电子能量损失谱仪用中高能电子枪的研制
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摘要
研制了一台电子能量损失谱仪用的中高能电子枪。其产生的电子与原子、分子发生碰撞,通过谱仪收集、分析散射电子的动量和能量,可以获得靶的电子结构和碰撞动力学信息。该电子枪结构简单,由热阴极、栅极、阳极、聚焦极和偏转板组成;电子能量可调范围大(1-3 keV),操作简单。为了获得最优的束流条件,利用SIMION电子光学软件模拟了电子发射源大小和初始发散角对靶点处的束斑大小和束流发散角的影响。在电子能量为1.5 keV条件下,实验检验给出在离电子枪出口27 mm处可获得束径约为0.95 mm、束流发散角约0.93°和束流强度6.27mA的电子束,满足电子能量损失谱仪的使用要求。
Background: In an electron energy-loss spectroscopy(EELS) experiment, the electron emitted by the electron gun collides with atoms and molecules, and the momentum and energy of the scattered electron are analyzed by EELS, then the information of electronic structure and collision dynamics of the target can be deduced. Purpose:A well designed intermediate-high energy electron gun with small beam size and divergence angle is needed to satisfy the requirement of EELS. Methods: To obtain the optimal beam condition, the electron optics software SIMION was utilized to simulate the space size and divergence angle of the electron beam at target position, the electron gun has a simple structure, i.e., consisting of thermionic cathode, grid electrode, anode electrode, focus electrode and deflection plates. The tuning range of electron energy is wide(1-3 keV) and easy to operate. Results: The beam size of 0.95 mm, divergence angel of 0.93°, and beam current of 6.27 mA of the constructed electron gun was obtained at 27 mm from the exit of electron gun at a beam energy of 1.5 keV. Conclusion: An electron gun which satisfies the requirements of EELS has been developed.
Background: In an electron energy-loss spectroscopy(EELS) experiment, the electron emitted by the electron gun collides with atoms and molecules, and the momentum and energy of the scattered electron are analyzed by EELS, then the information of electronic structure and collision dynamics of the target can be deduced. Purpose:A well designed intermediate-high energy electron gun with small beam size and divergence angle is needed to satisfy the requirement of EELS. Methods: To obtain the optimal beam condition, the electron optics software SIMION was utilized to simulate the space size and divergence angle of the electron beam at target position, the electron gun has a simple structure, i.e., consisting of thermionic cathode, grid electrode, anode electrode, focus electrode and deflection plates. The tuning range of electron energy is wide(1-3 keV) and easy to operate. Results: The beam size of 0.95 mm, divergence angel of 0.93°, and beam current of 6.27 mA of the constructed electron gun was obtained at 27 mm from the exit of electron gun at a beam energy of 1.5 keV. Conclusion: An electron gun which satisfies the requirements of EELS has been developed.
引文
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11凤任飞.高分辨快电子能量损失谱仪的研制[D].合肥:中国科学技术大学,1993.FENG Renfei.Development of a high-resolution electron energy-loss spectrometer[D].Hefei:University of Science and Technology of China,1993.
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15薛冬冬,孙秀宇,游燕,等.低能量电子枪的研发[J].真空电子技术,2016,(1):34?37.XUE Dongdong,SUN Xiuyu,YOU Yan,et al.Development of a low energy electron gun[J].Vacuum Electronics,2016,(1):34?37.
16 David J M,David A D.SIMION 8.0 user manual[M].United States of America:Scientific Instrument Services Inc.,2007.
17任黎明,陈宝钦.电子束曝光高斯分布束斑的Monte Carlo模拟[J].微细加工技术,2001,19(3):60?63.REN Liming,CHEN Baoqin.Monte Carlo simulation of Gauss-distribution beam spot in electron beam lithography[J].Microfabrication Technology,2001,19(3):60?63.
