电子能量损失谱仪用中高能电子枪的研制

Development of an electron gun operated at intermediate-high energies for electron energy-loss spectrometer

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 6.27μA 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.