强流电子束轫致辐射复合薄靶设计

针对目前脉冲硬X射线源能谱硬、辐照面积小、辐射场电子份额高无法开展系统电磁脉冲效应实验研究的技术难题,提出了采用复合薄靶软化脉冲硬X射线能谱、降低电子份额的方法。采用MCNP程序数值模拟了电子和光子在不同材料中的输运规律,分析了复合靶结构和材料厚度对X射线能谱、电子份额的影响。以闪光二号加速器为电子束源,设计了复合薄靶、X射线窗。实验得到的X射线参数：平均能量121 keV;均匀性2∶1情况下,700 cm2平均剂量40 rad（Si）,500 cm2平均剂量170 rad（Si）;光子数与电子数的比值大于103,可以开展系统电磁脉冲效应初步实验研究。     

强流电子束轫致辐射复合薄靶设计

针对目前脉冲硬X射线源能谱硬、辐照面积小、辐射场电子份额高无法开展系统电磁脉冲效应实验研究的技术难题,提出了采用复合薄靶软化脉冲硬X射线能谱、降低电子份额的方法。采用MCNP程序数值模拟了电子和光子在不同材料中的输运规律,分析了复合靶结构和材料厚度对X射线能谱、电子份额的影响。以闪光二号加速器为电子束源,设计了复合薄靶、X射线窗。实验得到的X射线参数:平均能量121 keV;均匀性2∶1情况下,700 cm2平均剂量40 rad（Si）,500 cm2平均剂量170 rad（Si）;光子数与电子数的比值大于103,可以开展系统电磁脉冲效应初步实验研究。     

Radiation induced synthesis of gold/iron-oxide composite nanoparticles using high-energy electron beam

Composite nanoparticles consisting of gold and iron oxide were synthesized in aqueous solution systems by using a high-energy electron beam. The electron irradiation induces radiation-chemical reaction to form metallic gold nanoparticles. These gold nanoparticles were firmly immobilized on the surface of the support iron oxide nanoparticles. Surface of the support iron oxide nanoparticles are almost fully coated with fine gold nanoparticles. The size of these gold nanoparticles depended on the concentrations of gold ions, polymers and iron oxide nanoparticles in the solutions before the irradiation.     

The interfacial effects on the conductive performance of the composite films based on materials with electron and ionic conductors

Laminated and blending composites are designed to study the interfacial effects on the overall conductivity based on materials with different conductive mechanisms. The blends exhibit porous morphology because of the phase separation among the components, providing lager contacting areas between polymer chains and ions, and also more moving spaces for them, and hence their conductivity increases with the addition of polyaniline (PAN) to a maximum value of 0.075?S?cm^?1 at 75% PAN of polyvinyl butyral (PVB) (wt.%). The laminated films also show conductivity improvement, but inferior to that of blends from room temperature to 60?°C. The element parameters of the interfaces have great effects on their conductive performances as tested by the electrode/solid polymer electrolytes (SPE)/electrode model. The values of the electrode/SPEs interface are in the same magnification, while the value between PAN and PVB/polyethylene glycol₄₀₀/LiClO₄ layers is much bigger than those of the electrode/SPEs, providing the fact that the interface effect between different materials (metal/polymer, polymer/polymer) plays a vital role in determining their overall conductive performances.     

Studying the microstructure of AlSiC metal matrix composite material by scanning electron microscopy

The microstructure of fractures in AlSiC metal matrix composite material obtained via vacuum compression impregnation of porous semi-finished materials is studied using a Quanta 200i 3D FEI scanning electron microscope. The disruption of AlSiC samples is shown to be due to the brittle fracturing of the largest grains of silicon carbide and disruption (during plastic deformation) of the material of the matrix alloy located between the grains of the filler. The character of SEM images testifies to considerable adhesion of selected aluminum matrix alloys at matrix-filler interfaces and the high mechanical strength of the material under study.     

