Research on Irradiation Electric Field for Charged Particles Beam with High Energy

Irradiation protection of the nonlinear optical devices used in the spacecraft and next generation active laser system must be solved. The first problem was to find the irradiation damage mechanism of the nonlinear materials. In this paper the irradiation electronic field originating from high speed charged particle beams was discussed. The calculating model of the electronic field, based on the relativistic mechanics and electro-magnetic theory, was founded. The common characters of the irradiation electronic field were predicted and the fields of α ray and β ray were calculated by means of our model. The simulating results showed that the intensity of the electric field increased with the energy or the intensity of the beam. The results also showed that the field change trend of α ray and β ray was similar, but the field value was quite different. When the beam intensity I = 100 μA and the beam energy εm = 500 Mev, the electronic field values were about 3.5 × 107 v/m for α ray and 2.4 × 1011 v/m for β ray.

Irradiation-induced void evolution in iron：A phase-field approach with atomistic derived parameters

A series of material parameters are derived from atomistic simulations and implemented into a phase field（PF） model to simulate void evolution in body-centered cubic（bcc） iron subjected to different irradiation doses at different temperatures.The simulation results show good agreement with experimental observations — the porosity as a function of temperature varies in a bell-shaped manner and the void density monotonically decreases with increasing temperatures; both porosity and void density increase with increasing irradiation dose at the same temperature. Analysis reveals that the evolution of void number and size is determined by the interplay among the production, diffusion and recombination of vacancy and interstitial.

THE EFFECTS OF MAGNETIC FIELD ON GRAFT COPOLYMERIZATION OF METHYL METHACRYLATE ONTO POLYVINYL ALCOHOL IN THE PRESENCE OF BENZOPHENONE DURING UV IRRADIATION

The effects of magnetic field on the graft ratio and stereoregularity of grafts of PVA-g-MMA in the presence ofbenzophenone during UV irradiation are discussed. By means of IR, it was found that the graft ratio was increased with the increment of magnetic field strength. Furthermore, application of relative weak magnetic field of 0.4 Tesla had been shown to substantially enhance the stereo-regularity of graft copolymer. The maximum stereo-regularity appeared when the graft ratio approached to 85% with the magnetic field of 1.2 Tesla (T). The resistance to moisture and heat resistance of the grafted copolymer in the presence of magnetic field were also improved.

Orientation Dependence of Photoelectron Angular Distribution in Nitrogen Molecule Irradiated by XUV Laser Field

We theoretically study the dependence of photoelectron angular distribution on laser polarization direction in nitrogen molecules. The approach is based on the time-dependent density functional theory at the level of local density approximation complemented by self-interaction correction. It is found that photoelectron emission in one photon regime could be considered as a probing tool for the main character of different types of molecular orbitals （σ or π）. The pattern of emitted photoelectrons strongly depends on the polarized angle of the laser, for σ orbital, the number of photoelectron decreases with increasing the polarized angle, while for π orbital, it has the inverse relation to the polarized angle, which reveals the multi-electron effect in molecules. On the other hand, concerning the total photoelectron emission, one should take into account a few occupied orbitals instead of only the outmost one.

Electron-Irradiation Induced Nanocrystallization of Pb（ll） in Silica Gels Prepared in High Magnetic Field

In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead （II） nanocrystallites were formed induced by electron irradiation to lead （ll）-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead （II） acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead （II） nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.

<i>γ</i>-Ray Irradiation Effect on MCF Rubber Solar Cells with both Photovoltaics and Sensing Involving Semiconductors Fabricated under Magnetic and Electric Fields

For cases in which a robot with installed solar cells and a sensor operates in a nuclear reactor building or in space for extravehicular activity, we require elastic and extensible solar cells. More than two different types of sensing are also required, minimally with photovoltaics and built-in electricity. Magnetic compound fluid (MCF) rubber solar cells are made of rubber, so they are elastic and extensible as well as sensitive. To achieve flexibility and an effective photovoltaic effect, MCF rubber solar cells must include both soluble and insoluble rubbers, Fe3O4, TiO2, Na2WO4∙2H2O, etc. On the basis of this constitution, we propose a consummate fabrication process for MCF rubber solar cells. The characteristics of these cells result from the semiconductor-like role of the molecules of TiO2, Fe3O4, Ni, Na2WO4∙2H2O, polydimethylsiloxane (PDMS), natural rubber (NR), oleic acid, polyvinyl alcohol (PVA), water and magnetic cluster involved in the MCF rubber. Their tendencies can be deduced by synthesizing knowledge about the enhancement of the reverse-bias saturation current IS and the diode ideality factor N, with conventional knowledge about the semiconductor affected by γ-irradiation and the attenuation of the photon energy of γ-rays.

