Editing CERN (section)

=== Current complex ===
{{CERNaccelerators}}

[[File:Location Large Hadron Collider.PNG|thumb|upright=1.3|A map of the [[Large Hadron Collider]] together with the [[Super Proton Synchrotron]] at CERN]]

CERN operates a network of seven accelerators and two decelerators, and some additional small accelerators. Each machine in the chain increases the energy of particle beams before delivering them to experiments or to the next more powerful accelerator. The decelerators naturally decrease the energy of particle beams before delivering them to experiments or further accelerators/decelerators. Before an experiment is able to use the network of accelerators, it must be approved by the various [[List of CERN Scientific Committees|Scientific Committees of CERN]].<ref name=":32">{{Cite web |title=CERN Scientific Committees {{!}} CERN Scientific Information Service (SIS) |url=https://scientific-info.cern/archives/history_CERN/Scientific_committees |access-date=2023-08-25 |website=scientific-info.cern}}</ref> Currently (as of 2022) active machines are the LHC accelerator and:
* The [[LINAC 3]] [[linear accelerator]] generating low energy particles. It provides heavy ions at 4.2&nbsp;MeV/[[Atomic mass unit|u]] for injection into the Low Energy Ion Ring (LEIR).<ref>{{cite web |url=https://linac2.home.cern.ch/linac2/default.htm |title=CERN Website – LINAC |publisher=CERN |access-date=20 November 2010 |archive-url=https://web.archive.org/web/20131027143216/https://linac2.home.cern.ch/linac2/default.htm |archive-date=27 October 2013 |url-status=dead }}</ref>
* The [[Low Energy Ion Ring]] (LEIR) accelerates the ions from the ion linear accelerator LINAC 3, before transferring them to the [[Proton Synchrotron]] (PS). This [[Particle accelerator|accelerator]] was commissioned in 2005, after having been reconfigured from the previous [[Low Energy Antiproton Ring]] (LEAR).<ref name="Chanel 2004 137–143">{{Cite journal|last=Chanel|first=Michel|year=2004|title=LEIR: the low energy ion ring at CERN|url=https://linkinghub.elsevier.com/retrieve/pii/S0168900204011994|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|language=en|volume=532|issue=1–2|pages=137–143|doi=10.1016/j.nima.2004.06.040|bibcode=2004NIMPA.532..137C}}</ref><ref>{{Cite book|last=Hübner|first=K.|url=https://cds.cern.ch/record/1058082|title=Fifty years of research at CERN, from past to future: The Accelerators|publisher=CERN|year=2006|doi=10.5170/cern-2006-004.1}}</ref>
* The [[Linac4]] [[linear accelerator]] accelerates negative hydrogen ions to an energy of 160 MeV. The ions are then injected to the Proton Synchrotron Booster (PSB) where both electrons are then stripped from each of the hydrogen ions and thus only the nucleus containing one proton remains. The protons are then used in experiments or accelerated further in other CERN accelerators. Linac4 serves as the source of all proton beams for CERN experiments.<ref>{{cite web |url=https://cerncourier.com/a/lhc-run-3-the-final-countdown/ |title=LHC Run 3: the final countdown |work=CERN Courier |date=18 February 2022 |access-date=22 March 2022}}</ref>
* The [[Proton Synchrotron Booster]] increases the energy of particles generated by the proton linear accelerator before they are transferred to the other accelerators.<ref>{{Cite journal|last=Hanke|first=K.|year=2013|title=Past and present operation of the CERN PS Booster|url=https://www.worldscientific.com/doi/abs/10.1142/S0217751X13300196|journal=International Journal of Modern Physics A|language=en|volume=28|issue=13|pages=1330019|doi=10.1142/S0217751X13300196|bibcode=2013IJMPA..2830019H|issn=0217-751X|url-access=subscription}}</ref>
