金属二次电子发射能谱的表面吸附势垒模型  被引量:5

A Model of Surface Adsorption Barrier on Secondary Electron Spectrum of Metal

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作  者:虞阳烨 曹猛[1] 张海波[1] 

机构地区:[1]西安交通大学电子物理与器件教育部重点实验室,西安710049

出  处:《西安交通大学学报》2015年第10期97-102,共6页Journal of Xi'an Jiaotong University

基  金:国家自然科学基金资助项目(11375139;11175140);空间微波技术国家重点实验室基金资助项目(9140C530101130C53013)

摘  要:为了改善加速器和高功率微波源中金属器壁的表面状况,采用数学建模并结合实验验证的方法,建立了二次电子能谱的吸附势垒模型。首先,以到达金属内表面二次电子为参考对象,分析金属壁的吸附过程,发现水蒸气吸附造成的能级扭曲会使金属表面势垒降低,由此建立了水吸附形态下的薛定谔方程,并求解得到吸附势垒的透射系数;然后,结合内二次电子能量分布建立吸附势垒模型,得到二次电子能谱特征参数与吸附量的定量关系。模型分析结果表明:吸附量的增加会引起表面势垒的降低,从而导致金属器壁二次电子发射增强,能谱变窄,加剧电子云效应;通过加热、氩离子清洗等手段可减少或去除加速器壁水蒸气吸附,抑制器壁表面二次电子发射。实验对比发现,离子清洗可减少吸附量,使Ag样品的吸附度从初始值0.5降至0,伴随能谱半峰宽从5.17eV展宽至12.5eV。A model of surface adsorption barrier on secondary electron (SE) spectrum is proposed to improve the surface state in accelerators and high power microwave sources. Mathematical modeling and experimental verification are used in building the model. Inner SEs are chosen as the initial condition of the SE emission. It is found through analysis that the adsorption of water vapor distorts the energy level and reduces the surface barrier. Then, Schrodinger equation for water adsorption is established to get the transmission coefficients. The adsorption barrier model is built and quantitative relationships between SE spectrum characteristic parameters and adsorption amount are obtained by considering the inner SE energy distribution. Analytical results from the model show that increasing the amount of adsorption reduces the surface barrier, and results in enhanced SE emission from metal wall, narrowed spectrum and aggravated electron cloud effect. It is also found that the water adsorption on accelerator wall can be reduced or eliminated, and the SE emission can be suppressed by heating and ion cleaning. Experiments show that ion cleaning reduces the amount of adsorption, and the adsorption of Ag samples reduces from its initial value 0. 5 to 0, while the soectrum width at half maximum increases from 5. 17 to 12.5 eV.

关 键 词:二次电子发射 二次电子能谱 吸附 表面势垒 透射系数 

分 类 号:TN16[电子电信—物理电子学] O462[理学—电子物理学]

 

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