Molecular Pumping Properties of the LHC Arc Beam Pipe and Effective Secondary Electron Emission from Cu Surface with Artificial Roughness

The simplified 2D method of angular coefficients is applied to calculate the molecular pumping properties of complicate vacuum systems. An optimisation of the cold LHC beam vacuum chamber geometry with electron shields is performed. An additional interesting application of the angular coefficients method is the estimation of an effective secondary electron emission from surface with artificial roughness. This method allows to take into account re-reflection of the electrons using experimental data of the secondary electron energy distributions and the surface reflectivity. The suppression affectivity of the secondary electron emission from Cu as a function of roughness parameter is presented. This result is a good input for designing of future accelerators with potential electron-cloud problems.