* The 28 [[Gigaelectronvolt|GeV]] [[Proton Synchrotron]] (PS), built during 1954–1959 and still operating as a feeder to the more powerful [[Super Proton Synchrotron|SPS]] and to many of CERN's experiments.<ref>{{Citation|last=Plass|first=Günther|title=The CERN Proton Synchrotron: 50 Years of Reliable Operation and Continued Development|url=https://link.springer.com/10.1007/978-3-642-30844-4_2|work=From the PS to the LHC – 50 Years of Nobel Memories in High-Energy Physics|pages=29–47|year=2012|editor-last=Alvarez-Gaumé|editor-first=Luis|place=Berlin & Heidelberg|publisher=Springer Berlin Heidelberg|language=en|doi=10.1007/978-3-642-30844-4_2|bibcode=2012fpl..book...29P|isbn=978-3-642-30843-7|access-date=2021-02-28|editor2-last=Mangano|editor2-first=Michelangelo|editor3-last=Tsesmelis|editor3-first=Emmanuel|url-access=subscription}}</ref>
* The [[Super Proton Synchrotron]] (SPS), a circular accelerator with a diameter of 2 kilometres built in a tunnel, which started operation in 1976. It was designed to deliver an energy of 300&nbsp;GeV and was gradually upgraded to 450&nbsp;GeV. As well as having its own beamlines for fixed-target experiments (currently [[COMPASS experiment|COMPASS]] and [[NA62 experiment|NA62]]), it has been operated as a [[proton]]–[[antiproton]] [[collider]] (the Sp{{overline|p}}S collider), and for accelerating high energy [[electron]]s and [[positron]]s which were injected into the [[Large Electron–Positron Collider]] (LEP). Since 2008, it has been used to inject protons and [[heavy ion]]s into the [[Large Hadron Collider]] (LHC).<ref>{{Cite book|last=Hatton|first=V.|title=Conference Record of the 1991 IEEE Particle Accelerator Conference |chapter=Operational history of the SPS collider 1981–1990 |year=1991|chapter-url=https://ieeexplore.ieee.org/document/165151|location=San Francisco|publisher=IEEE|pages=2952–2954|doi=10.1109/PAC.1991.165151|bibcode=1991pac..conf.2952H|isbn=978-0-7803-0135-1|s2cid=33676121}}</ref><ref>{{Cite book|last1=Watkins|first1=Peter|url=https://books.google.com/books?id=J808AAAAIAAJ|title=Story of the W and Z|last2=Watkins|publisher=CUP Archive|year=1986|isbn=978-0-521-31875-4|language=en}}</ref><ref>{{Cite book|last1=Brüning|first1=Oliver|url=https://books.google.com/books?id=28DACwAAQBAJ|title=Challenges and Goals for Accelerators in the XXI Century|last2=Myers|first2=Stephen|publisher=World Scientific|year=2015|isbn=978-981-4436-40-3|language=en}}</ref>
* The [[On-Line Isotope Mass Separator]] (ISOLDE), which is used to study [[radioactive decay|unstable nuclei]]. The radioactive ions are produced by the impact of protons at an energy of 1.0–1.4&nbsp;GeV from the Proton Synchrotron Booster. It was first commissioned in 1967 and was rebuilt with major upgrades in 1974 and 1992.<ref>{{Cite journal |last1=Borge |first1=Maria J. G. |last2=Jonson |first2=Björn |year=2017 |title=ISOLDE past, present and future |journal=Journal of Physics G: Nuclear and Particle Physics |volume=44 |issue=4 |pages=044011 |bibcode=2017JPhG...44d4011B |doi=10.1088/1361-6471/aa5f03 |issn=0954-3899|doi-access=free |hdl=10261/161319 |hdl-access=free }}</ref>
