59433578
Electron-positron collisions at 209 GeV in LEP
The Large Electron-Positron Collider (LEP) at CERN closed down in November 2000. During the year 2000 electron-positron collisions were established at centre-of-mass energies of up to 209 GeV. The energy reach of LEP was thus extended by another 7 GeV compared to the year 1999. At the same time the luminosity production was kept high and the total delivered luminosity for the year was 233 pb/sup -1/. High beam energy and high luminosity extended the discovery reach of LEP. The successful energy increase of LEP is analysed and the operation and performance in the regime of ultra-strong damping is described.
54676169
Measurement of chromatic effects in LEP
The chromaticity produced by the insertions and the lattice of LEP is corrected in the FODO lattice of the arcs which has horizontal and vertical phase advances of 90/spl deg/ and 60/spl deg/ for the LEP optics presently used. This is done with two horizontal and three vertical sextupole families. To check this correction scheme the non-linear chromaticities have been measured by observing the betatron tunes as a function of RF-frequency, i.e. of momentum deviation. The differences between the results and the expected effects of the sextupoles are interpreted in terms of octupole and decapole components in the dipole magnets. To check the distribution around the ring of the chromaticities and their corrections the betatron phase advances have been measured as a function of momentum deviation. This was done by observing an excited betatron oscillation for 1024 turns in all beam position monitors for different RF-frequencies. The results clearly show the negative chromaticity produced in the straight sections and its correction in the arcs. The parasitic sextupole components are found to be spread uniformly in the arcs within the measurement errors. Under this condition one finds that they have a negligible effect on the dynamic aperture.
12798237
Overview of LEP operation in 1998
After the installation of 32 additional RF cavities in the 1997-1998 shutdown LEP was operated at a beam energy of 94.5 GeV. The total integrated luminosity for the year 1998 clearly surpassed its target and reached 198 pb/sup -1/. Vertical beam-beam tuneshifts of more than 0.07 were obtained. The performance did not seem to be beam-beam limited, but the total beam current was limited by power dissipation problems to around 6 mA. A high phase advance optics (102/spl deg/, 90/spl deg/), with a smaller natural emittance, was used for regular operation in 1998. This contributed to the excellent performance of LEP, together with the further reduction of both the horizontal and vertical beta function at the interaction points. No dynamic aperture problems were encountered.
107933425
First trial of BOM harmonic analysis
61569699
The RTC-a software support system for the control of the CERN SPS
The RTC (Run Time Coordinator) is described. It is a software support system designed for the SPS (Super Proton Synchrotron) control system to provide a run time environment for application software. It coordinates the execution of individual programs or processes and supervises the process control, i.e. process synchronization, interprocess communication, data transfer, and operator I/O (input/output). This supervision includes the control of processes distributed on a Unix-based network. A standard language independent data interface is part of the system. The system includes tools for data presentation, error logging, and contention resolution. Separating system-dependent features for the body of the application programs leads to high flexibility and simplifies the software development. The basic philosophy of the RTC is discussed and its implementation is described.<<ETX>>
10489447
LEP OPERATION AND PERFORMANCE WITH 100 GEV COLLIDING BEAMS
Luminosity production in LEP was extended to 101 GeV beam energy in 1999 and 104.4 GeV in 2000. The performance was continually optimised, resulting in 1999 peak and integrated luminosities higher than in any previous year of LEP operation. In particular, the beambeam tune shift reached 0.083 per interaction point. This was achieved with the help of a faster luminosity monitoring, a new tune working point, a reduced design vertical dispersion and new dispersion and coupling optimisation tools. A higher beam rate from the injectors, a better injection efficiency, a faster ramp and a newly automated control of the horizontal damping partition number J x maximised the time available for physics and thus contributed to the higher integrated luminosity.
118467315
The Magnetic Levitation Electrometer: The Searches for Quarks and the Electron-Proton Charge Difference
The original subject of these lectures had to be the electron-proton charge difference;but because such a measurement has been,infact, a byproduct of a much longer experiment — the search of quarks in matter — and because both experiments use the same instrument and imply similar problems, I thought that it might be advisable to start describing the experiment of search for quarks.
121640423
Preliminary results in the search for fractionally charged particles by the magnetic levitation electrometer
Abstract The operation of the magnetic levitation electrometer suggested in ref. 1 is described. Measurements on the first five graphite grains (containing altogether ∼ 10 16 nucleons) exclude the presence of quarks in them; a future program of search for terrestrial quarks by this instrument is outlined.
120751442
Confirmation of the electric neutrality of matter at the milligram level
Abstract The procedure to identify, measure and subtract the magneto-electric force acting on levitating spheres is described. All the 25 steel spheres (with a total mass of 1.75 mg) examined after the elimination of the effects of such a force produce the result: N quarks / N nucleons ⩽ 10 −21 .
120916653
The relation between QCD and constituent quark models
123073842
QCD with pion exchange, double counting and the baryon magnetic moments