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2012年  第29卷  第4期

核物理
双中子集团结构研究进展
肖军, 叶沿林, 游海波, 杨再宏, 孙叶磊
2012, 29(4): 317-326. doi: 10.11804/NuclPhysRev.29.04.317
摘要:
回顾了晕核发现以来双中子集团结构的研究进展,分析了可能的发展方向。系统的理论研究表明, 在原子核的表面和低密度核物质中, 空间紧密关联的2n集团的出现是一个普遍的现象。 但在较重原子核表面出现2n集团的机制与核物质或轻晕核中的机制很不一样, 前者是由有限核的平均场造成的尺度效应(size effect),而后者主要是由低密度下对相互作用(或对能隙)的增强造成的。另外,在轻晕核或有限核表面,2n集团的均方根半径与它们到核芯的距离(或背景密度)有关,最小值普遍可以达到2~3 fm,然而在核物质中2n集团最小只能到~5 fm。 实验方面,在重靶上的库仑激发强度, 能够比较准确地给出2n系统到核芯的平均距离。 但到目前为止尚没有有效的实验方法给出基态中两个中子之间的间距, 主要原因是中子发射过程中末态相互作用(共振态或虚粒子态)造成的两步过程的干扰, 这个问题在库仑激发破碎(重靶)或核作用破碎(轻靶)中都出现。“拖出”反应和敲出核芯反应是下一步可以考虑的路径。 双中子的关联测量通常效率比较低,尤其是需要有效排除中子串扰(CT)事件。为此, 需要发展特殊设计的中子关联测量装置, 在提高探测效率的同时,能够通过运动学关系以及其他方法有效排除中子CT信号。 在数据处理阶段,通过反复迭代给出的双中子关联函数, 经验证明是比较有效的关联状态表达方式, 从中可以直接提取出双中子分布均方根半径。 This article outlines the progress in the study of the dineutron structure in various systems. Systematic theoretical investigations reveal that dineutron structure is a general phenomenon appeared at nucleus surface and in low density nuclear matter. But the underline mechanism of forming dineutron clusters at the surface of heavier nuclei is quite different to that for light halo nuclei or at the low density nuclear matter, with the former being basically due to the so called “size effect” and the latter due to the enhanced pairing interaction. It is also realized that the RMS radii of the dineutron cluster at the surface of light halo nuclei or heavier finite nuclei varies with the distance from the center of nuclei (or background density) and may attain a minimum of about 2~3 fm, whereas that in the low density nuclear matter may only attain about 5 fm. From experimental side, Coulomb excitation caused by heavy targets provides a good way to extract the mean distance from the center of the neutron pair to the center of nucleus. But up to now it is still difficult to experimentally determine the distance between the two valence neutrons, due primarily to the final state interactions which lead to two step emission of neutrons via resonances or virtual intermediate states. This problem happens in both Coulomb and nuclear breakup processes. Possible ways to avoid this problem might come from experiments based on “towing mode” or core knockout reactions. Detection of two neutrons in coincidence often suffers from low efficiencies and the need to reject the cross talk events. Therefore it is important to develop specially designed multineutron detection array to achieve high efficiency as well as good cross talk rejection performance using kinematics conditions. For data analysis, it was found that two neutron correlation function generated by iteration method is a good expression of the correlation situation, from which the RMS radii of the two neutron distribution may be deduced.
核反应截面替代测量方法介绍
韩金华, 张国辉
2012, 29(4): 327-335. doi: 10.11804/NuclPhysRev.29.04.327
摘要:
核反应截面替代测量方法是一种间接测定核反应截面的方法, 这种方法对于测定不稳定核的反应截面具有重要的意义。 详细介绍了替代方法的理论基础、 影响其精确性的重要因素, 以及基于该方法的3种变型方法: 外替代比率方法(ESRM)、 内替代比率方法(ISRM)和混合替代比率方法(HSRM)。 阐明了每一种方法的基本原理, 给出了相关的实验验证, 并且对每一种方法的优缺点进行了分析。发现在每一种方法中, 所求反应与替代反应之间的自旋宇称不匹配始终是不可消除的一个影响因素。 但是经过实验验证, 替代方法(包括3种变型方法)也可以达到较高的精确度, 因而在不能够直接测定核反应截面的情况下, 该方法不失为一种很好的间接测量方法。The surrogate nuclear reaction approach plays an important role in the determination of nuclear reaction cross sections that are difficult to be measured directly. In this paper, we investigate its basis, factors affecting its accuracy, and its three variants: the external surrogate ratio method (ESRM), the internal surrogate ratio method (ISRM) and the hybrid surrogate ratio method (HSRM). Each method was described, and their applications or experimental tests were given, from which we could see their respective advantages and disadvantages. And it is found that the spinparity mismatch, or the (weak) WeisskopfEwing limit equivalently, is an inherent limitation of the approach. It is also seen that the surrogate approach can reach a high accuracy, so it is a good indirect approach when the nuclear reaction cross sections are unavailable to be measured directly.
