2015年 第32卷 第2期
Recently, new low-energy modes of excitation called pygmy resonances have been observed.Their distinct feature is the close connection to nuclear skin oscillations. A successful description of the pygmy resonances could be achieved in a microscopic theoretical approach which incorporates the density functional theory and QRPA formalism extended with multi-phonon degrees of freedom. The latter is found of crucial importance for the understanding of the fine structure of nuclear electric and magnetic excitations at low energies. Corresponding microscopic multi-phonon response functions are implemented in the studies of s-process of nucleosynthesis.
Multinucleon transfer processes in low-energy heavy ion collisions open a new field of research in nuclear physics, namely, production and studying properties of heavy neutron rich nuclei. This not-yet-explored area of the nuclear map is extremely important for understanding the astrophysical nucleosynthesis and the origin of heavy elements. Beams of very heavy U-like ions are needed to produce new long-living isotopes of transfermium and superheavy elements located very close to the island of stability.The calculated cross sections are high enough to perform the experiments at available accelerators.Beams of medium-mass ions (such as 136Xe, 192Os, 198Pt) can be used for the production of neutron rich nuclei located along the neutron closed shell N = 126 (the last waiting point) having the largest impact on the astrophysical r-process. The Low-energy multinucleon transfer reactions is a very efficient tool also for the production and spectroscopic study of light exotic nuclei. The corresponding cross sections are 2 or 3 orders of magnitude larger as compared with high energy fragmentation reactions.
最近，STAR合作体在相对论重离子对撞机的束流能量扫描实验中观测到了正反粒子的椭圆流劈裂。基于输运模型，发现丰重子介质中正反粒子平均场势的不同可以解释其椭圆流的劈裂。利用Nambu-Jona-Lasinio 模型描述相对论重离子碰撞的部分子相，发现实验中正反粒子的相对椭圆流劈裂可以用来约束该模型中夸克矢量相互作用的耦合系数。这一发现对确定QCD相图的临界点位置和理解整个QCD的相结构有重要意义。The elliptic flow splitting between particles and their antiparticles has recently been observed by the STAR Collaboration in the beam-energy scan program at the Relativistic Heavy Ion Collider. In studies based on transport models, we have found that this splitting can be explained by the different mean-field potentials acting on particles and their antiparticles in the produced baryon-rich matter. In particular, we have shown that the experimentally measured relative elliptic flow difference can help constrain the vector coupling constant in the Nambu-Jona-Lasinio model used in describing the partonic stage of heavy-ion collisions. This information is useful for locating the critical point in the QCD phase diagram and thus understanding the phase structure of QCD.
基于最近更新的极端相对论量子分子动力学模型，研究了197Au+197Au 产生的中子和氢同位素的横动量依赖的椭圆流和轻带电粒子的产额比。发现中子和氢同位素的椭圆流之比vn2 /vH2 敏感于对称能的高密行为，而3H和3He 的产额比敏感于对称能的低密行为。通过比较FOPI/LAND 和FOPI 合作组的最新实验数据与模型模拟的结果，发现接近线性对称能的Skyrme 参数给出的结果能与这两个实验值都符合。Based on the newly updated version of the Ultra-relativistic quantum molecular dynamics (UrQMD) model, the transverse-momentum dependent elliptic flow ratio of free neutrons vs hydrogen isotopes and the yield ratio of 3H vs 3He clusters emitted from 197Au+197Au collisions at the incident energy 400 MeV/nucleon are studied. It is found that the elliptic flow ratio vn 2 /vH 2 is sensitive to the symmetry energy at supra-saturation densities, while the yield ratio 3H/3He is sensitive to the nuclear symmetry energy at sub-saturation densities. By comparing the data from FOPI/LAND and FOPI Collaborations with model calculations using various Skyrme interactions (all exhibiting similar values of isoscalar incompressibility but very different density dependences of the symmetry energy), we find that results using Skyrme interactions which parameterize a moderately soft to linear symmetry energy can reproduce both data quite well.
