SPEAR (originally Stanford Positron Electron Asymmetric Rings, now simply a name) was a collider at the SLAC National Accelerator Laboratory. 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.