Energy-resolved secondary-electron emission of candidate beam screen materials for electron cloud mitigation at the Large Hadron Collider

Schulte, Stefan; Hartung, G.; Himmerlich, Marcel; Petit, Valentine; Taborelli, M.

doi:10.1103/physrevaccelbeams.23.103101

Cited by 4 publications

(7 citation statements)

References 81 publications

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“…In order to model the samples, for the microgeometry, the trench cross-sections and nanostructure SEM images were collected according to Bajek et al [22], and XPS data was recorded following the procedure reported by Bez et al [34] For deriving modelling parameters untreated samples were characterised, SEY data was collected for AR copper, Cu 2 O and CuO, sputter-cleaned copper and amorphous carbon. As well as SEY-energy spectrum data for AR copper, sputtercleaned copper and amorphous carbon according to Schulte et al [48] Lastly, angle-dependent SEY data was collected for sputter-cleaned copper.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…The scaling variables are determined through recent SEY measurements of sputter-cleaned copper up to 50 0 incidence, illustrated in the supplementary material, and we assume that all emitted electrons follow a cosine angular distribution regardless of their energy. The emitted secondary electrons' energies are characterised by experimental SEY-energy spectrum data [48]. Then a particle tracking solver is used to record electron trajectories and the process is repeated on successive electron-matter interactions.…”

Section: Furman's Modelmentioning

confidence: 99%

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Modelling laser modified secondary electron yield response of surfaces

Din,

Uren,

Wackerow

et al. 2024

J. Phys. D: Appl. Phys.

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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.

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Section: Experimental Methodsmentioning

confidence: 99%

Section: Furman's Modelmentioning

confidence: 99%

Modelling laser modified secondary electron yield response of surfaces

Din,

Uren,

Wackerow

et al. 2024

J. Phys. D: Appl. Phys.

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“…While more accurate theories for low energy electron scattering are still to be explored, we have to rely on TEY measurements in this energy range. The latter, being a challenge on their own, have been performed mainly for materials that are used in space technologies by Balcon et al (2012) including for metals such as Cu by Schulte et al (2020), Ag, Au and crystalline silicon (c-Si) by Pierron et al (2017). Further experimental difficulties originate when performing such measurements on nonconductive surfaces prone to surface charging.…”

Section: Introductionmentioning

confidence: 99%

A comprehensive analysis of electron emission from a-Si:H/Al₂O₃ at low energies

Löffler¹,

Belhaj²,

Bundaleski³

et al. 2023

J. Phys. D: Appl. Phys.

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Recently developed microchannel plates based on amorphous silicon offer potential advantages with respect to glass based ones. In this context, secondary electron emission at very low energies below 100 eV has been studied for relevant materials for these novel devices. The aim of this work was to quantify the low energy electron emission - secondary emission and elastic scattering - from amorphous silicon and alumina and the dependence of the emission energy distribution on the primary electron energy, which was previously unknown. Secondary emission and energy distribution were both modelled and measured using equipment particularly designed for this energy range. The effects of roughness, angle of incidence and surface composition were analysed. We show crossover energies as well as the angular dependence of electron emission from amorphous silicon and alumina, with a maximum experimental emission yield value of 2 and 2.8, respectively, at an incident angle of 75°. A parameterization for the energy dependence of the emission energy spectrum at low energies was derived. This extensive analysis is fundamental for a comprehensive understanding of the performance of amorphous silicon-based microchannel plate detectors. It provides a complete model for secondary electron emission for a detailed description of the detector operation. The present results thus set the basis for a simulation framework, which is an essential element to increase the performance of these detectors and enable further developments.

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“…Low SEY materials or surfaces are aimed for reduction of surface charging of spacecrafts and satellites [1,2] as well as to mitigate formation of electron clouds in particle accelerators. [3][4][5][6][7] The primary electron energy dependence of the secondary electron yield as well as the kinetic energy distribution of the emitted electrons are subject of intensive studies since decades for elemental material surfaces and compounds [7][8][9][10][11][12][13][14][15][16][17] to accommodate the progressively developing technology demands. For many applications a SEY maximum below unity is sufficient to avoid cascade multiplication of the impinging electrons.…”

Section: Introductionmentioning

confidence: 99%