pp和pÞ碰撞中J/ψ的光生过程(英文)
朱佳庆, 何俊伟, 李云德
2012, 29(4): 336-343. doi: 10.11804/NuclPhysRev.29.04.336
摘要:
计算了pp和pÞ碰撞中J/ψ的领头阶光生过程的产额。运用非相对论量子色动力学回顾了重夸克偶素产生的色单态机制与色八重态机制,并将它们分别用于处理直接光子过程和分解光子过程。通过与J/ψ产生的领头阶结果的对比可以看出,光生过程对J/ψ产额的修正在大横动量区域变得明显。The production of J/ψ originating from photoproduction processes in pp and pÞ collisions at leading order is calculated. The color singlet and color octet mechanisms for heavy quarkonium production are reviewed within nonrelativistic QCD, and be used to deal with the direct photon and resolved photon processes respectively. Comparing with the leading order results of J/ψ production, the numerical results show that the modification of photoproduction processes for J/ψ production become obvious at large p-T region.
在具有QCD特征的程函近似和推广的QCD向量介子为主模型中光子-光子的相互作用(英文)
潘继环, 周丽娟, 马维兴
2012, 29(4): 344-352. doi: 10.11804/NuclPhysRev.29.04.344
摘要:
基于推广的QCD向量介子为主的模型(QCD-VMD)和具有QCD特征的程函近似, 研究了光子-光子的相互作用。与通常用费曼盒子图计算光子-光子的相互作用不同, 采用QCD理论揭示了光子-光子的相互作用过程, 认为光子-光子的弹性散射是通过两个散射的光子所涨落成的两个夸克反夸克对之间的强相互作用而进行的。 由于强相互作用的传播子是带色的胶子和胶子的自相互作用的性质, 交换的胶子可以形成无色的胶子球, 无色的张量胶子球(两个雷其化的胶子束缚态)和Odderon(三个雷其化的胶子束缚态), 可以是两个夸克反夸克对之间的作用的媒介子, 这个机制非常不同于其他理论描述, 特别是考虑了由虚胶子(束缚夸克和反夸克形成的涨落介子)的贡献。 计算了总截面σtot, 微分截面dσ/dt, 向前散射振幅实部与虚部的比率ρ和γγ弹性散射的核斜率参数函数β。在实验误差的范围内, 对总截面σtot的理论预言和实验数据是一致的, 但急需dσ/dt,ρ和β的实验数据来检验本理论模型。Based on the generalized QCD vector meson dominance model and the QCD Inspired Eikonalized approximation, γγ interaction has been studied in this paper. Unlike the usual calculations of the γγ interaction by the Feynman box diagram technique, we explore the process by QCD theory in which γγ elastic scattering proceeds through a strong interaction between two pairs of quarkantiquark fluctuated by two scattering photons. Due to the fact that the mediator of strong interaction is colorful gluon,and gluon has a property of self-interaction which can bind exchanging gluons together to form glueballs. The colorless tensor glueball (two Reggeized gluon bound state) and Odderon (three Reggeized gluon bound state) could be the mediators of the interaction between the two quarkantiquark pairs. This mechanism is very different from the other theoretical descriptions of the process. In particular, the contributions from virtual gluon, bound quarkantiquark to form a fluctuated meson, are taken into account. We calculate the total cross section σtot, the differential cross section dσ/dt, the ratio of the real part to the imaginary part of the forward scattering amplitude ρ, and the nuclear slope parameter function β of γγ elastic scattering. Our theoretical predictions for σtot are consistent with the experimental data within error bars of the data. The data for dσ/dt, ρ and β are urgently needed to test our theoretical model.
