55438680
THE ELECTRICAL CIRCUIT DESCRIPTION FOR THE LHC
The LHC is a very complex machine, made of about 8000 superconducting magnets along a circumference of 26.7 km. The magnets are powered in about 1700 different electrical circuits with currents ranging from 60 A (for small corrector magnets) up to 13 kA for the main dipoles and quadrupoles. The layout of the powering system reflects the complexity of the accelerator. About 80000 high current connections will have to be made. A minor fault in a circuit or one of the superconducting connections would have severe consequences for accelerator operation. For the integration of the electrical equipment, for supporting the assembly and verifying the correctness of the electrical circuits, all relevant information should be included in one coherent database. A simple method for the description of the electrical circuits is proposed, while an associated tool is translating this input into database information and back, checking the circuit description at the same time for inconsistencies. Out of the database information, electrical drawings and detailed views of the electrical connections at every LHC interconnection point can be recreated. This paper describes the approach and outlines several possible applications.
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.
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.
107933425
First trial of BOM harmonic analysis
118006705
Parametrizing the baryon magnetic moments
12690675
The general QCD parametrization and the large Nc description: Some remarks
Stimulated by a recent paper of Buchmann and Lebed,a comparison is presented of the two methods mentioned in the title for treating hadron properties in QCD.Doubts arise on the equivalence of the large Nc description to real QCD. (PACS: 12.38.Aw; 11.15.Pg; 13.40.Dk)
119968526
SEARCHES OF FRACTIONALLY CHARGED PARTICLES IN MATTER WITH THE MAGNETIC LEVITATION TECHNIQUE
Abstract A survey is given of the experiments performed with the magnetic levitation electrometer to search for stable fractional charges in matter. After a general introduction, illustrating the principle of the method, an analysis is presented of the electric forces acting on the levitating object (who se knowledge is essential to determine the residual charge). This is followed by a short account of the historical evolution of the subject, after which we proceed to a detailed description of the ferromagnetic levitation electrometer used in our laboratory and of the results obtained. The main differences with the Stanford diamagnetic (superconducting) instrument are also illustrated. The final section contains a concise summary of the other experiments of search of quarks in matter, in particular of the Millikan automated ones.
119592224
New Results in the Search of Quarks in Matter by the Magnetic Levitation Electrometer
Abstract The results of many runs performed levitating in succession several spheres without opening the levitation chamber show the existence of an additional (magneto-electric) force acting on the sphere. Ignoring this force in the analysis of the data produces “spurious” fractional charges.
121541770
SCALING OF THE NUCLEON E.M. ELASTIC FORM FACTORS: A GENERAL DERIVATION
Abstract The scaling of the elastic e.m. form factors of the nucleon ( p charge form factor and magnetic form factors of p and n ) has been discussed so far mainly in the non relativistic quark model. We ask: Can the scaling be derived in a model independent way from general properties of QCD? Using the QCD general parametrization we show that: (1) The magnetic form factors of p and n are expected to scale in QCD to a few percent; (2) As to the p electric and magnetic form factors, their scaling, in general, is not guaranteed. The most likely explanation of its empirical validity is that only the “valence quarks” determine the expectation values of both the local charge and magnetization density; the effects of “sea” quarks and antiquarks cancel locally, on the average, as far as the p form factors are concerned.