脉冲光电子枪中光电子束性能研究

利用新设计的脉冲光电子枪,研究了光电子束的能量分布,光电子数密度与激光强度的关系和光电子在电离区内的滞留时间。大部分电子的能量为光发射电子的剩余能量,但是由于电子的空间电荷效应,电子能量分布具有加宽现象·每个激光脉冲发射到电离区内的光电子数密度在109/cm3以上。     

Convolution of Velocity Distributions in a Pulsed Molecular Beam

The velocity distributions P(v) of pulsed molecular beams are conventionally measured via TOF techniques. To account for the finite pulse widths of beam valves, a convoluted TOF distribution function P(t) is derived. TOF data on Ar pulsed beams are analyzed accordingly.     

Effect of Plasma Treatment on Surface Wettability of Wheat Seeds

High Energy Chemistry - It has been shown that as a result of surface treatment of seeds in nonthermal atmospheric-pressure glow-discharge plasma, the surface becomes hydrophilic and is...     

Effect of Nanosecond Repetitively Pulsed X-Ray Radiation on the Sowing Quality of Seeds and the Productivity of Wheat

High Energy Chemistry - The effect of presowing treatment of wheat seeds with nanosecond repetitively pulsed X-ray (RPX-ray) radiation at a dose of 0.07 Gy and pulse repetition frequencies of 13...     

Plasma Jet and Dielectric Barrier Discharge Treatment of Wheat Seeds

Plasma Chemistry and Plasma Processing - Low-temperature plasma treatment of wheat seeds was performed by a plasma jet and dielectric barrier discharge, both at atmospheric pressure. The influence...     

Decomposition of Trimethylamine by an Electron Beam

To identify the decomposition characteristics of trimethylamine (TMA) by electron beam (EB), we conducted an experiment based on process parameters, including absorbed dose (2.5–10 kGy), background gas (air, O₂, N₂ and He), water content (1,200, 14,300, and 27,500 ppm), initial concentration (50, 100, and 200 ppm) and reactor type (batch or continuous flow system). Air background gas showed a maximum TMA removal efficiency of 86 % at 10 kGy and that was the highest efficiency of all background gases. Energy efficiencies were higher when the absorbed dose was lower (e.g., 2.5 kGy). Decomposition efficiencies of all initial TMA concentrations were approximately >90 % at 10 kGy. Removal efficiencies increased up to 30 % as water vapor increased. As a by-product, it is observed that CH₃ radical formed by EB irradiation was converted into CH₄ by reaction with residual TMA, (CH₃)₂NH, and H. These results suggest that EB technology can be applied for TMA treatment under low concentration and high flow rate conditions.     

Removal of Toxic Impurities from Air by Pulsed Electron Beams

The results of experimental studies on the removal of various impurities from gas mixtures excited by pulsed electron beams are presented. As found, it is the use of pulsed beams that ensures a significantly decrease in power consumption for the removal of impurities, as compared with continuous electron beams, and obtaining gaseous or solid substances as final products in some cases.     

Time Resolved Microwave Interferometry Measurement of the Electron Density in a Pulsed 1,3-Butadiene Discharge

Pulsed plasmas containing organic precursors are becoming increasingly common for multiple applications. To understand the nature of such discharges, in-situ time resolved microwave interferometry measurements of the electron density in a 60 W pulsed inductively coupled 1,3-butadiene discharge have been made. Measurements were also made for continuous wave plasmas at 40, 50, 60 and 70 W power for comparison. The data shows that the time averaged electron densities are independent of pulse width at a particular duty cycle. In addition, time averaged values increase approximately linearly with increasing duty cycle. Such linearity in average density is tied to the ambipolar loss rate. This knowledge is important for understanding the growth kinetics of plasma polymerized films.     

Degradation of Some Pesticides in Aqueous Solutions by Electron Beam and Gamma-Radiation

Decomposition by ionizing radiations of two pesticides (Lannate and Fenvalerate) present in an aqueous solution has been studied on laboratory-scale experiments. The effect of pH of the solution, the concentration of the pesticide and the irradiation dose on the degradation process was investigated. Gamma-irradiation was carried out in air and in combination with nitrogen, oxygen and ozone. Lannate showed more degradation than Fenvalerate in all conditions investigated. Radiation was not enough to achieve the complete decomposition of the pesticides. Adsorption of the pollutants after irradiation was achieved using granular activated carbon (GAC) and two anion exchangers (Dowex 1-X8 and Lewatit AP 246).     

