Dynamic pressure in the LHC: influence of ions induced by ionization of residual gas by both the proton beam and the electron cloud

For the future HL-LHC or FCC study, the understanding of the beam interactions with the vacuum chamber is fundamental to provide solutions to mitigate the pressure rises induced by electronic, photonic and ionic molecular desorption. The proton beam circulating in the LHC vacuum chamber ionizes the residual gas producing electrons as well as positive ions. In-situ measurements were carried out, on the LHC Vacuum Pilot Sector during the LHC RUN II, to monitor the dynamic pressure, and to collect the electrical signals due to the electron cloud and to the ions interacting with the vacuum chamber walls. Experimental measurements of electrical signals recorded by copper electrodes were compared to calculations taking into account both the Secondary Electron Yield of copper and electron energy distribution. Finally, it seems that copper electrodes were not fully conditioned and an ion current could be estimated. (paper)