Effect of rectangular grooves and checkerboard patterns on the electron emission yield

Abstract

The effect of rough structures on the electron emission under electron impact between 10 eV and 2 keV is investigated with a new version of the low energy electromagnetic model of GEANT4 (MicroElec). The inelastic scattering, is modeled thanks to the dielectric function theory and the Mott's model of partial waves to describe the elastic scattering. Secondary electron emission is modeled for grooved and checkerboard patterns of different dimensions for aluminum and silver. The analyses is performed according to two shape parameters h/L and d/L, h being the height, L the width of the structures and d the spacing between two neighboring structures. The secondary electron emission is demonstrated to decrease when h/L and d/L ratios increase. When the height reaches 10 times the lateral dimensions, the electron emission yield is divided by two compared to that of a flat sample. The optimization of the two aspects ratios lead to a reduction of the electron emission yield of 80 % for grooved patterns, and of 98 % for checkerboard patterns. This purely geometric effect is similar for aluminum and silver materials. A simple analytical model, capable to reproduce the effect on the electron emission yield of checkerboard and grooved patterns, is proposed. This model is found to be in good agreement with the Monte Carlo simulations and some experimental measurements performed in our irradiation facility.

Role of surface microgeometries on electron escape probability and secondary electron yield of metal surfaces

“…The simulated results find that compared to a flat copper surface, the SEY will lower by approximately 19% when trenches of aspect ratio 1.0 are introduced, and by 38% when the trenches are coated. Similar Monte Carlo simulations have recently confirmed this theory 18 .…”

Efficient Combination of Surface Texturing and Functional Coating for Very Low Secondary Electron Yield Surfaces and Rough Nonevaporable Getter Films

“…[29,37,38] Another approach for electron emission reduction is the roughening or texturing of the material surface on different length scales, which allows to trap and reabsorb emitted electrons in cavities at the surface. A SEY reduction can be obtained by surface roughening, [39][40][41][42][43] machining of deep trenches or grooves, [44][45][46][47] and several approaches to create a micro-or nanostructured morphology. Microporous structures [48][49][50] as well as a sponge or foam topology [51][52][53][54] enable trapping of impinging and emitted electrons as efficiently as textured surfaces formed by etching [55] or nanowires created by different techniques.…”

Modelling vacuum flashover mitigation with complex surface microstructure: mechanism and application

“…SEY is believed to be crucial to surface flashover properties and some progresses have been made. Pierron et al [27] have proved that the SEY of the grooved surface greatly reduces. Swanson et al obtained similar results but with a different surface structure [28][29][30].…”