Effects of electron beam irradiation on SnO_2 gas sensors

(Shanghai Applied Radiation Institute, Shanghai University Shanghai 201800) There are many traditional ways to improve sensitivity and selectivity of semiconductor gas sensors, such asmetal ions adulteration[1,2] and surface modification[3,4]. In this paper 1.75MeV electron beam was used to modifysurface structure of tin dioxide gas sensors, and the gas sensing characteristics were studied. Results showed thatthe sensitivity and selectivity of SnO2 sensors were improved after the electron …     

Preliminary Research Results for the Generation and Diagnostics of High Power Ion Beams on FLASH II Accelerator

The preliminary experimental results of the generation and diagnostics of highpower ion beams on FLASH II accelerator are reported, The high-power ion beams presently are being produced in a pinched diode, The method for enhancing the ratio of ion to electron current is to increase the electron residing time by pinching the electron flow, Furthermore, electron beam pinching can be combined with electron reflexing to achieve ion beams with even higher efficiency and intensity. The anode plasma is generated by anode foil bombarded with electron and anode foil surface flashover. In recent experiments on FLASH II accelerator, ion beams have been produced with a current of 160 kA and an energy of 500 keV corresponding to an ion beam peak power of about 80 GW. The ion number and current of high power ion beams were determined by monitoring delayed radioactivity from nuclear reactions induced in a ^12C target by the proton beams, The prompt γ-rays and diode bremsstrahlung X-rays were measured with a PIN semi-conductor detector and a plastic scintillator detector, The current density distribution of ion beam were measured with a biased ion collector array. The ion beams were also recorded with a CR-39 detector.     

Effects of CT based Voxel Phantoms on Dose Distribution Calculated with Monte Carlo Method

A few CT-based voxel phantoms were produced to investigate the sensitivity of Monte Carlo simulations of X-ray beam and electron beam to the proportions of elements and the mass densities of the materials used to express the patient‘s anatomical structure. The human body can be well outlined by air, lung, adipose, muscle, soft bone and hard bone to calculate the dose distribution with Monte Carlo method. The effects of the calibration curves established by using various CT scanners are not clinically significant based on our investigation. The deviation from the values of cumulative dose volume histogram derived from CT-based voxel phantoms is less than 1% for the given target.     

Shielding calculation for the thickness of the SR facility safety shutter

The safety shutter of the SR （synchrotron radiation） facility located at the front end of the facility is an indispensable component for radiation protection. Its thickness is decided by the gas bremsstrahlung produced in the SR facility storage ring by the interaction of electrons with the residual gas molecules in the vacuum chamber of the storage ring. In the calculation, the 3.5GeV, 300mA electron beam and a 15 m long insertion-device straight section （0.133 μPa） were taken into account, and the safety shutter was assumed to be located 12 m away from the end of the straight section. The EGSnrc code based on the Monte-Carlo method and empirical formulas were used, respectively, to calculate the thickness to satisfy the shielding requirement of the safety shutter at the front end of the SR facility, and the results were compared and the availability of EGSrlrc was proved.     

Hydrogenation of zirconium film by implantation of hydrogen ions

In order to understand the dnve-in target in a D-D type neutron generator,it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogenabsorbing metal film.The present research concerns the nucleation of hydride within zirconium film implanted with hydrogen ions.Doses of 30 keV hydrogen ions ranging from 4.30×10~(17) to1.43×10~(18) ions cm~(-2) were loaded into the zirconium film through the ion beam implantation technique.Features of the surface morphology and transformation of phase structures were investigated with scanning electron microscopy,atomic force microscopy and x-ray diffraction.Confirmation of the formation of 5 phase zirconium hydride in the implanted samples was first made by x-ray diffraction,and the different stages in the gradual nucleation and growth of zirconium hydride were then observed by atomic force microscope and scanning electron microscopy.     

