Carbon Based Surfaces with Low Secondary Electron Emission

• Main Author: Aguincha, Ruben Miguel Seixas
• Publication Date: 2018
• Format: Master thesis
• Language: eng
• Source: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Download full: http://hdl.handle.net/10362/56374
• topic: Accelerator; Satellite; SEY; Graphene; EPD; XPS; Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Low secondary electron emission materials have significant impact in accelerator and space technologies. Secondary electrons produced by the residual gas ionization or due to the irradiation of chamber walls by the synchrotron light influence trajectories of charged particles inside accelerators. Significant potential difference between the dielectric and conductive parts of satellites is caused by different secondary electron emission yields induced by cosmic rays, leading to discharges between different parts of a satellite, resulting in the malfunctioning of the communication systems and other sensitive equipment. One of the solutions to these problems is coating surfaces with thin films of amorphous carbon. Recent studies showed that graphene-based coatings have a potential in further reduction of secondary electron yields (SEY). For that reason, the deposition of free standing graphene (i.e. graphene in the form of powder) on technical surfaces of interest in space and accelerator technologies using Electrophoretic Deposition (EPD) was investigated in this work. Highly oriented pyrolytic graphite and pure graphene samples were used as references in order to compare them with graphene coatings produced by EPD. Apart from SEY measurements, X-ray photoelectron spectroscopy and scanning electron microscopy of the samples were performed for that purpose. Graphene depositions were successfully made and the maximum SEY of technical surfaces (stainless steel and copper) was reduced to 1. In order to achieve these results, various studies were performed concerning the deposition technique parameters, related to the process and the materials used. Three different alternatives were also explored.