IPAC2014 - List of Authors (Redaelli, S.)

Paper	Title	Page
MOOCB01	Beam-induced Quench Tests of LHC Magnets	52
	M. Sapinski, B. Auchmann, T. Bär, W. Bartmann, M. Bednarek, S. Bozyigit, C. Bracco, R. Bruce, F. Cerutti, V. Chetvertkova, K. Dahlerup-Petersen, B. Dehning, E. Effinger, J. Emery, A. Guerrero, E.B. Holzer, W. Höfle, A. Lechner, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, N.V. Shetty, A.P. Siemko, E. Skordis, M. Solfaroli Camillocci, J. Steckert, J.A. Uythoven, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth, E.N. del Busto CERN, Geneva, Switzerland
	At the end of the LHC Run1 a 48-hour quench-test campaign took place to investigate the quench levels of superconducting magnets for loss durations from nanoseconds to tens of seconds. The longitudinal losses produced extended from one meter to hundreds of meters and the number of lost protons varied from 10⁸ to 10¹³. The results of these and other, previously conducted quench experiments, allow the quench levels of several types of LHC magnets under various loss conditions to be assessed. The quench levels are expected to limit LHC performance in the case of steady-state losses in the interaction regions and also in the case of fast losses initiated by dust particles all around the ring. It is therefore required to accurately adjust beam loss abort thresholds in order to maximize the operation time. A detailed discussion of these quench test results and a proposal for additional tests after the LHC restart is presented.
	Slides MOOCB01 [2.737 MB]
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MOPRO021	Power Deposition in LHC Magnets With and Without Dispersion Suppressor Collimators Downstream of the Betatron Cleaning Insertion	112
	A. Lechner, B. Auchmann, R. Bruce, F. Cerutti, P.P. Granieri, A. Marsili, S. Redaelli, N.V. Shetty, E. Skordis, G.E. Steele, A.P. Verweij CERN, Geneva, Switzerland
	The power deposited in dispersion suppressor (DS) magnets downstream of the LHC betatron cleaning insertion is governed by off-momentum protons which predominantly originate from single-diffractive interactions in primary collimators. With higher beam energy and intensities anticipated in future operation, these clustered proton losses could possibly induce magnet quenches during periods of short beam lifetime. In this paper, we present FLUKA simulations for nominal 7 TeV operation, comparing the existing layout with alternative layouts where selected DS dipoles are substituted by pairs of shorter higher-field magnets and a collimator. Power densities predicted for different collimator settings are compared against present estimates of quench limits. Further, the expected reduction factor due to DS collimators is evaluated.
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MOPRO037	Collimator Fast Failure Losses for Various HL-LHC Configurations	157
	L. Lari, R. Bruce, S. Redaelli CERN, Geneva, Switzerland L. Lari IFIC, Valencia, Spain
	Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404 The upgrade of the Large Hadron Collider (LHC), in terms of beam intensity and energy, implies an increasing risk of severe damage in particular in case of fast failures losses. For this reason, efforts were put in developing simulation tools to allow studies of asynchronous dump accident, including realistic failure cases for collimator settings and machine parameters like orbit and optics. The scope of these studies is to understand realistic beam loads in different collimators, in order to improve the actual LHC collimator system design, to provide feedbacks on optic design and to evaluate different mitigation actions. Simulations were set up with a modified SixTrack collimation routine able to simulate erroneous firing of a single dump kicker or the simultaneous malfunction of all the 15 kickers. In such a context, results are evaluated from the whole LHC collimation system point of view.
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MOPRO039	Integrated Simulation Tools for Collimation Cleaning in HL-LHC	160
	R. Bruce, C. Bracco, F. Cerutti, A. Ferrari, A. Lechner, A. Marsili, A. Mereghetti, D. Mirarchi, P.G. Ortega, D. Pastor Sinuela, S. Redaelli, A. Rossi, B. Salvachua, V. Vlachoudis CERN, Geneva, Switzerland R. Appleby, J. Molson, M. Serluca UMAN, Manchester, United Kingdom R.W. Aßmann DESY, Hamburg, Germany R.J. Barlow, H. Rafique, A.M. Toader University of Huddersfield, Huddersfield, United Kingdom S.M. Gibson, L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom L. Lari IFIC, Valencia, Spain C. Tambasco University of Rome La Sapienza, Rome, Italy
