Modeling of reduced secondary electron emission yield from a foam or fuzz surface

TL;DR

This paper presents an analytic model and simulations showing how foam or fuzz structures on surfaces can reduce secondary electron emission yield by trapping secondary electrons, with a minimum achievable SEY of 0.3 of the flat surface value.

Contribution

The paper introduces a new analytic model and numerical simulations to quantify SEY reduction from foam or fuzz surfaces, identifying key parameters for minimization.

Findings

SEY can be reduced by trapping secondary electrons in foam structures

The condition for effective SEY minimization is ar{u}   >>1

Minimum achievable SEY is approximately 0.3 of the flat surface value

Abstract

Complex structures on a material surface can significantly reduce the total secondary electron emission yield from that surface. A foam or fuzz is a solid surface above which is placed a layer of isotropically aligned whiskers. Primary electrons that penetrate into this layer produce secondary electrons that become trapped and not escape into the bulk plasma. In this manner the secondary electron yield (SEY) may be reduced. We developed an analytic model and conducted numerical simulations of secondary electron emission from a foam to determine the extent of SEY reduction. We find that the relevant condition for SEY minimization is $\bar{u} \equiv AD/2 >>1 $, where $D$ is the volume fill fraction and $A$ is the aspect ratio of the whisker layer, the ratio of the thickness of the layer to the radius of the fibers. We find that foam can not reduce the SEY from a surface to less than 0.3 of its flat value.