Results 1 - 10 of 1822
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[en] In high energy storage-ring colliders, the nonlinear effect arising from beam-beam interactions is a major source that leads to the emittance growth, the reduction of beam life time, and limits the collider luminosity. In this paper, two models of beam-beam interactions are introduced, which are weak-strong and strong-strong beam-beam interactions. In addition, space-charge model is introduced.
[en] The thresholds of coherent beam instabilities in the NICA collider are analyzed in the present work. Studies were limited on the coherent oscillations in one of the rings due to the weakness of the beam-beam interaction forces when compared to the single-beam Coulomb forces. The thresholds of the single-beam and multiple-beam instabilities are estimated for the chosen collider operation scenario. Measures that have to be taken to suppress the instabilities are discussed.
[en] One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities
[en] In order to avoid the effects of long-range beam-beam interactions which produce beam blow-up and deteriorate beam life time, a compensation scheme with current carrying wires has been proposed. Two long-range beam-beam compensators were installed in RHIC rings in 2006. The effects of the compensators have been experimentally investigated. An indication was observed that the compensators are beneficial to beam life time in measurements performed in RHIC during 2009. In this paper, we report the effects of wire compensator on beam loss and emittance for proton-proton beams at collision energy.
[en] The working point tunes in the Tevatron at 900 GeV are nominally in an area in betatron tune space that borders the 7th and 5th order resonances. An attempt will be made in this 1992 collider run to measure whether the beam-beam interaction plays an important role in driving resonances in this region of tune space. Experimental results which identify the beam-beam driven resonances are presented. An experimental method of ensuring head-on collisions in order to minimize odd-ordered resonance effects in the Tevatron is also presented
[en] The limit in hadron colliders is understood phenomenologically. The beam-beam interaction produces nonlinear resonances and makes the transverse tunes amplitude dependent. Tune spreads result from the latter, and as long as these tune spreads do not overlap low order resonances, the lifetime and performance is acceptable. Experience is that tenth and sometimes twelfth order resonances must be avoided, and the hadron collider limit corresponds roughly to the space available between resonances of that and lower order when operating near the coupling resonance. The beam-beam interaction in e+e- colliders is not understood well. This affects the performance of existing colliders and could lead to surprises in new ones. For example. a substantial amount of operator tuning is usually required to reach the performance limit given above, and this tuning has to be repeated after each major shutdown. The usual interpretation is that colliding beam performance is sensitive to small lattice errors, and these are being reduced during tuning. It is natural to ask what these errors are, how can a lattice be characterized to minimize tuning time, and what aspects of a lattice should receive particular attention when a new collider is being designed. The answers to this type of question are not known, and developing ideas for calculations, simulations and experiments that could illuminate the details of the beam-beam interaction was the primary working group activity
[en] This document summarizes the talks and discussion that took place in the second session of the Chamonix 2012 workshop concerning results from machine studies performed in 2011. The session consisted of the following presentations: “LHC experience with different bunch spacings” by G. Rumolo; “Observations of beam-beam effects in MDs in 2011” by W. Herr; “Beam-induced heating/ bunch length/RF and lessons for 2012” by E. Metral; “Lessons in beam diagnostics” by R. Jones; “Quench margins” by M. Sapinski; “First demonstration with beam of the Achromatic Telescopic Squeeze (ATS)” by S. Fartoukh. (author)
[en] As two counter-rotating beams interact they can give rise to coherent dipole modes. Under the influence of impedance these coherent beam-beam modes can couple to higher order head-tail modes and lead to strong instabilities. A fully self-consistent approach including beam-beam and impedance was used to characterize this new coupled mode instability and study possible cures such as a transverse damper and high chromaticity
[en] The beam-beam interaction has been and continues to be a performance limiting effect in colliding beam systems. Electron-positron collisions are typically more than a factor of five lower in luminosity than expectations from beam design and with present understanding, extrapolations to future systems are not satisfactory. Prediction and optimized design are even more uncertain for proton-proton and proton-antiproton future systems with the ISR at CERN being the sole precedent. The very health of the high energy physics program in the next decades depends to a significant extent on our ability to unravel the mechanisms of this phenomenon and to control them. There have been a variety of studies, including a plasma model of e+e- collisions, models emphasizing the effects of noise and a model involving a diffusion-damping equilibrium. Various nonlinear analyses of the beam-beam systems have also been performed. And finally an entirely new form of beam-beam configuration has been proposed and studied - the very strong single pass collider. In view of this extensive and broad effort, there was organized an informal seminar to bring many of these ideas into an open forum. This seminar was held at SLAC on May 22 and 23, 1980. Contributors, totaling seventeen, came from universities and national laboratories across the United States. These proceedings represent a record of the seminar. The written versions of the papers presented were submitted by the authors and are included here without editing