Microstructural studies of composite Mughal period cannons of Daulatabad Fort,India, by electron backscattered diffraction and scanning electron microscopy

Historical data on ancient Indian cannons have systematically been researched, but there is lack of archaeometallurgical studies on bimetallic cannons. This study revolves around 16th–17th century bimetallic Indian cannons: copper barrel with inner iron sleeve at an approximate ratio of 5:1. Scanning electron microscopy and electron backscattered diffraction techniques have been employed to know the changes in the microstructures of the metals used in making cannons. Energy dispersive spectrometry confirmed that the outer copper barrel, with 4.5 wt% tin, had inclusions of cupric oxide (Cu₂O) and contained lead and sulfur. The inner sleeve, on the other hand, was primarily iron but contained fayalite (FeSiO₄) and inclusions with silicon and phosphorous. Both inner (bloomery iron) and outer (copper) material had strong signatures of plastic deformation, and the cannons were stipulated to be forge welded. Deformation twinning in recrystallized iron grains of inner iron sleeve and near-perfect extensive twinning in the inner copper barrel indicate exposures of the respective materials to such active usage. It is concluded from the deformed structures and from the presence of clear joints that the bimetallic cannons were made by a process of forge welding. This study brings actual manufacturing practices of bimetallic cannons in ancient India.     

The high-voltage electron microscope

The advantages of using very high voltages for electron microscopy are reviewed, in respect of greater specimen thickness and reduced chromatic aberration. For polymers and possibly with living material, the lower radiation damage in a given thickness is also valuable. The special problems in the design and construction of microscopes operating up to 1 Mv are discussed. We are still in a stage of rapid development, and some possibilities for the future are outlined. The main areas of application of high voltage microscopes are beginning to be defined; some examples are given of what has been done with the Toulouse and Cambridge microscopes to date.     

The holographic composite Higgs

Theories where the Higgs boson is a composite particle elegantly solve the hierarchy problem. This idea has been recently investigated in the framework of 5-dimensional warped models that, according to the AdS/CFT correspondence, have a 4-dimensional holographic interpretation in terms of strongly coupled field theories. We present a minimal model in which the Higgs arises as a pseudo-Goldstone boson and the electroweak symmetry is dynamically broken. This model can successfully solve the flavor problem and pass all the electroweak precision tests. To cite this article: R. Contino, A. Pomarol, C. R. Physique 8 (2007).     

A comparative study on radiation reliability of composite channel InP high electron mobility transistors

This paper proposes a reasonable radiation-resistant composite channel structure for In P HEMTs. The simulation results show that the composite channel structure has excellent electrical properties due to increased modulation doping efficiency and carrier confinement. Moreover, the direct current(DC) and radio frequency(RF) characteristics and their reliability between the single channel structure and the composite channel structure after 75-ke V proton irradiation are compared in detail. The results show that the composite channel structure has excellent radiation tolerance. Mechanism analysis demonstrates that the composite channel structure weakens the carrier removal effect. This phenomenon can account for the increase of native carrier and the decrease of defect capture rate.     

Transmission electron microscopy of composite materials based on hypercrosslinked polystyrenes with nanodispersed inorganic compounds

Nanocomposite materials with magnetic and catalytic properties based on hypercrosslinked polystyrenes (HLP) and inorganic compounds introduced into a polymer by means of chemical precipitation were investigated. Transmission electron microscopy (TEM) revealed that when ferric oxides are precipitated in hypercrosslinked gel-type polystyrene, nanodispersed particles 8 ± 2 nm in size are formed, and when the ferric oxides are precipitated in hypercrosslinked biporous polystyrene, larger nanoparticles (∼16 nm in size) are formed.     

Dynamics of a magnetized relativistic electron beam in composite drift tubes with virtual cathodes

A computer simulation of the dynamics of a magnetized electron beam in composite drift tubes with multiple virtual cathodes is presented. For a single-cavity tube, the value of the limiting current is found to equal that given by an exact formula. For two-and three-cavity tubes, it is revealed that the values of the limiting currents are smaller than those reported previously and that the current diagram may have a different structure. These phenomena are attributed to Pierce instability. The efficiency of microwave generation as a function of injection current is examined. It is established that the efficiency is minimum if the current equals any of the limiting values refined.     

