The operating principles of the two duoplasmatron ion sources and the PIG source available for the Van de Graaff accelerator have been determined qualitatively, mainly by studying the extensive literature on ion sourc...The operating principles of the two duoplasmatron ion sources and the PIG source available for the Van de Graaff accelerator have been determined qualitatively, mainly by studying the extensive literature on ion sources. The main characteristics of the three sources have therefore been determined experimentally on an ion source test bench. Important parameters of the sources such as the pressure and temperature in different regions of the sources not measured, because of space limitations. However, in spite of these limitations in quantitative understanding of the sources, sufficient information to continue with the study of the beam transport through the Van de Graaff accelerator and its beamlines could be obtained from these measurements. With regard to beam intensity, lifetime and gas consumption the measurements showed that the hotcathode duoplasmatron is at present by far the most suitable source for the van de Graaff accelerator. The emittance of the ion source was measured with two slits, 90 mm apart, and a Faraday cup in the ion source test bench at an arc voltage of 83 V, an arc current of 1 Amp, a filament voltage of 24 V and an extraction voltage of 5 kV. The measured emittance for 90% of the beam intensity is 48π mm mrad. This figure will be used to calculate the beam transmission through the Van de Graaf accelerator. Different computer programs have been used for these calculations from the ion source through the terminal section, the accelerator and beam line up to the Nuclear Microprobe (NMP) for beam quality.展开更多
In order to improve the surface adhesion of high strength and high modulus poluethylene (PE)fibers with epoxy resin,graft polymerization of some monomers by electron beam(EB)pre-radia-tion was performed on the sur...In order to improve the surface adhesion of high strength and high modulus poluethylene (PE)fibers with epoxy resin,graft polymerization of some monomers by electron beam(EB)pre-radia-tion was performed on the surtacc of PE fibers.In the paper,the Van de Graft accelerator waschosen as a radiation resource.And we found from our studies that no sensitizer was needed in EBpre-radiation polymerization under the atmosphere of N<sub>2</sub>,and acrylic acid was most effective inthe polymerization of methyl methacrylate,acrylic acid and methacrylic acid.The degree of graftincreased with the enhancing of pre-radiation dose,reaction temperature and reaction time.Acetone and benzene were effective solvents for acrylic acid.Oligomer which exists during thepolymerization could be removed by washing with benzene.Grafted fiber was analyzed by SEMand ATR-IR and it was confirmed that some polar groups were introduced to the surface of PE fi-ber.The tensile strength of PE fibers did not decrease greatly when pre-radiation dose was lessthan 1.56×10<sup>4</sup> Gy.展开更多
采用电子束蒸镀方法在Si(100)衬底上沉积了ZnO:Al(ZAO)薄膜.在氧气气氛下对ZnO:Al薄膜进行了退火处理,退火温度的范围为400~800℃.X射线衍射(XRD)图样表明所制备的ZnO:Al薄膜具有六方结构,为c轴(002)择优取向的多晶薄膜.用Van der Pau...采用电子束蒸镀方法在Si(100)衬底上沉积了ZnO:Al(ZAO)薄膜.在氧气气氛下对ZnO:Al薄膜进行了退火处理,退火温度的范围为400~800℃.X射线衍射(XRD)图样表明所制备的ZnO:Al薄膜具有六方结构,为c轴(002)择优取向的多晶薄膜.用Van der Pauw法测量了ZAO薄膜的电学特性,结果显示其电导率在500℃达到最大值.测量了ZAO薄膜的室温微区光致发光和变温发光光谱,观测到了ZnO自由激子、束缚在中性施主中心(D0)上的束缚激子以及束缚在离化施主中心(D+0)上的束缚激子发射.展开更多
A multiple-elastic beam model based on Euler-Bernoulli-beam theory is presented to investigate the nonlinear dynamic instability of double-walled nanotubes. Taking the geometric nonlinearity of structure deformation, ...A multiple-elastic beam model based on Euler-Bernoulli-beam theory is presented to investigate the nonlinear dynamic instability of double-walled nanotubes. Taking the geometric nonlinearity of structure deformation, the effects of van der Waals forces as well as the non- coaxial curvature of each nested tube into account, the nonlinear parametric vibration governing equations are derived. Numerical results indicate that the double-walled nanotube (DWNT) can be considered as a single column when the van der Waals forces are sufficiently strong. The stiffness of medium could substantially reduce the area of the nonlinear dynamic instability region, in particular, the geometric nonlinearity can be out of account when the stiffness is large enough. The area of the principal nonlinear instability region and its shifting distance aroused by the nonlinearity both decrease with the increment of the aspect ratio of the nanotubes.展开更多
