The ATLAS detector (A Toroidal LHC ApparatuS ) is the world’s largest general-purpose particle detector, measuring 46 meters long, 25 metres high and 25 meters wide; it weighs 7000 tons and consists of 100 million sensors that measure particles produced in proton-proton collisions in CERN’s Large Hadron Collider. The first piece of ATLAS was installed in 2003 and since then many detector elements have journeyed down the 100 metre shaft into the ATLAS underground cavern. This last piece (lowered in March 2008) completed this gigantic puzzle. ATLAS outreach

ATLAS is a worldwide collaboration comprising over 5500 members and almost 3000 scientific authors. and engineers from 181 institutions in 42 countries.

More information here...

Together with CMS, it contributed to the discovery of the Higgs boson in 2012-13. ATLAS  may also provide the answer for the mysterious dark matter and energy of the Universe and look for extra dimensions of spacetime. This detector is designed to be capable of discovering new particles and new phenomena expected from extensions of the Standard Model such as supersymmetry, and help to better understand the properties of the Higgs boson. (discovered in this detector together with CMS in 2012-13).

Some calculations ... 

ATLAS Live

(Taken from MELTRONX ©2009-2024. A Real Frisco Kid Production Not Affiliated with CERN)

 At each Long Shutdown (LS) the various accelerators, detectors and other devices undergo major maintenance, consolidation and upgrade operations.

Some of the improvements in ATLAS in LS2 (2019-2022) were carried out in the so-called Small WheelsT, detectors designed to catch muons. Even though “small” is part of their name, each wheel is 9 meters in diameter. These wheels hold 16 wedge-shaped detector slices (which in turn, consist of 16 detecting layers each). The New Small Wheels help ATLAS to more accurately measure the momenta and trajectories of muons created during the high energy collisions inside the LHC

ATLAS scientists have also updated their detector’s trigger system—which is responsible for quickly filtering the data coming off the detector—and the software that processes, reconstructs and analyzes the data.

[These comments are based on What’s new for LHC Run 3? By Sarah Charley. Symmetry (A joint Fermilab/SLAC publication)]

In more detail we can see the improvements made to this detector during the LS2 in the following image:

(Image CERN)

All information in Toda la información en ATLAS Upgrades LS2

The image at the bottom of the DETECTORS Section shows some of those performed on the larger detectors during LS2 (2019-2022).