IPAC2021 - List of Authors (Neupert, H.)

Paper	Title	Page
WEPAB339	Beam-Induced Surface Modification of the LHC Beam Screens: The Reason for the High Heat Load in Some LHC Arcs?	3479
	V. Petit, P. Chiggiato, M. Himmerlich, G. Iadarola, H. Neupert, M. Taborelli, D.A. Zanin CERN, Geneva, Switzerland
	All over Run 2, the LHC beam-induced heat load exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpectedly high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. During the Long Shutdown 2, the beam screens of a low and a high heat load dipole were extracted. Their inner copper surface was analysed in the laboratory to compare their SEY and surface composition. While findings on the low heat load beam screens are compatible with expectations from laboratory studies of copper conditioning and deconditioning mechanisms, an extremely low carbon amount and the presence of CuO (non-native surface oxide) are observed on the high heat-load beam screens. The azimuthal distribution of CuO correlates with the density and energy of electron impingement. Such chemical modifications increase the SEY and inhibit the full conditioning of affected surfaces. This work shows a direct correlation between the abnormal LHC heat load and the surface properties of its beam screens, opening the door to the development of curative solutions to overcome this critical limitation.
	Poster WEPAB339 [2.247 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB339
About •	paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 16 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Beam-Induced Surface Modification of the LHC Beam Screens: The Reason for the High Heat Load in Some LHC Arcs?

3479

V. Petit, P. Chiggiato, M. Himmerlich, G. Iadarola, H. Neupert, M. Taborelli, D.A. Zanin
CERN, Geneva, Switzerland

All over Run 2, the LHC beam-induced heat load exhibited a wide scattering along the ring. Studies ascribed the heat source to electron cloud build-up, indicating an unexpectedly high Secondary Electron Yield (SEY) of the beam screen surface in some LHC regions. During the Long Shutdown 2, the beam screens of a low and a high heat load dipole were extracted. Their inner copper surface was analysed in the laboratory to compare their SEY and surface composition. While findings on the low heat load beam screens are compatible with expectations from laboratory studies of copper conditioning and deconditioning mechanisms, an extremely low carbon amount and the presence of CuO (non-native surface oxide) are observed on the high heat-load beam screens. The azimuthal distribution of CuO correlates with the density and energy of electron impingement. Such chemical modifications increase the SEY and inhibit the full conditioning of affected surfaces. This work shows a direct correlation between the abnormal LHC heat load and the surface properties of its beam screens, opening the door to the development of curative solutions to overcome this critical limitation.

Poster WEPAB339 [2.247 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB339

About •

paper received ※ 19 May 2021 paper accepted ※ 22 June 2021 issue date ※ 16 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)