LEP's innovative dipole magnets are made of plates of steel with the intervening spaces filled out with concrete. For the relatively low bending fields used in LEP, this technique offers a much cheaper alternative to solid steel, costing about half the price. Around each of the experiments, very high field superconducting quadrupoles are used to give the beams a final squeeze before they are brought into collision. The OPAL experiment had the privilege to record the very first collision, at about five past midnight, but the other three experiments followed soon after. A Z particle disintegrates into quarks.
Lines show the particles' tracks, and boxes show the energy they have deposited.
The first full-fledged physics run began on 20 September and continued for three months. During this time, the experiments each recorded around 30,000 Z particles, enough for LEP's first analyses to get under way. The LEP inauguration LEP was officially inaugurated on 13 November 1989 in the presence of some 1,500 guests, including Heads of State and Ministers from all of CERN's 14 Member States. Eleven years later, CERN's membership had grown to 20 states, with the addition of Finland, the Czech and Slovak Republics, Hungary, Poland and Bulgaria. LEP results were not long in coming.