The Ion Impact Energy on the LHC Vacuum Chamber Walls

The proton beam circulating in the LHC vacuum chamber will ionise the residual gas. The created ions are accelerated away from the beam and reach the vacuum chamber wall with some stored energy. The value of the ion impact energy is very important for the estimation of the ion stimulated gas desorption. The ion energy is studied as function of beam parameters. It is shown that the ion energy increases for a higher beam current and a smaller b-function. The ion energy is also sensitive to the bunch length and the bunch spacing. The ion energies are estimated for a number of different elements of the LHC. The effect of the magnetic field has been also studied