2013年 第30卷 第4期
在X 射线暴高温高密度的环境中，18Ne( α, p)21Na 很可能是由热CNO 循环突破到rp 过程的一个重要反应。到目前为止，人们测得的反应率还存在很大的不确定性。实验中用CRIB(CNS RadioactiveIon Beam separator) 提供的21Na 放射性束轰击8.8 mg/cm2 的聚乙烯厚靶，利用放置在θlab = 14°，0°，14° 处的3 套硅条探测器望远镜阵列对反冲轻粒子进行鉴别和测量，测得在一段能区(Ex = 5:5 9:2MeV) 内21Na(p, p)21Na 的激发函数。通过对21Na(p, p) 共振弹性散射截面进行R矩阵拟合，得到了22Mg共振能级的自旋宇称以及质子宽度等信息，从而为计算18Ne( α,, p)21Na 反应率提供了实验参数。The 18Ne(α ,p)21Na reaction is thought to be one of the key breakout reaction from the hot CNO cycle to the rp-process in X-ray bursts. Over stellartemperatures achieved in XRBs, this rate has not been sufficiently determined.The experiment was performed using CRIB (CNS Radioactive Ion Beam separator) at the Center for Nuclear Study (CNS) of the University of Tokyo. An 89 MeV 21Na radioactive ion beam was produced and bombarded an 8.8 mg/cm2 thick polyethylene target. The recoiled light particles were detected with three Micron silicon ΔE-E telescopes centered at angles of θlab = 0°; +14° and 14°with respect to the beam direction, respectively. The 21Na+p elastic-scattering excitation functions were reconstructed with a thick-target method over energies Ex = 5:5 9:2 MeV. The resonance parameters have been determined through an R-matrix analysis，which will be used to evaluate the 18Ne( α, p)21Na reaction rate.
在双核模型的理论框架下系统研究了超重元素Z = 116 ~121 的蒸发剩余截面，计算过程中核子扩散由主方程描述，同时考虑了全熔合与准裂变的竞争。计算基本再现了利用热熔合反应48Ca+245Cm，48Ca+249Cf 和48Ca+249Bk 产生116~118 号同位素的合成截面。同样，分别以249Bk，249Cf 和243Am 为靶，以48Ca，50Ti 和58Fe 为炮弹，计算了Z = 119~ 121 号同位素的生成截面。结果表明，这些超重核的生成截面随着质子数的增大进一步变小。例如，利用58Fe+243Am 反应合成121 号同位素的最大蒸发剩余截面仅在fb 量级。基于对选择的几个反应系统的系统分析，发现双核系统在熔合蒸发过程中偶Z 奇N 和奇Z 偶N 复合核分别有强的3n 和4n 蒸发道。The production cross sections of superheavy elements with Z = 116~121 have been investigated systematically within the dinuclear system (DNS) concept, where the master equation is solved numerically to obtain the fusion probability. The competition between complete fusion and quasifission, which can strongly affect the cross section of the compound nucleus formation, is taken into account. The evaporation residue cross sections ER calculated for the hot fusion actinide-based reactions (48Ca+245Cm, 48Ca+249Cf and 48Ca+249Bk) are basically in agreement with the known experimental data within one order of magnitude. Similar calculations for the synthesis of superheavy elements up to Z = 121 are performed using the available 249Bk, 249Cf and 243Am as targets and 48Ca, 50Ti and 58Fe as projectiles. Their production cross sections are relatively small,especially for the 58Fe+243Am→301121 reaction. A systematic analysis indicates that the 3n and 4n channels
are respectively the most favorable fusion-evaporation channels in the synthesis of even- and odd-Z superheavy elements.
外推近似方法在原子核壳模型上取得了一些成功，然而人们对于其原理知道得比较少。这里主要研究并讨论了随机两体系综和高斯正交系综最小本征值。利用截断空间的外推解释了高斯正交系综下的外推公式以及随机两体系综下本征值外推收敛的鲁棒性，即对于壳模型有效相互作用而言，用外推法预言最低本征值收敛性很好。Although the extrapolation method of diagonalizing the nuclear shell model Hamiltonian is successful, its foundation has not yet been understand very well. In this paper, we study this approach by using random matrices with the focus on gaussian ensemble and two-body random ensemble. We derive the formula of the extrapolation method of diagonalizing the matrices of Gaussian orthogonal ensemble, and discuss the robustness of the extrapolation property by two-body random ensemble. We point out that the extrapolation method of diagonalizing the shell model Hamiltonian works better with the realistic interaction than other interactions.