Modification of short-range repulsive interactions in ReaxFF reactive force field for Fe–Ni–Al alloy

The short-range repulsive interactions of any force field must be modified to be applicable for high energy atomic collisions because of extremely far from equilibrium state when used in molecular dynamics(MD)simulations.In this work,the short-range repulsive interaction of a reactive force field(ReaxFF),describing Fe-Ni-Al alloy system,is well modified by adding a tabulated function form based on Ziegler-Biersack-Littmark(ZBL)potential.The modified interaction covers three ranges,including short range,smooth range,and primordial range.The short range is totally predominated by ZBL potential.The primordial range means the interactions in this range is the as-is ReaxFF with no changes.The smooth range links the short-range ZBL and primordial-range ReaxFF potentials with a taper function.Both energies and forces are guaranteed to be continuous,and qualified to the consistent requirement in LAMMPS.This modified force field is applicable for simulations of energetic particle bombardments and reproducing point defects'booming and recombination effectively.

IRRADIATION EFFECT OF 0．56 GeV C^（6＋） on Y_（1．6）Ca_（1．4）V_（0．45）Sn_（0．5）Fe_（4．05）O_（12）

Y1.6Ca1.4V 0.45Sn0.5Fe4.05O12 is irradiated by 0.56 GeV carbon ion. The irradiation effect is investigated by Mossbauer spectroscopy. The irradiation results in an isotropic distribution of the hyperfine magnetic field. The hyperfine magnetic fields decrease after the irradiation due to the change of supertransferred field. After the irradiation, the chain Fe(a)-oxygen-Fe(d) become longer and it leads to decrease of the supertransferred field.

Low Doses of Ionized Radiation and Hypomagnetic Field Alter Redox Properties of Water and Physiological Characteristics of Seeds of the Highest Plants

The influence of a 40-fold attenuated geomagnetic field and its combined action with low doses of α- and γ-irradiation on the physiological characteristics of seeds of the highest plants and redox properties of water was investigated. It established the reduction of seed germination both under direct and indirect effects due to water action of attenuated geomagnetic field. A negative effect of hypomagnetic field on grown characteristics of seeds under indirect effect via water was decreased by the low doses of γ-irradiation, and was increased by low doses of α-irradiation, i.e. ionized radiation was the dominant factor in their combined action. It was revealed the increasing of the value of the oxidation-reduction potential of water under the influence of low-intensive α-ir-radiation (239Pu), γ-irradiation (137Cs) and also that the magnetic induction attenuated pointing to a natural decline. The increasing of the oxidation-reduction potential value testifies about “the regular decreasing of internal energy of water molecules” and the increasing of its oxidative properties, which, in our opinion, is caused the inhibition of the germination of seeds. It is supposed that namely water is the main component in the effects of studying factors on bio-objects, which acts due to the alterations of the properties and structural content of water.

Development of Magnetic Compound Fluid Rubber Sensor for Practical Usage on &gamma;-Irradiation and Energy Harvesting for Broad-Band Electromagnetic Waves

We have performed sequential studies on new types of soft rubber for their application as artificial skin in robots and haptic sensors. Based on a proposed electrolytic polymerization method and novel adhesion technique for rubber and a metal that utilizes a metal complex hydrate, we have developed an MCF rubber sensor. This sensor uses a magnetic compound fluid (MCF), natural rubber (NR-latex) or chloroprene rubber latex (CR-latex), and requires the application of a magnetic field. The potential application of the developed sensor in various engineering scenarios and our daily lives is significant. In this regard, we investigated the effects of &gamma;-irradiation, infrared radiation, microwaves, and a thermal source on the MCF rubber sensor. We established that the MCF rubber is effective enough to be used for power generation of broadband electro-magnetic waves from &gamma;-rays to microwaves, including the range of the solar spectrum, which is the typical characteristic obtained in the present investigation. The remarkable attribute is that the MCF rubber sensor dose is not degraded by &gamma;-irradiation. We also demonstrated the effectiveness of the MCF rubber sensor in energy harvesting.

海水环境光场水下辐照度测量光学设计

为了实现海洋环境光场水下辐照度测量光学设计,根据海洋辐射传输理论,对海洋环境下行辐照度、上行辐照度进行估算,完成海洋环境光场辐照度测量模块光学设计,并对其测量能力、姿态误差校正能力进行仿真分析,分析了探测器光敏面面积和透射窗口相对探测器的张角对测量能力的影响、横摇测量误差和纵倾测量误差对姿态测量误差影响,并得到横摇误差可采用动态水平法利用数据处理手段消除,纵倾测量误差可用对称排布的双辐照度探头测量模式消除的结论。海洋环境光场水下辐照度测量的光学设计,为水下实现目标环境光学特性测量奠定了技术支撑。

IRRADIATION EFFECT OF 0.56 GeV C￣（6+） on Y1.6Ca1.4V0.45Sn0.5Fe4.05O12

Y1.6Ca1.4V 0.45Sn0.5Fe4.05O12 is irradiated by 0.56 GeV carbon ion. The irradiation effect is investigated by Mossbauer spectroscopy. The irradiation results in an isotropic distribution of the hyperfine magnetic field. The hyperfine magnetic fields decrease after the irradiation due to the change of supertransferred field. After the irradiation, the chain Fe(a)-oxygen-Fe(d) become longer and it leads to decrease of the supertransferred field.

