Editing International Linear Collider

{{short description|Proposed linear accelerator for subatomic particles}}
[[File:ILC SchemeTDR.jpg|thumb|400px|An overview graphic of the planned ILC based on the accelerator design of the Technical Design Report]]
The '''International Linear Collider''' ('''ILC''') is a proposed [[linear particle accelerator]].<ref>{{cite web
| title = The International Linear Collider – Gateway to the Quantum Universe
| url = http://www.linearcollider.org/cms/?pid=1000446
| date = 2007-10-18
| access-date = 2009-05-21
| publisher = ILC Community
| format = PDF
| archive-url = https://web.archive.org/web/20090302085802/http://www.linearcollider.org/cms/?pid=1000446
| archive-date = 2009-03-02
| url-status = dead
}}</ref> It is planned to have a collision [[energy]] of 500&nbsp;[[Electronvolt|GeV]] initially, with the possibility for a later upgrade to 1000&nbsp;GeV (1&nbsp;TeV). Although early proposed locations for the ILC were Japan, Europe ([[CERN]]) and the USA ([[Fermilab]]),<ref>{{cite web
| url = http://physicsworld.com/blog/2012/02/where_should_the_international.html
| title = Where should the International Linear Collider be built? 
| author=Hamish Johnston 
| publisher = physicsworld.com
| access-date = 2012-08-02
}}</ref> the [[Kitakami, Iwate|Kitakami]] highland in the [[Iwate Prefecture|Iwate]] prefecture of northern Japan has been the focus of ILC design efforts since 2013.<ref>{{Cite web|url=http://www.linearcollider.org/ILC/What-is-the-ILC/Status-of-the-project|title=ILC - Status of the project|website=www.linearcollider.org|access-date=2016-12-14|archive-url=https://web.archive.org/web/20160927001009/https://www.linearcollider.org/ILC/What-is-the-ILC/Status-of-the-project|archive-date=2016-09-27|url-status=dead}}</ref> The Japanese government is willing to contribute half of the costs, according to the coordinator of study for detectors at the ILC.<ref>{{cite web|url=http://www.uimp.es/blogs/prensa/2012/06/11/el-nuevo-acelerador-de-particulas-ilc-no-estara-finalizado-antes-de-2026-segun-francois-richard/|title=The new particle accelerator ILC will not be completed before 2026, says François Richard (Spanish)|date=2012-06-11|access-date=2012-08-02|archive-url=https://web.archive.org/web/20120702171908/http://www.uimp.es/blogs/prensa/2012/06/11/el-nuevo-acelerador-de-particulas-ilc-no-estara-finalizado-antes-de-2026-segun-francois-richard/|archive-date=2012-07-02|url-status=dead}}</ref>

The ILC would collide [[electron]]s with [[positron]]s. It will be between 30&nbsp;km and 50&nbsp;km (19–31&nbsp;mi) long, more than 10 times as long as the 50 GeV [[Stanford Linear Accelerator]], the longest existing linear particle accelerator. The proposal is based on previous similar proposals from Europe, the U.S., and Japan.

In a staged approach, the ILC could initially be constructed at 250 GeV, for use as a [[Higgs factory]].<ref>{{cite news |last1=List |first1=Jenny |title=ILC: beyond the Higgs |url=https://cerncourier.com/a/ilc-beyond-the-higgs/ |access-date=26 April 2022 |publisher=The CERN Courier |date=28 January 2021}}</ref>  Such a design would be approximately 20&nbsp;km in length.

Studies for an alternative project, the [[Compact Linear Collider]] (CLIC) are also underway, which would operate at higher energies (up to 3 TeV) in a machine of length similar to the ILC. These two projects, CLIC and the ILC, have been unified under the [[Linear Collider Collaboration]].<ref name=":0">{{Cite web|url=http://www.linearcollider.org/|title=LCC - Linear Collider Collaboration|website=www.linearcollider.org|access-date=2016-12-14}}</ref>

