High energy operation of LEP2

The LEP collider was operated during 1998 for the first time at a beam energy of 94.5 GeV. The 272 superconducting (SC) cavities were operated at an average gradient of more than 6 MV/m. The high current in short bunches caused severe higher order mode heating of components. Nevertheless the machine proved very reliable with excellent performance. The maximum integrated luminosity over a 24 hour period exceeded 3.5 pb/sup -1/ and the vertical beam-beam shift parameter reached more than .075 in three of the interaction regions with a record of .08 in the fourth. The present and future performance and limitations of the machine are reviewed as well as some of the crucial technical systems. During 1999 attempts will be made to increase the beam energy to around 100 GeV with the help of an additional 16 SC cavities and by operating at gradients around 7 MV/m.