Numerical simulation and experiment of error field measurement using luminous trace of electron beam in SST-1

In contrast to the earlier experiments conducted in other machines,here,in SST-1 the error field measurement experiment is performed with a filled gas pressure ～8×10~(-4) mbar which helped to create a luminescent toroidal beam of electron path originated due to impact excitation and guided by the toroidal magnetic field.Beam path deviations are observed and recorded from radial and top ports using visible range cameras.Such creation and detection of the electron beam path differs from the earlier works where the gun emitted electron beam deviation in ultrahigh vacuum was detected on a collector-grid/fluorescent screen.In the present experiment,large beam deviations were observed.Later investigation of the experimental set-up reveals existence of a possible source of radial electric field in between the source and the vacuum vessel which are separately grounded.Thus,to understand the observed phenomena,experiments are numerically modeled with deviated TF coil set,PF coil set and the electron source location.A particle tracing code is used to follow the electron path in the magnetic field generated by the coil set of interest.Simulation results suggest that the large deviation corresponds to the E×B drifts and not due to the large field errors.Toroidally averaged field errors of the SST-1 TF coils at toroidal field of B_0=15 kG are negligibly small～B_0×10~(-6) or less,which should not adversely affect the plasma performance.     

A Mutant of Bacillus Subtilis with High-Producing Surfactin by Ion Beam Implantation

In order to generate a mutant of Bacillus subtilis with enhanced surface activity through low energy nitrogen ion beam implantation, the effects of energy and dose of ions implanted were studied. The morphological changes in the bacteria were observed by scanning electron microscope （SEM）. The optimum condition of ions implantation, 20 keV of energy and 2.6 × 10^15N^＋/cm^2 in dose, was determined. A mutant, B.s-E-8 was obtained, whose surface activity of 50-fold and 100-fold diluted cell-free Landy medium was as 5.6-fold and 17.4-fold as the wild strain. The microbial growth and biosurfactant production of both the mutant and the wild strain were compared. After purified by ultrafiltration and SOURCE 15PHE, the biosurfactant was determined to be a complex of surfactin family through analysis of electrospray ionization mass spectrum （ESI/MS） and there was an interesting finding that after the ion beam implantation the intensities of the components were different from the wild type strain.     

Divertor Experiments with MBI and Strong Gas Puffing on HL-2A

In the HL-2A 2004 experiment campaign, pulsed molecular beam injection （MBI） and strong hydrogen gas puffing under the divertor configuration were used for gas fueling. The experimental results show that the MBI of hydrogen can reduce the heat flux to the divertor target plate. The electron temperature measured by the Langmuir probe array decreases significantly during the injection of the molecular beam whereas the electron density increases. This indicates that the plasma pressure near the target plates tends to be constant at a new equilibrium level. In the divertor plasmas with strong hydrogen gas puffing a high plasma density up to 4.4 × 10^19 m^-3 was achieved. In addition, a phenomenon similar to the partially detached divertor regime was observed, which is being studied in open divertor tokamaks such as DIII-D to reduce the peak heat flux on the target plates near the separatrix. After a strong gas puffing the electron temperature measured on the outer divertor target plate near the separatrix decreases till below 5 eV or even lower, but that of the farther outer divertor target plate does not change obviously; and the CIII and the Ha emissions at the plasma edge decrease as expected, but the Ha emission near the Xpoint increases. These results reflects some interesting characteristics, which needs to be studied by further modeling and experiments.     

Excited Electron Temperature and Molecular Vibration Temperature During Transition from Filamentary Discharge to Glow Discharge in Surface Discharge in Air

A dielectric barrier surface discharge device was used to investigate the transition from a filamentary discharge to a glow discharge in air at different gas pressures. Discharge images and waveforms of the applied voltage and discharge current were recorded simultaneously, and it was found that the discharge could transit from filamentary to glow with the decrease in pressure. Optical emission spectra during the transition from a filamentary discharge to a glow one were recorded. Excited electron temperature can be determined from the ratios of the relative intensities of spectral lines while molecular vibration temperature can be measured by analysing spectral lines of the N2 second positive band system. The results show that both the excited temperature and molecular vibration temperature increase with the decrease in the gas pressure. Qualitative explanations are given.     

SURFACE SEGREGATION EFFECTS IN AL_2O_3 IMPLANTED WITH HIGH DOSE INDIUM

Implantations of 100 keV In ions to high dose of 6 ×1016 In/cm2 were performed into a-axis oriented crystals of Al2O3 held at a liquid nitrogen temperature. The implantation produced about 80nm thick amorphous surface layer. Isothermal annealing in flowing Ar gas ambient was done at the temperatures of 600, 700, 800, and 900℃ . Rutherford backscattering and channeling (RBS-C), scanning electron microscope (SEM) and reflection high energy electron diffraction (RHEED) have been employed to investigate the annealing behaviors.The indium shows anomalous diffusion in amorphous layer. The migration of indium was composed of two parts: (a) some broadening of In profile corresponding to diffusion within the amorphous layer, (b) segregation of In to surface to form In2O3 which appears as islands on the surface. When the ambient is made oxygen free, the segregated In is lost by evaporation at the surface.     

