LEP accelerator tunnel construction. Tunnel for the large electron positron (LEP) accelerator at CERN (the European particle physics laboratory),near Geneva,Switzerland,under construction. Construction of the tunnel,which has a 27 kilometre circumference,started in 1983. The LEP,which was operational between 1989 and 2000,accelerated electrons and positrons in the opposite direction and then,at four points around the tunnel,focused them so that they collided. The subatomic particles produced by the collisions were then studied |