PT Journal AU ATLAS Collaboration (Aad, Gea Amoros, G Cabrera Urban, S Castillo Gimenez, V Costa, MJ Escobar, C Ferrer, A Fiorini, L Fuster, J Garcia, C Gonzalez de la Hoz, S Hernandez Jimenez, Y Higon-Rodriguez, E Irles Quiles, A Kaci, M Lacasta, C Lacuesta, VR Marti-Garcia, S Miñano, M Mitsou, VA Moles-Valls, R Moreno Llacer, M Oliver Garcia, E Perez Garcia-Estañ, MT Ros, E Salt, J Solans, CA Soldevila, U Sanchez, J Torro Pastor, E Valladolid Gallego, E Valls Ferrer, JA Villaplana Perez, M Vos, M Wildauer, A TI Performance of the ATLAS Trigger System in 2010 SO European Physical Journal C JI Eur. Phys. J. C PY 2012 BP 1849 EP 61pp VL 72 IS 1 DI 10.1140/epjc/s10052-011-1849-1 LA English AB Proton-proton collisions at root s = 7 TeV and heavy ion collisions at root(NN)-N-s = 2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented. ER