Between ALEPH's "bouchon" and "barrel"

7 June 2000

Display high resolution version

A person poised on a ladder gives a clue to the scale of ALEPH, one of the four large detectors at the Large Electron Positron Collider (LEP) at CERN, Geneva. Like the other detectors, ALEPH consists of many different layers, which form a massive cylindrical "barrel" around the pipe where LEP's beams of electrons and positrons collide. The ends of the barrel are plugged by equally large end-caps, or "bouchons", to ensure that as many as possible of the particles produced in the collisions are detected, no matter what direction they take. In the image, the detector is pulled apart, with the end of the barrel visible to the right, and one of the bouchons to the left. The segmented structure of ALEPH's iron barrel, which provides material to capture hadrons (particles made from quarks), is clearly seen.

Credit: CERN Photo