IPAC2021 - List of Keywords (collimation)

Paper	Title	Other Keywords	Page
MOPAB001	Power Deposition in Superconducting Dispersion Suppressor Magnets Downstream of the Betatron Cleaning Insertion for HL-LHC	proton, dipole, simulation, operation	37
	A. Waets, C. Bahamonde Castro, E. Belli, R. Bruce, N. Fuster-Martínez, A. Lechner, A. Mereghetti, S. Redaelli, M. Sabaté-Gilarte, E. Skordis CERN, Meyrin, Switzerland
	Funding: Research supported by the HL-LHC project The power deposited in dispersion suppressor magnets downstream of the Large Hadron Collider (LHC) betatron cleaning insertion is governed by off-momentum particles scattered out of the primary collimators. In order to mitigate the risk of magnet quenches during periods of short beam lifetime in future High-Luminosity (HL-LHC) operation, new dispersion suppressor (DS) collimators are considered for installation (one per beam). In this paper, we present FLUKA simulations for both protons and Pb ions at 7 TeV, predicting the power deposition in the DS magnets, including the new higher-field dipoles 11T which are needed to integrate the collimator in the cold region next to the cleaning insertion. The simulated power deposition levels for the adopted HL-LHC collimator configuration and settings are used to assess the quench margin by comparison with the present estimated quench levels.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB001
About •	paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 16 August 2021
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MOPAB002	Risk of Halo-Induced Magnet Quenches in the HL-LHC Beam Dump Insertion	proton, insertion, betatron, operation	41
	J.B. Potoine, A. Apollonio, E. Belli, C. Bracco, R. Bruce, M. D’Andrea, R. García Alía, A. Lechner, G. Lerner, S. Morales Vigo, S. Redaelli, V. Rizzoglio, E. Skordis, A. Waets CERN, Meyrin, Switzerland F. Wrobel IES, Montpellier, France
	Funding: Research supported by the HL-LHC project After the High Luminosity (HL-LHC) upgrade, the LHC will be exposed to a higher risk of magnet quenches during periods of short beam lifetime. Collimators in the extraction region (IR6) assure the protection of magnets against asynchronous beam dumps, but they also intercept a fraction of the beam halo leaking from the betatron cleaning insertion. In this paper, we assess the risk of quenching nearby quadrupoles during beam lifetime drops. In particular, we present an empirical analysis of halo losses in IR6 using LHC Run 2 (2015-2018) beam loss monitor measurements. Based on these results, the halo-induced power density in magnet coils expected in HL-LHC is estimated using FLUKA Monte Carlo shower simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB002
About •	paper received ※ 19 May 2021 paper accepted ※ 13 July 2021 issue date ※ 22 August 2021
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MOPAB006	Optics Configurations for Improved Machine Impedance and Cleaning Performance of a Multi-Stage Collimation Insertion	optics, impedance, collider, scattering	57
	R. Bruce, R. De Maria, M. Giovannozzi, N. Mounet, S. Redaelli CERN, Geneva, Switzerland
	For a two-stage collimation system, the betatron phase advance between the primary and secondary stages is usually set to maximise the absorption of secondary particles outscattered from the primary. Another constraint is the contribution to the ring impedance of the collimation system, which can be decreased through an optimized insertion optics, featuring large values of the beta functions. In this article we report on first studies of such an optics for the CERN LHC. In addition to a gain in impedance, we show that the cleaning efficiency can be improved thanks to the large beta functions, even though the phase advance is not set at the theoretical optimum.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB006
About •	paper received ※ 17 May 2021 paper accepted ※ 28 May 2021 issue date ※ 11 August 2021
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MOPAB283	Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring	electron, simulation, HOM, GUI	898
	O. Sedláček, N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang The University of Liverpool, Liverpool, United Kingdom P. Forck, S. Udrea GSI, Darmstadt, Germany N. Kumar, A. Salehilashkajani, O. Sedláček, C.P. Welsch, H.D. Zhang Cockcroft Institute, Warrington, Cheshire, United Kingdom S. Mazzoni, O. Sedláček CERN, Geneva, Switzerland
	Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB283
About •	paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 19 August 2021
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TUPAB192	Studies on Momentum Collimation for CSNS-RCS Upgrades	bunching, betatron, space-charge, emittance	1855
	Y.W. An, J. Chen, S.Y. Xu, Y. Yuan IHEP, Beijing, People’s Republic of China X.H. Lu, J.B. Yu IHEP CSNS, Guangdong Province, People’s Republic of China
	The CSNS project was a high intensity pulsed facility, and achieved the the design goal of 100kW in 2020. The upgrades of the CSNS are proposed, and the momentum collimator is a component of the upgrades. This paper will show the design scheme of the momentum collimator and the simulation results are also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB192
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 28 August 2021
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TUPAB194	Operation Status of CSNS/RCS Transverse Collimation System	shielding, radiation, radioactivity, monitoring	1862
	J.B. Yu, J.X. Chen, L. Liu, X.J. Nie, C.J. Ning, G.Y. Wang, A.X. Wang, J.S. Zhang IHEP CSNS, Guangdong Province, People’s Republic of China L. Kang, Q.B. Wu, S.Y. Xu IHEP, Beijing, People’s Republic of China
	Funding: Natural Science Foundation of Guangdong Province 2018A030313959 In order to meet the requirements of daily maintenance of CSNS/RCS, the transverse collimation system was designed to concentrate the uncontrollable beam loss in this region. Based on physical parameters, considering the processing technology, the area was rationally arranged; combined with the requirements of physical and radiation protection, under the premise of meeting the use requirements, fully consider the limit switch, mechanical hard limit and other components, increasing the output control signals of rotary encoder and displacement sensor, the movement of the absorbers were monitored. At present, the beam collimation system has been running with no mechanical failure for two years on CSNS, and it plays an active role in beam power boost and beam loss control, which proves that the structural design of the system is reasonable.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB194
