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Title: Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC

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 β* and type of optics (flat or round), and possible compensation or additive effects between several low-β 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 throughmore » a careful adjustment of the aspect ratio of the β 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-β insertions of the ring. Furthermore, 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.« less

Authors:
 [1];  [2];  [1];  [3]
  1. European Organization for Nuclear Research (CERN), Geneva (Switzerland)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. Russian Academy of Sciences (RAS), Novosibirsk (Russian Federation). Budker Inst. of Nuclear Physics (BINP)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1227334
Alternate Identifier(s):
OSTI ID: 1235051
Report Number(s):
FERMILAB-PUB-15-539-APC
Journal ID: ISSN 1098-4402; PRABFM
Grant/Contract Number:
AC02-07CH11359
Resource Type:
Journal Article: Published Article
Journal Name:
Physical Review Special Topics. Accelerators and Beams
Additional Journal Information:
Journal Volume: 18; Journal Issue: 12; Journal ID: ISSN 1098-4402
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS

Citation Formats

Fartoukh, Stéphane, Valishev, Alexander, Papaphilippou, Yannis, and Shatilov, Dmitry. Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC. United States: N. p., 2015. Web. doi:10.1103/PhysRevSTAB.18.121001.
Fartoukh, Stéphane, Valishev, Alexander, Papaphilippou, Yannis, & Shatilov, Dmitry. Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC. United States. doi:10.1103/PhysRevSTAB.18.121001.
Fartoukh, Stéphane, Valishev, Alexander, Papaphilippou, Yannis, and Shatilov, Dmitry. Tue . "Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC". United States. doi:10.1103/PhysRevSTAB.18.121001.
@article{osti_1227334,
title = {Compensation of the long-range beam-beam interactions as a path towards new configurations for the high luminosity LHC},
author = {Fartoukh, Stéphane and Valishev, Alexander and Papaphilippou, Yannis and Shatilov, Dmitry},
abstractNote = {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 β* and type of optics (flat or round), and possible compensation or additive effects between several low-β 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 β 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-β insertions of the ring. Furthermore, 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.},
doi = {10.1103/PhysRevSTAB.18.121001},
journal = {Physical Review Special Topics. Accelerators and Beams},
number = 12,
volume = 18,
place = {United States},
year = {Tue Dec 01 00:00:00 EST 2015},
month = {Tue Dec 01 00:00:00 EST 2015}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1103/PhysRevSTAB.18.121001

Citation Metrics:
Cited by: 3works
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  • 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 β* and type of optics (flat or round), and possible compensation or additive effects between several low-β 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,more » 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 β 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-β insertions of the ring. Furthermore, 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.« less
  • In the baseline scenario of the High-Luminosity LHC (HL-LHC), the geometric loss of luminosity in the two high luminosity experiments due to collisions with a large crossing angle is recovered by tilting the bunches in the interaction region with the use of crab cavities. A possible backup scenario would rely on a reduced crossing angle together with flat optics (with different horizontal and verticalmore » $$\beta^{\ast}$$values) for the preservation of luminosity performance. However, the reduction of crossing angle coupled with the flat optics significantly enhances the strength of long-range beam-beam interactions. This paper discusses the possibility to mitigate the long-range beam-beam effects by current bearing wire compensators (or e-lens). We develop a new HL-LHC parameter list and analyze it in terms of integrated luminosity performance as compared to the baseline. Further, we evaluate the operational scenarios using numerical simulations of single-particle dynamics with beam-beam effects.« less
  • Long-range beam-beam (LRBB) interactions can be a source of emittance growth and beam losses in the LHC during physics and will become even more relevant with the smaller '* and higher bunch intensities foreseen for the High Luminosity LHC upgrade (HL-LHC), in particular if operated without crab cavities. Both beam losses and emittance growth could be mitigated by compensat-ing the non-linear LRBB kick with a correctly placed current carrying wire. Such a compensation scheme is currently being studied in the LHC through a demonstration test using current-bearing wires embedded into col-limator jaws, installed either side of the high luminosity interactionmore » regions. For HL-LHC two options are considered, a current-bearing wire as for the demonstrator, or electron lenses, as the ideal distance between the particle beam and compensating current may be too small to allow the use of solid materials. This paper reports on the ongoing activities for both options, covering the progress of the wire-in-jaw collimators, the foreseen LRBB experiments at the LHC, and first considerations for the design of the electron lenses to ultimately replace material wires for HL-LHC.« less
  • Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beammore » program at RHIC and report on head-on compensations studies based on simulations.« less