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SPEAR (originally Stanford Positron Electron Accelerating Ring, now simply a name)^[1][a] was a collider at the SLAC National Accelerator Laboratory.^[2] It began running in 1972, colliding electrons and positrons with an energy of 3 GeV. During the 1970s, experiments at the accelerator played a key role in particle physics research, including the discovery of the
J/ψ
meson (awarded the 1976 Nobel Prize in Physics), many charmonium states, and the discovery of the tau (awarded the 1995 Nobel Prize in Physics).

Today, SPEAR is used as a synchrotron radiation source for the Stanford Synchrotron Radiation Lightsource (SSRL). The latest major upgrade of the ring in that finished in 2004 rendered it the current name SPEAR3.

a:^ The original design consists of a single ring, an upgraded proposal for a pair of asymmetric rings did not receive enough funding and finally the acronym was kept as a simple name.^[1] Though the name Stanford Positron Electron Asymmetric Ring is also used in official sources.

• Official website
• Brief explanation of the acronym in SLACspeak
• 25th Anniversary Info from SLAC
• SPEAR3 status

37°25′06″N 122°12′04″W / 37.41847°N 122.20116°W / 37.41847; -122.20116

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