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Description: The collaboration ATLAS Experiment. A part of the ATLAS detector.
ATLAS detector comprises four main components: the Inner Detector, the Calorimeters, the Muon Spectrometer, Solenoidal and Toroidal Magnets, and data acquisition and Computing.
The Inner Detector measure the tracks of the hundreds of charged particles that are produced in the proton-proton collisions in the middle of the detector every 25 nanoseconds. It consists of concentric layers of tracking detectors, with the highest precision detectors closest to the collision point. The colliding beams produce intense levels of radiation with fluxes of up to 350 000 particles per square millimetre per second, making radiation hardness a top priority for the detector and readout electronics.
The Calorimeters, which surround the Inner Detector, absorb and measure the energies of most charged and neutral particle produced in the collisions. Energy deposits in the Calorimeter are detected and converted to electrical signals that are read out by data-taking electronics.
The Muon Spectrometer measures the electrical charges and momenta of muons. The muon is a fundamental particle that is part of the Standard Model of particle physics. It is from the group of leptons with mass 200 times greater than the mass of the electron. The mass of a muon is about 105.7 MeV/c², with a negative charge and a spin of 1/2. The muon is an unstable particle which exists for only a fraction of a second (10̄ 6 seconds) and after it decaying into an electron, electron-antineutrino, and a muon neutrino. In 1936, the muons were discovered by Carl Anderson, during the study of cosmic rays. They are able to pass through the calorimeter without being absorbed. The trajectories of muons are bent by a second set of powerful (after the Solenoid magnet), allowing the charges and momenta to be calculated.
The Magnet System bends charged particles for momentum measurement. The Solenoid Magnets surrounds the Inner detector. The Central Solenoid is located outside of the Inner detector. The 5 tonne coil contains 9 km of superconducting wire colled by liquid helium, and an electric current of 8 000 Amperes produces a 2 Tesla magnetic field. The powerful magnetic field causes the charged tracks, provides important information for determining the momentum and electrical charge of each particle.
The Project ATLAS is designed to observe up to nearly one billion proton-proton collisions per second, with combined data volume of more than 60 million megabytes per second.
Source of information: Official information materials and publications of CERN.
photo - personal archive by source-materials of CERN (Credit: CERN).