SPEAR

SPEAR (originally Stanford Positron Electron Accelerating Ring)^[1]^[a] was a particle physics collider at the SLAC National Accelerator Laboratory.^[2] It began running in 1972, colliding electrons and positrons with an energy of 3 GeV, and collecting data about the resulting particles with the Mark I detector. 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 τ⁻
lepton (awarded the 1995 Nobel Prize in Physics).^{[citation needed]}

After its use as a particle collider had been superseded, the facility built for SPEAR was converted to a dedicated synchrotron radiation source for the Stanford Synchrotron Radiation Lightsource (SSRL) beamlines, known as SPEAR2.^[3] A major upgrade of the ring completed in 2004 gave it the current name SPEAR3.^[4]

Notes

^ 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.

References

^ ^a ^b "SLACspeak: S". AHRO.SLAC.Stanford.edu. SLAC Archives, History & Records Office. Retrieved July 11, 2025.
^ Williams, Shawna (May 31, 2003). "The Ring on the Parking Lot". CERN Courier. Retrieved March 29, 2022.
^ Wootton, Kent (January 23, 2018). "Storage Ring Light Sources; US Particle Accelerator School, Fundamentals of Accelerator Physics" (PDF). Retrieved July 11, 2025.
^ "SPEAR3 Accelerator". Retrieved July 11, 2025.