Dynamic secondary electron emission in rough composite materials

Leandro Olano,John R Dennison,Maria E Dávila,Isabel Montero,Petronilo Martín-Iglesias

doi:10.1038/s41598-019-50353-3

Abstract

The interaction of ionizing radiation with matter is of critical importance in numerous areas of science and technology like space and vacuum technology and even medicine and biotechnology. Secondary electron emission is a consequence of electron irradiation on materials. We achieve extremely low secondary electron emission yield values smaller than 0.2, even up to incident electron energies ~1 keV, due to an undocumented synergy between neighbouring metal and dielectric domains in composite samples. To investigate this experimental discovery, we propose a simple 3D model where the dielectric and metallic domains are arranged in parallel and interleaved. The proposed surface profile has a triangular shape to model the surface roughness. We obtain a continuous equation to describe the electric field that arises between grounded conductors and charged dielectrics domains. The calculated trajectories of secondary electrons in this 3D geometry are used to predict dynamic secondary emission yield, which strongly depends on the charge accumulated in the dielectric domains. This research paves the way to design new materials of low secondary emission yield, addressing the technological problem not yet resolved to inhibit the electron avalanche in RF equipment that limit their maximum working power.

Highlights

The effects of exposure to ionizing radiation is of great importance in different areas of science and technology from space and vacuum technology to even medicine and biotechnology
The resonance conditions of the multipactor discharge can often be inhibited by an adequate design of parameters pertaining to the RF electromagnetic field, but there always remain some critical regions where resonance conditions can only be avoided by using surfaces with low secondary electron emission
We proposed a unique model of secondary electron emission that explains physical experiments and give us insight into the extremely low Secondary electron Emission Yield (SEY) values obtained in the experiment for metal/dielectric composite coatings

Summary

Introduction

The effects of exposure to ionizing radiation is of great importance in different areas of science and technology from space and vacuum technology to even medicine and biotechnology. The multipactor effect develops when free electrons are accelerated by the electric field of an RF signal transmitted through an RF device, hitting its inner walls and emitting secondary electrons. The resonance conditions of the multipactor discharge can often be inhibited by an adequate design of parameters pertaining to the RF electromagnetic field, but there always remain some critical regions where resonance conditions can only be avoided by using surfaces with low secondary electron emission For this reason, one of the www.nature.com/scientificreports/. The most suitable materials for space applications are those with σmax < 1 In this case, the number of secondary electrons emitted is less than the number of primary electrons hitting the surface, for all primary electron energies, so that the electron population decreases over time and the electron avalanche is prevented

Results

Discussion

Conclusion