	The Large Hadron Collider is designed to accommodate an unprecedented stored beam energy of 362~MJ in the nominal configuration and about the double in the high-luminosity upgrade HL-LHC that is presently under study. This requires an efficient collimation system to protect the superconducting magnets from quenches. During the design, it is therefore very important to accurately predict the expected beam loss distributions and cleaning efficiency. For this purpose, there are several ongoing efforts in improving the existing simulation tools or developing new ones. This paper gives a brief overview and status of the different available codes.
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MOPRO040	Collimation Cleaning for HL-LHC Optics Scenarios with Error Models	163
	A. Marsili, R. Bruce, S. Redaelli CERN, Geneva, Switzerland
	Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404 The upgrade of the LHC collimation system in view of the High-Luminosity upgrade of the Large Hadron Collider (LHC) foresees, amongst other scenarios, local collimation in the dispersion suppressors (DS) of IR7. Layouts have been worked out which rely on using stronger and short bending dipoles to free space for a collimator in the cold DS. In this paper, the effectiveness of the proposed layouts is studied with different imperfection models such as collimator alignment, jaw tilt and surface errors, optics errors and aperture imperfections. The effect of local DS collimation on the global losses around the ring is also addressed for different optics configurations.
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MOPRO041	Multi-turn Tracking of Collision Products at the LHC	166
	A. Marsili, R. Bruce, F. Cerutti, L.S. Esposito, S. Redaelli CERN, Geneva, Switzerland
	Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404 The luminosity expected at the interaction points in LHC at 7 TeV will be unprecedented, up to 1034 cm−2 s−1 . Part of the debris produced by the collisions is lost locally im- mediately downstream the Interaction Point (IP), in the matching section and dispersion suppressor. In this paper, the dynamics of collision debris protons is discussed. First, the loss distributions close to the collision points, simulated with two codes – SixTrack and FLUKA – are compared for different layout configurations. Then, SixTrack is used to simulate the fraction of protons that have undergone inelastic interactions with smaller energy and and betatron offsets, which could travel for several turns around the ring and might be lost in other collimation insertions. A preliminary comparison is made between the resulting loss distribution and measurements.
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MOPRO042	Cleaning Performance with 11T Dipoles and Local Dispersion Suppressor Collimation at the LHC	170
	R. Bruce, A. Marsili, S. Redaelli CERN, Geneva, Switzerland
	The limiting location of the present LHC machine in terms of losses on cold magnets are the dispersion suppressors downstream of the betatron collimation insertion (IR7). These losses are dominated by off-energy protons that have by-passed the upstream secondary collimation system but are lost where the dispersion starts to rise. A solution under consideration for intercepting these losses is the addition of new collimators in the dispersive area. This paper discusses first a proposition for the new layout in the DS, where space is made for the new collimators by replacing an existing dipole by shorter and stronger magnets. Furthermore, simulations with SixTrack are presented, which quantify the gain in cleaning from the new collimators.
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MOPRO043	Handling 1 MW Losses with the LHC Collimation System	174
	B. Salvachua, R. Bruce, F. Carra, M. Cauchi, E.B. Holzer, W. Höfle, D. Jacquet, L. Lari, D. Mirarchi, E. Nebot Del Busto, S. Redaelli, A. Rossi, M. Sapinski, R. Schmidt, G. Valentino, D. Valuch, J. Wenninger, D. Wollmann, M. Zerlauth CERN, Geneva, Switzerland M. Cauchi UoM, Msida, Malta L. Lari IFIC, Valencia, Spain
