CERN-OBJ-DE-124
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The crystals used in CMS’s electromagnetic calorimeter may look like simple bricks of glass, but they are in fact mostly metal and are heavier than steel! Lead tungstate crystal with a touch of oxygen in this crystalline form is highly transparent and scintillates when electrons and photons pass through it. This means it produces light in proportion to the particle’s energy. CMS contains nearly 80’000 such crystals, each of which took two days to grow. This technology developed at CERN has applications in medical imaging, for example improving cancer diagnosis. The Compact Muon Solenoid (CMS) is a general-purpose detector at the Large Hadron Collider (LHC).