在过去的十余年中，对非对称核物质的对称能的研究无论从实验还是理论上都取得了较大的突破，这对中子结构及其物态方程的理解具有十分重要的意义。本研究将采用一个相对保守的对称能斜率范围(25 MeV <L< 105MeV) 来研究其对快速转动中子星性质的约束，这些性质包括：质量-半径关系、转动惯量、引力红移以及转动形变等。通过该对称能斜率的约束，发现典型中子星(M =1.4M⊙) 的半径约束在10.28~13.43 km范围内，这与最近的相关观测相一致。如果观察发现了质量较小的毫秒脉冲星，则将为核物质的对称能较软提供有效的证据。另外还发现，对角动量的一致性可为快转中子星转动惯量的上限提供约束。最后，根据具有低质量伴星的双星EXO0748-676的红移观测，给出了该脉冲星的质量下限(>1.5M⊙)。During the past decade, theoretical researches and terrestrial nuclear laboratory experiments have made impressive progresses on the researches of symmetry energy of the asymmetric nuclear matters, which is very important in understanding the equation of states and the structures of neutron stars. In this work, by making use of a conservative symmetry energy slope (SES) range (25 MeV
给出了反对称分子动力学模型(AMD) 计算的50 MeV/nucleon 112Sn+112Sn 反应的分析结果。该研究是反对称分子动力学模型中统计冻结概念的部分研究结果。利用自洽法结合修正的Fisher 模型，提取了发射源的温度和密度分别为T =(6.1±0.2)MeV MeV, ρ/ρ0=0.69±0.03。通过与AMD模型计算的系统在时间演化过程中的最大密度比较，得出碎片发射源的密度远小于系统的最大密度。利用自洽法提取的温度和密度与35 MeV/nucleon的40Ca+40Ca 反应系统及40 MeV/nucleon 的64Zn + 112Sn 反应系统所提取的温度和密度非常接近。该结果表明反对称分子动力学模型中，系统在中等质量碎片形成时刻处于统计冻结体积。As a part of statistical freeze-out study in antisymmetrized molecular dynamics (AMD), an analysis of 112Sn+112Sn at 50 MeV/nucleon is presented. Using the self-consistent method combined with the Modified Fisher model, the fragmenting source density, ρ/ρ0=0.69±0.03, temperature, T =(6.1±0.2)MeV, are extracted. By comparing the maximum density in the system during the time evolution of AMD calculation, a significantly lower density is found for the fragmenting source density. The extracted fragmenting source density and temperature are very similar to those for 40Ca + 40Ca at 35 MeV/nucleon and 64Zn + 112Sn at 40 MeV/nucleon. These indicate that there is a common statistical freeze-out volume at the time of the formation of intermediate mass fragments (IMFs) in AMD transport model.
A theoretical evaluation of the collective excitation spectra of nucleus at large deformations is possible within the framework of the dinuclear system (DNS) model, which treats the wave function of the fissioning nucleus as a superposition of a mononucleus configuration and two-cluster configurations in a dynamical way, permitting exchange of nucleons between clusters. In this work the method of calculation of the potential energy and the collective spectrum of fissioning nucleus at scission point is presented. Combining the DNS model calculations and the statistical model of fission we calculate the angular distribution of fission fragments for the neutron–induced fission of 239Pu.
核耗散降低了裂变截面值(σdropf )。基于Langevin 模型，研究了角动量对σdropf 作为鞍点前摩擦强度β 函数的影响。发现在低自旋，摩擦对σdropf的影响显著增强。通过考察系统195Bi，201Bi 和207Bi 的σdropf 随β 的演化，发现摩擦效应随着Bi 核中质比(N/Z) 的增加而变大。这些结果建议，为了更好地在实验上用裂变截面探测β，应产生那些具有低自旋、高N/Z 的热核系统。Using the Langevin model, we study the effect of angular momentum on the drop of fission cross sections caused by friction over its standard statistical-model value, σdropf as a function of presaddle friction strength β. It is found that friction effects on σdropf are substantially enhanced at low spin. In addition, by investigating the evolution of σdropf with β for 195Bi, 201Bi and 207Bi nuclei, we find that friction effects become greater with increasing the neutron-to-proton ratio (N/Z) of Bi nucleus. These results suggest that on the experimental side, to precisely probe presaddle dissipation by measuring fission excitation functions, it is best to yield excited nuclear systems with a small spin and a large N/Z.