== Background: linacs and synchrotrons ==

There are two basic shapes of accelerators. Linear accelerators ("linacs") accelerate [[elementary particle]]s along a straight path. Circular accelerators ("synchrotrons"), such as the [[Tevatron]], the [[Large Electron–Positron Collider|LEP]], and the [[Large Hadron Collider]] (LHC), use circular paths. Circular geometry has significant advantages at energies up to and including tens of [[GeV]]: With a circular design, [[particle physics|particle]]s can be effectively accelerated over longer distances. Also, only a fraction of the particles brought onto a collision course actually collide. In a linear accelerator, the remaining particles are lost; in a ring accelerator, they keep circulating and are available for future collisions. The disadvantage of circular accelerators is that charged particles moving along bent paths will necessarily emit electromagnetic radiation known as [[synchrotron radiation]]. Energy loss through synchrotron radiation is inversely proportional to the fourth power of the [[rest mass|mass]] of the particles in question. That is why it makes sense to build circular accelerators for heavy particles—hadron colliders such as the LHC for [[proton]]s or, alternatively, for [[lead]] [[atomic nucleus|nuclei]]. An electron–positron collider of the same size would never be able to achieve the same collision energies. In fact, energies at the LEP which used to occupy the tunnel now given over to the LHC, were limited to 209 GeV by energy loss via synchrotron radiation.

Even though the nominal collision energy at the LHC will be higher than the ILC collision energy (14,000&nbsp;[[GeV]] for the LHC<ref>Since the actual collisions happen between the constituent of protons—[[quark]]s, antiquarks and [[gluon]]s—the effective energy for collisions will be lower than 14,000&nbsp;GeV but still higher than 500&nbsp;GeV), a typical collision at the LHC will be of higher energy than a typical ILC collision.
</ref> vs. ~500&nbsp;GeV for the ILC), measurements could be made more accurately at the ILC. Collisions between electrons and positrons are much simpler to analyze than collisions in which the energy is distributed among the constituent [[quark]]s, [[antiquark]]s and [[gluon]]s of [[baryon]]ic particles. As such, one of the roles of the ILC would be making precision measurements of the properties of particles discovered at the LHC.

==ILC physics and detectors==
It is widely expected that effects of physics beyond that described in the current [[Standard Model]] will be detected by experiments at the proposed ILC.<ref>{{Citation 
| title = International Linear Collider Reference Design Report Volume 2: Physics at the ILC
| author = G. Aarons
| url = http://ilcdoc.linearcollider.org/record/6321/files/ILC_RDR_Volume_2-Physics_at_the_ILC.pdf?version=4
| year = 2007
| arxiv = 0709.1893 
|bibcode = 2007arXiv0709.1893D |display-authors=etal}}</ref> In addition, particles and interactions described by the Standard Model are expected to be discovered and measured. At the ILC physicists hope to be able to:
* Measure the mass, spin, and interaction strengths of the [[Higgs boson]]
* If existing, measure the number, size, and shape of any [[Electronvolt|TeV]]-scale [[Kaluza–Klein theory|extra dimensions]]
* Investigate the lightest [[supersymmetry|supersymmetric]] particles, possible candidates for [[dark matter]]

To achieve these goals, new generation particle detectors are necessary.

== Merging of regional proposals into a worldwide project ==

In August 2004, the International Technology Recommendation Panel (ITRP) recommended<ref>{{cite web
| title = Final International Technology Recommendation Panel report
| url = http://www.fnal.gov/directorate/icfa/recent_lc_activities_files/ITRP_Report_Final.pdf
| year = 2004
| access-date = 2012-11-19
| publisher = ICFA (International Committee for Future Accelerators)
}}</ref> a [[Superconducting Radio Frequency|superconducting radio frequency]] technology for the accelerator. After this decision the three existing linear collider projects – the Next Linear Collider (NLC), the Global Linear Collider (GLC) and Teraelectronvolt Energy Superconducting Linear Accelerator (TESLA) – joined their efforts into one single project (the ILC). In March 2005, the International Committee for Future Accelerators (ICFA) announced Prof. [[Barry Barish]], director of the [[LIGO]] Laboratory at [[Caltech]] from 1997 to 2005, as the Director of the [[Global Design Effort]] (GDE). In August 2007, the Reference Design Report for the ILC was released.<ref>{{cite web
| title = ILC Reference Design Report
| url = http://www.linearcollider.org/rdr/
| date = August 2007
| access-date = 2009-05-21
| publisher = ILC [[Global Design Effort]] and World Wide Study
| format = PDF
| archive-url = https://web.archive.org/web/20081218073609/http://www.linearcollider.org/rdr/
| archive-date = 2008-12-18
| url-status = dead
}}</ref> [[Physicists]] working on the GDE completed a detailed ILC design report, publishing it in June 2013.<ref name=":0" />

== Design ==
The electron source for the ILC will use 2-nanosecond [[laser]] light pulses to eject electrons from a [[photocathode]], a technique allowing for up to 80% of the electrons to be polarized; the electrons then will be accelerated to 5&nbsp;GeV in a 370-meter linac stage.  Synchrotron radiation from high energy electrons will produce electron-positron pairs on a titanium-alloy target, with as much as 60% polarization; the positrons from these collisions will be collected and accelerated to 5&nbsp;GeV in a separate linac.

