ATLAS detector, CERN. ATLAS (A Toroidal LHC Apparatus) is one of six detector experiments at the Large Hadron Collider (LHC) particle accelerator at CERN, Geneva, Switzerland. The LHC is designed to create high energy substances, such as quark-gluon plasma, thought to exist very early in the universe's history. ATLAS is a broad-range detector that measures all particles and physical processes that emerge during proton collision within the LHC.