离子俘获电子和被碰撞电离的两个作用过程达到平衡，出射离子的平衡平均电荷态约为1.2。Distribution of charge state for O5+ ions penetrating the H2 gas targets with a certain length and different atomicity densities was measured. Both the average charge state and the equilibrium average charge state were calculated by a computer program, and that agrees well with the experimental data. The results indicate that the electron capture cross section is increased during the collisions, and the charge state is reduced with the increasing target atomicity density. When the atomicity density reaches the order of 1014 cm-3, there is balance between the electron capture and ionization of the incident ions, as a result, the projectile achieves the equilibrium average charge state of 1.2.
加速器驱动次临界系统(ADS) 液态Pb-Bi 散裂靶的设计中，需要可靠的理论计算工具精确地预言几个GeV 能量范围的质子引起的散裂反应产生的各种粒子和核素。利用蒙特卡罗模拟软件包Geant4 计算研究了800 MeV至3 GeV 质子入射铅、铋材料引起的中子产生双微分截面。比较了Geant4 不同物理模型得到的模拟结果与现有的实验数据。其中，Geant4 的QGSP BERT和QGSP INCL ABLA 物理模型模拟结果很好地再现了实验数据。本工作证实了Geant4 蒙特卡罗模拟软件包适合用于能量高达3 GeV 的质子入射铅、铋引起的中子产生双微分截面的模拟计算。A detailed design of the liquid Pb-Bi spallation target of the Accelerator Driven Systems (ADS) requires powerful and reliable computational tools that can accurately predict particles and nuclides production by the proton induced spallation reactions in the energy range of a few GeV. In this paper, the neutron production double-differential cross sections for Pb and Bi target materials at incident proton kinetic energies between 800 MeV and 3 GeV are studied by calculations with Monte Carlo simulation package Geant4. The simulated results of Geant4 with several physics models are compared with available experimental data. The simulated results generated by QGSP BERT and QGSP INCL ABLA physics models of Geant4 well reproduce the available experimental data. The present results validated that Geant4 Monte Carlo simulation package is suitable for simulations of neutron production double-differential cross sections of proton induced reaction on Pb and Bi targets in the incident energy range up to 3 GeV.
在质子与48Ti，51V和52Cr 反应的去弹截面、弹性散射角分布实验数据的基础上，获得了一组入射质子能量在150 MeV 以下的质子与52Cr 反应的光学势参数。应用光学模型、扭曲波玻恩近似理论、核内级联模型、蒸发模型、带宽度涨落修正的Hauser-Feshbach 理论以及激子模型(含改进的Iwamoto–Harada 模型)计算得到了质子与52Cr 反应的所有截面、角分布、能谱和双微分截面。对理论计算结果与实验数据以及TENDL 中的数据进行了比较分析，结果显示，理论计算结果与实验数据符合较好，且反应道截面优于TENDL的结果。Based on the experimental data of non-elastic and elastic scattering istributions for p+48V,p+51V and p+52Cr reactions, a set of optical potential parameters for p+52Cr reaction with incident proton energies below 150 MeV are obtained. All cross sections, elastic and inelastic scattering angular distributions,energy spectra and double differential cross sections of six outgoing particles (n, p, d, t, helium-3 and ) for p+52Cr reaction are calculated and analyzed. The optical model, the intra-nuclear cascade model, evaporation model, Hauser-Feshbach theory with width fluctuation correction, exciton model including the improved Iwamoto–Harada model and distorted wave Born approximation theory are involved in the calculation. The calculated results are compared with existing experimental data and the evaluated data from TENDL data base.It is found that our calculated results agree with the experimental data and the calculated cross sections are more consistent with the related experimental data than the results from TENDL data base.
Z-Pinch 惯性约束聚变是未来一种有竞争力的能源候选方案。Z-Pinch 驱动的聚变裂变混合堆可高效地嬗变反应堆乏燃料中分离出的超铀元素。对美国Sandia 国家实验室提出的In-Zinerater 混合堆概念进行了中子学分析和数值模拟。在三维输运燃耗耦合程序MCORGS 中增加了处理在线添加燃料与去除裂变产物的功能，实现了对液态燃料燃耗过程的模拟。增加6Li 丰度和燃料初装量保持寿期初反应性不变，可以减缓寿期内反应性下降趋势。逐步增加包层内超铀元素装量，可以控制整个寿期内反应性基本恒定。聚变功率取20 MW，通过反应性控制，5 年内包层能量放大倍数在160~180 之间，氚增殖比在1.5~1.7 之间，优于In-Zinerater 基准设计方案。Z-Pinch Inertial confinement fusion is a competitive candidate for future energy solution. A fusion-fission hybrid driven by Z-Pinch can be used to transmute transuranic elements from spent fuels of reactors efficiently. Analysis and numerical simulation of blanket neutronics of In-Zinerater, which is a fusionfission hybrid concept design in Sandia National Laboratories, is given in this paper. Modification to the three dimension transport and burnup code MCORGS are done, so as to simulate continuous feeding and continuous chemical processing of the liquid fuel. Different combination of initial enrichment of 6Li and fuels loading in the blanket are selected to keep the same reactivity at begin of core. By this way, the decreasing trend of reactivity at life of the core can be lowered. The reactivity can be maintained constant by increasing the fuel loading in the core gradually as the burnup deepens. Given a 20 MW fusion power, by reactivity control, the blanket energy multiplication is around 160 ~ 180 and tritium breed ratio 1.5 ~1.7 in 5 years, which is a better result
than Sandia’s original design.