Photon-stimulated desorption from laser-etched vacuum structural materials of accelerators

The electron multipacting (EM) and the electron cloud (e-cloud) can have detrimental impact on the operation of the high energy or high current intensity particle accelerators. The enhanced performance of new generation particle accelerators has necessitated the development of advanced structural materials and vacuum systems. The EM and e-cloud effect have emerged as significant challenges which cannot be ignored during the design and construction of these advanced accelerators. Laser-etching technique represents a promising approach for the suppression of secondary electron emission from materials, which can lower the secondary electron yield (SEY) of the structural materials to below 1. Nevertheless, the deployment of laser-etching technique in the next generation of large particle accelerators requires a comprehensive investigation into its vacuum performance. In this work, a photo-stimulated desorption (PSD) experimental beamline was constructed on the Hefei Light Source II. The PSD yields of the structural materials (oxygen-free copper, chrome zirconium copper, stainless steel, and aluminum alloy) with and without laser-etching of the vacuum chambers were tested at normal incidence using the throughput method. The main gases desorbed from all sample surfaces are H2, CO, CO2, CH4, and H2O. The initial PSD yield of laser-etched material is higher than that of unetched material. However, the PSD yield of the laser-etched material decreases at a faster rate, and after a certain photon dose, the PSD yield of the laser-etched material is in the same order of magnitude as that of the unetched material.