在中子核反应研究中，尤其是在利用活化法进行中子核反应截面测量研究时，需要准确测量样品辐照的中子注量。监督反应标准截面法简便可行，在一些核反应截面测量研究中经常用来定量样品辐照的中子注量。在利用监督片核反应剩余核的放射性活度计算平均中子注量率时，中子注量率波动修正因子是一个很重要的参数。对中子注量率波动修正因子进行了详细阐述，通过理论推导给出了中子注量率波动修正因子的定义，从实际应用出发讨论了中子注量率波动修正因子的使用条件和监督反应的选择原则。Incident neutron flux has to be measured accurately in the neutron reaction study especially in the neutron reaction cross-section measurement with activation method. Average neutron flux in the irradiated sample is usually determined by the monitor reaction with reference cross-section values. However, the average incident neutron flux, based on the radioactivity of the residual nuclei produced in the monitor reaction, is dependent upon the neutron flux fluctuation. In the procedure of the average neutron flux calculation, the correction factor for the neutron flux fluctuation plays a key role. In this paper, definition of the neutron flux fluctuation correction factor is inferred heoretically. The selection principles of the monitor reaction and the utilization of the correction factor have been discussed.
Manohar 和Georgi 提出了一种基于QCD的有效组份夸克模型(MG 模型)，用于解释唯象夸克模型成功的原因。最近Weinberg 指出，该模型在大Nc (夸克颜色数目) 极限下是可重整化的。从QCD 配分泛函出发，对MG模型的有效理论进行了分析，并通过将胶子-夸克耦合做唯象的Skyrme 作用近似，提出了核子的一种有效手征夸克模型，它包括了夸克和pion 云以及pion 云的非线性自耦合。利用有效手征夸克模型计算的核子静态性质的结果与实验值相符很好。Manohar-Georgi proposed an effective constituent quark model(MG model) based on QCD, explaining the success of quark models. Recently, Weinberg has shown that the MG model is renormalizable in the large Nc limit of the color number. In this paper, we present a functional QCD analysis of the MG model and propose an effective chiral quark model of the nucleons, which includes the nonlinear interaction between quark-pions and pions among themselves by
approximating the quark-gluon coupling with the phenomenological Skyrme interaction. The calculation for the nucleon static properties is in good agreement with experimental data.
为了进一步探究高电荷态电子回旋共振(ECR) 离子源引出束流品质和横向相空间耦合情况，根据中国科学院近代物理研究所高电荷态离子源引出束流发射度测量需求，针对束流流强为1 eμA8764;1 emA，能量范围为108764;35 keV/q 的直流或脉冲高电荷态重离子束，设计了一台实时四维Pepper-pot 发射度测量仪。该Pepper-pot 型发射度测量仪具有响应时间快和工作范围宽等特点。针对强流重离子束诊断的特点，在结构与材料选择上做了设计与优化，并对获得图像的处理方法提出了具体的解决办法。For the purpose of on-line beam quality diagnostics and transverse emittance coupling investigation of the ion beams delivered by an Electron Cyclotron Resonance (ECR) ion source, a real-time 4D Pepper Pot type emittance scanner is under development at IMP(Institute of Moden Physics, Chinese Academy of Sciences). The high charge state ECR ion source at IMP could produce CW or pulsed heavy ion beam intensities in the range of 1 eμA8764;1 emA with the kinetic energy of 108764;35 keV/q, which needs the design of the Pepper Pot scanner to be optimized accordingly. The Pepper Pot scanner has many features, such as very short response time and wide dynamic working range that the device could be applied. Since intense heavy ion beam bombardment is expected for this device, the structure and the material selection for the device is specially considered during the design, and a feasible solution to analyze the pictures acquired after the data acquisition is also made.