* The [[Antiproton Decelerator]] (AD), which reduces the velocity of antiprotons to about 10% of the [[speed of light]] for research of [[antimatter]].<ref>{{Cite book|last1=Ajduk|first1=Zygmunt|url=https://books.google.com/books?id=Y5HsCgAAQBAJ&q=Antiproton+Decelerator&pg=PA1749|title=Proceedings Of The 28th International Conference On High Energy Physics (In 2 Volumes)|last2=Wroblewski|first2=Andrzej Kajetan|publisher=World Scientific|year=1997|isbn=978-981-4547-10-9|pages=1749|language=en}}</ref> The AD machine was reconfigured from the previous [[Antiproton Collector]] (AC) machine.<ref>{{Cite journal|last1=Bartmann|first1=W.|last2=Belochitskii|first2=P.|last3=Breuker|first3=H.|last4=Butin|first4=F.|last5=Carli|first5=C.|last6=Eriksson|first6=T.|last7=Maury|first7=S.|last8=Oelert|first8=W.|last9=Pasinelli|first9=S.|last10=Tranquille|first10=G.|year=2014|title=Past, present and future low energy antiproton facilities at CERN|url=https://www.worldscientific.com/doi/abs/10.1142/S2010194514602610|journal=International Journal of Modern Physics: Conference Series|language=en|volume=30|pages=1460261|doi=10.1142/S2010194514602610|bibcode=2014IJMPS..3060261B|issn=2010-1945|url-access=subscription}}</ref>
* The [[Extra Low ENergy Antiproton ring (ELENA)|Extra Low Energy Antiproton ring]] (ELENA), which takes antiprotons from AD and decelerates them into low energies (speeds) for use in antimatter experiments.
* The [[AWAKE]] experiment, which is a proof-of-principle [[plasma acceleration|plasma wakefield accelerator]].<ref>{{Cite journal|last1=Adli|first1=E.|last2=Ahuja|first2=A.|last3=Apsimon|first3=O.|last4=Apsimon|first4=R.|last5=Bachmann|first5=A.-M.|last6=Barrientos|first6=D.|last7=Batsch|first7=F.|last8=Bauche|first8=J.|last9=Berglyd Olsen|first9=V. K.|last10=Bernardini|first10=M.|last11=Bohl|first11=T.|year=2018|title=Acceleration of electrons in the plasma wakefield of a proton bunch|url= |journal=Nature|language=en|volume=561|issue=7723|pages=363–367|doi=10.1038/s41586-018-0485-4|issn=0028-0836|pmc=6786972|pmid=30188496|bibcode=2018Natur.561..363A}}</ref><ref>{{Cite journal|last1=Gschwendtner|first1=E.|last2=Adli|first2=E.|last3=Amorim|first3=L.|last4=Apsimon|first4=R.|last5=Assmann|first5=R.|last6=Bachmann|first6=A.-M.|last7=Batsch|first7=F.|last8=Bauche|first8=J.|last9=Berglyd Olsen|first9=V.K.|last10=Bernardini|first10=M.|last11=Bingham|first11=R.|year=2016|title=AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN|url=https://linkinghub.elsevier.com/retrieve/pii/S0168900216001881|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|language=en|volume=829|pages=76–82|doi=10.1016/j.nima.2016.02.026|arxiv=1512.05498|bibcode=2016NIMPA.829...76G|s2cid=53605890}}</ref>
* The [[CERN Linear Electron Accelerator for Research]] (CLEAR) accelerator research and development facility.<ref>{{Cite journal|last1=Sjobak|first1=Kyrre|last2=Adli|first2=Erik|last3=Bergamaschi|first3=Michele|last4=Burger|first4=Stephane|last5=Corsini|first5=Roberto|last6=Curcio|first6=Alessandro|last7=Curt|first7=Stephane|last8=Döbert|first8=Steffen|last9=Farabolini|first9=Wilfrid|last10=Gamba|first10=Davide|last11=Garolfi|first11=Luca|year=2019|others=Boland Mark (Ed.), Tanaka Hitoshi (Ed.), Button David (Ed.), Dowd Rohan (Ed.), Schaa, Volker RW (Ed.), Tan Eugene (Ed.)|title=Status of the CLEAR Electron Beam User Facility at CERN|url=https://jacow.org/ipac2019/doi/JACoW-IPAC2019-MOPTS054.html|journal=Proceedings of the 10th Int. Particle Accelerator Conf.|language=en|volume=IPAC2019|pages=4 pages, 0.190 MB|doi=10.18429/JACOW-IPAC2019-MOPTS054}}</ref><ref>{{Cite journal|last1=Gamba|first1=D.|last2=Corsini|first2=R.|last3=Curt|first3=S.|last4=Doebert|first4=S.|last5=Farabolini|first5=W.|last6=Mcmonagle|first6=G.|last7=Skowronski|first7=P.K.|last8=Tecker|first8=F.|last9=Zeeshan|first9=S.|last10=Adli|first10=E.|last11=Lindstrøm|first11=C.A.|year=2018|title=The CLEAR user facility at CERN|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|language=en|volume=909|pages=480–483|doi=10.1016/j.nima.2017.11.080|bibcode=2018NIMPA.909..480G|s2cid=106403923|doi-access=free|hdl=10852/63044|hdl-access=free}}</ref>

