IPAC2015 - List of Authors (Redaelli, S.)

Paper	Title	Page
TUPTY024	Updated Simulation Studies of Damage Limit of LHC Tertiary Collimators	2053
	E. Quaranta, A. Bertarelli, R. Bruce, F. Carra, F. Cerutti, P. Gradassi, A. Lechner, S. Redaelli, E. Skordis CERN, Geneva, Switzerland
	The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10³ halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impact scenarios with one single bunch hitting the jaw with a given impact parameter. In this paper, more realistic failure conditions, including a train of bunches and taking into account the full collimation hierarchy, are used to derive updated damage limits. The results are used to update the margins in the collimation hierarchy and could thus potentially have an influence on the LHC performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY024
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TUPTY025	Betatron Cleaning for Heavy Ion Beams with IR7 Dispersion Suppressor Collimators	2057
	P.D. Hermes, R. Bruce, J.M. Jowett, S. Redaelli CERN, Geneva, Switzerland
	The betatron collimators in IR7 constitute the backbone of the collimation system of the LHC. A fraction of the secondary halo protons or heavy-ion fragments, scattered out of the primary collimator, is not captured by the secondary collimators but hit cold magnets in the IR7 dispersion suppressor (DS) where the dispersion starts to increase. A possible approach to reduce these losses is based on the installation of additional collimators in the DS region. In this paper, simulations of the cleaning efficiency for Pb⁸²⁺ ions are used to evaluate the effect of the additional collimators. The results indicate a significant improvement of the heavy-ion cleaning efficiency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY025
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TUPTY028	Collimator Layouts for HL-LHC in the Experimental Insertions	2064
	R. Bruce, F. Cerutti, L.S. Esposito, J.M. Jowett, A. Lechner, E. Quaranta, S. Redaelli, M. Schaumann, E. Skordis, G.E. Steele CERN, Geneva, Switzerland H. Garcia Morales, R. Kwee-Hinzmann JAI, Egham, Surrey, United Kingdom
	This paper presents the layout of collimators for HL-LHC in the experimental insertions. On the incoming beam, we propose to install additional tertiary collimators to protect potential new aperture bottlenecks in cells 4 and 5, which in addition reduce the experimental background. For the outgoing beam, the layout of the present LHC with three physics debris absorbers gives sufficient protection for high-luminosity proton operation. However, collisional processes for heavy ions cause localized beam losses with the potential to quench magnets. To alleviate these losses, an installation of dispersion suppressor collimators is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY028
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TUPTY029	Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials	2068
	E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi CERN, Geneva, Switzerland
	The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY029
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TUPTY040	Comparison of Beam Sizes at the Collimator Locations from Measured Optics and Beam-based Collimator Alignment at the LHC	2101
	G. Valentino, R. Bruce, A. Langner, S. Redaelli, R. Tomás CERN, Geneva, Switzerland
	At the LHC, the collimation hierarchy is defined in units of the betatron beam size using the sizes at each collimator location. The beam size at a given collimator can be inferred from the gap measurement during beam-based alignment campaigns, when the collimator touches a reference beam halo defined with the primary collimators. On the other hand, the beta functions at each collimator are also measured as a part of the standard LHC optics validation. This paper presents a comparison of the beam size measurements at the collimator locations applying these two techniques for different machine configurations. This work aims at determining which is the most reliable method for setting the collimator gaps at the LHC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY040
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TUPTY046	Impact of Beam Losses in the LHC Collimation Regions	2116
	E. Skordis, R. Bruce, F. Cerutti, A. Ferrari, P.D. Hermes, A. Lechner, A. Mereghetti, P.G. Ortega, S. Redaelli, V. Vlachoudis CERN, Geneva, Switzerland
	The upgrade of the LHC energy and brightness, from the 2015 restart at close to design energy until the HL-LHC era with considerable hardware development and layout renewal, poses tight challenges in terms of machine protection. The collimation insertions and especially the one dedicated to betatron cleaning (IR7), where most of the beam halo is intercepted to spare from losses the cold sectors of the ring, will be subject to a significant increase of radiation load, whose leakage to the nearby dispersion suppressors must be kept sustainable. The past LHC run, while displaying a remarkable performance of the collimation system, offered the opportunity for a demanding benchmarking of the complex simulation chain describing the beam losses and the macroscopic effects of the induced particle showers, this way strengthening the confidence in the reliability of its predictions. This paper discusses the adopted calculation strategy and its evolution options, showing the accuracy achieved with respect to Beam Loss Monitor measurements in controlled loss scenarios. Expectations at design energy, including lifetime considerations concerning critical elements, will also be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY046
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TUPTY066	Beam Cleaning in Experimental IRs in HL-LHC for Incoming Beam	2181
	H. Garcia Morales Royal Holloway, University of London, Surrey, United Kingdom R. Bruce, S. Redaelli CERN, Geneva, Switzerland
	The HL-LHC will store 675 MJ of energy per beam, about 300 MJ more than the nominal LHC. Due to the increase in stored energy and a different interaction region (IR) optics design, the collimation system for the incoming beam must be revisited in order to avoid dangerous losses that could cause quenches and machine damage. This paper studies the ffectiveness of the current LHC collimation system in intercepting cleaning losses close to the experiments in the HL-LHC. The study reveals that additional tertiary collimators would be beneficial in order to protect not only the final focusing triplets but also the two quadrupoles further upstream.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY066
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TUPTY069	Simulation of Hollow Electron Lenses as LHC Beam Halo Reducers using Merlin	2188
	H. Rafique, R.J. Barlow University of Huddersfield, Huddersfield, United Kingdom R.B. Appleby, S.C. Tygier UMAN, Manchester, United Kingdom R. Bruce, S. Redaelli CERN, Geneva, Switzerland
	Funding: Research supported by FP7 HiLumi LHC (Grant agreement 284404) The Large Hadron Collider (LHC) and its High Luminosity (HL) upgrade foresee unprecedented stored beam energies of up to 700 MJ. The collimation system is responsible for cleaning the beam halo and is vital for successful machine operation. Hollow electron lenses (HEL) are being considered for the LHC, based on Tevatron designs and operational experience, for active halo control. HELs can be used as soft scraper devices, and can operate close to the beam core without undergoing damage. We use the Merlin C++ accelerator libraries to implement a HEL and examine the effect on the beam halo for various test scenarios.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY069
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEBB1	Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation	2462
	S. Redaelli, A. Bertarelli, R. Bruce, D. Perini, A. Rossi, B. Salvachua CERN, Geneva, Switzerland G. Stancari, A. Valishev Fermilab, Batavia, Illinois, USA
	Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed.
	Slides WEBB1 [3.216 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEBB1
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Paper