膨胀QGP的热双轻子产生(英文)
傅永平, 杨光弟, 郗勤
2012, 29(4): 353-357. doi: 10.11804/NuclPhysRev.29.04.353
摘要:
研究了QGP中次级热双轻子的产生。在RHIC能区, 次级热双轻子的产生在低质量范围0.2 GeV<M<0.8 GeV内加强了热双轻子谱。 次级热双轻子产生机制能够较好地解释PHENIX Au-Au 200AGeV碰撞实验的双轻子增强现象。 对于LHC能区的Pb-Pb 5.5ATeV碰撞, 理论计算结果表明, 在低质量区域双轻子增强现象会更加明显, 增强区域在1.0 GeV<M<2.5 GeV范围内。The secondary thermal dileptons produced from the quark-gluon plasma are investigated. The secondary thermal dileptons produced at RHIC energy were concentrated in the low mass region of 0.2 GeV
加速器
强流脉冲束在静电加速管中传输研究及模拟计算
李超龙, 石海泉, 吕建钦
2012, 29(4): 358-363. doi: 10.11804/NuclPhysRev.29.04.358
摘要:
为了研究强流脉冲束流在静电加速管中的传输, 采用矩阵法分析了非强流脉冲束流与强流脉冲束流在静电加速管中的传输矩阵, 编写了束流在静电加速管等元件中传输的计算程序ACCT。 用优化方法实现给定的光学条件, 用迭代方法计算强流脉冲束流的空间电荷效应对束流传输的影响以获得自洽解。 在不同束流流强条件下, 利用ACCT、TRACE-3D和TRANSPORT等程序进行了模拟计算, 并对模拟结果进行了比较分析。 模拟结果表明, 提高加速电压比, 可以增强静电加速管的聚焦能力、 减少束流损失和提高传输效率。To study intense pulsed beam transfer in electrostatic accelerate tube, the matrix method was applied to analyze the transport matrixes in electrostatic accelerate tube of non-intense pulsed beam and intense pulsed beam, and a computer code was written for the intense pulsed beam transporting in electrostatic accelerate tube. Optimization techniques were used to attain the given optical conditions and iteration procedures were adopted to compute intense pulsed beam for obtaining self-consistent solutions in this computer code. The calculations were carried out by using ACCT, TRACE-3D and TRANSPORT for different beam currents, respectively. The simulation results show that improvement of the accelerating voltage ratio can enhance focusing power of electrostatic accelerate tube, reduce beam loss and increase the transferring efficiency.
SECRAL控制系统软件设计(英文)
周文雄, 王彦瑜, 周德泰, 张建川, 林福元, 冯玉成, 卢旺
2012, 29(4): 364-370. doi: 10.11804/NuclPhysRev.29.04.364
摘要:
为提高兰州重离子加速器HIRFL的超导离子源SECRAL的控制效率,2011年7月份设计和建立了一个远程控制系统。 作为该系统的一个部分, 这个控制软件使用C++来实现。 它能够控制和监视SECRAL的所有设备,大概110个参数。而且,为了控制不同种类的设备,该软件使用了很多不同的控制协议。 除此以外, 在SECRAL的运行过程中, 若有误操作发生, 便有可能导致超导离子源的失超。为了不发生这样的误操作, 在硬件和软件中都增加了报警和连锁保护功能。该软件能够在1 s内进行报警和连锁保护。同时,为了以后的分析,该软件能够将从控制器上每隔1 s获取的数据存储到硬盘上。To improve the control efficiency of Superconducting Electron Cyclotron Resonance Ion source (SECRAL) for Heavy Ion Research Facility in Lanzhou(HIRFL), a remote control system was designed and set up in July 2011. The control software package, as a part of the system, was implemented by Visual C++, which is able to control and monitor all of the equipments for the SECRAL system with about 110 parameters. And many kinds of control protocols were used for controlling different types of equipments in this software. Moreover, in order to prevent the misoperation which may cause the quench of the superconducting magnet, alarm and interlockprotection functions are added to the software and hardware too. If some errors occur during the running of SECARL, those functions should take effect within 1 s. Simultaneously, the data acquired from the equipments can be stored in disk every 1 s for following analysis.