石墨烯场效应晶体管的X射线总剂量效应

本文针对不同结构、尺寸的石墨烯场效应晶体管(graphene field effect transistors,GFET)开展了基于10 keV-X射线的总剂量效应研究.结果表明,随累积剂量的增大,不同结构GFET的狄拉克电压V_(Dirac)和载流子迁移率μ不断退化;相比于背栅型GFET,顶栅型GFET的辐射损伤更加严重;尺寸对GFET器件的总剂量效应决定于器件结构;200μm×200μm尺寸的顶栅型GFET损伤最严重,而背栅型GFET是50μm×50μm尺寸的器件损伤最严重.研究表明:对于顶栅型GFET,辐照过程中在栅氧层中形成的氧化物陷阱电荷的积累是V_(Dirac)和μ降低的主要原因.背栅型GFET不仅受到辐射在栅氧化层中产生的陷阱电荷的影响,还受到石墨烯表面的氧吸附的影响.在此基础上,结合TCAD仿真工具实现了顶栅器件氧化层中辐射产生的氧化物陷阱电荷对器件辐射响应规律的仿真.相关研究结果对于石墨烯器件的抗辐照加固研究具有重大意义.

双沟槽SiC金属-氧化物-半导体型场效应管重离子单粒子效应

本文针对第四代双沟槽型碳化硅场效应晶体管升展了不同源漏偏置电压下208 MeV锗离子辐照实验,分析了器件产生单粒子效应的物理机制.实验结果表明,辐照过程中随着初始偏置电压的增大,器件漏极电流增长更明显;在偏置电压为400 V时,重离子注量达到9×10^(4)ion/cm^(2),器件发生单粒子烧毁,在偏置电压为500 V时,重离子注量达到3×10^(4)ion/cm^(2),器件发生单粒子烧毁,单粒子烧毁阈值电压在器件额定工作电压的34%(400 V)以下.对辐照后器件进行栅特性测试,辐照过程中偏置电压为100 V的器件泄漏电流无明显变化;200 V和300 V时,器件的栅极泄漏电流和漏极泄漏电流都增大.结合TCAD仿真模拟进一步分析器件单粒子效应微观机制,结果表明在低偏压下,泄漏电流增大是因为电场集中在栅氧化层的拐角处,导致了氧化层的损伤;在高偏压下,辐照过程中N-外延层和N+衬底交界处发生的电场强度增大,引起显著的碰撞电离,由碰撞电离产生的局域大电流密度导致晶格温度超过碳化硅的熔点,最终引起单粒子烧毁.

碳纤维复合材料激光辐照温度场分布规律仿真

基于碳纤维复合材料激光辐照理论,应用有限元方法,开展了碳纤维复合材料激光辐照温度场仿真分析。首先,研究了碳纤维复合材料激光辐照温度场分布规律,建立了不同位置线上的温度场表征方程,定量分析了辐照表面温度变化规律,并通过文献数据验证了有限元模型的有效性。然后,基于该模型,探究了复合材料板材不同铺层方向、不同光斑直径和不同激光功率下的温度场变化规律。结果表明:在不同铺层方向下,热影响区为椭圆形,[0]_(16)和[0/90]_(4S)板材的长轴方向为碳纤维0°铺层方向,而[45/90/-45/0]_(2S)板材的长轴方向为碳纤维45°铺层方向,且三者最高温度均约为1830℃;当光斑直径分别为6 mm、10 mm和14 mm时,热影响区面积逐步增大,而中心最高温度逐步降低,整个过程中最高温度分别为3347℃、2401℃和1838℃;在200 W、400 W和600 W激光功率下,板材中心温度随激光功率增大而增大,中心点最高温度分别为1750℃、2401℃和2789℃。

基于中值滤波改进的辐射图像降噪算法

为了解决核废物处置热室等辐照场中图像的降噪问题,本研究基于中值滤波,针对辐射噪点对算法进行相应改进,提出适用于强辐照场下图像降噪的算法。算法流程为噪点识别、噪点处理、细节保护。噪点识别从视觉观感出发,将像素值高出其周围并达到一定数值的标记为可疑点,并根据辐射噪点设定最大面积阈值,将大于面积阈值的区域排除;噪点处理基于中值滤波,自适应调整滤波窗口的大小;通过图像融合进行细节保护。通过与其他降噪算法进行比较可见,本算法对于辐射噪点的识别准确,降噪效果明显,并且最大程度地保护了画面的细节。本算法对于不同剂量率条件的辐射环境下具有较好的鲁棒性,在100 Gy/h的强辐照场下仍具有较好的去噪效果,可为核废物处置的智能化应用提供技术支持。