	Funding: Research supported by EU FP7 HiLumi LHC (Grant agree. 284404) The LHC superconducting magnets in the dispersion suppressor of IR7 are the most exposed to beam losses leaking from the betatron collimation system and represent the main limitation for the halo cleaning. In 2013, quench tests were performed at 4 TeV to improve the quench limit estimates, which determine the maximum allowed beam loss rate for a given collimation cleaning. The main goal of the collimation quench test was to try to quench the magnets by increasing losses at the collimators. Losses of up to 1 MW over a few seconds were generated by blowing up the beam, achieving total losses of about 5.8 MJ. These controlled losses exceeded by a factor 2 the collimation design value, and the magnets did not quench.
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MOPRO044	Construction and Bench Testing of a Prototype Rotatable Collimator for the LHC	178
	T.W. Markiewicz, E.L. Bong, L. Keller SLAC, Menlo Park, California, USA O. Aberle, A. Bertarelli, P. Gradassi, A. Marsili, S. Redaelli, A. Rossi, B. Salvachua, G. Valentino CERN, Geneva, Switzerland
	Funding: This work partially supported by the U.S. Department of Energy through the US LHC Accelerator Research Program (LARP) and contract DE-AC02-76SF00515. A second generation prototype rotatable collimator has been fabricated at SLAC and delivered to CERN for further vacuum, metrology, function and impedance tests. The design features two cylindrical Glidcop jaws designed to each absorb 12kW of beam in steady state and up to 60kW in transitory beam loss with no damage and minimal thermal distortion. The design is motivated by the use of a radiation resistant high Z low impedance readily available material. A vacuum rotation mechanism using the standard LHC collimation jaw positioning motor system allows each jaw to be rotated to present a new 2cm high surface to the beam if the jaw surface were to be damaged by multiple full intensity beam bunch impacts in a asynchronous beam abort. Design modifications to improve on the first generation prototype, pre-delivery functional tests performed at SLAC and post-delivery test results at CERN are presented.
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MOPRO046	Comparison of MERLIN/SixTrack for LHC Collimation Studies	185
	M. Serluca, R. Appleby, J. Molson UMAN, Manchester, United Kingdom R.J. Barlow, H. Rafique, A.M. Toader University of Huddersfield, Huddersfield, United Kingdom R. Bruce, A. Marsili, S. Redaelli, B. Salvachua CERN, Geneva, Switzerland C. Tambasco University of Rome La Sapienza, Rome, Italy
	Simulations of the LHC collimation system have been carried out in previous years with the well known SixTrack code with collimation features. MERLIN is a C++ accelerator physics library that has been extended to perform collimation studies. The main features of the code are: its modular nature, allowing the user to easily implement new physics processes such as resistive wakefields and synchrotron radiation, improved scattering routines and the MPI protocol for parallel execution. MERLIN has been configured to use the same scattering routines as SixTrack in order to benchmark the code for the LHC collimation system. In this paper we present a detailed comparison between MERLIN and SixTrack for optics and cleaning inefficiency calculation.
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MOPRO116	Mechanical Engineering and Design of Novel Collimators for HL-LHC	369
	F. Carra, A. Bertarelli, A. Dallocchio, L. Gentini, P. Gradassi, A. Manousos, N. Mariani, G. Maîtrejean, N. Mounet, E. Quaranta, S. Redaelli, V. Vlachoudis CERN, Geneva, Switzerland
	In view of LHC intensity upgrades, collimator materials may become a limit to the machine performance: the high RF impedance of Carbon-Carbon composites can lead to beam instabilities, while the Tungsten alloy adopted in tertiary collimators exhibits low robustness in case of beam-induced accidents. An R&D program has been pursued to develop new materials overcoming such limitations. Molybdenum-Graphite, in addition to its outstanding thermal conductivity, can be coated with pure molybdenum, reducing collimator impedance by a factor of 10. A new secondary collimator is being designed around this novel composite. New high-melting materials are also proposed to improve the robustness of tertiary collimators. All the new collimators will be equipped with BPMs, significantly enhancing the alignment speed and the beta-star reach. This implies additional constraints of space, as well as detailed static and fatigue calculations on cables and connectors. This paper describes the mechanical design and the engineering calculations of such future collimators, focusing on the study via state-of-the-art numerical methods of interactions between the particle beams and the new materials adopted.
