Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC
Open Access
- 1 December 2015
- journal article
- research article
- Published by American Physical Society (APS) in Physical Review Special Topics - Accelerators and Beams
- Vol. 18 (12)
- https://doi.org/10.1103/physrevstab.18.121001
Abstract
Colliding bunch trains in a circular collider demands a certain crossing angle in order to separate the two beams transversely after the collision. The magnitude of this crossing angle is a complicated function of the bunch charge, the number of long-range beam-beam interactions, of and type of optics (flat or round), and possible compensation or additive effects between several low- insertions in the ring depending on the orientation of the crossing plane at each interaction point. About 15 years ago, the use of current bearing wires was proposed at CERN in order to mitigate the long-range beam-beam effects [J. P. Koutchouk, CERN Report No. LHC-Project-Note 223, 2000], therefore offering the possibility to minimize the crossing angle with all the beneficial effects this might have: on the luminosity performance by reducing the need for crab-cavities or lowering their voltage, on the required aperture of the final focus magnets, on the strength of the orbit corrector involved in the crossing bumps, and finally on the heat load and radiation dose deposited in the final focus quadrupoles. In this paper, a semianalytical approach is developed for the compensation of the long-range beam-beam interactions with current wires. This reveals the possibility of achieving optimal correction through a careful adjustment of the aspect ratio of the functions at the wire position. We consider the baseline luminosity upgrade plan of the Large Hadron Collider (HL-LHC project), and compare it to alternative scenarios, or so-called “configurations,” where modifications are applied to optics, crossing angle, or orientation of the crossing plane in the two low- insertions of the ring. For all these configurations, the beneficial impact of beam-beam compensation devices is then demonstrated on the tune footprint, the dynamical aperture, and/or the frequency map analysis of the nonlinear beam dynamics as the main figures of merit.
Keywords
Funding Information
- U.S. Department of Energy
- Seventh Framework Programme (284404)
This publication has 6 references indexed in Scilit:
- Stability diagrams of colliding beams in the Large Hadron ColliderPhysical Review Special Topics - Accelerators and Beams, 2014
- Pile up management at the high-luminosity LHC and introduction to the crab-kissing conceptPhysical Review Special Topics - Accelerators and Beams, 2014
- Detecting chaos in particle accelerators through the frequency map analysis methodChaos: An Interdisciplinary Journal of Nonlinear Science, 2014
- Achromatic telescopic squeezing scheme and application to the LHC and its luminosity upgradePhysical Review Special Topics - Accelerators and Beams, 2013
- Long-range beam-beam experiments in the Relativistic Heavy Ion ColliderPhysical Review Special Topics - Accelerators and Beams, 2011
- Application of frequency map analysis to beam-beam effects study in crab waist collision schemePhysical Review Special Topics - Accelerators and Beams, 2011