To compact the 5&nbsp;GeV electron and positron bunches to a sufficiently small size to be usefully collided, they will circulate for 0.1–0.2 seconds in a pair of damping rings, 3.24&nbsp;km in circumference, in which they will be reduced in size to 6&nbsp;mm in length and a vertical and horizontal [[Beam emittance|emittance]] of 2&nbsp;pm and 0.6&nbsp;nm, respectively.

From the damping rings the particle bunches will be sent to the [[Superconducting Radio Frequency|superconducting radio frequency]] main linacs, each 11&nbsp;km long, where they will be accelerated to 250&nbsp;GeV.  At this energy each beam will have an average power of about 5.3 [[Watt|megawatts]].  Five bunch trains will be produced and accelerated per second.

To maintain a sufficient [[Luminosity (scattering theory)|luminosity]] to produce results in a reasonable time frame after acceleration the bunches will be focused to a few [[nanometre|nanometers]] in height and a few hundred nanometers in width.  The focused bunches then will be collided inside one of two large [[particle detector]]s.

<gallery mode="packed" class="center">
File:A 1.3 GHz nine-cell superconducting radio frequency.JPG|A [[niobium]]-based 1.3&nbsp;GHz nine-cell superconducting radio frequency cavity to be used at the main linac<ref>{{cite book|title=The International Linear Collider Technical Design Report 2013|date=2013|publisher=International Linear Collider|url=http://edmsdirect.desy.de/edmsdirect/file.jsp?edmsid=D00000001021265&fileClass=native|access-date=14 August 2015}}</ref>
File:A 1.3 GHz nine-cell superconducting radio frequency - cross section.JPG|An interior view of the niobium superconducting radio frequency cavity
File:International Linear Collider main linac cryomodule - exterior.jpg|A [[cryomodule]] being tested at [[Fermilab]]
File:International Linear Collider main linac cryomodule - cross section.jpg|Cross section of the cryomodule. A large tube at the center is helium gas return pipe. The closed tube below it is the beam axis.
File:International Linear Collider main linac cryomodule - flange.jpg|A flange of the cryomodule is used to connect instrumentation wires and cables.
</gallery>

==Proposed sites==
Originally, three sites for the International Linear Collider were leading contenders at established High Energy Physics centers in Europe.<ref>{{cite web
| title = Siting Study for European ILC Sites
| author = Wilhelm Bialowons, John Andrew Osborne and Grigori Shirkov
| url = http://www.ilc-higrade.eu/e83212/e99561/e99568/ILC-HiGrade-2010-004-1.pdf
| date = March 31, 2010
| publisher = ILC-HiGrade-Report-2010-004-1
}}</ref> At [[CERN]] in Geneva the tunnel is located deep underground in non-permeable bedrock. This site was considered favorable for a number of practical reasons but due to the [[LHC]] the site was disfavored. At [[DESY]] in Hamburg the tunnel is close to the surface in water saturated soil. Germany leads Europe for scientific funding and was therefore considered reliable in terms of funding. At [[JINR]] in [[Dubna]] the tunnel is close to the surface in non-permeable soil. [[Dubna]] has a pre-accelerator complex which could have been easily adapted for the needs for the ILC. But all three were more or less well suited for housing a Linear Collider and one had ample choice for a site selection process in Europe.{{Cn|date=October 2024}}

Outside Europe a number of countries expressed interest. Japan receives a large amount of funding for neutrino activities, such as the [[T2K experiment]], a factor not in its favor, although 20 huge caverns with access tunnels have already been constructed in Japan for hydroelectric power plants (e.g. the [[Kannagawa Hydropower Plant]]). Following the closure of the [[Tevatron]] some groups within the USA had expressed interest, with [[Fermilab]] being a favored site because of the facilities and experts already present. Much of the speculated interest from other countries was hearsay from within the scientific community, and very few facts were published officially. The information presented above is a summary of that contained in the International Workshop on Linear Colliders 2010 (ECFA-CLIC-ILC Joint Meeting) at CERN.<ref>{{cite web
| title = International Workshop on Linear Colliders 2010 
| url = https://espace.cern.ch/LC2010/default.aspx
| date = 22 October 2010
}}</ref>