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MOPME033	Beam Dynamics in an Electron Lens with the Warp Particle-in-cell Code	451
	G. Stancari Fermilab, Batavia, Illinois, USA V. Moens EPFL, Lausanne, Switzerland S. Redaelli CERN, Geneva, Switzerland
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404. Electron lenses are a mature technique for beam manipulation in colliders and storage rings. In an electron lens, a pulsed, magnetically confined electron beam with a given current-density profile interacts with the circulating beam to obtain the desired effect. Electron lenses were used in the Fermilab Tevatron collider for beam-beam compensation, for abort-gap clearing, and for halo scraping. They will be used in RHIC at BNL for head-on beam-beam compensation, and their application to the Large Hadron Collider for halo control is under development. At Fermilab, electron lenses will be implemented as lattice elements for nonlinear integrable optics. The design of electron lenses requires tools to calculate the kicks and wakefields experienced by the circulating beam. We use the Warp particle-in-cell code to study generation, transport, and evolution of the electron beam. For the first time, a fully 3-dimensional code is used for this purpose.
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MOPRI110	Final Layout and Expected Cleaning for the First Crystal-assisted Collimation Test at the LHC	882
SUSPSNE046	use link to see paper's listing under its alternate paper code
	D. Mirarchi, S. Montesano, S. Redaelli, W. Scandale CERN, Geneva, Switzerland F. Galluccio INFN-Napoli, Napoli, Italy A.M. Taratin JINR, Dubna, Moscow Region, Russia
	The installation in the CERN Large Hadron Collider (LHC) of two crystals in the horizontal and vertical planes was accomplished during the present LHC long shutdown (LS1) for crystal collimation studies. An appropriate layout was designed to demonstrate the principle feasibility of crystal collimation at the LHC. Extensive simulation campaigns were made to evaluate different crystal positions and parameters, in order to ensure that the main goals of these first feasibility tests in the LHC are within reach. In this paper, the final layout is presented. An overview of the considerations behind the design choices and the crystal parameters is given, and the expected performance of the system is discussed.
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MOPRI111	Improvements of the Crystal Routine for Collimation Studies	886
	D. Mirarchi, S. Redaelli, W. Scandale CERN, Geneva, Switzerland A.M. Taratin JINR, Dubna, Moscow Region, Russia I.A. Yazynin IHEP, Moscow Region, Russia
	A routine has been implemented to simulate interactions of protons with bent crystals in the collimation version of \texttt{SixTrack}. This routine is optimized in view of producing high-statistics tracking simulations of collimation cleaning assisted by bent crystals. Fine tuning and comparisons with experimental data of coherent effects which a particle can experience in a bent crystal have been carried out. The data taken with 400 GeV beams at the CERN-SPS North Area in the framework of the UA9 experiment are used to benchmark the routine. Further checks on low probability interactions have been made, leading to significant improvements in the description of interactions with crystals. Comparisons with other simulations tools are used to increase our confidence in the scaling to higher energies.
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TUOBA01	Electron Lenses for the Large Hadron Collider	918
	G. Stancari, A. Valishev Fermilab, Batavia, Illinois, USA R. Bruce, S. Redaelli, A. Rossi, B. Salvachua CERN, Geneva, Switzerland
	Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404. Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in RHIC at BNL. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, hollow electron beam collimation was studied as an option to complement the collimation system for the LHC upgrades. This project is moving towards a technical design in 2014, with the goal to build the devices in 2015-2017, after resuming LHC operations and re-assessing needs and requirements at 6.5 TeV. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles.
	Slides TUOBA01 [9.709 MB]
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Paper

