Scientist checking the sense wires of the muon detector inside the clean room of CERN's L-3 experiment during construction in 1988. The detector consists of 250, 000 beryllium and tungsten wires mounted in 80 chambers. A pair of positive and negative muons may be produced by the collision of an electron and a positron, the wires detect the muons and measure their momentum. The L-3 experiment is part of CERN's Large Electron- Positron collider (LEP), inaugurated on 13 November 1989.