辐射伏特效应用于核衰变能发电的初步研究

提出了利用半导体探测器的ＰＮ结内建电场收集辐射诱发电离空穴对，进而实现从核衰变能的电能转换的全新技术路线，成功地模拟了这一转换过程，在不加任何外场情况下，实现了对＾２３９Ｐｕ发射α粒子产生的电离电子空穴对高达９４％的收集率和对＾９０Ｓｒ－＾９０Ｙ发射β粒子产生的电离电子空穴对的７２％收集率。     

^12C离子与铜相互作用中的平均线性动量转移

使用离线γ能谱法和厚靶－厚收集箔技术测定了２０－４６ＭｅＶ／ｕ＾１２Ｃ离子和Ｃｕ相互作用中剩余核的前向平均反冲射程。根据这些数据得到了所有碰撞参数积分的平均线性动量转移和初始复合体系的平均激发能，实验结果与献值吻合较好。     

离子在近电子能损阈值能区诱发云母表面小丘形成

利用0.65 MeV的He⁺离子轰击白云母膜,并在大气环境下用原子力显微镜(AFM)的轻敲模式分析了辐照后的膜表面。实验结果显示,在不同温度下离子诱导的小丘高度在小于1 nm到几nm之间,且室温条件下能诱发小丘生成的He⁺离子电子能损阈值在0.44 keV/nm以下。此外,升高温度至973 K并在其中选取不同温度进行表面辐照来验证观测到的小丘结构。实验发现,相比于室温,小丘直径和高度的统计分布在更高温度下表现出了更大的歧离。分别利用分析热峰模型和双温热峰模型计算了辐照过程中的核能损与电子能损,并选取了用能损在阈值附近的离子辐照所产生的小丘的实验数据与模拟结果相比较,发现实验结果与双温热峰模型吻合较好。     

电子能损的潜径迹形成机制及理论模型的新进展

潜径迹是荷能离子与固体相互作用的一个重要效应，可以借助化学蚀刻，电子显微镜，卢瑟福散射和其他方法所显同，通过研究依赖于离子能量和各种靶参数的径迹尺寸的变化可以获得关于微观机制的信息，本文概括地介绍了在电子能损体制下径迹形成的基本现象，观测技术以及所获得的重要的实验结果，评价了描述径迹形成机制的理论模型和最新进展。     

铑自给能中子探测器的灵敏度

本文给出了铑自给能探测器的热中子灵敏度和中子灵敏度的理论计算公式、燃耗修正公式以及不同中子温度下的换算公式。运用这些公式对ZTRh 123型铑自给能探测器的热中子灵敏度和中子灵敏度进行了理论计算,并在反应堆中对其进行了实验验证。其结果表明,理论计算值和实验标定值是相吻合的。其偏差:热中子灵敏度为8.5％,中子灵敏度为3.9％。     

高能136Xe离子辐照聚酰亚胺化学改性的电子能损效应

用1．755GeV^136Xe离子在真空室温环境下辐照叠层聚酰亚胺薄膜,通过红外和紫外光谱测量研究了高电子能损离子辐照引起的化学降解及炔基产生效应。红外测量结果表明,典型官能团随辐照注量的增加指数降解,且径迹芯中所有官能团均遭到破坏;对应8．8(最小能损,第一层)和11．5keV／nm(最大能损,第五层)电子能损,^136Xe辐照聚酰亚胺的平均降解半径分别为3．6和4．1nm。而相应能损条件下炔基的生成截面分别为5．6和5．9nm大于官能团的降解截面。紫外结果表明辐照引起的吸光度的改变随辐照注量线性增加,发色团的产生效率随电子能损的增大而增加。     

闪烁光纤电磁量能器

本文介绍了塑料闪烁光纤及其做成的铅－闪烁光纤电磁量能器，详细描述了两个电磁量能器模型的结构及其在瑞士ＰＳＩ实验束上测得的能量和时间分辨性能，介绍了单根光纤传输衰减性能研究的初步结果。     

电子能损引起的潜径迹

潜径迹是电子能损在凝聚态物质中引起重要效应之一,给出了一个关于引起潜径迹电子能损阈值,损伤截面以及径迹形貌的综合评述。     

MC方法计算自给能铑中子探测器灵敏度

利用MC方法结合自给能探测器空间电场效应,计算了典型的铑探测器信号电流和灵敏度并与公开文献中的实验测量值做对比验证。结果表明:使用该方法的理论计算值与实验测量值吻合良好,证明该计算方法正确可靠,而且具备相当的精度,可为大型先进压水堆堆芯测量和自给能探测器的设计研发提供参考和借鉴。     