Title

Page

Beam-induced Quench Tests of LHC Magnets

52

M. Sapinski, B. Auchmann, T. Bär, W. Bartmann, M. Bednarek, S. Bozyigit, C. Bracco, R. Bruce, F. Cerutti, V. Chetvertkova, K. Dahlerup-Petersen, B. Dehning, E. Effinger, J. Emery, A. Guerrero, E.B. Holzer, W. Höfle, A. Lechner, A. Priebe, S. Redaelli, B. Salvachua, R. Schmidt, N.V. Shetty, A.P. Siemko, E. Skordis, M. Solfaroli Camillocci, J. Steckert, J.A. Uythoven, D. Valuch, A.P. Verweij, J. Wenninger, D. Wollmann, M. Zerlauth, E.N. del Busto
CERN, Geneva, Switzerland

At the end of the LHC Run1 a 48-hour quench-test campaign took place to investigate the quench levels of superconducting magnets for loss durations from nanoseconds to tens of seconds. The longitudinal losses produced extended from one meter to hundreds of meters and the number of lost protons varied from 10⁸ to 10¹³. The results of these and other, previously conducted quench experiments, allow the quench levels of several types of LHC magnets under various loss conditions to be assessed. The quench levels are expected to limit LHC performance in the case of steady-state losses in the interaction regions and also in the case of fast losses initiated by dust particles all around the ring. It is therefore required to accurately adjust beam loss abort thresholds in order to maximize the operation time. A detailed discussion of these quench test results and a proposal for additional tests after the LHC restart is presented.

Slides MOOCB01 [2.737 MB]

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MOPRO021

Power Deposition in LHC Magnets With and Without Dispersion Suppressor Collimators Downstream of the Betatron Cleaning Insertion

112

A. Lechner, B. Auchmann, R. Bruce, F. Cerutti, P.P. Granieri, A. Marsili, S. Redaelli, N.V. Shetty, E. Skordis, G.E. Steele, A.P. Verweij
CERN, Geneva, Switzerland

The power deposited in dispersion suppressor (DS) magnets downstream of the LHC betatron cleaning insertion is governed by off-momentum protons which predominantly originate from single-diffractive interactions in primary collimators. With higher beam energy and intensities anticipated in future operation, these clustered proton losses could possibly induce magnet quenches during periods of short beam lifetime. In this paper, we present FLUKA simulations for nominal 7 TeV operation, comparing the existing layout with alternative layouts where selected DS dipoles are substituted by pairs of shorter higher-field magnets and a collimator. Power densities predicted for different collimator settings are compared against present estimates of quench limits. Further, the expected reduction factor due to DS collimators is evaluated.

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MOPRO037

Collimator Fast Failure Losses for Various HL-LHC Configurations

157

L. Lari, R. Bruce, S. Redaelli
CERN, Geneva, Switzerland
L. Lari
IFIC, Valencia, Spain

Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404
The upgrade of the Large Hadron Collider (LHC), in terms of beam intensity and energy, implies an increasing risk of severe damage in particular in case of fast failures losses. For this reason, efforts were put in developing simulation tools to allow studies of asynchronous dump accident, including realistic failure cases for collimator settings and machine parameters like orbit and optics. The scope of these studies is to understand realistic beam loads in different collimators, in order to improve the actual LHC collimator system design, to provide feedbacks on optic design and to evaluate different mitigation actions. Simulations were set up with a modified SixTrack collimation routine able to simulate erroneous firing of a single dump kicker or the simultaneous malfunction of all the 15 kickers. In such a context, results are evaluated from the whole LHC collimation system point of view.

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MOPRO039

Integrated Simulation Tools for Collimation Cleaning in HL-LHC

160

R. Bruce, C. Bracco, F. Cerutti, A. Ferrari, A. Lechner, A. Marsili, A. Mereghetti, D. Mirarchi, P.G. Ortega, D. Pastor Sinuela, S. Redaelli, A. Rossi, B. Salvachua, V. Vlachoudis
CERN, Geneva, Switzerland
R. Appleby, J. Molson, M. Serluca
UMAN, Manchester, United Kingdom
R.W. Aßmann
DESY, Hamburg, Germany
R.J. Barlow, H. Rafique, A.M. Toader
University of Huddersfield, Huddersfield, United Kingdom
S.M. Gibson, L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom
L. Lari
IFIC, Valencia, Spain
C. Tambasco
University of Rome La Sapienza, Rome, Italy

The Large Hadron Collider is designed to accommodate an unprecedented stored beam energy of 362~MJ in the nominal configuration and about the double in the high-luminosity upgrade HL-LHC that is presently under study. This requires an efficient collimation system to protect the superconducting magnets from quenches. During the design, it is therefore very important to accurately predict the expected beam loss distributions and cleaning efficiency. For this purpose, there are several ongoing efforts in improving the existing simulation tools or developing new ones. This paper gives a brief overview and status of the different available codes.