==== Large Hadron Collider ====
{{Main|Large Hadron Collider}}

Many activities at CERN currently involve operating the [[Large Hadron Collider]] (LHC) and the experiments for it. The LHC represents a large-scale, worldwide scientific cooperation project.<ref>{{Cite book|last1=Binoth|first1=T.|url=https://books.google.com/books?id=sMZDMZKLLx0C|title=LHC Physics|last2=Buttar|first2=C.|last3=Clark|first3=P. J.|last4=Glover|first4=E. W. N.|publisher=CRC Press|year=2012|isbn=978-1-4398-3770-2|language=en}}</ref>
[[File:View inside detector at the CMS cavern LHC CERN.jpg|upright|thumb|right|[[Compact Muon Solenoid|CMS]] detector for LHC]]

The LHC tunnel is located 100 metres underground, in the region between [[Geneva International Airport]] and the nearby [[Jura mountains]]. The majority of its length is on the French side of the border. It uses the 27&nbsp;km circumference circular tunnel previously occupied by the [[Large Electron–Positron Collider]] (LEP), which was shut down in November 2000. CERN's existing PS/SPS accelerator complexes are used to pre-accelerate protons and lead ions which are then injected into the LHC.

Eight experiments ([[Compact Muon Solenoid|CMS]],<ref>{{Cite journal |last1=The CMS Collaboration |last2=Chatrchyan |first2=S. |last3=Hmayakyan |first3=G. |last4=Khachatryan |first4=V. |last5=Sirunyan |first5=A. M. |last6=Adam |first6=W. |last7=Bauer |first7=T. |last8=Bergauer |first8=T. |last9=Bergauer |first9=H. |last10=Dragicevic |first10=M. |last11=Erö |first11=J. |year=2008 |title=The CMS experiment at the CERN LHC |journal=Journal of Instrumentation |volume=3 |issue=8 |pages=S08004 |bibcode=2008JInst...3S8004C |doi=10.1088/1748-0221/3/08/S08004 |issn=1748-0221 |s2cid=250668481|doi-access=free |hdl=10067/730480151162165141 |hdl-access=free }}</ref> [[ATLAS experiment|ATLAS]],<ref>{{Cite book|last=The ATLAS Collaboration|url=https://www.worldscientific.com/worldscibooks/10.1142/11030|title=ATLAS: A 25-Year Insider Story of the LHC Experiment|publisher=World Scientific|year=2019|isbn=978-981-327-179-1|series=Advanced Series on Directions in High Energy Physics|volume=30|language=en|doi=10.1142/11030}}</ref> [[LHCb]],<ref>{{cite journal|last1=Belyaev|first1=I.|last2=Carboni|first2=G.|last3=Harnew|first3=N.|last4=Teubert|first4=C. Matteuzzi F.|year=2021|title=The history of LHCb|journal=European Physical Journal H|volume=46|issue=1|page=3|doi=10.1140/epjh/s13129-021-00002-z|arxiv=2101.05331|bibcode=2021EPJH...46....3B|s2cid=231603240}}</ref> [[MoEDAL experiment|MoEDAL]],<ref>{{Cite web |date=2010-05-05 |title=MoEDAL becomes the LHC's magnificent seventh |url=https://cerncourier.com/a/moedal-becomes-the-lhcs-magnificent-seventh/ |access-date=2023-09-27 |website=CERN Courier |language=en-GB}}</ref> [[TOTEM]],<ref>{{Cite journal |last1=The TOTEM Collaboration |last2=Anelli |first2=G. |last3=Antchev |first3=G. |last4=Aspell |first4=P. |last5=Avati |first5=V. |last6=Bagliesi |first6=M. G. |last7=Berardi |first7=V. |last8=Berretti |first8=M. |last9=Boccone |first9=V. |last10=Bottigli |first10=U |last11=Bozzo |first11=M. |year=2008 |title=The TOTEM Experiment at the CERN Large Hadron Collider |journal=Journal of Instrumentation |volume=3 |issue=8 |pages=S08007 |bibcode=2008JInst...3S8007T |doi=10.1088/1748-0221/3/08/S08007 |issn=1748-0221 |s2cid=250680293|doi-access=free }}</ref> [[LHCf]],<ref>{{Cite journal |last1=The LHCf Collaboration |last2=Adriani |first2=O. |last3=Bonechi |first3=L. |last4=Bongi |first4=M. |last5=Castellini |first5=G. |last6=D'Alessandro |first6=R. |last7=Faus |first7=D. A. |last8=Fukui |first8=K. |last9=Grandi |first9=M. |last10=Haguenauer |first10=M. |last11=Itow |first11=Y. |year=2008 |title=The LHCf detector at the CERN Large Hadron Collider |journal=Journal of Instrumentation |volume=3 |issue=8 |pages=S08006 |bibcode=2008JInst...3S8006L |doi=10.1088/1748-0221/3/08/S08006 |issn=1748-0221 |s2cid=250679205|doi-access=free |hdl=10550/42770 |hdl-access=free }}</ref> [[FASER experiment|FASER]]<ref>{{Cite journal|last1=Feng|first1=Jonathan L.|last2=Galon|first2=Iftah|last3=Kling|first3=Felix|last4=Trojanowski|first4=Sebastian|year=2018|title=ForwArd Search ExpeRiment at the LHC|url=https://link.aps.org/doi/10.1103/PhysRevD.97.035001|journal=Physical Review D|language=en|volume=97|issue=3|pages=035001|doi=10.1103/PhysRevD.97.035001|arxiv=1708.09389|bibcode=2018PhRvD..97c5001F|s2cid=119101090|issn=2470-0010}}</ref> and [[A Large Ion Collider Experiment|ALICE]]<ref>{{cite arXiv|last1=Fabjan|first1=C.|last2=Schukraft|first2=J.|year=2011|title=The story of ALICE: Building the dedicated heavy ion detector at LHC|class=physics.ins-det|eprint=1101.1257}}</ref>) are located along the collider; each of them studies particle collisions from a different aspect, and with different technologies. Construction for these experiments required an extraordinary engineering effort. For example, a special [[Crane (machine)|crane]] was rented from Belgium to lower pieces of the CMS detector into its cavern, since each piece weighed nearly 2,000 tons. The first of the approximately 5,000 magnets necessary for construction was lowered down a special shaft at in March 2005.

The LHC has begun to generate vast quantities of data, which CERN streams to laboratories around the world for distributed processing, making use of a specialized [[grid computing|grid]] infrastructure, the [[LHC Computing Grid]]. In April 2005, a trial successfully streamed 600&nbsp;MB/s to seven different sites across the world.

In August 2008, the initial particle beams were injected into the LHC.<ref name="NYT2008/07/29">{{Cite news |last=Overbye |first=Dennis |date=2008-07-29 |title=Let the Proton Smashing Begin. (The Rap Is Already Written.) |language=en-US |work=The New York Times |url=https://www.nytimes.com/2008/07/29/science/29cernrap.html |access-date=2023-09-27 |issn=0362-4331}}</ref> The first beam was circulated through the entire LHC on 10 September 2008,<ref name="CERNPR06.08">{{cite web |url=https://press.cern/past-events/lhc-first-beam |title=LHC First Beam |publisher=CERN |access-date=12 November 2016 |archive-url=https://web.archive.org/web/20161113035627/https://press.cern/past-events/lhc-first-beam |archive-date=13 November 2016 |url-status=dead }}</ref> but the system failed 10 days later because of a faulty magnet connection, and it was stopped for repairs on 19 September 2008.