CMOS器件辐照后热退火过程中激发能分布的确定

对CNMOS晶体管辐照后的等温、等时退火特性进行讨论，给出辐照敏感参数在等温、等时退火过程中随退火时间、退火温度的变化关系。根据退火模型计算了CMOS器件辐照后25、100^oC等温和25～250℃等时退火过程中激发能的分布。结果表明：25、100℃等温退火激发能范围分别在0.65～0.76eV和0.75～0.95eV之间；25～250℃等时退火的激发能范围在0.5～1.1eV之间，峰值位于0.81eV。     

Measurement of mean excitation energy by energy loss

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Pressure dependence of the mean excitation energy of atomic systems

Changes in the mean ionization energy of atoms in compressed matter are estimated through cage models of atomic confinement whereby pressure is obtained in terms of the rate of change of total atomic energy with volume. Resort is taken to a recently implemented shellwise Thomas–Fermi–Dirac–Weizsacker theory for confined atoms to construct the atomic energy functional, which is self-consistently optimized for different confinement conditions. The resulting modified atomic orbital densities are then used within the Local Plasma Approximation to evaluate the corresponding orbital and total mean excitation energies. Good agreement is obtained with accurate calculations for free atoms. For compressed atoms agreement is found with a previously derived universal expression [J.M. Peek, Phys. Rev. A 36 (1987) 5429] for total mean excitation energies suggesting its adequacy for this class of studies.     

Precision comparison of the mean kinetic energy of U235 fission fragments from thermal neutrons and neutrons with a mean energy of 5 Mev

A double ionization chamber containing a grid has been used to investigate how the mean kinetic energy of U²³⁵ fission fragments depends on the excitation energy of the fission nucleus. It has been found that the mean kinetic energies of the fragments from fission by thermal neutrons and neutrons with a mean energy of 5 Mev are the same to within 0.1%.     

高能重离子在聚合物中的辐照效应研究

Ion irradiation of polymers can induce irreversible changes in their macroscopic properties such as electrical and optical properties and the surface-related mechanical properties. Electronic excitation, ionization, chains scission, cross-links and mass losses are accepted as the fundamental events that give rise to the observed macroscopic changes. Detailed and systematic study of radiation induced effects in polymers enriches not only the knowledge of ion-material interactions but also supplies new bases for polymeric materials synthesis through ion-beam technologies. Previous work has concentrated mainly on effects induced by low-ionization particles such as γ-rays and electrons. Since 1980,s the application of high energy heavy ion accelerators enables the use of high energy heavy ion as an irradiation source, and many new and exciting effects and phenomena have been revealed.Energetic heavy ions in matter lose energy mainly through electronic excitation and ionization. Compared to low-ionization particles, high energy heavy ion possesses higher LET(linear energy transfer) values which can reach several to several tens keV/nm. As most of the primary ionizations and excitations occur close to the ion trajectory in a core of a few nanometers in diameter, a continuous damaged zone along the ion path can be induced,in which all bonds inside the zone can be destroyed due to the high rate energy deposition. Studies on this particularity of high energy heavy ion irradiation and its effects in materials will cause great influence on industry as well as on our daily life.The previous work has revealed the great difference in the effects induced by high energy heavy ions compared to the other particles. It has been shown that under irradiation with lower LET particles gas release depends on molecular structure and material composition, whereas under irradiation with high LET particles, such as high energy heavy ions, it is not the case. Some materials that undergo degradation under γ-irradiation can be cross-linked by irradiation with high energy heavy ions. In some cases new molecular structures were induced by high energy heavy ions with sufficiently high LET values. In recent years we have irradiated polyethylterephthalate (PET), polystyrene (PS), polycarbonate (PC) and polyimide (PI) with high energy Ar, Kr, Xe and U ion beams.Chemical and physical changes of the materials induced by the high energy heavy ion beams were investigated by Fourier-transform infrared ray spectroscopy, ultraviolet and visible transmission spectroscopy and X-ray diffraction measurements, from which damage cross-sections of various functional groups were determined[1]. An energy loss threshold for damage of phenyl ring in PET has been derived and difference in amorphization of PET under high and low LET irradiations was observed. It is found that alkyne end groups can be induced in all the materials above a certain electronic energy loss threshold, which is found to be about 0.8 keV/nm for PS and 0.4 keV/nm for PC. The production cross-section of alkyne end group increases with increasing electronic energy loss and shows saturation at high electronic energy loss values.     