研究了t 道、s 道、u 道和由张量相互作用项导致的接触项对矢量介子和重子八重态之间的相互作用势的贡献。在分波分析的框架下，求解了耦合道的李普曼–施温格方程，研究了动力学生成的奇异数S = 0，同位旋为I =1/2 的重子共振态N(1650)1/2− 和N(1700)3/2−，N(1895)1/2− 和N(1875)3/2−，N(2120)3/2−，以及同位旋I = 3/2 的重子共振态Δ(1620)1/2− 和Δ(1700)3/2−的质量、衰变宽度、和角动量等性质。另外，计算结果表明，在2 000 MeV附近存在着JP =1/2− 的N(2120)3/2− 的对偶共振态。The interaction kernels between vector mesons and octet baryons are calculated explicitly with a summation of t-, s-, u- channel diagrams and a contact term originating from the tensor interaction.Many resonances are generated dynamically in different channels of strangeness zero by solving the coupled-channel Lippman-Schwinger equations with the method of partial wave analysis, and their total angular momenta are determined. The spin partners N(1650)1/2− and N(1700)3/2−, N(1895)1/2− and N(1875)3/2−, and the state N(2120)3/2− are all produced respectively in the isospin I =1/2 sector. In the isospin I =3/2 sector, the spin partners Δ(1620)1/2− and Δ(1700)3/2− are also associated with the pole in the complex energy plane. According to the calculation results, a JP =1/2− state around 2 000 MeV is predicted as the spin partner of N(2120)3/2−.
粒子云网格(Particle In cell，PIC) 方法是研究带电粒子在加速器中运动的关键工具之一。基于PIC 算法，开发了模拟强流条件下的束流动力学模拟程序TOPOPIC(Trace of Particle Orbit with PIC method)，并且利用TOPOPIC，研究了束流在四极铁周期结构(FODO) 中的传输问题。结果表明，在强流条件下空间电荷效应显著地影响了束流的整体行为和单粒子的运动轨迹。最后比较了TOPOPIC 程序和通用的BEAMPATH 程序在相同条件下的计算结果，可以看到两个程序给出的模拟结果吻合得非常好，这表明TOPOPIC程序的计算结果是合理、可靠的。The Particle in cell (PIC) method is one of the key techniques in the research of charged particles in accelerators. Based on the PIC method, a new beam simulation code for high intensity beam named TOPOPIC (Trace of particle orbit with PIC method) has been developed. With the code TOPOPIC，the beam behavior during passing through the periodic quadrupole (FODO) structure has been studied. The results show that the nonlinear space charge affects the single particle behavior and beam envelope a lot. At last, the PIC code BEAMPATH is used for benchmark, the results given by TOPOPIC and BEAMPATH show good agreements,which means the code TOPOPIC is reliable.
中国科学院近代物理研究所自主研发的ADS注入器Ⅱ第一代高频低电平(LLRF) 控制系统，工作频率为162.5 MHz；LLRF 系统是由基于I/Q 采样的正交解调技术构成的全数字闭环反馈控制系统，其主要功能是实现超导腔腔体电压幅值稳定控制、相位稳定控制与腔体谐振频率控制；LLRF 控制系统在液氦温区超导腔上进行了系统稳定度和性能的在线测试，根据实验数据计算得超导腔体电压幅度稳定度为3.4‰，相位稳定度为0.3°，腔体表面峰值电场(Epk) 能长时间稳定在25.1 MV/m。通过实验测试，检验了LLRF 控制系统的性能，并对测试过程中出现的问题进行了分析，为将来超导腔LLRF 控制系统运行积累了经验。The first generation Low-Level radio frequency(LLRF) control systemfor China ADS injector Ⅱis developed by IMP, CAS(Institute of Modern Physics, Chinese Academy of Sciences). This system is composed by superconducting cavity amplitude stability controller, phase stability controller and the cavity resonance frequency controller; the operation frequency is 162.5 MHz. This is an all-digital closed-loop feedback control system which based on the IQ quadrature sampling demodulation technique. The performance of the system has been tested on the superconducting cavity, which is running in the temperature range of liquid helium and the Epk=25.1 MV/m (the peak electricon the surface of the superconducting cavity). The amplitude stability is less than 4 ‰ and the phase stability is less than 0.3°. Superconducting cavity bandwidth is about 230 Hz. From the spectrum, the phase noise suppression can reach 70 dBm.
