Taking a closer look at LHC

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  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 it was with CMS the key to discover the Higgs boson.

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.

[This last part ist based on What’s new for LHC Run 3? By Sarah Charley. Symmetry (A joint Fermilab/SLAC publication)]

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

Some calculations ...


ATLAS is a worldwide collaboration comprising over 2100 scientists and engineers from 167 institutions in 37 countries and regions including: Argentina, Armenia, Australia, Austria, Azerbaijan, Belarus, Brazil, Canada, Chile, China, Colombia, Czech Republic, Denmark, France, Georgia, Germany, Greece, Hungary, Israel, Italy, Japan, Morocco, Netherlands, Norway, Poland, Portugal, Romania, Russia, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Taiwan, Turkey, United Kingdom and the United States of America.


Xabier Cid Vidal, PhD in experimental Particle Physics for Santiago University (USC). Research Fellow in experimental Particle Physics at CERN from January 2013 to Decembre 2015. Currently, he is in USC Particle Physics Department ("Ramon y Cajal", Spanish Postdoctoral Senior Grants).

Ramon Cid Manzano, secondary school Physics Teacher at IES de SAR (Santiago - Spain), and part-time Lecturer (Profesor Asociado) in Faculty of Education at the University of Santiago (Spain). He has a Degree in Physics and in Chemistry, and is PhD for Santiago University (USC).



CERN Directory

CERN Experimental Program

Theoretical physics (TH)

CERN Physics Department

CERN Scientific Committees

CERN Structure

CERN and the Environment



Detector CMS

Detector ATLAS

Detector ALICE

Detector LHCb

Detector TOTEM

Detector LHCf

Detector MoEDAL



 For the bibliography used when writing this Section please go to the References Section

© Xabier Cid Vidal & Ramon Cid -  | SANTIAGO (SPAIN) |