Collider
History
History
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The first serious proposal for a collider originated with a group at the [Midwestern Universities Research Association](/wiki/Midwestern_Universities_Research_Association "Midwestern Universities Research Association") (MURA). This group proposed building two tangent radial\-sector [FFAG accelerator](/wiki/FFAG_accelerator "FFAG accelerator") rings. [Tihiro Ohkawa](/wiki/Tihiro_Ohkawa "Tihiro Ohkawa"), one of the authors of the first paper, went on to develop a radial\-sector FFAG accelerator design that could accelerate two counterrotating particle beams within a single ring of magnets.Science: Physics \& Fantasy, [Time](https://web.archive.org/web/20121106173215/http://www.time.com/time/magazine/article/0,9171,809067-1,00.html), Monday, Feb. 11, 1957\. The third FFAG prototype built by the MURA group was a 50 MeV electron machine built in 1961 to demonstrate the feasibility of this concept.

[Gerard K. O'Neill](/wiki/Gerard_K._O%27Neill "Gerard K. O'Neill") proposed using a single accelerator to inject particles into a pair of tangent [storage rings](/wiki/Storage_ring "Storage ring"). As in the original MURA proposal, collisions would occur in the tangent section. The benefit of storage rings is that the storage ring can accumulate a high beam flux from an injection accelerator that achieves a much lower flux.

The first [electron](/wiki/Electron "Electron")\-[positron](/wiki/Positron "Positron") colliders were built in late 1950s\-early 1960s in Italy, at the [Istituto Nazionale di Fisica Nucleare](/wiki/Istituto_Nazionale_di_Fisica_Nucleare "Istituto Nazionale di Fisica Nucleare") in [Frascati](/wiki/Frascati "Frascati") near Rome, by the Austrian\-Italian physicist [Bruno Touschek](/wiki/Bruno_Touschek "Bruno Touschek") and in the US, by the Stanford\-Princeton team that included William C.Barber, Bernard Gittelman, Gerry O’Neill, and [Burton Richter](/wiki/Burton_Richter "Burton Richter"). Around the same time, the *VEP\-1* electron\-electron collider was independently developed and built under supervision of [Gersh Budker](/wiki/Gersh_Budker "Gersh Budker") in the [Institute of Nuclear Physics](/wiki/Budker_Institute_of_Nuclear_Physics "Budker Institute of Nuclear Physics") in [Novosibirsk](/wiki/Novosibirsk "Novosibirsk"), [USSR](/wiki/USSR "USSR"). The first observations of particle reactions in the colliding beams were reported almost simultaneously by the three teams in mid\-1964 \- early 1965\. 

In 1966, work began on the [Intersecting Storage Rings](/wiki/Intersecting_Storage_Rings "Intersecting Storage Rings") at [CERN](/wiki/CERN "CERN"), and in 1971, this collider was operational.Kjell Johnsen, The ISR in the time of Jentschke, [CERN Courier](http://cerncourier.com/cws/article/cern/28876), June 1, 2003\. The ISR was a pair of storage rings that accumulated and collided protons injected by the CERN [Proton Synchrotron](/wiki/Proton_Synchrotron "Proton Synchrotron"). This was the first [hadron](/wiki/Hadron "Hadron") collider, as all of the earlier efforts had worked with [electrons](/wiki/Electrons "Electrons") or with electrons and [positrons](/wiki/Positrons "Positrons").

In 1968 construction began on the highest energy proton accelerator complex at [Fermilab](/wiki/Fermilab "Fermilab"). It was eventually upgraded to become the [Tevatron](/wiki/Tevatron "Tevatron") collider and in October 1985 the first [proton](/wiki/Proton "Proton")\-[antiproton](/wiki/Antiproton "Antiproton") collisions were recorded at a center of mass energy of 1\.6 TeV, making it the highest energy collider in the world, at the time. The energy had later reached 1\.96 TeV and at the end of the operation in 2011 the collider luminosity exceeded 430 times its original design goal. 

Since 2009, the most high\-energetic collider in the world is the [Large Hadron Collider](/wiki/Large_Hadron_Collider "Large Hadron Collider") (LHC) at CERN. It currently operates at 13 TeV center of mass energy in proton\-proton collisions. More than a dozen future particle collider projects of various types \- circular and linear, colliding hadrons (proton\-proton or ion\-ion), leptons (electron\-positron or muon\-muon), or electrons and ions/protons \- are currently under consideration for detail exploration of the Higgs/electroweak physics and discoveries at the post\-LHC energy frontier. 


What is the current center of mass energy in proton-proton collisions at the Large Hadron Collider?