设计了一款小型化、低噪声、大动态范围的前端处理电路，包括电荷灵敏前放、成形放大电路、单道脉冲幅度分析电路。前放的等效输入噪声≤1.5 keV，动态范围可达0~11 V，积分非线性 ≤0.11%。该电路为模块化电路，当前放与主放模块构成系统时，其分辨可以达到0.12%。当前放、主放模块与中国科学院近代物理研究所制作的离子注入型硅探测器构成系统时，采用239Pu 源进行测试，测得在5.157 MeV时的能量分辨约为0.82%；当主放、单道脉冲幅度分析模块与中国科学院近代物理研究所制作的碘化铯晶体探测器构成系统时，采用60Co 源进行测试，对于能量为1.332 MeV 的 射线，测得其能量分辨约为7.9%。该电路可用于半导体探测器、光电倍增管及电子倍增器等探测器信号的处理。目前，小型前端电路已经应用于中国科学院近代物理研究所自行研制的便携式盐湖卤水铀、钍、钾快速测量仪的原型样机，达到了预期效果。A small dimension front-end circuit with low noise and wide output dynamic range is introduced in this paper. The front-end circuit is made up of a charge sensitive preamplifier, a shaping circuit and a single channel pulse height analyzer. The equivalent input noise is under 1.5 keV. The output integral nonlinearity is less than 0.11% within the dynamic range of 011 V. And the circuit can be suitable for different conditions by different modules. The resolution was about 0.12% with the charge sensitive preamplifier and the main amplifier. The energy resolution of 0.82% was achieved for 5.157 MeV -rays from a 239Pu source with the charge sensitive preamplifier, the main amplifier and anion-injection silicon detector designed by the Institute of Modern Physics(IMP). An energy resolution of 7.9% was achieved for 1.332 MeV rays from a stationary 60Co source with the main amplifier, the single channel pulse height analyzer and a CsI scintillator detector designed by the IMP. The front-end circuit has the features of wide output dynamic range, simple structure, high level of integration,small dimensions, low noise, fast rise time of the output pulse and excellent stability. The front-end circuit can be applied to signal processing of semiconductor detectors, photomultiplier tubes and electrons multiplier. And the front-end circuit had been applied to a prototype of the portable rapid measuring instrument designed by IMP for measuring Uranium, Thorium and Potassium in the salt lake brine with good
用射线全吸收型装置(Gamma-ray Total Absorption Facility，GTAF)，可以对中子俘获反应截面进行高精度测量。为了降低实验本底，实验中需要对源中子进行准直和屏蔽，还要对被样品散射的中子进行吸收以减少它们进入探测器后所形成的干扰。采用MCNP对中子的准直器、屏蔽体和中子吸收体进行了模拟设计，中子准直屏蔽体材料选用含硼聚乙烯(BC4 的质量分数为3%) 和铅。准直孔直径为13 mm，长度为500mm，经准直后样品处中子束斑坪顶直径为21 mm。中子吸收体材料选用聚乙烯和碳化硼，吸收体球壳内腔半径30 mm，聚乙烯壳层厚度60 mm，碳化硼壳层厚度10 mm，被样品散射的中子经吸收体后衰减93.7%。Neutron capture cross section can be measured by Gamma-ray Total Absorption Facility (GTAF) with high precision. To reduce the background of experiments, the neutron source must be collimated and shielded, and the neutrons scattered from the sample must be absorbed to minimise interference after they go into the detector. The shield, collimator and absorber were simulated and designed with MCNP code. Boron-ontaining
polyethylene with 3% BC4 and lead are used as the materials for the neutron collimator and shield. The diameter of the collimating aperture is 13 mm, and the length of the collimator is 500 mm. After being collimated, the diameter of neutron beam plateau at the sample position is 21 mm. The neutron absorber is made of polyethylene and BC4, and the thickness of polyethylene shell and BC4 shell are 60 and 10 mm, respectively. The simulated result shows that neutrons scattered from the sample can decay 93.7% through the neutron absorber.