RFQ (射频四极透镜) 是直线加速器中最重要的前级聚焦加速结构，其工作模式下束流孔中的电
场四极对称性是保证束流品质及加速效率的关键。为了解决其各自存在的工作模式下四极场的不对称问题，分别对四杆型RFQ 和四翼型RFQ 的结构和模式谐振特性做了研究。针对四翼型RFQ，模拟显示双端口对称耦合的方式从抵消二极模式和提高结构对称性两方面来达到削弱工作模式下的场分布中二极量的目的，对一个1 m段四翼RFQ 模型腔的测量证实了双端口对称耦合抵消腔内二极模式的有效性；针对四杆型RFQ 的二极场，以SSC-Linac 项目的RFQ 为原型，利用三维模拟计算软件CST-MWS 进行模拟，通过改进支撑板的结构并调整参数，完全地消除了工作模式下的极间二极场，且理论上此种改进方法对支撑板结构的四杆型RFQ 均有效。Radio Frequency Quadruple(RFQ) is the most important front-end acceleration structure in linear accelerators.It can focus and accelerate beam in longitudinal and transversal direction, simultaneously. Symmetric of electric field in acceleration aperture is very important for the beam dynamics. To an idea RFQ, there is only quadruple electric field in the acceleration aperture. The dipole field in aperture is harmful and need be as small as possible. The methods to reduce it are studied in a four-rod RFQ and a four-vane RFQ in the article ndependently. To a four-vane RFQ, the symmetrical double-port couplers are employed to counteract the neighboring dipole modes. The availability is confirmed by the simulation with the 3-D Finite Element tool, CST-MWS. And it is also observed by measuring a model-cavity with a symmetrical double-port couplers. To a four-rod RFQ, a new structure of stems is proposed to reduce the dipole mode.
Taking the RFQ for the SSC-LINAC project as example, the dipole mode contributions to the electric filed is completely eliminated by selecting stem’s parameters carefully. It is confirmed by the simulation of CST-MWS. heoretically, this method is independent with the frequency of an RFQ and serves for all RFQs with 4-rod or 4-wane structure.
介绍了兰州重离子研究装置(HIRFL) 主回旋加速器(SSC) 高频系统高频电压的相位稳定与幅度
稳定系统，重点介绍了设备的组成和稳定环路设计以及正交变换与稳定环路滤波器的设计方法。通过在SSC 腔体上进行的长期的现场测试，得到了调制抑制度与长期稳定度的测试方法，并对结果进行了分析。其中，设备的长期相位稳定度达到0:014°，长期幅度稳定度达到1.29x10-4，远高于改造前的指标。The phase and amplitude stabilization system of high-frequency voltage on the main cyclotron SSC of Heavy Ion Research Facility in Lanzhou (HIRFL) is introduced. The system composition, negative feedback loop design and other important aspects about the development of the system are particularly presented in this paper. Designing method of digital PLL orthogonal transformation and loop filter of phase and amplitude stabilization are introduced in detail. Control systems of SSC have been tested through a long-term stability experiments, the test method of the parasitic modulation suppression and stabilization in long term is proposed. According to the analyzing data, it shows that phase control accuracy in long term is within 0:014° and the amplitude deviation in long term is lower than 1.29x10-4. Compared with the traditional system, its capability and target is much better.
采用基于蒙特卡罗方法的Geant4 软件设计了由40 个载Gd 液闪探测器组成的多单元4π 立体角探测系统。该探测系统与置于其几何中心的裂变室构成了一个研究平台，该平台主要用于可裂变核(n, 2n)反应截面的测量工作。首先对该系统的物理模型进行了初步检验，然后计算并分析了该探测系统的一些基本性能。通过计算发现，系统空腔半径的变化对中子探测效率的影响十分有限；而探测效率随探测器的厚度增加先是迅速增大，然后逐渐趋于平缓；计算还表明，Gd 同位素俘获中子后发射的级联γ 射线的能量主要沉积在局部几个相邻的探测器中。基于以上计算，初步确定了系统的厚度以及空腔半径的大小，并对下一步将要开展的工作做了初步规划。A gadolinium-loaded neutron detection system with 40 liquid scintillators is designed and simulated by using Geant4 Package based on Monte Carlo method. This system with a fission chamber placed in its center is mainly used for the cross section measurement of (n, 2n) reaction of fissile nuclides. We firstly test the physics model, and then calculate and analyze some basic performance of this system. According to the calculation, the detecting efficiency is not sensitive to the inner radius of the detecting system. The efficiency increase with the system thickness at limited thickness value . The calculated results also indicate that the energy of the γ rays emitted from Gd isotope after capturing a thermal neutron is mainly deposited in a few adjacent detectors. Based on above calculations, the thickness and inradius of this detecting system have been preliminarily determined.