一种新的磷化铟复合沟道高电子迁移率晶体管小信号物理模型

针对磷化铟(InP)复合沟道高电子迁移率晶体管(HEMT)的特点，对常规单沟道HEMT的小信号物理模型进行了修正，提出了一种新的用于复合沟道HEMT的小信号物理模型，用商用器件模拟软件ISE(integrated systems engineering)对其进行了仿真验证，对比了实测和仿真的I-V特性及转移特性曲线，重点研究了在InGaAs/InP双层沟道中考虑量子效应后的电场和电流密度随着不同栅电压的变化趋势，研究结果表明，由于在沟道中存在量子效应，在栅下靠源端低电场区域，电流主要分布在InGaAs沟道 关键词： 高电子迁移率晶体管 复合沟道 物理模型 磷化铟     

The secondary-electron background problem in electron excited auger electron spectroscopy

Dynamic background subtraction is used to demonstrate that the recently suggested spline-polynomial scheme for characterizing the secondary electron background neglects an important aspect of the Auger feature. As a consequence of this neglect, area measurements using the spline approximation are difficult to relate to the true Auger current.     

Bias voltage effect on electron tunneling across a junction with a ferroelectric-ferromagnetic two-phase composite barrier

The effect of bias voltage on electron tunneling across a junction with a ferroelectric-ferromagnetic composite barrier is investigated theoretically. Because of the inversion symmetry breaking of the spontaneous ferroelectric polarization, bias voltage dependence of the electron tunneling shows significant differences between the positive bias and the negative one. The differences of spin filtering or tunnel magnetoresistance increase with the increasing absolute value of bias voltage. Such direction preferred electron tunneling is found intimately related with the unusual asymmetry of the electrical potential profile in two-phase composite barrier and provides a unique change to realize rectifying functions in spintronics.     

The electron neutrino oscillation problem

If we accept the Moscow tritium decay results, indicating that v_e is mostly made of mass 14–44 eV components, and if we exclude near degeneracies between these heavier components, we find rather tight correlations betweenv_e → v_e oscillations in different ranges of distance/energy. This argument allows a closer comparison between experiments in different ranges, and suggests that some results (or interpretations) are in conflict. For example, the absence of oscillations in accelerator experiments puts a stringent bound on reactor and solar effects, contrary to some reactor results and to the popular interpretation of the solar neutrino puzzle. Non-diagonal v_e → v_α(α ≠ e) effects are also bounded. This adds further interest to checking the tritium decay result and to examining possible theoretical reasons for mass degeneracy.     

The electron cut-off wavelength transistor

We propose a transistor based on the transverse quantization of electron waves. The spread of non-degenerate electrons is some 20 nm at room temperature. In a wire-like structure having a diameter of this or smaller size, the electron transport will be cut-off like that of electromagnetic modes in a wave guide. Accelerated in electric fields, hot electrons have smaller spread and may now propagate through the narrow electron waveguide. This principle presents the basis for novel minuscule and versatile simple devices.     

The diffraction-dependence of electron damage in a high voltage electron microscope

Abstract

In a high voltage electron microscope the intense electron beam used for imaging can cause visible aggregates of point defects to form in metals in just a few minutes. The diffraction-dependence of the defect cluster production was studied experimentally in Cu and Fe using a 1000 kV electron microscope. Also, a simple method for calculating the diffraction-dependence of the atomic displacement rate was devised from multiple-beam wave-mechanical diffraction theory. The calculations indicate that the rate of point defect production should vary at most by a factor of ～1.7 with Bragg deviation in systematic diffraction cases, and that this variation should decrease rapidly with increasing depth in the crystal. The experimental observations are consistent with these predictions. In addition, the theory allows the diffraction-dependence of the displacement rate to be explained in terms of Bloch wave properties. Some new observations of the defect structures in electron-irradiated Cu and Fe are also described.