涉氚核设施在检修及退役时，其产生的氚化粒子容易被工作人员误吸入，并在呼吸系统的不同部位停留，部分尺寸较小的粒子可能在肺泡间质区(AI 区) 停留超过1 年的时间。氚粒子通过 衰变释放电子，在释放电子的同时以及释放的电子与周围原子相互作用还会分别产生出内、外轫致辐射，这些都会对人体肺部组织造成辐射损伤。本文采用蒙特卡罗程序PENELOPE 对多种氚化粒子在人体肺部组织中的吸收剂量进行了模拟计算，特别是讨论了氚 衰变的内轫致辐射的贡献。研究发现，电子辐射对人体肺泡产生的吸收剂量大于外、内轫致辐射，但后两者作用距离较长，对人体造成的影响重要；电子辐射吸收剂量随着粒子尺寸的增大以及金属原子序数的增大而减小；外轫致辐射吸收剂量随着粒子尺寸的增大而减小，随着金属原子序数的增大而增大；内轫致辐射吸收剂量随着粒子尺寸的增大以及金属原子序数的增大而减小。Some tritium relevant nuclear facilities, such as Tokamak, can produce tritiated particles. There is the possibility for the staffs to inhale the tritiated particles by accident in the process of maintenance or decommission of these facilities. Tritium decays to 3He, during which the beta electron and the internal bremsstrahlung are released. Meanwhile, the released electrons will interact with the surrounding atoms, and the external bremsstrahlung will be generated. All the electrons, internal bremsstrahlung and external bremsstrahlung will deposit the radiation energies to lung tissues and generate the radiation damage. In this paper we studied the radiation doses by inhaled tritiated particles in lung tissues by Monte Carlo code PENELOPE, in particular, internal bremsstrahlung contribution was included. Our results demonstrated that (1) the dose caused by electron radiation is far higher than those of external and internal bremsstrahlung, which however shall not be negligible due to their long-distance effects; (2) the dose caused by electron radiation decreases as the particle size and metal atomic number Z increase; (3) the dose caused by external bremsstrahlung decreases as the particle size increases, but increases as the metal Z increases; (4) the dose caused by internal bremsstrahlung decreases as the particle size and metal Z increase.
使用不同的方法来确定LaBr3晶体信号的到达时间。在文中信号经过光电倍增管的放大之后由DSR4 测试板进行数字采集，其中DRS4 是由瑞士PSI 研究所生产的高带宽、低功耗以及快读出时间的开关电容阵。这些优势使得DRS4 很具有吸引力，很多实验将传统的ADC与TDC替换为DRS4。采集的波形可以通过不同的方法进行后续处理。其中包括：(1) 恒分甄别、(2) 波形拟合、(3) PMT脉冲模型法以及(4) 均值过滤法。文中实现的恒分甄别的时间分辨与使用模拟电路获取的平均时间分辨相比没有提高。高斯波形拟合法虽然与数字CFD 的结果相当，但是却更加耗时。均值滤波法虽然容易实现，但是通过这个方法得到的时间分辨与采样时间在一个量级。而PMT脉冲模型法得到的平均时间分辨为195.4 ps，优于模拟信号的恒分甄别的时间分辨254.7 ps。Various digital methods were examined for determining the relative arrival times of pulses from 20 mm x 5 mm LaBr3 scintillators. In this study, pulses from the photomultiplier tubes (PMTs) were digitized by DRS4 evaluation board, a switched capacitor array (SCA) produced by the Paul Scherrer Institute (PSI). The high bandwidth, low power consumption and short readout time make DRS4 attractive for many experiments, replacing traditional ADCs and TDCs. The sampling signals were post processed with multiple techniques. These techniques include: (1) constant-raction discrimination (CFD), (2) pulse-shape fitting, (3) mean PMT pulse model and (4) median filtered zero crossing method.The implemented CFD in the digital regimes did not improve the resolution of using analog equipmentwith average time resolution. The pulse-shape fitting yielded as good resolution as digital CFD, however,is much more time consuming. The median filtered method were easy to implement, and had a resolution on the order of sampling time. Average timing resolutions of 195.4 ps were obtained with mean PMT pulse model, which is better than the analog constant-fraction-zero-crossing with average resolution of 254.7 ps.