与传统的地雷探测技术相比，热中子分析(Thermal Neutron Analysis，简称TNA) 探雷技术具有准确率高、虚警率低和对环境适应性强的特点，但探测速度较慢，制约了其广泛应用。为了提高地雷位置处的慢热中子通量，缩短探测时间，提出了一种基于252Cf 的中子源慢化装置设计构型，主要包含中子慢化层、中子反射层、本底 屏蔽层和侧向中子吸收层4 个部分。采用数值模拟的方法比较了4种常用中子慢化(反射) 材料的性能，优选高密度聚乙烯作为慢化材料，石墨作为反射材料。同时，为了满足辐射安全要求，对屏蔽材料的结构进行了优化计算。按照设计构型搭建了TNA 探雷实验平台。在104 n/s 中子源强下优化了慢化层和反射层的厚度，测试了装置慢化效能，在107 n/s 中子源强下评估了装置辐射安全性能。结果表明，采用该装置可使地雷位置处的慢热中子通量提升11 倍以上，并能有效保障辐射安全。Compared with the traditional landmine detection methods, Thermal Neutron Analysis (TNA) landmine detection has the advantages of high accuracy, low false alarm rate and strong adaptability to the environmental change.But the long detection time restrict the wide application of this technology. In order to shorten the detection time, one possible design of neutron moderation device based on 252Cf neutron source is proposed to enhance the moderated neutron
flux in mine position. The device consists of four parts, the neutron moderator, the neutron reflector, the background shield and the useless neutron absorbing layer. Then, the performance of four widely used materials in neutronics was compared with MCNP5 code, and HDPE was chosen as the neutron moderator material, graphite as the neutron reflector material. The thickness of the useless neutron absorbing layer was optimized at the same time. Finally, an experimental platform of 252Cf neutron moderation device was assembled on the basis of simulation results, and a series of experiments were carried out to optimize the geometric dimensions and evaluate the dose equivalent with two different strengths neutron source, 104 and 107 n/s. The results indicate that this device can effectively enhance the thermal neutron flux at mine position by more than 11 times and ensure the radiation safety.
分析了神经网络方法和bagging 算法在实验高能物理和核物理数据分析中的应用现状。分别对神经网络方法和bagging 算法的基本原理进行了介绍。以蒙特卡罗产生器产生的夸克胶子喷注样本为例，详细讨论了神经网络方法以及bagging 算法与神经网络结合对粒子鉴别中信号和背景区分问题的应用过程，并对结果进行了讨论和分析。实验结果表明，应用bagging 算法后，神经网络能够较大幅度地提高实验高能物理和核物理数据分析中粒子鉴别的精度，以及能够得到较高的信噪比。The paper presents the application of neural network and bagging algorithm in experimental high-energy physics and nuclear physics data analysis. Paper also introduces the basic principles of neural network method and bagging algorithm. We use the data samples of quark-gluon jets, which are generated by Monte Carlo generator, to solve the problem of discriminating signal events and background events by the combined algorithm of bagging algorithm and neural network. Experimental results show that, to apply bagging algorithm, neural networks can greatly improve the accuracy of the identification of particles in the experiments of high energy physics and nuclear physical data analysis,and also obtains a larger SNR (Signal to Noise Ratio).
