Diffraction physics program in ATLAS experiment

A possible diffraction physics program for the ATLAS experiment is discussed. It includes physics channels feasible at low luminosities, even at a start-up of the LHC, and those at high luminosities. At low luminosities, a rapidity gap L1 trigger could be used, while at high luminosities, the use of proton taggers proposed to be placed at 220 and 420 m from the interaction point is foreseen. Among the diffraction physics processes to be studied at LHC, those induced by photons play an important role at any luminosity scenario.