利用蒙特卡罗程序FLUKA模拟计算了聚乙烯慢化球和辅助材料慢化球对低能中子到高能中子的响应函数曲线。结果表明，对纯聚乙烯球来说，随着聚乙烯层厚度的增加，响应曲线峰逐步右移，峰值在高能区有所下降，对20 MeV 以上的中子，无论纯聚乙烯球的尺寸有多大，其响应均下降到很低的程度；对辅助材料慢化球来说，中子能量小于1 MeV时，辅助材料慢化球与聚乙烯慢化球的响应曲线相似，但当中子能量大于20 MeV 时，中子与辅助材料层发生(n，xn) 反应，慢化球的响应呈显著上升趋势。分析计算结果，最终能够确定宽能谱多球中子谱仪的尺寸组合。The responses of an extended range Multisphere Neutron Spectrometer as function of neutron energy were calculated by Monte Carlo code，FLUKA. The results show that peak value of the response curve shift to the right with the increasing of polyethylene thickness, but decreases in the high energy region. For neutron with energy >20 MeV, the response of polyethylene moderator will be decreased to be a very low level no matter what size it is. For neutron energies below 1 MeV, the response curve of moderator with auxiliary materials behave like the one of polyethylene moderator, but above 20 MeV the responses increase signi cantly due to increasing (n, xn) cross-sections of auxiliary materials. Based on the present discussion, the size of an extended range multisphere neutron spectrometer can be determined.
系统阐述了与金纳米粒子(GNPs) 放射增敏效应相关实验的方法与结果、影响GNPs 放射增敏的因素、GNPs 放射增敏的细胞和动物实验表现及其相关机制。同时结合相关实验，分析和比较了15 nm 柠檬酸钠包被的GNPs 的放射增敏效应，发现GNPs 在高LET 的碳离子束和低LET 的X射线辐照下对Hela细胞的杀伤力随其浓度的增加而增大；在50% 的细胞存活率下，当GNPs 的质量浓度为7.5 g/mL时，其X射线的剂量减少率和碳离子的相对生物学效应值(RBE) 的增加率达到了最大，分别为65.3% 和43.6%，同时GNPs 共培养细胞24 和48 h 后，未出现细胞周期同步化的现象。This paper describes the methods and results of the previous experiments, the experimental phenomena of the cell and animal tests and the relative mechanisms on the radiosensitizing effect of GNPs. Together with our experiments, the radiosensitizing effects of 15 nm citrate-capped GNPs and related mechanisms are analyzed and compared, finding that Hela cell killing of GNPs increase along with their concentration after exposure to high- and low-LET radiation such as carbon ions and X-rays. In addition, the percentages of dose reduction of the X-rays and RBE increment of the carbon ions reached their maximums 65.3% and 43.6%, respectively,at 50% survival level when Hela cells were pre-treated with 7.5 g/mL GNPs. Moreover, Hela cells showed no cell-cycle synchronization after 24 and 48 h exposure to GNPs.
利用不同剂量的碳离子辐照二硫苏糖醇(2.5 mmol/L) 预处理的HeLa 细胞，探讨了内质网应激反应对碳离子辐照宫颈癌HeLa 细胞的影响。实验发现：与单独辐照组相比，二硫苏糖醇联合碳离子辐照后细胞的存活率下降，而凋亡率增加；二硫苏糖醇联合碳离子辐照加重了碳离子辐照引起的细胞周期阻滞；且联合辐照组的自噬被明显激活。结果表明，持续的内质网应激可改变宫颈癌HeLa 细胞对碳离子辐照反应，且二硫苏糖醇可能通过影响HeLa 细胞的自噬性细胞死亡通路发挥作用。To investigate the effect of endoplasmic reticulum stress on HeLa cells to 12C6+ ion irradiation,HeLa cells were pretreated with 2.5 mmol/L dithiothreitol and irradiated by 12C6+ ions with different doses.The results showed that, compared with IR alone, dithiothreitol combined with carbon ion irradiation caused HeLa cell survival decreased, and the apoptosis increased. Moreover, dithiothreitol and carbon ion radiation combination treatment led to a significant increase of G2/M phase, and autophagy was activated obviously in combination treatment group. The results imply that continuous endoplasmic reticulum stress can change the response of HeLa cells to 12C6+ irradiation, and dithiothreitol may affect HeLa cells through the autophagy cell death pathway.