核技术
离子微束技术及其多学科应用
杜广华
2012, 29(4): 371-378. doi: 10.11804/NuclPhysRev.29.04.371
摘要:
通过微米孔准直或电磁聚焦技术可将加速器产生的MeV离子束形成微米尺寸的离子束斑(微束), 从而用来研究固体和生物样品的微米空间分辨的材料信息和辐照响应。 结合MeV离子微束的发展历史综述了微束技术和跨学科应用, 包括利用微束开展具有空间分辨的离子束分析、 单粒子效应、 微纳加工和细胞辐射响应等研究。 介绍了中国科学院近代物理研究所的高能重离子微束辐照装置, 该装置成功地将总能量为1 GeV的C离子在大气中聚焦为1 μm×2 μm的微米束斑。

Beam of MeV ions from particle accelerators can be confined by collimators or focused by electrical/magnetic quadruples into micrometer size, and this microbeam can be used to obtain spatial information or radiation effect in solids and biological samples. This paper reviews the technical developments and the multidisciplinary applications of microbeam, including ion beam analysis, single event effect in semiconductor devices, proton beam writing and cellular response to targeted particle irradiations. Finally, the high energy heavy ion microbeam facility at the Institute of Modern Physics of Chinese Academy of Sciences is introduced, which has successfully focused 1 GeV Carbon ions into a beam spot of 1 μm×2 μm in air.
三级GEM探测器的增益一致性实验研究
董丽媛, 祁辉荣, 李玉红, 吕新宇, 欧阳群, 陈元柏
2012, 29(4): 379-383. doi: 10.11804/NuclPhysRev.29.04.379
摘要:
随着二维GEM气体探测器在X射线成像探测领域的应用, 三级GEM的探测结构和电场均匀性带来的增益一致性修正问题, 成为需要深入研究的课题内容。 介绍了有效探测面积为100 mm×100 mm的三级倍增GEM探测器, 共采用100路阵列读出, 每路读出Pad面积为9.5 mm×9.5 mm。 测量了55Fe放射源准直入射的全能峰谱。 实验表明, 随着时间的变化, 探测器的增益基本上保持稳定; 随气流的增大, 增益由变化明显到变化不大。 GEM探测器各个阵列单元的增益一致性良好(>80%); 能量分辨率在0.18~0.22之间, 运用最小二乘法拟合给出增益一致性的修正结果, 修正后相差约0.1, 为GEM气体探测器的增益一致性修正方法提供了参考方案。 With the application of the twodimensional GEM gaseous detector in X ray imaging, the correction method of gain uniformity caused by tripleGEM avalanche structures and electric field uniformity should be studied. The paper reported the study of the tripleGEM detector with effective area 100 mm×100 mm used the Pad’s size of 9.5 mm×9.5 mm. In the test, 100 readout channels were designed. Results showed that gain remained stable over time; as air flow increases, gain from increases obviously to changes very little. Particularly, triple GEM’s gain uniformity was very good (more than 80%) and the range of energy resolution was from 0.18 to 0.22. To improve gain consistency of results, the difference value revised was obtained to be about 0.1 by the least square method. It provided a better method to improve gain uniformity of GEM detector.
水下干式储存取样的乏燃料破损检测技术
苏容波, 夏文友, 吴中义, 涂俊
2012, 29(4): 384-387. doi: 10.11804/NuclPhysRev.29.04.384
摘要:
介绍了通用的乏燃料破损检测方法, 分析了已有的乏燃料破损检测技术存在的缺陷, 针对其缺陷以及根据自身的需求设计了新的乏燃料破损检测工艺与工作流程, 并介绍了检测样品的测量及样品与乏燃料包壳状态的判断依据。 实际应用结果表明: 该技术可以在水下实现一次对一批乏燃料进行逐个取样, 每个样品对应一盒确定的乏燃料, 检测效率高; 该采样系统对乏燃料的操作在水下进行, 现场辐射防护容易满足。 In the present article, several previous methods for damage detection of spent fuel assembly, as well as the existing limitations of these methods are reviewed. A new sampling system, including the working procedure and operating schedule, was developed in order to meet the practical demands and to solve the disadvantages mentioned. The measurement method for sampling and the criterion practical results provided evidence that, in this system, each operating process could successfully achieve a sample for a single certain spent fuel assembly with high precision. Moreover, all the operations were carried out under water, which made the radiation protection much easier.
