Study on the anisotropy of the secondary electron yield and resistance of the laser-etched copper

Abstract

The performance of modern accelerators has been seriously affected by the electron cloud effect (e-cloud) caused by the accumulation of secondary electrons. Such problem can be effectively eliminated by laser-etching the inner surface of the vacuum chambers of the modern accelerators. In this work, surfaces of oxygen-free copper (OFC) were laser etched following either parallel lines or square-grid pattern with different scanning speeds. The secondary electron yields (SEYs), resistance, and roughness of the etched OFC samples were measured from various directions. The surfaces of etched OFC samples have been proven to form some regularly arranged grooves or cones, the geometries of which are directly related to the etching parameters. As a result, the parallelly etched samples exhibit apparent anisotropy. The sample etched along parallel lines, present higher SEYs, resistance and roughness when measured in the direction perpendicular to the groove-lines. But the sample etched following square-grid have little difference in the two directions and have a lower SEY value than the parallelly etched samples. Moreover, low-speed etching is more favorable to producing large aspect ratio and porosity structures, which is conducive to obtain lower SEY values.