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MOPRO040

Collimation Cleaning for HL-LHC Optics Scenarios with Error Models

163

A. Marsili, R. Bruce, S. Redaelli
CERN, Geneva, Switzerland

Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404
The upgrade of the LHC collimation system in view of the High-Luminosity upgrade of the Large Hadron Collider (LHC) foresees, amongst other scenarios, local collimation in the dispersion suppressors (DS) of IR7. Layouts have been worked out which rely on using stronger and short bending dipoles to free space for a collimator in the cold DS. In this paper, the effectiveness of the proposed layouts is studied with different imperfection models such as collimator alignment, jaw tilt and surface errors, optics errors and aperture imperfections. The effect of local DS collimation on the global losses around the ring is also addressed for different optics configurations.

DOI •

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MOPRO041

Multi-turn Tracking of Collision Products at the LHC

166

A. Marsili, R. Bruce, F. Cerutti, L.S. Esposito, S. Redaelli
CERN, Geneva, Switzerland

Funding: Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404
The luminosity expected at the interaction points in LHC at 7 TeV will be unprecedented, up to 1034 cm−2 s−1 . Part of the debris produced by the collisions is lost locally im- mediately downstream the Interaction Point (IP), in the matching section and dispersion suppressor. In this paper, the dynamics of collision debris protons is discussed. First, the loss distributions close to the collision points, simulated with two codes – SixTrack and FLUKA – are compared for different layout configurations. Then, SixTrack is used to simulate the fraction of protons that have undergone inelastic interactions with smaller energy and and betatron offsets, which could travel for several turns around the ring and might be lost in other collimation insertions. A preliminary comparison is made between the resulting loss distribution and measurements.

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MOPRO042

Cleaning Performance with 11T Dipoles and Local Dispersion Suppressor Collimation at the LHC

170

R. Bruce, A. Marsili, S. Redaelli
CERN, Geneva, Switzerland

The limiting location of the present LHC machine in terms of losses on cold magnets are the dispersion suppressors downstream of the betatron collimation insertion (IR7). These losses are dominated by off-energy protons that have by-passed the upstream secondary collimation system but are lost where the dispersion starts to rise. A solution under consideration for intercepting these losses is the addition of new collimators in the dispersive area. This paper discusses first a proposition for the new layout in the DS, where space is made for the new collimators by replacing an existing dipole by shorter and stronger magnets. Furthermore, simulations with SixTrack are presented, which quantify the gain in cleaning from the new collimators.

DOI •

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MOPRO043

Handling 1 MW Losses with the LHC Collimation System

174

B. Salvachua, R. Bruce, F. Carra, M. Cauchi, E.B. Holzer, W. Höfle, D. Jacquet, L. Lari, D. Mirarchi, E. Nebot Del Busto, S. Redaelli, A. Rossi, M. Sapinski, R. Schmidt, G. Valentino, D. Valuch, J. Wenninger, D. Wollmann, M. Zerlauth
CERN, Geneva, Switzerland
M. Cauchi
UoM, Msida, Malta
L. Lari
IFIC, Valencia, Spain

Funding: Research supported by EU FP7 HiLumi LHC (Grant agree. 284404)
The LHC superconducting magnets in the dispersion suppressor of IR7 are the most exposed to beam losses leaking from the betatron collimation system and represent the main limitation for the halo cleaning. In 2013, quench tests were performed at 4 TeV to improve the quench limit estimates, which determine the maximum allowed beam loss rate for a given collimation cleaning. The main goal of the collimation quench test was to try to quench the magnets by increasing losses at the collimators. Losses of up to 1 MW over a few seconds were generated by blowing up the beam, achieving total losses of about 5.8 MJ. These controlled losses exceeded by a factor 2 the collimation design value, and the magnets did not quench.