中子辐照奥氏体不锈钢晶内/晶间孔隙形貌演化的相场模拟

奥氏体不锈钢或镍基合金等FCC构型的核反应堆堆芯结构件材料中易于观测到晶间孔隙或晶内各向异性孔隙.孔隙内填充有少量气体,其形貌与晶体表面各向异性有关,又易于在晶界形核受晶界特性调控.本文通过建立耦合晶面各向异性与孔隙-晶界交互作用的自由能泛函模拟孔隙及其形貌演化,研究结果表明,He气体诱导孔隙形核,He气体浓度越高,孔隙的孕育期越短,形核越快,长大速率越大.晶界为孔隙形核提供非均质位点,孔隙优先在晶界处形核长大,形成沿晶析出的高密度弥散孔隙.晶内孔隙呈各向异性特征,受界面能各向异性模数、强度及晶体取向调控;晶间高密度孔隙相互作用且受晶界影响,各向异性形貌不显著,位于晶界中间的孔隙近似呈现椭圆形.本文的结果与实验结果符合得较好,启发堆芯服役构件的寿命预测和堆芯材料设计.

高温栅偏和电子辐照对SiC MOSFET阈值电压影响研究

为研究栅氧化物在不同老化程度下电子辐照对SiC MOSFET可靠性的影响,结合高温栅偏和电子辐照2种实验对SiC MOSFET电学特性进行分析,讨论栅氧化物受到高温和强电场应力后电子辐照对SiC MOSFET阈值电压的影响。为避免封装材料在高温和电子辐照下对阈值电压产生影响,实验时将被测器件裸露于空气中。实验结果表明,高温正栅偏后器件阈值电压对电子辐照更加敏感,因此提出了电子辐照对SiC MOSFET高温栅偏老化后阈值电压影响的指数关系,且0.2 MeV电子能量辐照300 kGy剂量可将39 V、150℃、2 h高温栅偏后的器件阈值电压恢复至初始值。在Sentaurus TCAD仿真软件中建立SiC MOSFET基础数值模型,设置氧化物内电子浓度和空穴陷阱,模拟高温栅偏和电子辐照对器件阈值电压的影响,讨论阈值电压恢复机制。

工业辐照加速器迷道辐射场分布研究

针对目前常用的工业辐照加速器,通过现场监测和理论分析等方法,对加速器迷道内辐射场主要影响来源进行分析,在实际测量的基础上,对迷道辐射场分布情况进行模拟分析和量化研究。迷道内纵向辐射场分布较均匀,第一段迷道,迷道内的辐射场主要来源于迷道内的散射线,而透射线对其影响很小;对于第二段迷道,迷道内的辐射场主要来源于迷道内的散射线和透射线,而且两者贡献相当。该文研究成果为该类加速器迷道辐射场分布提供了有价值的参考和数据,对完善该类辐照加速器辐射防护标准体系有着重要的现实意义。

从鼻咽癌放疗后复发部位探讨放疗设野范围

背景与目的:自上世纪90年代,中山大学肿瘤医院鼻咽癌常规外照射采用面颈联合野、耳前野和低熔点挡铅技术,本研究通过分析部分常规放疗后局部区域复发患者的资料探讨常规鼻咽癌面颈联合野和耳前野照射范围的合理性。方法:收集1999年在中山大学肿瘤医院按常规面颈联合野和耳前野设野治疗的,放疗后局部区域出现复发,有放疗前后和复发CT检查的鼻咽癌患者资料,分析复发灶所侵犯的部位。对于有照射野设置资料患者,在三维治疗计划系统(3DTPS)下进一步行局部复发灶和照射野模拟剂量学分析,观察复发灶与95%等剂量线的关系,若复发灶95%以上(包括95%)的体积在95%等剂量线内,判断为野内复发,20%以上(包括20%)～95%以下体积在95%等剂量线内,边缘复发,20%以下体积在95%等剂量线内,野外复发。结果:共收集了40例可供分析的患者,其中15例患者材料完整可供局部复发灶和照射野模拟剂量学分析。局部复发的主要部位为鼻咽腔、颅底骨质;局部复发灶和照射野模拟剂量学分析发现野内复发9例,边缘复发4例,野外复发2例。6例边缘和野外复发的患者,经过进一步分析发现复发与未严格遵循常规设野原则或对病灶范围判断失误造成不适当的照射野边界导致靶区出现低剂量区有关。结论:常规鼻咽癌面颈联合野和耳前野照射范围基本是合理的。