200 GEV A HEAVY-IONS AT CERN - WHAT HAS BEEN LEARNT

Ultrarelativistic heavy ions became available at the end of 1986, when a O-16 beam was accelerated at the CERN SPS up to an energy of 200 GeV per nucleon. Three multipurpose and a number of specialized experiments have been performed in two runs in 1986/87 with O-16 and S-32 beams, respectively. Measured data on transverse energies and particle multiplicities provide evidence for the formation of a state of high energy density close to values predicted by lattice QCD calculations for a quark gluon phase transition. Different characteristic signals from this deconfined state are being investigated by different collaborations and are discussed.