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MOPRO044

Construction and Bench Testing of a Prototype Rotatable Collimator for the LHC

178

T.W. Markiewicz, E.L. Bong, L. Keller
SLAC, Menlo Park, California, USA
O. Aberle, A. Bertarelli, P. Gradassi, A. Marsili, S. Redaelli, A. Rossi, B. Salvachua, G. Valentino
CERN, Geneva, Switzerland

Funding: This work partially supported by the U.S. Department of Energy through the US LHC Accelerator Research Program (LARP) and contract DE-AC02-76SF00515.
A second generation prototype rotatable collimator has been fabricated at SLAC and delivered to CERN for further vacuum, metrology, function and impedance tests. The design features two cylindrical Glidcop jaws designed to each absorb 12kW of beam in steady state and up to 60kW in transitory beam loss with no damage and minimal thermal distortion. The design is motivated by the use of a radiation resistant high Z low impedance readily available material. A vacuum rotation mechanism using the standard LHC collimation jaw positioning motor system allows each jaw to be rotated to present a new 2cm high surface to the beam if the jaw surface were to be damaged by multiple full intensity beam bunch impacts in a asynchronous beam abort. Design modifications to improve on the first generation prototype, pre-delivery functional tests performed at SLAC and post-delivery test results at CERN are presented.

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MOPRO046

Comparison of MERLIN/SixTrack for LHC Collimation Studies

185

M. Serluca, R. Appleby, J. Molson
UMAN, Manchester, United Kingdom
R.J. Barlow, H. Rafique, A.M. Toader
University of Huddersfield, Huddersfield, United Kingdom
R. Bruce, A. Marsili, S. Redaelli, B. Salvachua
CERN, Geneva, Switzerland
C. Tambasco
University of Rome La Sapienza, Rome, Italy

Simulations of the LHC collimation system have been carried out in previous years with the well known SixTrack code with collimation features. MERLIN is a C++ accelerator physics library that has been extended to perform collimation studies. The main features of the code are: its modular nature, allowing the user to easily implement new physics processes such as resistive wakefields and synchrotron radiation, improved scattering routines and the MPI protocol for parallel execution. MERLIN has been configured to use the same scattering routines as SixTrack in order to benchmark the code for the LHC collimation system. In this paper we present a detailed comparison between MERLIN and SixTrack for optics and cleaning inefficiency calculation.

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MOPRO116

Mechanical Engineering and Design of Novel Collimators for HL-LHC

369

F. Carra, A. Bertarelli, A. Dallocchio, L. Gentini, P. Gradassi, A. Manousos, N. Mariani, G. Maîtrejean, N. Mounet, E. Quaranta, S. Redaelli, V. Vlachoudis
CERN, Geneva, Switzerland

In view of LHC intensity upgrades, collimator materials may become a limit to the machine performance: the high RF impedance of Carbon-Carbon composites can lead to beam instabilities, while the Tungsten alloy adopted in tertiary collimators exhibits low robustness in case of beam-induced accidents. An R&D program has been pursued to develop new materials overcoming such limitations. Molybdenum-Graphite, in addition to its outstanding thermal conductivity, can be coated with pure molybdenum, reducing collimator impedance by a factor of 10. A new secondary collimator is being designed around this novel composite. New high-melting materials are also proposed to improve the robustness of tertiary collimators. All the new collimators will be equipped with BPMs, significantly enhancing the alignment speed and the beta-star reach. This implies additional constraints of space, as well as detailed static and fatigue calculations on cables and connectors. This paper describes the mechanical design and the engineering calculations of such future collimators, focusing on the study via state-of-the-art numerical methods of interactions between the particle beams and the new materials adopted.

