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The International Linear Collider (ILC) is a proposed linear particle accelerator. It is planned to have a collision energy of 500 GeV initially, with the possibility for a later upgrade to 1000 GeV (1 TeV). The host country for the accelerator has not yet been chosen and proposed locations are Japan, Europe (CERN) and the USA (Fermilab). Japan is considered the most likely candidate, as the Japanese government is willing to contribute half of the costs, according to the coordinator of study for detectors at the ILC .〔(【引用サイトリンク】 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/ )〕 Construction could begin in 2015 or 2016 and will not be completed before 2026. Studies for an alternative project called the Compact Linear Collider (CLIC) are also underway, which would operate at higher energies (up to 3 TeV) in a machine with comparable length as the ILC. The ILC would collide electrons with positrons. It will be between 30 km and 50 km (19–31 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. == Comparison with LHC == There are two basic shapes of accelerators. Linear accelerators ("linacs") accelerate elementary particles along a straight path. Circular accelerators, such as the Tevatron, the 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, particles 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 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 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 protons or, alternatively, for lead 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 209GeV 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 GeV for the LHC〔Since the actual collisions happen between the constituent of protons—quarks, antiquarks and gluons—the effective energy for collisions will be lower than 14,000 GeV but still higher than 500 GeV), a typical collision at the LHC will be of higher energy than a typical ILC collision. 〕 vs. ~500 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 quarks, antiquarks and gluons of baryonic particles. As such, one of the roles of the ILC would be making precision measurements of the properties of particles discovered at the LHC. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「International Linear Collider」の詳細全文を読む スポンサード リンク
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