2,974 research outputs found
Monte Carlo Simulation of Deffuant opinion dynamics with quality differences
In this work the consequences of different opinion qualities in the Deffuant
model were examined. If these qualities are randomly distributed, no different
behavior was observed. In contrast to that, systematically assigned qualities
had strong effects to the final opinion distribution. There was a high
probability that the strongest opinion was one with a high quality.
Furthermore, under the same conditions, this major opinion was much stronger
than in the models without systematic differences. Finally, a society with
systematic quality differences needed more tolerance to form a complete
consensus than one without or with unsystematic ones.Comment: 8 pages including 5 space-consuming figures, fir Int. J. Mod. Phys. C
15/1
Measurements of heavy ion beam losses from collimation
The collimation efficiency for Pb ion beams in the LHC is predicted to be
lower than requirements. Nuclear fragmentation and electromagnetic dissociation
in the primary collimators create fragments with a wide range of Z/A ratios,
which are not intercepted by the secondary collimators but lost where the
dispersion has grown sufficiently large. In this article we present
measurements and simulations of loss patterns generated by a prototype LHC
collimator in the CERN SPS. Measurements were performed at two different
energies and angles of the collimator. We also compare with proton loss maps
and find a qualitative difference between Pb ions and protons, with the maximum
loss rate observed at different places in the ring. This behavior was predicted
by simulations and provides a valuable benchmark of our understanding of ion
beam losses caused by collimation.Comment: 12 pages, 20 figure
Development of hollow electron beams for proton and ion collimation
Magnetically confined hollow electron beams for controlled halo removal in
high-energy colliders such as the Tevatron or the LHC may extend traditional
collimation systems beyond the intensity limits imposed by tolerable material
damage. They may also improve collimation performance by suppressing loss
spikes due to beam jitter and by increasing capture efficiency. A hollow
electron gun was designed and built. Its performance and stability were
measured at the Fermilab test stand. The gun will be installed in one of the
existing Tevatron electron lenses for preliminary tests of the hollow-beam
collimator concept, addressing critical issues such as alignment and
instabilities of the overlapping proton and electron beams.Comment: 3 pp. 1st International Particle Accelerator Conference: IPAC'10,
23-28 May 2010: Kyoto, Japa
Vergleich internationaler Konsensus-Empfehlungen zur Erkennung des präsymptomatischen Hochrisikopatienten für den Herzinfarkt in Deutschland
Summary : The recommendations of the International Task Force for the Prevention of Coronary Heart Disease/International Atherosclerosis Society (ITF/IAS), the US-American Adult Treatment Panel III of the National Cholesterol Education Programs (ATP III) and the 3rd Joint European Guidelines (3JE) for the prevention coronary heart disease (CHD) show good agreement in tertiary prevention. All three guidelines recommend that patients with manifest CHD should have a blood pressure below 140/90 mm Hg and LDL-cholesterol below 2.6 mmol/l (100 mg/dl). By contrast, the three recommendations differ with respect to the prevention of cardiovascular events in asymptomatic high risk patients (secondary prevention), notably in the strategy to be used for risk assessment. Both the ITF/IAS guidelines and the 3JE guidelines can be adapted and realized in the various European countries. We therefore compared the prognostic values of the three recommendations by applying them to the data of male participants of the Prospective Cardiovascular MĂĽnster (PROCAM) Study. The ITF/IAS recommendations show the highest specificity (94.5%), positive predictive value (32.0%) and diagnostic efficacy (90.5%); the 3JE guidelines have the highest sensitivity (64.6%) but lowest specificity (77.9%), positive predictive value (17.5%) and diagnostic efficacy (77.0%). The application of the 3JE recommendations would target 25% of German men aged 35-65 years as cardiovascular high risk patients, by contrast to 7.5% through application of the ITF/IAS guidelines. In view of the limited resources in the public health systemthe application of the ITF/IAS guidelines in Germany appears more appropriat
Measurements of the effect of collisions on transverse beam halo diffusion in the Tevatron and in the LHC
Beam-beam forces and collision optics can strongly affect beam lifetime,
dynamic aperture, and halo formation in particle colliders. Extensive
analytical and numerical simulations are carried out in the design and
operational stage of a machine to quantify these effects, but experimental data
is scarce. The technique of small-step collimator scans was applied to the
Fermilab Tevatron collider and to the CERN Large Hadron Collider to study the
effect of collisions on transverse beam halo dynamics. We describe the
technique and present a summary of the first results on the dependence of the
halo diffusion coefficient on betatron amplitude in the Tevatron and in the
LHC.Comment: 4 pages, 2 figures. Submitted to the Proceedings of the ICFA
Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva,
Switzerland, 18-22 March 201
A Method for Simultaneous Optimisation of Orbit and Dispersion in Storage Rings
An algorithm for the simultaneous optimisation of orbit and dispersion in a storage ring is presented. Based on orbit and dispersion measurements the algorithm determines the optimal corrector settings in order to simultaneously minimize the r.m.s orbit, the r.m.s dispersion and the r.m.s strenght of the dipoles correctors. A number of different options for error handling of beam position monitors, weighting, and correction have been introduced to ensure the stability of the algorithm in the environment of a large accelerator. Experimental results are presented for the LEP collider demonstrating the efficiency of the method. The use of this correction algorithm for LEP in 1999 allowed achieving about a factor of two smaller vertical emittances than in previous years
Comparison between measured and simulated beam loss patterns in the CERN SPS
A prototype of an LHC collimator has been tested with proton beams at the CERN SPS. The interaction of the circulating proton beam with the carbon collimator jaws generated secondary proton beams that were lost in the downstream SPS aperture. The measured beam loss patterns are compared with the results of dedicated loss simulations. The simulation package includes (1) a 6D particle tracking through the SPS lattice; (2) the scattering interaction of protons with the collimator jaw material; (3) the timedependent displacement of the collimator jaws with respect to the beam orbit; (4) a detailed aperture model of the full SPS ring. It is shown that the simulation tools can reliably predict the measured location of losses. This provides an important assessment of the simulation tools in view of the beam loss studies for the Large Hadron Collider (LHC)
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