The LHC resumed operation on 20 November 2009 by successfully circulating two beams, each with an energy of 3.5&nbsp;[[electronvolts|teraelectronvolts]] (TeV). The challenge for the engineers was then to line up the two beams so that they smashed into each other. This is like "firing two needles across the Atlantic and getting them to hit each other" according to Steve Myers, director for accelerators and technology.

On 30 March 2010, the LHC successfully collided two proton beams with 3.5 TeV of energy per proton, resulting in a 7 TeV collision energy. This was enough to start the main research program, including the search for the [[Higgs boson]]. When the 7 TeV experimental period ended, the LHC increased to 8 TeV (4 TeV per proton) starting March 2012, and soon began particle collisions at that energy. In July 2012, CERN scientists announced the discovery of a new sub-atomic particle that was later confirmed to be the [[Higgs boson]].<ref>{{cite journal |author=Cho |first=Adrian |date=13 July 2012 |title=Higgs Boson Makes Its Debut After Decades-Long Search |journal=Science |volume=337 |issue=6091 |pages=141–143 |bibcode=2012Sci...337..141C |doi=10.1126/science.337.6091.141 |pmid=22798574}}</ref>

In March 2013, CERN announced that the measurements performed on the newly found particle allowed it to conclude that it was a Higgs boson.<ref name="intersitetunnel">{{cite web|url=https://press.cern/press-releases/2013/03/new-results-indicate-particle-discovered-cern-higgs-boson |title=New results indicate that particle discovered at CERN is a Higgs boson |publisher=CERN |access-date=12 November 2016}}</ref> In early 2013, the LHC was deactivated for a two-year maintenance period, to strengthen the electrical connections between magnets inside the accelerator and for other upgrades.

On 5 April 2015, after two years of maintenance and consolidation, the LHC restarted for a second run. The first ramp to the record-breaking energy of 6.5 TeV was performed on 10 April 2015.<ref>{{cite web|last1=O'Luanaigh|first1=Cian|title=First successful beam at record energy of 6.5 TeV|url=https://home.cern/about/updates/2015/04/first-successful-beam-record-energy-65-tev|website=CERN: Accelerating science|publisher=CERN|access-date=24 April 2015}}</ref><ref>{{cite web|last1=O'Luanaigh|first1=Cian|title=Proton beams are back in the LHC|url=https://home.cern/about/updates/2015/04/proton-beams-are-back-lhc|website=CERN: Accelerating science|publisher=CERN|access-date=24 April 2015}}</ref> In 2016, the design collision rate was exceeded for the first time.<ref>{{cite web |url=https://home.cern/about/opinion/2016/11/lhc-smashes-targets-2016-run-0 |title=LHC smashes targets for 2016 run |date=1 November 2016 }}</ref> A second two-year period of shutdown begun at the end of 2018.<ref>{{Cite web|last=Schaeffer|first=Anaïs|title=LS2 Report: Review of a rather unusual year|url=https://home.cern/news/news/accelerators/ls2-report-review-rather-unusual-year|url-status=live|access-date=2021-03-01|website=CERN|language=en|archive-url=https://web.archive.org/web/20201217093833/https://home.cern/news/news/accelerators/ls2-report-review-rather-unusual-year |archive-date=17 December 2020 }}</ref><ref>{{Cite web|last=Mangano|first=Michelangelo|date=2020-03-09|title=LHC at 10: the physics legacy|url=https://cerncourier.com/a/lhc-at-10-the-physics-legacy/|url-status=live|access-date=2021-03-01|website=CERN Courier|language=en-GB|archive-url=https://web.archive.org/web/20200325025256/https://cerncourier.com/a/lhc-at-10-the-physics-legacy/ |archive-date=25 March 2020 }}</ref>