界、界面的纳米晶、金属和氮化物纳米多层膜，具备良好的自愈合抗辐照能力，从而成为近年来的研究热点。综述了抗辐照纳米多层膜的研究进展，内容包括：材料的设计与制备，各种辐照模拟手段(如中子辐照、离子辐照和多束离子辐照)。重点介绍了离子束辐照模拟反应堆辐照，多层膜在离子束辐照下的行为(如微观结构和机械性能的演变) 及纳米多层膜抗辐照机理。通过对CrN/AlTiN 多层膜的离子辐照，验证了纳米多层膜中界面对缺陷的吸收作用。对纳米多层膜未来研究方向做了展望。Numerous studies show that interface can serve as effective sinks for radiation-induced defects such as interstitials and vacancies. Owning a large number of interfaces, multilayer nanofilms attract a great research interest. In this paper, we review recent research progress on the development of the multilayer nanofilms for the purpose of radiation tolerance. The paper includes following parts: how to design and prepare multilayer nanofilms materials; evaluation with radiation simulation, such as neutron irradiation, ion irradiation and multi-beam ion irradiation; behaviors of multilayer nanofilms under ion beam irradiation, such as microstructure evolution and changes in mechanical properties; theoretical study on the mechanism of radiation tolerance of multilayer nanofilms. Finally, the challenge and future research directions are briefly discussed.
子辐照AlN 晶体薄膜的光学特性变化。辐照后出现了A1(To)，A1(Lo)，E1(To) 和E2 等声子振动吸收模式，并且辐照使其在样品近表面Al—N 等振动模式遭到破坏后悬空的Al— 键很快与空气中的O离子发生结合，形成了Al—O 键。综合分析得出了蓝光发射带是与O 离子相关的VAl-ON-3N 和VAl-2ON-2N两种类型缺陷以及F-型缺陷聚合所致；绿光发射带是由基底中Al 原子产生的价带之间的跃迁所致。AlN thin film irradiated with 100 MeV 238U ions delivered from HIRFL (Heavy Ion Research Facility in Lanzhou) were investigated by Fourier Transform Infrared spectra, Raman spectra and Photoluminescence spectra. Phonon vibration absorption modes including A1(To), A1(Lo), E1(To) and E2 appeared in the irradiated samples. The irradiation made the Al—N bonds broken and the formation of Al—dangling bonds, which combined soon with oxygen atoms existing in air to form Al—O bonds. Blue light emission band are related to the two types of defects of VAl-ON-3N and VAl-2ON-2N and F-type defects aggregation. Green light emission band is due to energy transition among valence band of Al atoms in sapphire substrate.
以金属Zr 的一种嵌入原子形式(EAM) 的势函数为基础，通过引入一个调制函数的办法，在不同
范围内修改了EAM 势函数的对势部分和原子电子密度分布部分，然后采用分子动力学方法计算点缺陷(间隙原子(SIA) 和空位) 形成能和初级离位原子(PKA) 的阈值能，从而探讨这些物理量对势函数的不同部分的敏感程度。计算结果表明：势函数的对势部分长程范围内的形式对缺陷的形成影响较小，其短程范围的形式对SIA 的形成比对空位的形成影响程度更大；对于PKA 的阈值能，其敏感区域来自于势函数的对势部分和原子电子密度分布的短程范围部分，但在不同晶向上的PKA 的阈值能对势函数的敏感程度有所不同。这些研究结果对于在研究Zr 金属的辐照损伤中势函数的选择或构建有指导意义。For the purpose of detecting the sensitive parts of an embedded atom method(EAM) potential which is considered to be used in molecular dynamics simulation of radiation effects of Zirconium, we introduce a modulation function to modify the pairwise potential and the atomic electron-density distribution of the EAM potential. Based on the modified potential function, the formation energies of the self-interstitial atom (SIA) and the vacancy atom are calculated as well as the displacement threshold energy of primary knock-on atom (PKA). The results indicate that the short range part of the pairwise potential has more greater influence on the SIAs formation than the vacancy formation. The defect formation energies are also very sensitive to the behavior of the atomic electron-density function in the range which is close to the cutoff distance. The displacement threshold is sensitive to the short range behaviors of both the airwise potential and the atomic electron-density function, however, the sensitivity is strongly dependent on the crystal-direction.
