Detectors at LHC

The 50th anniversary of the creation of CERN falls during the construction of its most ambitious project. The construction of the LHC, machine and experiments, is advancing well and proton–proton collisions are expected to take place in the summer of 2007. This paper outlines the challenges posed by the operation at a high-luminosity hadron collider, the design of the experiments, the R&D and prototyping that was required to select the detector technologies to face the challenges, the anticipated performance of the experiments, and the state of their construction.