利用金属蒸发真空多弧离子源(MEVVA 源) 注入机将Ti+ 离子注入到高纯石英玻璃衬底中，离子注入的加速电压为20 kV，注入剂量为1.5x1017 和3x1017 ions/cm2，将注入样品在氧气气氛下进行热退火处理，制备了TiO2 纳米薄膜。采用光吸收谱、拉曼光谱、X射线光电子能谱、扫描电子显微镜和透射电子显微镜对注入样品进行了测试和表征，分析了TiO2 薄膜的形成机理。在热退火过程中衬底中离子注入的Ti原子向外扩散到衬底表面被氧化形成了TiO2。TiO2 的形成、晶粒尺寸和晶体结构依赖于热退火温度，而形成TiO2 薄膜的厚度主要受离子注入剂量和热退火时间的影响。实验结果表明，该方法制备的TiO2 纳米薄膜将有望应用于制备具有光催化、自清洁等特殊性能的自清洁玻璃。TiO2 nanofilms on the surface of fused silica have been fabricated by Ti+ ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by Ti+ ions at 20 kV with fluences of 1.5 and 3x1017 ions/cm2 using a metal vapor vacuum arc (MEVVA) ion source implanter. The optical absorption spectroscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements were done to figure out formation mechanism of the TiO2 nanofilms. The formation of TiO2 nanofilms resulted from outdiffusion of the implanted Ti ions to the substrate surface, where they were oxidized intoTiO2. The formation,grain size and the crystallographic phase of TiO2 are annealing temperature dependent, and TiO2 nanofilm thickness can be well tailored by controlling the implantation fluence and annealing time. Results show that the TiO2 nanofilms fabricated by this novel method have great potential in applications such as photocatalytic,antibacterial and self-cleaning glass.
对1:55 μm波长DFB 结构的InGaAsP 多量子阱激光二极管开展电子和60Co- 射线辐照试验。试验结果表明，激光二极管的斜度效率主要受带电粒子沉积的电离总剂量影响，而阈值电流和光功率主要受位移损伤剂量的影响。利用位移损伤剂量方法评价激光二极管的辐射损伤特征，并且预测其在空间辐射环境中的光功率衰退情况。模拟计算结果表明，MEO轨道辐射环境对激光二极管光功率辐射损伤远大于GEO轨道的影响，这主要是由于MEO轨道辐射环境的高能电子通量密度远大于GEO轨道的通量密度。The 1.55 μm InGaAsP multi-quantum-well laser diodes with distributed feedback structures were irradiated by electrons and 60Co- rays. The experimental results show the slope efficiency of laser diode is mostly affected by the total ionizing dose produced by charging particles, and the threshold current and the optical power mainly by displacement damage dose. The displacement damage dose methodology was employed to evaluate radiation damage of the laser diodes, and to predict the power degradations of these diodes in space. The calculated results indicate that the optical powers of the diodes will have more serious degradation for medium Earth orbit than for geosynchronous Earth orbit,due to higher fluence density of high energy electrons in GEO orbits.
无论对深入理解电子-原子的作用机制，还是在材料等领域的实际应用，电子轰击原子的内壳电离截面都具有重要意义。当前电子碰撞引起原子内壳电离的实验数据多集中在几十keV 入射能量和中小Z 靶原子,其它数据相对比较缺乏。本工作以能量为1.0 MeV电子轰击Ta 和Au 靶，通过测量靶原子特征X射线的产额，获得其K壳电离截面分别为13.3 和10.1 b，L 壳电离截面分别为554 和338 b。并将实验结果和相应的理论进行了对比，结果显示，本实验测得的K壳电离截面与Casnati、Hombourger 理论值、L 壳电离截面与Scoeld和Born-Bethe 的理论值相符。Accurate experimental data for atomic inner-shell ionization cross-sections by electrons are of basic importance both in understanding inelastic electron-atom interaction and its application. Up to now, most of available data on this process were mainly concentrated on the low and medium Z atoms by the bombardment of low energy electrons. In present experiments K-shell and L-shell ionization cross-sections of Ta and Au in collisions with 1.0 MeV eleltron were determined by measuring the characteristic X-rays emitted from the target atoms. For the present collision systems the K-shell ionization cross-sections were found to be 13.3 and 10.1 b,and the L-shell ionization cross sections were 554 and 338 b, respectively. The measured K-shell ionization cross sections are in reasonable agreement with the theoretic predictions of Casnati and Hombourger, while L-shell ionization cross sections are consistent with the theoretical results of Soc eld and Born-Bethey.