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ALICE detector photon spectrometer, CERN. The photon spectrometer is a module of the ALICE (A Large Ion Collider Experiment) detector. It measures the energy of ion collisions by detecting the photons released from them. It uses lead tungstate crystals (transparent cubes) that glow (scintillate) when struck by high energy photons and the amount of glow is recorded. ALICE 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, though to exist very early in the universe's history. Photographed in April 2006. (KEYSTONE/SCIENCE PHOTO LIBRARY/MAXIMILIEN BRICE, CERN/SCIENCE PHOTO LIBRARY)