Transverse Resistive Wall Impedance and Wake Function with "Inductive Bypass"

A new physical regime is revealed by the LHC collimators. Small aperture paired with large wall thickness ask for a different physical picture of the resistive wall effect than the classical one. Two general formulae for multi-layer resistive-wall impedances recently derived are reviewed and compared in the particular case of an LHC collimator. The corresponding wake function, which is useful for the simulation of beam stability in the time domain, has been obtained.