Resistivity and Field Electron Emission of Nanowires Formed by Electron Beam Induced Chemical Vapor Deposition

"Self-standing iron nanowires were fabricated at the apex of a tungsten needle tip by electron beam induced deposition. This sharp needle tip which adhered to the nanowire can be moved with a stepping motor and piezo-driving device, and was attached inside a specially designed transmission electron microscope pecimen holder. A copper conductor substrate, with which the approaching nanowires will build up a closed electric circuit, was set on the holder. The tungsten needle tip accompanied with the EBICVD nanowires made contact with the substrate and then a voltage was applied between the two electrodes. Resistivity values of the examined nanowires, by a devised Lock-in-Amplifier circuit, range from 0.1 -m to 10-3 -m. Our investigation might have implications in the fabrication and characterization of nano-electronics device. Precursor with phenanthrene (C4H10) was used and the deposition experiment was done using a scanning electron microscope at room temperature. It was found that the surface structure at the top of the nanorod, such as a small protrusion within only several nanometers scale, has significant influence on the field emission property. An emission current of several tens of nano-ampere flowing through this nanorod could induce resistance heating. In several minutes, this thermal energy could transform the original amorphous carbon into a graphite-like structure embedded with fullerenes. The turn-on voltage of the graphite-like nanorod was about 11 V less than that of the original amorphous case."     

Abnormal Optical Emissions in a Condensing Monosilane–Argon Gas Jet Activated by Electron Beam Plasma

Emissions from Si, SiH, H, Ar, and Ar⁺ are investigated for a free supersonic jet of a mixture of monosilane 5% (or 10%) with argon; the jet is activated by electron- beam plasma, and all the emissions are measured as a function of pressure, temperature in the gas source, the nozzle-to-electron beam distance, and the beam current. It is found that for certain parameters a process initiates which inhibits radiation of the spectral lines of Si, SiH, and H, and stimulates radiation of some spectral lines of argon atoms. It is shown that these anomalies are connected with a condensation process in the jet and, apparently, they are caused by electron-induced fluorescence of monosilane-containing clusters. The mechanisms for abnormal emissions of argon atoms and electron-excited fragments of monosilane molecule are suggested.     

Characterization in the Toughening Process of CTBN Modified Epoxy Resins Induced by Electron Beam Radiation

Epoxy resins are widely utilized as high performance thermosetting resins for many industrial applications but characterized by a relatively low toughness. Electron beam (EB) curing of polymer resins has a number of advantages over conventional thermal curing, such as shorter curing time, low energy consumption, low cure temperature, dimensional stability, reduced manufacturing cost. In the present work liquid carboxyl-terminated butadiene acrylonitrile (CTBN) copolymers containing 8% acrylonitrile is added at different contents to improve the toughness of diglycidyl ether of bisphenol A (DGEBA) epoxy resins using triarylsulfonium hexafluoroanimonate as a photointiator. The EB irradiation was conducted 5 kGy to 250 kGy in nitrogen. The physics properties of CTBN modified epoxy resins were examined by determine gel content, DMA (dynamic mechanical analysis), UTM (Instron model 4443), SEM (scanning electron microscopy).     

Direct Measurement of Electron Beam Scattering in the Low Vacuum SEM

The beam-gas interactions in the low-vacuum SEM is investigated through experimental and simulation approaches. An original experimental way to characterise the skirting is proposed. We obtained directly image distribution of the primary electron beam and the scattered electrons in the low-vacuum SEM. The experimental results are compared to the electron beam profile obtained with Monte-Carlo simulation.     

