V W Hatton

LEP operation in 1992 with a 90/spl deg/ optics

The optics for physics operation in LEP was changed from 60/spl deg/ to 90/spl deg/ at the start of 1992 with a view to improved Z/sup 0/ production, preparation for future operation at higher energies and the use of the same optics in machine developments. The developments included running LEP with twice the number of bunches and using resonant depolarisation for energy calibration, Perturbation to steady operation was felt at the start of the year but was soon overcome as the benefits of smaller emittances were realised. The peak luminosity increased to 1.15 10/sup 31/ and the luminosity lifetime improved. New operational software halved the time taken between dumping one coast and the start of data taking on the next. The 8+8 bunch operation was introduced as routine operation for the last month. Overall, there was an increase in integrated luminosity from 17.6 inverse picobarns per experiment in 1991 to 28.6 in 1992. Along with improvements in detector efficiency, almost 3 million hadronic Z/sup 0/s were recorded by the four experiments, an increase from 1.27 million in 1991.<<ETX>>

High luminosity performance of the SPS proton-antiproton collider

In September 1988, the CERN SPS (Super Proton Synchrotron) collider was brought into operation for the first physics production run with the improved antiproton production and accumulation complex (AAC). The increased antiproton flux immediately resulted in a considerable improvement in the machine performance with initial luminosities exceeding 2.4*10/sup 30//cm/sup 2/ s, and weakly integrated luminosities an order of magnitude greater than achieved in the past. A total integrated luminosity of 3.4 inverse pbarns was produced, a factor of 5 greater than the best achieved in previous years. Performance statistics and operational experience in this new regime are discussed.<<ETX>>

First two years operational experience with LEP

The authors summarize the experience over the first two years of LEP (Large Electron-Positron colliding beam accelerator) operation giving typical and peak performance figures. During 1989 a beam of positrons was injected into LEP from the SPS (Super Proton Synchrotron) and the first full turn was completed. Experiments detected their first Z/sup 0/ particles. The machine was operated in a mixed mode of machine studies and operation for physics. At the end of this period a total of over 1.7 inverse picobarns of integrated luminosity had been recorded per experiment, resulting in a total of more than 70000 Z/sup 0/s detected. The energy of each fill was varied, and half the number of fills were at the Z/sup 0/s peak. During 1990, LEP was operated in the same way as in 1989; 12.1 inverse picobarns and three quarters of a million Z/sup 0/s were produced. Physics fills of 6-h duration in 1989 were increased to 10-12 h in 1990 as the lifetimes of the beams increased with the steadily improved vacuum in the ring.<<ETX>>

Operational history of the SPS collider 1981-1990

In June 1978 approval was given for the construction of an antiproton production and storage facility, the AA complex, and for the modification of the SPS to be able to inject, accelerate, and store bunches of 270-GeV protons and antiprotons with collisions in the center of two large experimental detectors. Two years later, after the construction of the necessary equipment and preparatory excavation of the two underground zones, the SPS fixed target operation was interrupted for nearly 12 months to complete the installations. First collisions of two bunches of protons against one bunch of antiprotons were observed on July 10, 1981. Along with the increase in the number of antiprotons produced and stored in the antiproton accumulator and the smaller and smaller beam sizes in the region of the experimental detectors, the understanding and control of the collider as a complicated machine physics experiment has gradually increased.<<ETX>>