The LEP accelerator was in operation between 1989 and 2000. Then the whole machine was dismantled to make room for a new accelerator in the same tunnel. The name of the new accelerator is Large Hadron Collider, LHC.
LHC will, in contrast to LEP, collide beams consisting of protons. Collisions with much higher energy, 14 TeV, will be possible by replacing the electrons and positrons from LEP to protons. Currently (2003) is LHC under construction. It will be operational in 2007.
Several detectors will be constructed at LHC to register what happens in the particle collisions. One of these experiments is ATLAS. Click on the link below to start an animation that shows how the protons move through the accelerator system at CERN and then collides in the ATLAS detector. The animation needs the program Macromedia Flash Player.
To understand what happens in a particle collision registered in ATLAS you can study the chapter "Detectors".