电子束降解1,2,4-三氯苯及机理研究

1, 2, 4-trichlorobenzene is a kind of organic contamination which is difficult to be decomposed by normal methods[1-5].1, 2, 4-trichlorobenze at initial mass concentration of 200 mg/L in aqueous was irradiated with electron beam in a laboratory-scale. The irradiation was performed at room temperatures with a GJ-2-Ⅱ accelerator (Shanghai X ianfeng Motors), with 1.5 MeV 1 mA E-beams. Practical range of the electrons is about 0.7g/cm2. The samples, each of 20mL with a 4 mm depth, were placed at 30 cm under the titanium window and scanned by the E-beams at a dose rate of 3.5 kGy/s, as was determined by membrane. concentration method with GC. Doses delivered to the samples were 35, 70, 105, 140, 210 and 280kGy, respectively.It was found that trichlorobenzene concentration of the sample solution decreased after the irradiation,whereas its mass concentration of chlorine ions increased, with pH value of the irradiated solution being 2 to 3.Trichlorobenzene was decomposed completely by 105kGy irradiation, and dechloride rate of trichlorobenzene reached 100% at 210kGy. Benzene collar was destroyed by the irradiation. Fig. 1 and Fig.2 are GC results oftrichlorobenzene at initial concentration and after being irradiate to 70 kGy.The results show that decomposion of trichlorobenzenes by E-beam irradiation is an efficient method.Dechloride of chlorobenzenes can be done by 105 kGy E-beam irradiation. And conbined with other methods, the radiation treatment would be efficiently to remove chlorobenzenes in wastewater and to protect the environment.     

6 MeV electron irradiation effects on electrical properties of Al/TiO2/n-Si MOS capacitors

The irradiation effects of 6 MeV electrons on the electrical properties of Al/TiO₂/n-Si metal-oxide-semiconductor capacitors have been investigated. Nine Al/TiO₂/n-Si capacitors were fabricated using radio frequency magnetron sputtering and divided into three groups. Groups were irradiated with 6 MeV electrons at 10, 20, and 30 kGy doses, respectively, keeping the dose rate ∼1 kGy/min. The variations in the capacitance-voltage and leakage current-voltage characteristics, in addition to the electrical parameters, such as conductance (G/ω), flat-band voltage, interface trap density and the surface charge density with electron dose were studied. The Poole-Frenkel coefficient of the MOS capacitors was determined from current-voltage characteristics. Possible mechanisms for the enhanced leakage current in the electron irradiated MOS capacitors are discussed.     

对硝基苯胺的辐照降解研究

采用电子束辐照对硝基苯胺水溶液,研究了对硝基苯胺的辐照降解过程,并对吸收剂量、初始浓度、溶液pH及H202加入等因素对辐照降解效果的影响进行了探讨。结果表明,电子束辐照能够有效地降解对硝基苯胺。初始浓度为100mg／L,吸收剂量为20kGy时,对硝基苯胺的降解率可达95％以上,化学需氧量（Chemical oxygen demand,COD）的去除率可达41％以上。     

Spectroscopic and thermal studies of 8 MeV electron beam irradiated HPMC films

Radiation-induced changes in hydroxypropyl methylcellulose (HPMC) films under electron irradiation were investigated and correlated with dose. Polymer samples were irradiated in air at room temperature by an electron beam accelerator in the range of 0-100 kGy. Various properties of the irradiated films were studied using a Ultraviolet-Visible spectrophotometer and Fourier transform infrared spectroscopy and thermogravimetric analysis. Electron irradiation was found to induce changes in the physical, chemical and thermal properties, depending on the irradiation dose.     