Title

Page

Updated Simulation Studies of Damage Limit of LHC Tertiary Collimators

2053

E. Quaranta, A. Bertarelli, R. Bruce, F. Carra, F. Cerutti, P. Gradassi, A. Lechner, S. Redaelli, E. Skordis
CERN, Geneva, Switzerland

The tertiary collimators (TCTs) in the LHC, installed in front of the experiments, in standard operation intercept fractions of 10³ halo particles. However, they risk to be hit by high-intensity primary beams in case of asynchronous beam dump. TCT damage thresholds were initially inferred from results of destructive tests on a TCT jaw, supported by numerical simulations, assuming simplified impact scenarios with one single bunch hitting the jaw with a given impact parameter. In this paper, more realistic failure conditions, including a train of bunches and taking into account the full collimation hierarchy, are used to derive updated damage limits. The results are used to update the margins in the collimation hierarchy and could thus potentially have an influence on the LHC performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY024

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY025

Betatron Cleaning for Heavy Ion Beams with IR7 Dispersion Suppressor Collimators

2057

P.D. Hermes, R. Bruce, J.M. Jowett, S. Redaelli
CERN, Geneva, Switzerland

The betatron collimators in IR7 constitute the backbone of the collimation system of the LHC. A fraction of the secondary halo protons or heavy-ion fragments, scattered out of the primary collimator, is not captured by the secondary collimators but hit cold magnets in the IR7 dispersion suppressor (DS) where the dispersion starts to increase. A possible approach to reduce these losses is based on the installation of additional collimators in the DS region. In this paper, simulations of the cleaning efficiency for Pb⁸²⁺ ions are used to evaluate the effect of the additional collimators. The results indicate a significant improvement of the heavy-ion cleaning efficiency.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY025

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY028

Collimator Layouts for HL-LHC in the Experimental Insertions

2064

R. Bruce, F. Cerutti, L.S. Esposito, J.M. Jowett, A. Lechner, E. Quaranta, S. Redaelli, M. Schaumann, E. Skordis, G.E. Steele
CERN, Geneva, Switzerland
H. Garcia Morales, R. Kwee-Hinzmann
JAI, Egham, Surrey, United Kingdom

This paper presents the layout of collimators for HL-LHC in the experimental insertions. On the incoming beam, we propose to install additional tertiary collimators to protect potential new aperture bottlenecks in cells 4 and 5, which in addition reduce the experimental background. For the outgoing beam, the layout of the present LHC with three physics debris absorbers gives sufficient protection for high-luminosity proton operation. However, collisional processes for heavy ions cause localized beam losses with the potential to quench magnets. To alleviate these losses, an installation of dispersion suppressor collimators is proposed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY028

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY029

Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials

2068

E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi
CERN, Geneva, Switzerland