文摘The operating principles of the two duoplasmatron ion sources and the PIG source available for the Van de Graaff accelerator have been determined qualitatively, mainly by studying the extensive literature on ion sources. The main characteristics of the three sources have therefore been determined experimentally on an ion source test bench. Important parameters of the sources such as the pressure and temperature in different regions of the sources not measured, because of space limitations. However, in spite of these limitations in quantitative understanding of the sources, sufficient information to continue with the study of the beam transport through the Van de Graaff accelerator and its beamlines could be obtained from these measurements. With regard to beam intensity, lifetime and gas consumption the measurements showed that the hotcathode duoplasmatron is at present by far the most suitable source for the van de Graaff accelerator. The emittance of the ion source was measured with two slits, 90 mm apart, and a Faraday cup in the ion source test bench at an arc voltage of 83 V, an arc current of 1 Amp, a filament voltage of 24 V and an extraction voltage of 5 kV. The measured emittance for 90% of the beam intensity is 48π mm mrad. This figure will be used to calculate the beam transmission through the Van de Graaf accelerator. Different computer programs have been used for these calculations from the ion source through the terminal section, the accelerator and beam line up to the Nuclear Microprobe (NMP) for beam quality.
文摘In order to improve the surface adhesion of high strength and high modulus poluethylene (PE)fibers with epoxy resin,graft polymerization of some monomers by electron beam(EB)pre-radia-tion was performed on the surtacc of PE fibers.In the paper,the Van de Graft accelerator waschosen as a radiation resource.And we found from our studies that no sensitizer was needed in EBpre-radiation polymerization under the atmosphere of N<sub>2</sub>,and acrylic acid was most effective inthe polymerization of methyl methacrylate,acrylic acid and methacrylic acid.The degree of graftincreased with the enhancing of pre-radiation dose,reaction temperature and reaction time.Acetone and benzene were effective solvents for acrylic acid.Oligomer which exists during thepolymerization could be removed by washing with benzene.Grafted fiber was analyzed by SEMand ATR-IR and it was confirmed that some polar groups were introduced to the surface of PE fi-ber.The tensile strength of PE fibers did not decrease greatly when pre-radiation dose was lessthan 1.56×10<sup>4</sup> Gy.
文摘采用电子束蒸镀方法在Si(100)衬底上沉积了ZnO:Al(ZAO)薄膜.在氧气气氛下对ZnO:Al薄膜进行了退火处理,退火温度的范围为400~800℃.X射线衍射(XRD)图样表明所制备的ZnO:Al薄膜具有六方结构,为c轴(002)择优取向的多晶薄膜.用Van der Pauw法测量了ZAO薄膜的电学特性,结果显示其电导率在500℃达到最大值.测量了ZAO薄膜的室温微区光致发光和变温发光光谱,观测到了ZnO自由激子、束缚在中性施主中心(D0)上的束缚激子以及束缚在离化施主中心(D+0)上的束缚激子发射.
基金supported by the National Natural Science Foundation of China (No.10872066)
文摘A multiple-elastic beam model based on Euler-Bernoulli-beam theory is presented to investigate the nonlinear dynamic instability of double-walled nanotubes. Taking the geometric nonlinearity of structure deformation, the effects of van der Waals forces as well as the non- coaxial curvature of each nested tube into account, the nonlinear parametric vibration governing equations are derived. Numerical results indicate that the double-walled nanotube (DWNT) can be considered as a single column when the van der Waals forces are sufficiently strong. The stiffness of medium could substantially reduce the area of the nonlinear dynamic instability region, in particular, the geometric nonlinearity can be out of account when the stiffness is large enough. The area of the principal nonlinear instability region and its shifting distance aroused by the nonlinearity both decrease with the increment of the aspect ratio of the nanotubes.