室温下将130 keV，5x1014 cm-2 B离子和55 keV，1x1016 cm-2 H离子单独或顺次注入到单晶Si中，采用横截面试样透射电子显微镜(XTEM)和慢正电子湮没技术(SPAT) 研究了离子注入引起的微观缺陷的产生及其热演变。XTEM观测结果显示，B 和H 离子顺次注入到单晶Si 可有效减少(111) 取向的H板层缺陷，并促进了(100) 取向的H板层缺陷的择优生长。SPAT 观测结果显示，在顺次注入的样品中，B 离子平均射程处保留了大量的空位型缺陷。以上结果表明，B离子本身及B 离子注入所产生的空位型缺陷对板层缺陷的生长起到了促进作用。Abstract：Cz n-type Si (100) wafers were singly or sequentially implanted at room temperature with 130 keV B ions at a fluence of 5x1014 cm-2 and 55 keV H ions at a fluence of 1x1016 cm-2. The implantation-induced defects were investigated in detail by using cross-sectional transmission electron microscopy (XTEM) and slow positron annihilation technique (SPAT). XTEM results clearly show that sequential implantation of B and H ions into Si could eliminate the (111) platelets and promote growth of (100) platelets during annealing. SPAT
measurements demonstrate that in B and H sequentially implanted and annealed Si, more vacancy-type defects could remain in sample region around the range of B ions. These results indicat e that the promotion effect should
be attributed to the role of both B and B implanted induced vacancy-type defects.
利用兰州重离子研究装置(HIRFL) 提供的12C6+ 离子束辐照菘蓝干种子(辐照剂量为10，35，60，90 和140 Gy，剂量率20 Gy/min)，探讨了重离子束辐照对菘蓝M1代的生物学效应。研究发现，不同剂量的12C6+ 离子束辐照后，菘蓝种子的发芽率、成苗率、株高、根长和根冠比等生物学性状以及对菘蓝中靛玉红和4(3H) 喹唑酮含量均发生了变化，其中株高和根长随辐照剂量的增加而降低；菘蓝叶和根中的4(3H) 喹唑酮和靛玉红的含量随辐照剂量增加呈马鞍形增加关系。这表明：12C6+ 重离子束辐照菘蓝种子具有明显的当代损伤效应, 并可显著提高菘蓝中靛玉红和4(3H) 喹唑酮的含量，其辐照适宜诱变剂量为35 Gy。To investigate the M1 biological effects of heavy ions on Isatis indigotica Fort, its dry seeds were irradiated by 12C6+ beam with the dose of 0, 10, 35, 60, 90 and 140 Gy respectively，at the rate of 20 Gy/min delivered by the Heavy Ion Research Facility in Lanzhou (HIRFL). The results showed that biological characters such as germinating rate, germinating potential, survival rate, plant height, root height and root-shoot ratio were changed after irradiation. Moreover, the plant height and root height decreased in a dos dependent manner. The indirubin and 4(3H) quinazolinone content of Isatis indigotica Fort was improved and exhibited obviously “saddle” trends with irradiation dose increasing.Data suggest that exposure with low-dose 12C6+ to seeds of Isatis indigotica Fort has obvious injury effects at the first generation, and the active ingredient content of Isatis indigotica Fort may be improved by carbon ion beamirradiation. It is concluded that the suitable irradiation dose of mutation breeding is 35 Gy for the seeds of Isatis indigotica Fort.
应用大剂量重离子束12C6+ 对菌株H3001 进行二次辐照选育，对初选获得的高产柠檬酸菌株进行摇瓶发酵试验及10~ 100 L 中试发酵罐试验，采用酸碱中和法测定发酵液中柠檬酸的含量。结果表明：当二次重离子12C6+剂量为857.8 Gy 时，致死率和正突变率达到最大值，分别为94.5% 和8%。通过摇瓶发酵试验，最终获得一株高产柠檬酸菌株hw317，控制该菌株发酵周期为60 h，柠檬酸酸度能达到19.2±0.2%。Heavy 12C6+ ion beams in various high doses were employed to irradiate H3001 strain for screening Aspergillus niger strain for hyper citric acid production. Three high-yield strains were obtained after shaker fermentation test. Among the three strains, the strain hw317 was implemented shaker fermentation for stability test and 10~100 L pilot fermentation tank for citric acid productive maximization. Acid-base neutralization method was applied to determinate the content of citric acid in fermented liquid. The results showed that: when the secondary heavy ion 12C6+ dose was 857.8 Gy, both of the fatality rate (94.5%) and the positive mutation rate (8%) were highest. Through the shaker fermentation tests and 10 ~ 100 L pilot fermentation test, one strain hw317 was screened and obtained for hyper citric acid production. Consequently, the final citric acid acidity can reach up to 19.2±0.2% with controlling fermentation cycle for 60 h.