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MOPME033

Beam Dynamics in an Electron Lens with the Warp Particle-in-cell Code

451

G. Stancari
Fermilab, Batavia, Illinois, USA
V. Moens
EPFL, Lausanne, Switzerland
S. Redaelli
CERN, Geneva, Switzerland

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404.
Electron lenses are a mature technique for beam manipulation in colliders and storage rings. In an electron lens, a pulsed, magnetically confined electron beam with a given current-density profile interacts with the circulating beam to obtain the desired effect. Electron lenses were used in the Fermilab Tevatron collider for beam-beam compensation, for abort-gap clearing, and for halo scraping. They will be used in RHIC at BNL for head-on beam-beam compensation, and their application to the Large Hadron Collider for halo control is under development. At Fermilab, electron lenses will be implemented as lattice elements for nonlinear integrable optics. The design of electron lenses requires tools to calculate the kicks and wakefields experienced by the circulating beam. We use the Warp particle-in-cell code to study generation, transport, and evolution of the electron beam. For the first time, a fully 3-dimensional code is used for this purpose.

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MOPRI110

Final Layout and Expected Cleaning for the First Crystal-assisted Collimation Test at the LHC

882

SUSPSNE046

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D. Mirarchi, S. Montesano, S. Redaelli, W. Scandale
CERN, Geneva, Switzerland
F. Galluccio
INFN-Napoli, Napoli, Italy
A.M. Taratin
JINR, Dubna, Moscow Region, Russia

The installation in the CERN Large Hadron Collider (LHC) of two crystals in the horizontal and vertical planes was accomplished during the present LHC long shutdown (LS1) for crystal collimation studies. An appropriate layout was designed to demonstrate the principle feasibility of crystal collimation at the LHC. Extensive simulation campaigns were made to evaluate different crystal positions and parameters, in order to ensure that the main goals of these first feasibility tests in the LHC are within reach. In this paper, the final layout is presented. An overview of the considerations behind the design choices and the crystal parameters is given, and the expected performance of the system is discussed.

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MOPRI111

Improvements of the Crystal Routine for Collimation Studies

886

D. Mirarchi, S. Redaelli, W. Scandale
CERN, Geneva, Switzerland
A.M. Taratin
JINR, Dubna, Moscow Region, Russia
I.A. Yazynin
IHEP, Moscow Region, Russia

A routine has been implemented to simulate interactions of protons with bent crystals in the collimation version of \texttt{SixTrack}. This routine is optimized in view of producing high-statistics tracking simulations of collimation cleaning assisted by bent crystals. Fine tuning and comparisons with experimental data of coherent effects which a particle can experience in a bent crystal have been carried out. The data taken with 400 GeV beams at the CERN-SPS North Area in the framework of the UA9 experiment are used to benchmark the routine. Further checks on low probability interactions have been made, leading to significant improvements in the description of interactions with crystals. Comparisons with other simulations tools are used to increase our confidence in the scaling to higher energies.

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TUOBA01

Electron Lenses for the Large Hadron Collider

918

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

Funding: Fermi Research Alliance, LLC operates Fermilab under Contract DE-AC02-07CH11359 with the US Department of Energy. Research supported in part by US LARP and EU FP7 HiLumi LHC, Grant Agreement 284404.
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam. Electron lenses were used in the Fermilab Tevatron collider for bunch-by-bunch compensation of long-range beam-beam tune shifts, for removal of uncaptured particles in the abort gap, for preliminary experiments on head-on beam-beam compensation, and for the demonstration of halo scraping with hollow electron beams. Electron lenses for beam-beam compensation are being commissioned in RHIC at BNL. Within the US LHC Accelerator Research Program and the European HiLumi LHC Design Study, hollow electron beam collimation was studied as an option to complement the collimation system for the LHC upgrades. This project is moving towards a technical design in 2014, with the goal to build the devices in 2015-2017, after resuming LHC operations and re-assessing needs and requirements at 6.5 TeV. Because of their electric charge and the absence of materials close to the proton beam, electron lenses may also provide an alternative to wires for long-range beam-beam compensation in LHC luminosity upgrade scenarios with small crossing angles.

Slides TUOBA01 [9.709 MB]

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