2朱林繁,凤任飞,王映雪,等.高分辨快电子能量损失谱仪的改进[J].核技术,2001,24(8):663?667.ZHU Linfan,FENG Renfei,WANG Yingxue,et al.New development of high resolution fast electron-energy-loss spectrometer[J].Nuclear Techniques,2001,24(8):663?667.
3 Ibach H.Electron energy loss spectrometers[M].Heidelberg:Springer-Verlag,1991.
4 Tanaka H,Brunger M J,Campbell L,et al.Scaled plane-wave born cross sections for atoms and molecules[J].Reviews of Modern Physics,2016,88(2):025004.DOI:10.1103/Rev Mod Phys.88.025004.
5 Jones D B,Neves R F C,Lopes M C A,et al.Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural[J].Journal of Chemical Physics,2016,144(12):124309.DOI:10.1063/1.4944615.
6 Suzuki T Y,Suzuki H,Ohtani S,et al.Asymptotic behavior of apparent generalized oscillator strengths for optically forbidden transitions in rare-gas atoms[J].Physical Review A,2007,75(3):032705.DOI:10.1103/Phys Rev A.75.032705.
7 Hoshino M,Ishijima Y,Kato H,et al.Change in resonance parameters of a linear molecule as it bends:evidence in electron-impact vibrational transitions of hot COS and CO2 molecules[J].The European Physical Journal D,2016,70(5):1?13.DOI:10.1140/epjd/e2016-70085-9.
8 Feng R,Cooper G,Burton G R,et al.Absolute photoabsorption oscillator strengths by electron energy loss methods:the valence and S 2p and 2s inner shells of sulphur dioxide in the discrete and continuum regions(3.5-260 e V)[J].Chemical Physics,1999,240(3):371?386.
9 Suzuki T Y.Studies for excitation in rare gas atoms by electron impact:asymptotic behaviors of generalized oscillator strengths[D].Tokyo:University of ElectronicCommunications,2000.
10 Da Silva F F,Duflot D,Hoffmann S V,et al.Electronic state spectroscopy of halothane As studied by ab initio calculations,vacuum ultraviolet synchrotron radiation,and electron scattering methods[J].Journal of Physical Chemistry A,2015,119(31):8503?8511.DOI:10.1021/acs.jpca.5b05308.
11凤任飞.高分辨快电子能量损失谱仪的研制[D].合肥:中国科学技术大学,1993.FENG Renfei.Development of a high-resolution electron energy-loss spectrometer[D].Hefei:University of Science and Technology of China,1993.
12 Xu W Q,Sun J M,Wang Y Y,et al.Generalized oscillator strengths and integral cross sections for the valence-shell excitations of oxygen studied by fast electron impact[J].Physical Review A,2010,82(4):042716.DOI:10.1103/Phys Rev A.82.042716.
13 Vos M,Mc Eachran R P,Zhu L F.A comparison of the theoretical and experimental results for ke V electron scattering from argon[J].Journal of Physics B:Atomic,Molecular and Optical Physics,2014,47(5):055201.
14 Lin M,Liu Y W,Zhong Z P,et al.Decay pathways of superexcited states of nitrous oxide[J].Chinese Physics B,2014,23(5):053403.
15薛冬冬,孙秀宇,游燕,等.低能量电子枪的研发[J].真空电子技术,2016,(1):34?37.XUE Dongdong,SUN Xiuyu,YOU Yan,et al.Development of a low energy electron gun[J].Vacuum Electronics,2016,(1):34?37.
16 David J M,David A D.SIMION 8.0 user manual[M].United States of America:Scientific Instrument Services Inc.,2007.
17任黎明,陈宝钦.电子束曝光高斯分布束斑的Monte Carlo模拟[J].微细加工技术,2001,19(3):60?63.REN Liming,CHEN Baoqin.Monte Carlo simulation of Gauss-distribution beam spot in electron beam lithography[J].Microfabrication Technology,2001,19(3):60?63.