Modelling laser modified secondary electron yield response of surfaces

Amin Ahmed Din (Lead / Corresponding author), Robin Uren, Stefan Wackerow, Ana Teresa Perez Fontenla, Stephan Pfeiffer, Elisa Garcia Tabares, Svetlana Zolotovskaya, Amin Abdolvand

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Abstract

Electron clouds hinder the operation of particle accelerators. In the Large Hadron Collider (LHC), the copper beam screens are located within close proximity to the beam path, resulting in beam-induced electron multipacting, which is the main source of electron cloud formation. Conditions for multipacting are encountered when such surfaces have a secondary electron yield (SEY) greater than unity. Roughening the surface through laser processing offers an effective solution for reducing secondary electrons. Laser ablation leaves behind a complex rough, multi-scale geometrical surface with an altered chemical composition. Current models often over-simplify the geometry, do not have sufficient experimental data to derive input parameters, and exclude SEY-reducing mechanisms such as the surface chemistry. Leading to electron-matter interactions which do not resemble that of a real surface. Here, this complex surface is studied on copper used in the LHC, and the influence of microgeometry, inhomogeneous nanostructure and complex surface chemistry on the SEY is investigated. A novel, improved model is proposed that characterises these sophisticated structures, enabling the efficient design of surfaces to reduce SEY. To validate the model, samples were made using a variety of laser parameters. Modelling insights revealed that secondary electron suppression is not only caused by the microgeometry but also the nanostructure and chemical modification play a role. Contrary to the conventional theory, high aspect ratio structures are not necessarily required for effective SEY reduction. Currently, the model is applicable to a variety of surface morphologies and could be employed for other materials.

Original languageEnglish
Article number385103
JournalJournal of Physics D: Applied Physics
Volume57
Issue number38
Early online date17 Jun 2024
DOIs
Publication statusE-pub ahead of print - 17 Jun 2024

Keywords

  • Large Hadron Collider
  • Monte Carlo methods
  • laser materials processing
  • multipactor effect
  • nanostructures
  • secondary electron yield

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films

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