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Article
Title	Pulse Duration Dependence of Infrared Laser-Induced Secondary Electron Yield Reduction of Copper Surfaces
Author(s)	Lorenz, Pierre (TROPOS, Leibniz) ; Bez, Elena (CERN ; Leipzig U.) ; Himmerlich, Marcel (CERN) ; Ehrhardt, Martin (CERN) ; Taborelli, Mauro (CERN) ; Zimmer, Klaus
Publication	2023
Number of pages	6
In:	10.2961/jlmn.2023.03.2002
DOI	10.2961/jlmn.2023.03.2002
Subject category	Health Physics and Radiation Effects ; Engineering
Abstract	The irradiation of metals with ultrashort laser pulses enables the rapid and cost-effective production of nanostructured surfaces with a wide range of industrial applications. The laser-induced surface roughening modifies the interaction processes upon electron impact, leading to a modification of the secondary electron emission. In this study, the nanostructuring as well as the secondary electron yield (SEY) variation of polycrystalline copper surfaces was investigated by irradiation with 1030 nm infrared ultrashort laser pulses at a constant repetition rate of 100 kHz. The influence of varying the pulse duration between 238 fs and 10 ps, the laser power and the number of laser pulses per unit area (induced by varying the scanning speed) on the surface topography and the SEY was investigated. Irrespective of the pulse duration, irradiation with low scan speed (v ≤ 20 mm/s) and high laser power (P ≥ 2.6 W) results in the formation of a surface with compact nanostructures and a very low maximum SEY δmax < 0.7. The δmax increased slightly with increasing pulse duration at similar laser parameters. Increasing the pulse duration also resulted in a slight decrease in the ablation threshold and volume. The observed SEY dependence is probably explained by the pulse duration dependence of the ablation. The results suggest that nanostructured copper surfaces with very low SEY can be produced with ultrashort laser pulses over a wide range of pulse durations

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