基于MCNP多群伴随计算与正算分析的比较
王超, 邓力
2012, 29(4): 388-394. doi: 10.11804/NuclPhysRev.29.04.388
摘要:
为研究MCNP伴随计算与正算的一致性及其差异, 利用3个模型作为算例进行比较计算, 并对其结果进行分析。 模型I的计算结果表明, 伴随计算与正算结果基本一致, 而且伴随计算的FOM值大约为正算的2倍左右; 模型Ⅱ研究了伴随计算对不同材料的适用性, 结果显示, 在散射截面较大的情况下, 伴随计算的通量与正算通量的差异在20%左右, 而且正算的FOM值比伴随计算的大; 模型Ⅲ研究了伴随在产生重要函数中的应用, 并与权窗进行比较, 经分析, 虽然它们产生重要函数的机制不同, 但所得函数的性质基本相同, 而且使用伴随重要函数的FOM值大约是使用权窗的1.5倍。 In order to investigate the agreement and difference between adjoint and forward calculations with Monte Carlo method, three models have been simulated, and the calculated results are compared and analyzed. First, the comparison shows that the calculated results of the adjoint calculation are basically consistent with those of the forward calculation in modelⅠ. The FOM value of adjoint calculation is about two times of the value of forward calculation. Second, it is investigated with modelⅡ that the applicability of the adjoint calculation for the different materials, and the results show that the difference is about 20% for the case of strong scattering between the adjoint calculation and forward calculation. The FOM value of the forward calculation is larger than that of the adjoint calculation. Finally, the important function is generated by the adjoint calculation in model Ⅲ, and the results are compared with ones of the weight window game. Although their important functions are produced by different mechanisms, the values of functions are in agreement with each other, and the FOM value of ajoint calculation is about 1.5 times of the value from the weight windows.
电子束辐照改性铀吸附材料中官能团的性能研究
赵梁, 殷小杰, 秦芝
2012, 29(4): 395-398. doi: 10.11804/NuclPhysRev.29.04.395
摘要:
探讨了带有肟胺基官能团材料的制备、 吸附铀的机理及其对盐湖卤水中铀的吸附效果。 利用电子束辐照法制备肟胺化无纺布, 红外光谱显示材料中含有肟胺基存在, 表明肟胺基成功的接枝在无纺布基体上。 研究了铀溶液的初始pH、 吸附时间和固液比等因素对铀吸附效果的影响, 吸附过程中络合反应为控速步骤。 肟胺化纤维和肟胺化无纺布对盐湖卤水样品具有较高的吸附效率, 可以作为盐湖提铀的备选材料。 Amidoximed fiber and fabric were synthesized with the purpose of adsorbing U in salt lake and the adsorption mechanism was discussed. IR indicated that amidoxime was graft to the fabric which was irradiated by electron beam. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, shaking time on uranium sorption efficiency. The sorption of uranium on amidoxime was dependent on the pH value of the solution, and the optimal pH was 4.0. Uranyl was taken out from solution in the form of complex with amidoxime. Uranium recovery efficiency from salt lake was more than 50% with amidoximed fiber and fabric which can be used as uranium extraction material.
交叉学科
电离辐射引起的线粒体DNA损伤及突变研究进展
周鑫, 王振华, 张 红
2012, 29(4): 399-405. doi: 10.11804/NuclPhysRev.29.04.399
摘要:
指出了线粒体DNA损伤及突变研究与核DNA相关研究的区别,并总结了国内外关于电离辐射引起线粒体DNA损伤突变的研究进展。 针对放射生物学中线粒体学方面研究还有待进一步加强的现状, 中国科学院近代物理研究所的研究人员在方法学上建立起了real-time PCR和long PCR等手段对线粒体DNA损伤及突变进行定量检测, 并以此为基础, 对电离辐射引起的线粒体功能变化进行了较为深入的研究。总结了线粒体DNA损伤及突变研究对阐明电离辐射引起的生物学效应所具有的贡献, 提出未来在放射生物学中以远后效应, 能量代谢为主的线粒体学研究方向。 Current advance in ionizing radiationinduced mitochondrial DNA damage and mutations is reviewed, in addition with the essential differences between mtDNA and nDNA damage and mutations. To extent the knowledge about radiation induced mitochondrial alterations, the researchers in Institute of Modern Physics, Chinese Academy of Sciences developed some technics such as realtime PCR, longPCR for accurate quantification of radiation induced damage and mutations, and indepth investigation about the functional changes of mitochondria based on mtDNA damage and mutations were also carried out. In conclusion, the important role of mitochondrial study in radiation biology is underlined, and further study on mitochondrial study associated with late effect and metabolism changes in radiation biology is pointed out.
