基于微陷阱结构的金属二次电子发射系数抑制研究

近年来,金属二次电子发射系数的抑制研究在加速器、大功率微波器件等领域得到了广泛关注.为评估表面形貌对抑制效果的影响,利用唯象概率模型计算方法对三角形沟槽、矩形沟槽、方孔及圆孔4种不同形状微陷阱结构的二次电子发射系数进行了研究,分析了微陷阱结构的形状、尺寸对二次电子发射系数抑制特性的影响规律.理论研究结果表明:陷阱结构的深宽比、孔隙率越大,则其二次电子发射系数抑制特性越明显;方孔形和圆孔形微陷阱结构的二次电子发射系数抑制效果优于三角形沟槽和矩形沟槽;具有大孔隙率的微陷阱结构表面的二次电子发射系数对入射角度的依赖显著弱于平滑表面.制备了具有不同表面形貌的金属样片并进行二次电子发射系数测试,所得实验规律与理论模拟规律符合较好.

Suppression of secondary electron emission by micro-trapping structure surface

Suppression of secondary electron yield attracted much attention in areas such as accelerator and high power microwave components in recent years. To evaluate the suppression efficiencies of different surface topographies, the secondary electron yields (SEYs) of four kinds of micro-structured surfaces for trapping secondary electrons, i.e., triangular groove, rectangular groove, cuboid, cylindrical, are obtained by the phenomenological probabilistic model of secondary electron emission. The simulation results show that the SEYs of these structures are much dependent on the shape parameters such as aspect ratio or porosity. There are mainly three findings: 1) the SEY decreases with increasing aspect ratio and porosity; 2) the traps with cuboid or cylindrical shape are more efficient than triangular or rectangular traps for the SEY suppression; 3) the SEY dependence of micro-structured surface on incident angle is not as obvious as that of flat surface. Micro-trapping structure surfaces are fabricated by mechanical method, photolithography process and chemical etching respectively. The measured SEYs of these samples validate the theoretical results. All these results show that the proposed micro-structures as secondary electron traps have potential applications in SEY suppression in fields such as multipactor and electron-cloud effects.
Keywords： secondary electron yield suppression micro-trapping structure surface phenomenological probabilistic model