Secondary electron yield (SEY) evolution of laser processed oxygen-free high conductivity copper induced by different ultrasonic cleaning durations

Abstract

Laser treated material surface has highly regular curves and greatly reduces the secondary electron yield of surface. As one of the most typically used materials in the vacuum system of particle accelerators, the surface of oxygen-free high conductivity copper (OFHC) is processed by laser. Moreover, ultrasonic cleaning can effectively remove powders and impurities produced by laser ablation. The secondary electron yield (SEY), surface morphology and surface composition of laser treated oxygen-free copper samples before and after ultrasonic cleaning were compared. Experiments were conducted by using the secondary electron yield test device, X-ray diffractometer, X-ray photoelectron spectroscopy, and scanning electron microscope to characterize the SEY, crystal structures, surface composition and surface morphology of laser-treated oxygen-free copper samples, respectively. The SEY evolution of the samples was investigated and analyzed at electron doses of 7.6 × 10−6 C mm−2: after 15-min ultrasonic cleaning, the δmax of sample #1, #2 and #3 increased from 1.09, 1.23, and 1.38 to 1.19, 1.2, and 1.63, respectively, with the maximum increase of 18.12 %. Ultrasonic cleaning could greatly reduce the accumulation of spherical particles and the fibrous or flocculent structures produced by laser processing, thereby reducing the capture of secondary electrons.