面向HIRFL-CSR主动式点扫描技术的剂量标定方法研究(英文)
戴中颖, 李强, 刘新国, 叶飞
2012, 29(4): 406-413. doi: 10.11804/NuclPhysRev.29.04.406
摘要:
基于HIRFL-CSR肿瘤重离子治疗终端主动式束流配送系统发展了面向三维点扫描适形调强治疗技术的在线监测器点扫描剂量标定方法。为了验证点扫描剂量标定方法的稳定性和可靠性,利用HIRFL-CSR提供的C离子束考察了在线监测器剂量标定因子的能量依赖以及不同扫描步长的影响。结果表明:在线监测器剂量标定因子存在能量依赖;不同扫描步长对剂量标定因子影响较小(偏差小于1.8%)。证明了点扫描剂量标定方法的稳定性和可靠性。鉴于在三维点扫描适形调强治疗技术中影响在线监测器点扫描剂量标定因子的因素较多,建议今后续继续研究点扫描剂量标定因子影响因素,修正和完善点扫描剂量标定方法。As an important step of the application of spot scanning technique to heavy ion therapy, an experimental calibration procedure of online beam monitors based on standard of absorbed dose to water has recently been developed for scanned pencillike carbon ion beam in the deep seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL). In this work, creating homogeneous irradiation field with steerable spot beam was tested using a 207 MeV/u penci like carbon ion beam. Then the verification of energy dependence of the calibration factors (CFs) and the influence of scanning step on the CF were also shown, as a part of the heavy ion clinic dosimetry researches. The results showd that the monitor CF presented energy dependence and performed stable response with deviation of 1.8% for the variation of scan steps. In this paper, the suitability and effectiveness of beam monitor calibration procedure for dynamic particle beam delivery were verified and the further research points to improve the calibration procedure were suggested.
Co+离子注入单晶TiO2铁磁性来源与微结构研究
钟火平, 李公平, 许楠楠, 李天晶, 龚恒风, 陈景升
2012, 29(4): 414-418. doi: 10.11804/NuclPhysRev.29.04.414
摘要:
在室温下,将能量为80 keV, 注量分别为1×1016和1×1017ions/cm2的Co+离子注入到10 mm×10 mm×0.5 mm的单晶TiO2样品。在氮气保护下, Co+离子注量为1×1017 ions/cm2时样品在温度为900 ℃的条件下退火30 min。 利用超导量子干涉仪 (SQUID)测量样品磁性, 并应用X射线衍射(XRD)和扩展边X射线吸收精细结构谱(EXAFS)研究Co+离子注入后样品的微观结构。 样品磁性测量结果表明:Co+离子注入后的样品具有室温铁磁性, 并且其饱和磁化强度的大小与Co+离子注量及样品是否经退火处理有关。 EXAFS研究表明: Co元素在Co+离子注量为1×1017ions/cm2的样品中主要以团簇形式存在;样品经退火处理后, Co团簇消失, 并发现Co部分替代TiO2单晶中的Ti。Co+离子注入后, 在样品中形成Co团簇与否受离子注量的影响。 阐述了样品微观结构与铁磁性来源之间的关系。 At room temperature, monocrystalline plates of rutile (TiO2) were implanted with cobalt ions of an energy of 80 keV to fluences of 1×1016 and 1×1017 ions/cm2 respectively . The 1×1017 ions/cm2 Co implanted samples were annealed in nitrogen at 900 ℃ for 30 min. The magnetic properties of Co implanted samples were measured with a superconducting quantum interference device magnetometer (SQUID) at room temperature. Furthermore, the X ray diffraction (XRD) and Extended X ray Absorption Fine Structure (EXAFS) were applied to investigate the structural and compositional properties of Co implanted samples. The magnetic measurements of samples showed that the size of the saturation magnetization of the Co implanted samples were related to the fluence of ions, and the saturation magnetization of the sample after annealed decreased significantly. The EXAFS measurements showed the presence of cobalt metallic clusters in the sample implanted to ion fluence of 1×1017 ions/cm2. The Co metallic clusters disappeared in the sample after annealed, and resulted in the oxidized Co, which is presumed to substitute into the Ti site. The formation of Co clusters or not was determined by the ion fluence. The relation between ferromagnetic behavior and microscopic structure of the Co implanted samples is discussed.
