SPEAR

This article is about the particle accelerator. For other uses, see spear (disambiguation).

SPEAR (originally Stanford Positron Electron Accelerating Ring) was a particle physics collider at the SLAC National Accelerator Laboratory. 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).

After its use as a particle collider had been superseded, the facility built for SPEAR was converted to a dedicated synchrotron radiation source for the Stanford Synchrotron Radiation Lightsource (SSRL) beamlines,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


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