Investigation of the Formation and Energy Density of High-Current Pulsed Electron Beams

High-current pulsed electron beams (HCPEB) irradiation is a new potential method to polish hard steels and alloys. After HCPEB machining, the performance of machined surface, such as corrosion resistance and microstructure, has been greatly improved. Because of its good performance, HCPEB irradiation is playing more and more important roles in polishing hard steels and alloys. However, it is not clear about the energy density of HCPEB under different beam conditions. In this study, experiments have been conducted to investigate the formation of HCPEB and its energy density. Then, effects of argon gas pressure and the applied voltage to solenoid coil on the formation of HCPEB are analyzed. Finally, a mathematical model is developed to describe the relationship between five dominant beam parameters with the energy density of HCPEB, which has a good accuracy in comparison to the experimental results.     

Towards a Consistent Chemical Kinetic Model of Electron Beam Irradiation of Humid Air

A chemical kinetic model has been assembled based upon previous literature to assist in developing a better understanding of the mechanism behind the electron beam irradiation of humid air. Thermodynamic determination of the feasibility of particular product sets was used to eliminate certain reactions proposed previously, dynamical models were used to guide the choice of product sets, and updated rate constants were obtained from the current literature. Tracers were also used to determine significant sources and sinks of hydroxyl radical, an important species in the irradiation process. Modeling results for selected species have been presented for 1 atm of air at 298.15 K and 50% relative humidity, at doses of 1, 5, 10, 25, and 50 kGy delivered over 0.8 s. The concentrations of the most abundant ions, radicals, and stable reaction products have been included, as well as the calculated major sources and sinks of hydroxyl radical.     

衬底温度对强流脉冲离子束烧蚀沉积类金刚石薄膜化学结构的影响

采用强流脉冲离子束(High-intensitypulsedionbeam,HIPIB)烧蚀技术在Si(100)基体上沉积类金刚石(Diamond-likecarbon,DLC)薄膜,衬底温度的变化范围为298～673K.利用Raman光谱和X射线光电子谱(XPS)对DLC薄膜的化学结合状态与衬底温度之间关系进行研究.薄膜XPS的C1s谱的解谱分析得出薄膜中含有sp³C(结合能为285.5eV)和sp²C(结合能为284.7eV)成分,根据解谱结果评价薄膜中sp³C含量.根据XPS分析可知,衬底温度低于473K时,sp³C的含量大约为40%左右;随着沉积薄膜时衬底温度的提高,sp³C的含量降低,由298K时的42.5%降到673K时的8.1%,从573K开始发生sp³C向sp²C转变.Raman光谱表明,随着衬底温度的提高,Raman谱中G峰的峰位靠近石墨峰位,G峰的半峰宽降低,D峰与G峰的强度比I_D/I_G增大,说明薄膜中的sp³C的含量随衬底温度增加而减少.     

脉冲射频治疗骶髂关节疼痛疗效分析

目的探讨脉冲射频技术治疗难治性骶髂关节疼痛的疗效。方法对13例应用脉冲射频技术方法治疗的难治性骶髂关节疼痛患者,随访半年后,记录其术后2周、出院后1个月、3个月、6个月时的疼痛缓解程度及并发症,以及患者对治疗效果的满意度。结果术后2周患者疼痛不同程度缓解,优良率100%,但随着时间延长,大部分患者不同程度复发,6个月后优良率只有46.2%;患者对治疗效果满意度为97.3%。结论脉冲射频治疗短期内可显著降骶髂关节疼痛,部分患者疗效可靠,满意度达标,值得临床推广应用。     

Effect of Low Temperature Plasma Treatment on Biological Characteristics and Yield Components of Wheat Seeds (Triticum aestivum L.)

Plasma Chemistry and Plasma Processing - The impacts of a low temperature plasma treatment on wheat seed germination and field growth were investigated using a plasma system about the first...     

The Development of iDPC-STEM and Its Application in Electron Beam Sensitive Materials

The main aspects of material research: material synthesis, material structure, and material properties, are interrelated. Acquiring atomic structure information of electron beam sensitive materials by electron microscope, such as porous zeolites, organic-inorganic hybrid perovskites, metal-organic frameworks, is an important and challenging task. The difficulties in characterization of the structures will inevitably limit the optimization of their synthesis methods and further improve their performance. The emergence of integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM), a STEM characterization technique capable of obtaining images with high signal-to-noise ratio under lower doses, has made great breakthroughs in the atomic structure characterization of these materials. This article reviews the developments and applications of iDPC-STEM in electron beam sensitive materials, and provides an outlook on its capabilities and development.