Editing ATLAS experiment (section)

==History==

===Particle accelerator growth===
[[File:CERN Atlas Caverne.jpg|thumb|ATLAS detector under construction in October 2004 in the experiment pit. Construction was completed in 2008 and ATLAS has been successfully collecting data since November 2009, when colliding beam operation at the LHC started. Note the people in the background, for size comparison.]]

The first [[cyclotron]], an early type of particle accelerator, was built by [[Ernest O. Lawrence]] in 1931, with a radius of just a few centimetres and a particle [[energy]] of 1 [[electron volt#MeV|megaelectronvolt (MeV)]]. Since then, accelerators have grown enormously in the quest to produce new particles of greater and greater [[mass]]. As accelerators have grown, so too has the [[list of particles|list of known particles]] that they might be used to investigate.

===ATLAS Collaboration===

The ATLAS Collaboration, the international group of physicists belonging to different universities and research centres who built and run the detector, was formed in 1992 when the proposed EAGLE (Experiment for Accurate Gamma, Lepton and Energy Measurements) and ASCOT (Apparatus with Super Conducting Toroids) collaborations merged their efforts to build a single, general-purpose particle detector for a new [[particle accelerator]], the [[Large Hadron Collider]].<ref>{{cite web |url=http://library.cern.ch/archives/isad/isaatlas.html |title=ATLAS Collaboration records |access-date=2007-02-25 |publisher=CERN Archive |archive-date=2007-01-01 |archive-url=https://web.archive.org/web/20070101230746/http://library.cern.ch/archives/isad/isaatlas.html |url-status=dead }}</ref> At present, the ATLAS Collaboration involves 6,003 members, out of which 3,822 are [[physicist]]s (last update: June 26, 2022) from 257 institutions in 42 countries.<ref name=fact_sheets/><ref name=collaboration/>

===Detector design and construction===
The design was a combination of two previous projects for LHC, EAGLE and ASCOT, and also benefitted from the detector research and development that had been done for the [[Superconducting Super Collider]], a [[United States|US]] project interrupted in 1993. The ATLAS experiment was proposed in its current form in 1994, and officially funded by the CERN member countries in 1995. Additional countries, [[universities]], and [[laboratories]] have joined in subsequent years. Construction work began at individual institutions, with detector components then being shipped to CERN and assembled in the ATLAS experiment pit starting in 2003.

===Detector operation===
Construction was completed in 2008 and the experiment detected its first single [[proton]] beam events on 10 September of that year.<ref>{{cite web|url=http://atlas.cern/updates/atlas-news/first-beam-and-first-events-atlas|title=First beam and first events in ATLAS|date=2008-09-10|publisher=Atlas.ch|access-date=2016-08-16}}</ref>
<!-- old cites that might be useful: <ref>{{cite web| url = http://atlasexperiment.org/news/2007/progress-on-magnets.html | title = Progress on Toroid Magnets | publisher = Cern - Atlas Experiment |author1=Colin Barras |author2=Michael Barnett |date=December 2007}}</ref> -->
Data-taking was then interrupted for over a year due to an LHC [[Large Hadron Collider#Quench incident|magnet quench incident]]. On 23 November 2009, the first proton–proton collisions occurred at the LHC and were recorded by ATLAS, at a relatively low injection energy of 900&nbsp;GeV in the [[center of mass]] of the collision. Since then, the LHC energy has been increasing: 1.8&nbsp;TeV at the end of 2009, 7&nbsp;TeV for the whole of 2010 and 2011, then 8&nbsp;TeV in 2012. 
The first data-taking period performed between 2010 and 2012 is referred to as Run I. After a long shutdown (LS1) in 2013 and 2014, in 2015 ATLAS saw 13 TeV collisions.<ref>[https://www.forbes.com/sites/chadorzel/2015/05/21/things-to-know-as-the-large-hadron-collider-breaks-energy-records/#2715e4857a0b4588cb75b112 "Eight Things To Know As The Large Hadron Collider Breaks Energy Records"].</ref><ref>[http://atlas.ch/news/2015/atlas-completes-first-year-at-13-tev.html "ATLAS Completes First Year at 13 TeV"] {{Webarchive|url=https://web.archive.org/web/20160117090052/http://atlas.ch/news/2015/atlas-completes-first-year-at-13-tev.html |date=2016-01-17 }}.</ref><ref>[http://www.atlas.ch/news/2015/atlas-begins-recording-physics-data-at-13-tev.html "ATLAS Begins Recording Physics Data at 13 TeV"] {{Webarchive|url=https://web.archive.org/web/20160305002833/http://www.atlas.ch/news/2015/atlas-begins-recording-physics-data-at-13-tev.html |date=2016-03-05 }}.</ref>
The second data-taking period, Run II, was completed, always at 13&nbsp;TeV energy, at the end of 2018 with a recorded integrated [[Luminosity (scattering theory)|luminosity]] of nearly 140 fb<sup>−1</sup> (inverse [[femtobarn]]).<ref>{{Cite web |url=https://twiki.cern.ch/twiki/bin/view/AtlasPublic/LuminosityPublicResultsRun2|title=LuminosityPublicResultsRun2 < AtlasPublic < TWiki|website=twiki.cern.ch|access-date=2020-03-10}}</ref> 
A second long shutdown (LS2) in 2019-22 with upgrades to the ATLAS detector<ref>{{Cite book|title=ATLAS|date=2018-05-05|publisher=World Scientific|isbn=978-981-327-179-1|series=Advanced Series on Directions in High Energy Physics|volume=30|language=en|doi=10.1142/11030}}</ref> was followed by Run III, which started in July 2022.<ref>{{cite web|url=https://home.cern/news/news/physics/atlas-moves-top-gear-run-3|title=ATLAS moves into top gear for Run 3|date=16 December 2022|access-date=24 January 2022}}</ref>

{|
|-
| '''Periods of LHC''' || '''operation'''
|-
| 2010 – 2012 || Run I
|-
| 2013 – 2014 || LS1
|-
| 2015 – 2018 || Run II
|-
| 2019 – 2022 || LS2
|-
| 2022 – 2025 || Run III
|}

=== Leadership ===
[[File:Andreas Hoecker.jpg|thumb|Andreas Hoecker, ATLAS Spokesperson 2021-2025.]]

The ATLAS Collaboration is currently led by Spokesperson [[Stephane Willocq]] and Deputy Spokespersons [[Anna Sfyrla]] and [[Guillaume Unal]].<ref>{{Cite web |title=ATLAS: now under new management |url=https://atlas.cern/Updates/News/New-Management-Steers-Forward |access-date=2025-03-15 |website=ATLAS |language=en}}</ref> Former Spokespersons have been:
{|
|-
| [[Friedrich Dydak]] and [[Peter Jenni]] || (1992 – 1995) 
|-
| [[Peter Jenni]] || (1995 – 2009)
|-
| [[Fabiola Gianotti]] || (2009 – 2013)
|-
| [[David Charlton]] || (2013 – 2017)
|-
| [[Karl Jakobs]]|| (2017 – 2021)
|-
| [[Andreas Hoecker]]|| (2021 - 2025)
|-
| [[Stephane Willocq]]|| (2025 – Present)

|}