Diffraction and rapidity gap measurements with ATLAS

Two diffraction related measurements of proton-proton collisions in the ATLAS experiment of the Large Hadron Collider at $\surd s$ = 7 TeV centre-of-mass energy are reviewed. First of them is a fraction of diffractive contribution to the inelastic cross section. Second measurement is dedicated to the identification of Single Diffractive interactions with large pseudo-rapidity gaps using early 2010 data sample of integrated luminosity 7.1 $\mu b^{-1}$. Differential cross sections of largest forward areas of the ATLAS detector starting at its most forward edges $\eta = \pm 4.9$ without any particle activity above different transverse momentum thresholds are measured. Results are compared to several distinctive Monte Carlo models resulting in constraint of Pomeron intercept value in triple Pomeron based approach. Furthermore, proton-proton interactions in small pseudo-rapidity gap region test qualitatively a description of different hadronisation models as well as statistical fluctuations during hadronisation processes.