Thermal desorption of cryopumped gases from laser treated copper

Abstract

Recently, laser processing of copper samples has been demonstrated to produce rough surfaces whose nanostructuring ensures unquestionable advantages for electron cloud mitigation in future particle accelerators. The actual application of laser treated surfaces in accelerators implies that this new material is compliant with many issues, going from impedance vacuum properties to many others. A significant experimental effort is therefore ongoing to study and optimize their various properties of interest. Here we analyze their vacuum behavior versus temperature. To this end, we studied thermal programmed desorption from CO, ${\mathrm{CH}}_{4}$ and ${\mathrm{H}}_{2}$ once cryosorbed on laser treated copper substrate and on its flat counterpart. These molecules are typically present in the residual vacuum of any accelerator. The results show that the desorption of such gases from the laser treated substrates occurs in a much broader and higher temperature range with respect to what is observed from the flat substrate. We also show that, at equal doses, treated samples adsorb/desorb significantly more gas than their flat counterpart. These findings can be ascribed to their nanostructured porous morphology. A quantitative analysis is given, allowing to properly estimate fluctuations of the number of molecules during unavoidable temperature variations of the cryogenic vacuum system.