Electron-beam radiation effects on the structure and properties of polypropylene at low dose rates

While the high-energy radiation effects on polypropylene, which are crucial for the cable industry for nuclear power plants, have been thoroughly studied, the property changes of PP at low-dose-rate electron-beam irradiation are far from elucidated. Herein, the influence of electron-beam irradiation on the structure and properties of PP was examined. The static EB irradiation conditions were 1.2 MeV at a low dose rate of 20 kGy/h to achieve absorbed doses ranging from 45, to 60, 100, and 200 kGy.The molecular structure was first evaluated by measuring the carboxyl index and the relative radical concentrations via Fourier transform infrared spectroscopy and electron spin resonance, respectively. Mechanical, differential scanning colorimetric, and rheological tests were carried out to further investigate the changes in the properties(tensile, crystalizing, and viscoelastic properties) of irradiated PP, which showed good agreement with the structural analysis results. We found that radio-oxidative degradation(chain scission) was predominant, which can be due to the low dose rate facilitating oxygen diffusion into the PP matrix during electron-beam irradiation.     

Dose intercomparison studies for 60Co gamma-ray and electron beam irradiation in the year 2002

1 Introduction With the rapid development of radiation process- ing by electron beam irradiation in China, it is more Ever since 1962, alanine/EPR dosimetry system and more needed to establish a transfer dosimetryhas been used to measure the absorbed dose.[1] Its ad- system with high accuracy to assure the quality of thevantages over othe…     

电子辐照PVA/CMC共混水凝胶的成胶研究

本试验利用电子辐照PVA/CMC共混水凝胶,通过外观透明度、凝胶分数、溶胀度和红外光谱分析,研究了样品中结构的变化与外观透明度、凝胶分数和溶胀度的关系,以及辐照剂量对样品中结构和性能的影响.结果表明,不同比例的PVA与相同比例的CMC组成的共混水凝胶,经电子辐照后呈现不同的宏观特性.辐照样品萃取后得到的凝胶比萃取前的混合凝胶拥有更强的吸水性,表明辐照PVA/CMC共混凝胶形成了网状结构凝胶.几种竞争反应导致不同辐照剂量下混合凝胶中凝胶含量随PVA含量的变化变得复杂.辐照后样品的红外光谱分析显示,辐照使凝胶中部分仲醇中C上链接的H原子被取代而转变为叔醇,从而产生交联.     

大型工业电子束脱硫脱硝装置辐射等效剂量场模拟与系统参数优化

为优化大型工业电子束脱硫脱硝装置和配套大功率电子加速器工程参数,应用Geant4模拟分析了不同出射能量的单能电子束在烟气中的径迹和偏转后电子束在烟气中的等效剂量场。计算得到1.75 MeV电子束更符合1 000 MWe级火电机组烟气系统工程设计需要,计算结果将为工业化设计提供参考。     

快中子照射唐菖蒲球茎的损伤作用初探

用快中子脉冲堆(China fast burst reactor Ⅱ,CFBR-Ⅱ)对唐菖蒲"超级"球茎进行不同剂量的照射处理,研究快中子对唐菖蒲球茎表面的刻蚀情况及对蛋白质表达的阻遏作用.扫描电镜观察发现球茎受损伤情况随照射剂量和照射角度的不同而变化,受垂直方向照射的球茎表面刻蚀程度最严重,且刻蚀程度随着剂量增大而增大.通过田间栽培试验和SDS-聚丙烯酰胺凝胶电泳(SDS-polyacrylamide gel electrophoresis,SDS-PAGE)分析发现,随照射剂量的增大,植株生长发育受到明显的抑制,蛋白表达数量显著减少.由此表明,快中子照射对植株能产生明显的影响.     

电子束辐照处理模拟甲苯废气实验研究

以甲苯作为挥发性有机化合物的代表物质,在800keV电子束的辐照下,模拟甲苯废气的气量在0.5—1.2m3/h范围内,研究了甲苯初始质量浓度为1600—4630mg/m3时吸收剂量、甲苯初始浓度和湿度对于甲苯分解效率的影响。实验结果表明,电子束辐照可有效去除甲苯,甲苯初始质量浓度为1600mg/m3,辐照10kGy和40kGy,甲苯去除率分别为46.5%和72.2%;增加湿度也可提高甲苯去除率。用气相色谱-质谱仪(GC-MS)和离子色谱仪(IC)定性研究了辐解产物。甲苯辐解产物比较复杂,主要含有苯甲醛、甲酸等物质。也探讨了电子束辐照处理甲苯气体的主要机理,讨论了O2和.OH对于电子束辐照分解甲苯中的重要作用。