The 2008 economic crisis led the United States and United Kingdom to cut funds to the collider project,<ref>{{cite journal
| title = Accelerator plans stalled after US and UK cuts
|journal = Nature
|volume = 451
|issue = 7175
|pages = 112–113
| date = 9 January 2008
|doi = 10.1038/451112a
|pmid = 18185548
|last1 = Hand
|first1 = Eric
|last2 = Brumfiel
|first2 = Geoff
|bibcode = 2008Natur.451..112H
|doi-access = free
}}</ref> leading to Japan's position as the most likely host for the International Linear Collider.<ref>{{cite journal
| title = Japan in pole position to host particle smasher 
| journal = Nature
| url = http://www.nature.com/news/japan-in-pole-position-to-host-particle-smasher-1.12047
| date = 14 December 2012
| doi = 10.1038/nature.2012.12047
| last1 = Brumfiel
| first1 = Geoff
| s2cid = 124158663
| url-access = subscription
}}</ref> On August 23, 2013, the Japanese high-energy physics community's site evaluation committee proposed it should be located in the [[Kitakami Mountains]] of the [[Iwate Prefecture|Iwate]] and [[Miyagi Prefecture|Miyagi]] [[Prefectures of Japan|Prefectures]].<ref name='jsite'>
{{cite journal |author1=Kelen Tuttle |author2=Kathryn Jepsen |date=August 23, 2013
|title=Japan selects candidate site for linear collider
|journal=Symmetry Magazine |publisher=Fermilab
|url=http://www.symmetrymagazine.org/article/august-2013/japan-selects-candidate-site-for-linear-collider |access-date=2013-08-23}}</ref> As of March 7, 2019, the Japanese government has stated that it is not ready to support the construction of the Collider due to its high proposed cost of approximately $7 billion. This decision was informed partly by the [[Science Council of Japan]]. The Japanese government sought monetary support from other countries to help fund this project.<ref>{{Cite web|url=https://www.scientificamerican.com/article/japan-delays-decision-for-hosting-next-big-particle-collider/|title=Japan Delays Decision for Hosting Next Big Particle Collider|last=Garisto|first=Daniel|website=Scientific American|language=en|access-date=2019-03-14}}</ref>

In 2022, the Japanese plan for the ILC was "shelved" by a panel for Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT) <ref name=iop2022>{{cite news |author=Michael Banks  |title=Panel calls on physicists to 'shelve' notion of Japan hosting the International Linear Collider|url=https://physicsworld.com/a/panel-calls-on-physicists-to-shelve-notion-of-japan-hosting-the-international-linear-collider/|publisher=Physics World, IOP Publishing |date=March 1, 2022 }}</ref> Several reasons were given, including potentially insufficient international support and the CERN proposal for the [[Future Circular Collider]], which has overlapping physics goals with the ILC.

In March 2024, the "Federation of Diet Members for the ILC" met to receive "Reports on the ILC project's progress and initiatives by relevant organizations".<ref name=":1">{{Cite web |last=Takahashi |first=Rika |title=Federation of Diet Members resolves to promote the ILC in Japan {{!}} ILC Newsline |url=https://newsline.linearcollider.org/2024/07/08/federation-of-diet-members-resolves-to-promote-the-ilc-in-japan/ |access-date=2024-10-24 |language=en-US}}</ref> Fifty participants, including Diet members and other government agencies, as well as researchers and businesses, received reports on the project's progress. Participants discussed the ILC's future.<ref name=":1" /> The meeting resulted in three recommendations:

{{Block quote|text=1. The ILC project will be further promoted by the research community, industry, organizations promoting the candidate sites, relevant ministries and agencies, the Diet members and other political organizations within an all-Japan framework. 
2. For the ILC project, international collaboration will be further strengthened as a global initiative involving the research community. This will be achieved through close cooperation between the ILC International Development Team (IDT), an international promotion organization established under ICFA, and the domestic research community. 
3. The Ministry of Education, Culture, Sports, Science and Technology (MEXT) should play an active role in collaborating with the international research community to achieve the global accelerator program. This collaboration should utilize the framework of the Liaison Committee on Future High-Performance Accelerators, in partnership with the Cabinet Office, as well as other relevant ministries and agencies.|author=Federation of Diet Members for ILC|title=Recommendation for the Promotion of the International Linear Collider Project<ref>{{Cite web |date=March 21, 2024 |title=Recommendation for the Promotion of the International Linear Collider Project |url=https://newsline.linearcollider.org/wp-content/uploads/2024/07/Proposal-for-the-Promotion-of-the-International-Linear-Collider-Program-1.pdf}}</ref>}}