Geant4模拟δ电子对单粒子翻转的影响
刘建德, 孙友梅, 刘杰, 侯明东, 张战刚, 段敬来, 姚会军, 翟鹏飞
2012, 29(4): 419-424. doi: 10.11804/NuclPhysRev.29.04.419
摘要:
利用Geant4蒙特卡洛程序包, 基于RPP (Rectangular ParallelePiped Volume)模型构建SRAM器件单元的灵敏体积, 编写了重离子在器件材料中的输运程序和单粒子翻转截面计算方法, 得到了简化器件结构的单粒子翻转截面σ与线性能量转移LET的关系曲线, 计算得到的翻转LET阈值和饱和截面与实验结果基本一致。模拟获得了LET值为99.69 MeV/(cm-2·mg)的Bi离子及LET值为69 MeV/(cm-2·mg)的Bi离子和Xe离子在器件材料中产生的δ电子分布图像,讨论了δ电子分布对翻转截面的影响。 计算了灵敏体积中能量沉积与δ电子分布的关系,认为δ电子分布对单粒子效应的影响随着器件的特征尺寸减小将更加严重。In this paper, the sensitive volume of SRAMs was constructed based on RPP(Rectangular ParallelePiped Volume) model using the Monte-Carlo code Geant4. The interactions of heavy ion with materials and the SEU(Single Event Upset) cross section calculation method were presented in the program. The SEU crosssection curves with the linear energy deposition ware obtained. The SEU threshold value and saturation cross section were consistent with the testing data with heavy ions beam. The δ electrons distribution were different in the device material, which were generated by Bi ion with LETs of 99.67 MeV/(cm2·mg) and Bi ion, Xe ion with LETs of 69 MeV/(cm-2·mg). These results indicate δ electrons distribution impacts on the SEU cross section. According to the relation of energy deposition in the sensitive volume, the δ electrons distribution have more and more important effect on the Single Event Effect with reducing the feature size of semiconductor devices.
平行玻璃板对105 keV Ar7+离子的导向效应
刘俊亮, 薛迎利, 于得洋, 武晔虹, 陈婧, 杜凡, 张明武, 阮芳芳, 王伟, 李锦钰, 王平志, 康龙, 蔡晓红
2012, 29(4): 425-429. doi: 10.11804/NuclPhysRev.29.04.425
摘要:
研究了平行玻璃板对高流强(约80 nA)105 keV Ar7+离子的导向效应, 利用一维位置灵敏探测器测量了不同倾斜角下出射离子的强度及角分布。 实验结果表明, 平行玻璃板对Ar7+离子有导向作用。 与离子在微孔膜中的导向效应不同, 从平行玻璃板出射的Ar离子角分布的FWHM随着倾斜角的改变而改变, 并且出射离子角分布最大值处对应的观察角不等于倾斜角。 The transmission of 105 keV Ar7+ ions with high incident current (about 80 nA) through the gap formed by a paired parallel glass plates was investigated. The intensity and angular distribution of the transmitted ions for various tilt angles were measured using a onedimensional position sensitive detector. The results indicate the existence of a guiding effect when Ar7+ ions pass through the gap, but it is different from that for ions passing through nonacapillaries. We found a measurable dependence of the full width at half maximum (FWHM) of the transmitted ions as a function of the tilt angle. In addition, when the gap was tilted with respect to the direction of the incident beam, the observation angle related to the center of the transmitted ions profile was not equal to the tilt angle.
核能与核数据
高温度ACE格式连续能量点截面数据产生程序SIGACE的验证
李志峰, 于涛, 谢金森, 秦勉
2012, 29(4): 430-435. doi: 10.11804/NuclPhysRev.29.04.430
摘要:
以最新发布的ENDF/BVII.1评价库为基础, 使用SIGACE程序将低温ACE格式中子截面文件加工成较高温度的ACE格式文件, 生成了一个与温度相关的中子截面文档。 为校核截面数据, 选取ICT、 标准CANDU组件燃料温度反应性系数、 LWR栅格多普勒系数以及SEFOR基准题对SIGACE加工的核数据进行了验证。 基准题计算结果均与参考值符合较好, 表明SIGACE生成的高温度ACE格式截面数据可用于反应堆相关中子学参数的计算。 Based on the recently released ENDF/B-VII.1 library, high temperature neutron cross section files are generated through SIGACE code using low temperature ACE format files. To verify the processed ACE file of SIGACE, benchmark calculations are performed in this paper. The calculated results of selected ICT, standard CANDU assembly, LWR Doppler coefficient and SEFOR benchmarks are well conformed with reference value, which indicates that high temperature ACE files processed by SIGACE can be used in related neutronics calculations.