ALICE detector doors being opened at CERN. ALICE (A Large Ion Collider Experiment) is a detector built around the Large Hadron Collider (LHC) at CERN (the European particle physics laboratory) near Geneva, Switzerland. The LHC, the world's largest and most powerful particle collider, began operating in 2008. For ALICE, beams of ions are accelerated to collide head-on. The collision energy creates new particles that will decay into other particles. These are detected by the many detector layers around the central collision point. The LHC energies have allowed study of exotic material like quark-gluon plasma, a form of quark matter. The LHC and its detectors are inspected, maintained and upgraded during shutdowns such as this. Photographed on 11 December 2018.