==Cost==
The Reference Design Report estimated the cost of building the ILC, excluding R&D, prototyping, land acquisition, underground easement costs, detectors, contingencies, and inflation, at US$6.75 [[1000000000 (number)|billion]]<ref>{{cite news|url=https://www.nytimes.com/2007/02/08/science/08cnd-collider.htm|title=Price of Next Big Thing in Physics: $6.7 Billion|publisher=NYTimes | first=Dennis | last=Overbye | date=2007-02-08 | access-date=2010-05-05}}</ref> (in 2007 prices).  From formal project approval, completion of the accelerator complex and detectors is expected to require seven years.  The host country would be required to pay $1.8 billion for site-specific costs like digging tunnels and shafts and supplying water and electricity.

Former U.S. Secretary of Energy [[Steven Chu]] estimated the total cost to be US$25 billion. ILC Director [[Barry Barish|Barish]] said this is likely to be an overestimate. Other Department of Energy officials have estimated a $20 billion total.<ref>{{cite web|url=http://blogs.sciencemag.org/scienceinsider/2009/05/chu-pegs-ilc-co.html |title=Chu Pegs ILC Cost at $25 Billion |publisher=ScienceInsider |year=2009 |url-status=dead |archive-url=https://web.archive.org/web/20100105091936/http://blogs.sciencemag.org/scienceinsider/2009/05/chu-pegs-ilc-co.html |archive-date=January 5, 2010 }}</ref> Upon completion of the 2013 ILC Design Report, Barish said the cost of building the ILC was the equivalent of 7.78 billion 2012 U.S. dollars; it will require "22.6 million hours of labor and location-specific costs including site preparation, scientific detectors and facility operations."<ref>{{Cite news|url=http://www.symmetrymagazine.org/article/february-2013/linear-collider-plans-move-forward|title=Linear collider plans move forward|last=Tuttle|first=Ken|date=2013-02-22|work=symmetry magazine|access-date=2017-03-08|language=en}}</ref>

==Notes==
{{Reflist|35em}}

==External links==
*{{Commons category-inline}}
* [http://www.linearcollider.org/ International Linear Collider Website]
* [http://newsline.linearcollider.org/ ILC NewsLine]
* [https://www.youtube.com/watch?v=40Ap98o-4tU The ILC in 2 minutes] (video, 2:07)
* [https://www.youtube.com/watch?v=ZIKTKP2Y0XA Go for it! Tohoku Big Bang. ~Making the International Linear Collider (ILC) a Reality~] (video, 21:31)
* [https://web.archive.org/web/20000819004646/http://www.llnl.gov/str/VanBibber.html Karl Van Bibber about the NLC]
* In ''symmetry'' magazine:
**[https://web.archive.org/web/20061004084259/http://www.symmetrymagazine.org/cms/?pid=1000146 Special issue], August 2005
**[https://archive.today/20130113085903/http://www.symmetrymagazine.org/cms/?pid=1000286 "out of the box: designing the ILC"], March 2006
*[https://www.nytimes.com/2007/02/08/science/08cnd-collider.html?ex=1328590800&en=9b7528c9bc5aeb8b&ei=5090&partner=rssuserland&emc=rss New York Times article]
*[http://www.sciencemag.org/cgi/content/full/315/5813/746 Science Magazine article]
*[http://www.sciam.com/article.cfm?id=building-the-next-generation-collider Scientific American article preview]
*[https://web.archive.org/web/20080310214424/http://tardis-db.co.uk/2008/02/electron-particle-accelerator-or-ilc.html 1600 International Linear Collider Article]
*arXiv:
**[https://arxiv.org/abs/1306.6327 The International Linear Collider Technical Design Report - Volume 1: Executive Summary]
**[https://arxiv.org/abs/1306.6352 The International Linear Collider Technical Design Report - Volume 2: Physics]
**[https://arxiv.org/abs/1306.6353 The International Linear Collider Technical Design Report - Volume 3.I: Accelerator R&D in the Technical Design Phase]
**[https://arxiv.org/abs/1306.6328 The International Linear Collider Technical Design Report - Volume 3.II: Accelerator Baseline Design]
**[https://arxiv.org/abs/1306.6329 The International Linear Collider Technical Design Report - Volume 4: Detectors]

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[[Category:Proposed particle accelerators]]
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