其与肿瘤的关系，并对肿瘤细胞适应乏氧环境的机制进行了阐述。总结了线粒体作为供能细胞器，对肿瘤细胞在乏氧条件下生长、侵袭和转移及获取能量过程中的作用，并介绍了中国科学科院近代物理研究所利用重离子辐照所做的相关研究成果，包括不同剂量重离子对线粒体DNA超螺旋构象及线粒体功能的影响，同一剂量不同时间重离子辐照后对线粒体DNA 4 977 大片段损伤累积的影响。The hypoxia environment on the cells and mitochondria, and the damage of normal cells mitochondrial respiratory chain in hypoxia and its relationship with tumors are reviewed. In addition, the tumor radiation resistance mechanism in hypoxia are summarized. It also expounds that mitochondria, as energy supply organelles for cells, are related to tumor cells growth, invasion and metastasis in hypoxia environment, besides, it gives a brief introduction to the mitochondria study of the Institute of Modern Physics, Chinese Academy of Sciences with heavy ion irradiation, including effects of different dose of heavy ion on mitochondrial DNA superhelix conformation and function of mitochondria,
and the influence on mitochondrial DNA 4 977 damage cumulation in different time after the same dose of heavy ion irradiation.
采用高传能线密度(LET) 的12C6+离子束和低LET 的X 射线辐照人正常肝细胞系HL-7702 细胞，利用微卫星不稳定性(MSI) 检测来分析直接受照射细胞和通过转移培养基方式旁细胞传代八代子细胞以MSI 表征的远后效应。实验结果表明，12C6+离子束诱导的远后效应较X射线的低；旁细胞的远后效应较直接受照射细胞的高；辐射引起的MSI 与杂合性丢失(LOH) 的发生率具有位点特异性。结果提示，重离子放射治疗较X 射线放射治疗对正常组织引发的辐射风险要小，可通过对MSI 高发位点的筛选来评估放疗后患者长期生存状况和二次癌症发生风险。Human normal liver cell line HL-7702 cells were irradiated with high linear energy transfer (LET) 12C6+ ions and low-LET X-rays, respectively. Delayed effect in terms of microsatellite instability (MSI) in progenies of the directly irradiated cells and bystander cells, obtained in the way of medium transfer at the 8th passage postirradiation,were examined. The delayed effect induced by the high-LET 12C6+ ions was different from that induced by the low-LET X-rays, and a higher incidence of MSI was observed in the progenies of the cells after exposure to the X-rays than to the 12C6+ ions. We also found that the delayed effect in the progenies of the bystander cells was much more severe than those
of directly irradiated cells. Furthermore, the events of MSI and loss of heterozygosity (LOH) induced by the ionizing radiations were not randomly distributed throughout the genome and specific loci existed indeed. These results imply that the radiation risk to normal tissues is lower in heavy ion therapy than in conventional X-ray radiotherapy, and the analysis of microsatellite loci with MSI high frequency occurrence can be applied to access long-term survival condition and second cancer risk for the patients after radiotherapy.
利用傅里叶方法得到了非齐次中子扩散方程格林函数的解析形式，通过格林函数计算了当外源在堆芯任意位置时的中子通量密度分布，分析了在次临界反应堆系统中，次临界倍增系数ks 与外源位置和相同次临界深度下堆芯尺寸的依赖关系。发现，ks 随着堆芯尺寸的增加而减小，这点变化虽小，但能量增益对ks 以及堆芯尺寸是相当敏感的，加速器驱动的次临界系统(ADS) 设计时应必须予以考虑。The analytical form of the Green’s functions of the inhomogeneous diffusion equation for neutrons are obtained using the Fourier method. The neutron flux distributions with the external neutron source locatedat arbitrary positions are calculated from the Green’s functions. In a subcritical system, the ependences of the subcritical multiplication factor ks on the source position and the core size with the fixed subcriticality keff are analyzed based on the series solution. It is found that ks decreases with the core size. Although this variation is small, the energy gain is sensitive to ks and then the core size, which has to be taken into account in the design of the source driven subcritical system.