Effective energy deposition and latent track formation of swift heavy ions in solids

In the present paper, latent track formation in yttrium iron garnet (YIG) produced by high energy Ar ions is briefly reported at first. Then, in the framework of thermal spike model, a phenomenological parameter describing the effective energy transfer from excited electrons to lattice atoms, effective energy deposition Qeff, is deduced. Qeff is a function of ion velocity, electronic energy loss (Se) and mean free path λ of excited electrons in the matter, and is a time moderate term in…     

Ionization and excitation collision processes of electrons in liquid water

This paper reports on Monte Carlo simulations of electrons in liquid water using a set of electron collision cross-sections constructed with data published recently. The track history of electrons having initial energy ranged from 1 keV to 10 keV is investigated looking at the ionization and excitation processes. The results show that the ratio of the ionization and excitation events per track history is unique independent of the initial electron energy above a couple of 100 eV and these inelastic processes occur with low energy electrons frequently below 100 eV. In particular, the excitation processes are dominated by the electrons below 50 eV. Flight distance distributions between the inelastic collisions are also discussed.     

Mean excitation energy for the stopping power of light elements

We have evaluated the mean excitation energy or I value for Coulomb excitations by swift charged particles passing through carbon, aluminum and silicon. A self-consistent Kramers–Kronig analysis was used to treat X-ray optical spectra now available from synchrotron light sources allowing us to carry out Bethe’s original program of evaluating I from the observed dielectric response. We find that the K and L shell are the dominant contributors to I in these light elements and that the contribution of valence electrons is relatively small, primarily because of their low binding energy. The optical data indicate that Si and Al have nearly equal I values, in contrast to Bloch’s Thomas–Fermi result, I ∝ Z. The optically based I values for C and Al are in excellent agreement with experiment. However, the dielectric-response I value for Si is 164 ± 2 eV, at variance with the commonly quoted value of 173 ± 3 eV derived from stopping-power measurements.     

基于Geant4-DNA工具包的单能电子微剂量学模拟研究

应用Geant4－DNA工具包分析和评估了不同物理过程影响因素对低能电子在液态水中的影响,为建立放射治疗与辐射防护所关心的微剂量学基本数据库提供理论支撑。在最新版本的Geant4中,Geant4-DNA工具包中共有7个物理模型可模拟电子在液态水中的输运。根据不同模型的特点,本文选择其中5个适用的模型来模拟单能入射电子(0.1～20 keV)在液态水中的输运过程;比较各模型记录的径迹结构具体信息,包括相互作用过程总次数、电离和激发次数及相应沉积能量占比等;分析Geant4-DNA选项模型、抽样位点小球半径及相互作用过程等因素对线能均值的影响。模拟结果显示:“option0”与“option2” 之间、“option4”与“option5”之间的模拟结果基本吻合;由于各个模型相互作用截面的不同,“option2”、“option4”和“option6”的径迹信息及线能均值均存在差异;模型对线能均值的影响随着抽样位点小球半径的增大而减小。本工作通过设置不同输运控制条件较全面地比较了Geant4-DNA工具包中的不同选项模型,对用户根据需要选择合适的模型模拟单能电子有帮助和指导作用,为完善电子在液态水中的微剂量学数据库并用于评估电离辐射在微观尺度的生物学效应提供依据。     

Comparison between Monte Carlo and experimental aluminum and silicon electron energy loss spectra

A Monte Carlo (MC) simulation is described and used to calculate the energy distribution spectra of backscattered electrons from Al and Si. For the simulations, elastic scattering cross sections are calculated by numerically solving the Dirac equation in a central field. Inelastic scattering cross sections are computed within the dielectric response theory developed by Ritchie, and by Tung et al. Extension from the optical case to non-zero momentum transfer is done according to Ritchie and Howie. To evaluate surface and bulk contributions to the spectra, the Monte Carlo model treats the surface excitations according to the Werner differential surface and volume excitation probability theory. The Monte Carlo calculations are compared with the experimental reflection electron energy loss (REEL) spectra acquired in our laboratory.     

Calculated energy loss of a swift fullerene ion beam in InP

Bombardment of semiconductors with fullerene has been used to induce the formation of tracks. It is now accepted that target electronic excitation and ionization, which gives rise to the slowing down of the projectile is essential to calculate the track diameter. In the case of cluster beams, like fullerenes, the electronic excitation induced by each of the cluster constituents is enhanced, for certain projectile energies and target depths, by the so-called vicinage effects. Here we use a simulation code to calculate the energy lost by a swift fullerene ion beam in InP, paying special attention to the vicinage effects where they are significative. The code describes classically the movement of each cluster constituent under the influence of the self-retarding force, the Coulomb repulsion among molecular fragments, the wake forces responsible for the vicinage effects and the multiple scattering with the target nuclei. The simulation code also takes into account the possibility that the molecular fragments can also capture or loss electrons from the target, changing its charge state in their travel through the solid.Our simulations show that the energy deposited by the atomic ions that constitute the C₆₀ ion is clearly higher than the energy deposited by the same atomic ions but isolated. This difference being larger as the incident energy increases. We have predicted that track diameters of can be obtained in an InP target when using C₆₀ ions with an initial energy of 300 MeV.