The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY029

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY040

Comparison of Beam Sizes at the Collimator Locations from Measured Optics and Beam-based Collimator Alignment at the LHC

2101

G. Valentino, R. Bruce, A. Langner, S. Redaelli, R. Tomás
CERN, Geneva, Switzerland

At the LHC, the collimation hierarchy is defined in units of the betatron beam size using the sizes at each collimator location. The beam size at a given collimator can be inferred from the gap measurement during beam-based alignment campaigns, when the collimator touches a reference beam halo defined with the primary collimators. On the other hand, the beta functions at each collimator are also measured as a part of the standard LHC optics validation. This paper presents a comparison of the beam size measurements at the collimator locations applying these two techniques for different machine configurations. This work aims at determining which is the most reliable method for setting the collimator gaps at the LHC.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY040

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY046

Impact of Beam Losses in the LHC Collimation Regions

2116

E. Skordis, R. Bruce, F. Cerutti, A. Ferrari, P.D. Hermes, A. Lechner, A. Mereghetti, P.G. Ortega, S. Redaelli, V. Vlachoudis
CERN, Geneva, Switzerland

The upgrade of the LHC energy and brightness, from the 2015 restart at close to design energy until the HL-LHC era with considerable hardware development and layout renewal, poses tight challenges in terms of machine protection. The collimation insertions and especially the one dedicated to betatron cleaning (IR7), where most of the beam halo is intercepted to spare from losses the cold sectors of the ring, will be subject to a significant increase of radiation load, whose leakage to the nearby dispersion suppressors must be kept sustainable. The past LHC run, while displaying a remarkable performance of the collimation system, offered the opportunity for a demanding benchmarking of the complex simulation chain describing the beam losses and the macroscopic effects of the induced particle showers, this way strengthening the confidence in the reliability of its predictions. This paper discusses the adopted calculation strategy and its evolution options, showing the accuracy achieved with respect to Beam Loss Monitor measurements in controlled loss scenarios. Expectations at design energy, including lifetime considerations concerning critical elements, will also be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY046

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY066

Beam Cleaning in Experimental IRs in HL-LHC for Incoming Beam

2181

H. Garcia Morales
Royal Holloway, University of London, Surrey, United Kingdom
R. Bruce, S. Redaelli
CERN, Geneva, Switzerland

The HL-LHC will store 675 MJ of energy per beam, about 300 MJ more than the nominal LHC. Due to the increase in stored energy and a different interaction region (IR) optics design, the collimation system for the incoming beam must be revisited in order to avoid dangerous losses that could cause quenches and machine damage. This paper studies the ffectiveness of the current LHC collimation system in intercepting cleaning losses close to the experiments in the HL-LHC. The study reveals that additional tertiary collimators would be beneficial in order to protect not only the final focusing triplets but also the two quadrupoles further upstream.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY066

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPTY069

Simulation of Hollow Electron Lenses as LHC Beam Halo Reducers using Merlin

2188

H. Rafique, R.J. Barlow
University of Huddersfield, Huddersfield, United Kingdom
R.B. Appleby, S.C. Tygier
UMAN, Manchester, United Kingdom
R. Bruce, S. Redaelli
CERN, Geneva, Switzerland

Funding: Research supported by FP7 HiLumi LHC (Grant agreement 284404)
The Large Hadron Collider (LHC) and its High Luminosity (HL) upgrade foresee unprecedented stored beam energies of up to 700 MJ. The collimation system is responsible for cleaning the beam halo and is vital for successful machine operation. Hollow electron lenses (HEL) are being considered for the LHC, based on Tevatron designs and operational experience, for active halo control. HELs can be used as soft scraper devices, and can operate close to the beam core without undergoing damage. We use the Merlin C++ accelerator libraries to implement a HEL and examine the effect on the beam halo for various test scenarios.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-TUPTY069

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEBB1

Plans for Deployment of Hollow Electron Lenses at the LHC for Enhanced Beam Collimation

2462

S. Redaelli, A. Bertarelli, R. Bruce, D. Perini, A. Rossi, B. Salvachua
CERN, Geneva, Switzerland
G. Stancari, A. Valishev
Fermilab, Batavia, Illinois, USA

Hollow electron lenses are considered as a possible mean to improve the LHC beam collimation system, providing an active control of halo diffusion rates and suppressing the population of transverse halos. After a very successful experience at the Tevatron, a conceptual design of a hollow e-lens optimized for the LHC was produced. Recent further studies have led to a mature preliminary technical design. In this paper, possible scenarios for the deployment of this technology at the LHC are elaborated in the context of the scheduled LHC long shutdowns until the full implementation of the HL-LHC upgrade in 2023. Possible setups of electron beam test stands at CERN and synergies with other relevant electron beam programmes outside CERN are also discussed.

Slides WEBB1 [3.216 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEBB1

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)