About •	paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021
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WEPAB023	Crystal Collimation of 20 MJ Heavy-Ion Beams at the HL-LHC	operation, hadron, collider, luminosity	2644
	M. D’Andrea, R. Bruce, M. Di Castro, I. Lamas Garcia, A. Masi, D. Mirarchi, S. Redaelli, R. Rossi, B. Salvachua, W. Scandale CERN, Geneva, Switzerland F. Galluccio INFN-Napoli, Napoli, Italy L.J. Nevay Royal Holloway, University of London, Surrey, United Kingdom
	The concept of crystal collimation at the Large Hadron Collider (LHC) relies on the use of bent crystals that can deflect halo particles by a much larger angle than the standard multi-stage collimation system. Following an extensive campaign of studies and performance validations, a number of crystal collimation tests with Pb ion beams were performed in 2018 at energies up to 6.37 Z TeV. This paper describes the procedure and outcomes of these tests, the most important of which being the demonstration of the capability of crystal collimation to improve the cleaning efficiency of the machine. These results led to the inclusion of crystal collimation into the LHC baseline for operation with ion beams in Run 3 as well as for the HL-LHC era. A first set of operational settings was defined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB023
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 27 August 2021
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WEPAB024	Release of Crystal Routine for Multi-Turn Proton Simulations within SixTrack v5	simulation, proton, collider, hadron	2648
	M. D’Andrea, A. Mereghetti, D. Mirarchi, V.K.B. Olsen, S. Redaelli CERN, Geneva, Switzerland
	Crystal collimation is studied as a possible scheme to further improve the efficiency of ion collimation at the High Luminosity Large Hadron Collider (HL-LHC), as well as for possible applications in the CERN program of Physics Beyond Colliders. This concept relies on the use of bent crystals that can deflect high-energy halo particles at large angles, of the order of tens of urad. In order to reproduce key experimental results of crystal collimation tests and predict the performance of this system when applied to present and future machines, a dedicated simulation routine was developed. This routine is capable of modeling both coherent and incoherent interactions of beam particles with crystal collimators, and is fully integrated into the magnetic tracking and collimator modeling provided by the single-particle tracking code SixTrack. This paper describes the implementation of the routine in the latest version of SixTrack and its most recent improvements, in particular regarding the treatment of the crystal miscut angle.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB024
About •	paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 14 August 2021
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WEPAB360	Future Prospective for Bent Crystals in Accelerators	lattice, scattering, experiment, SRF	3545
	M. Romagnoni INFN-Ferrara, Ferrara, Italy M. Romagnoni Universita’ degli Studi di Milano, Milano, Italy
	Super magnet dipoles employed to steer high energy particle beams are massive instruments requiring cryogenic cooling and featuring large energy consumption. A bent crystal has the potential in a few millimeters to deflect 100-1000 GeV particle beams as much as an hundreds-tesla magnetic dipole. Indeed, within the lattice of a crystal, large electric fields up to several GeV/cm are present. Positive charged particles can be efficiently channeled between two adjacent lattice planes, thus following their curvature. These features and the possibility to selectively affect only the portion of the beam intercepting the crystal led to the proposal of exploiting bent crystals for several purposes, such as the collimation of ions at LHC. In this scheme, the particles on the beam halo instead of being scattered by tens-centimeters long collimators are directly separated from the beam using a 4 mm long silicon crystal. The production of a bent crystal suitable for installation in the LHC beamline requires strict control over lattice features and bending apparatus. The results obtained by the years long research of the INFN research team in Ferrara are presented in this work.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB360
About •	paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 18 August 2021
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THPAB158	BEAM COLLIMATION IN THE PIP-II LINAC TO BOOSTER TRANSFER LINE	injection, booster, linac, proton	4068
	D.E. Johnson, V.V. Kapin, J.-F. Ostiguy, V.I. Sidorov, M. Xiao Fermilab, Batavia, Illinois, USA D.G. Georgobiani FRIB, East Lansing, Michigan, USA
	Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The new PIP-II superconducting linac will deliver a 2 mA average H^- beam to the existing Booster synchrotron. The injected beam is accumulated by charge exchange over approximately 300 turns; phase space painting is used to mitigate space charge effects. To limit the power load on the internal waste beam absorber from the transverse tails of the H⁻ distribution missing the foil, the beam will be collimated in both planes in the linac to Booster transfer line using compact collimators of a novel design. Both the number of parasitic hits and the fraction of the beam missing the foil are sensitive functions of the H⁻ beam centroid position with respect to the edge of the foil. The positioning of the collimation is constrained by the availability of suitable space in the transfer line lattice, by specifics of the collimator design, by the phase space orientation at the collimator, and by the betatron phase advance to the foil needed to achieve proper orientation of the spatial distribution at the injection point. In this contribution, we describe the procedure by which collimator positions were optimized. We then discuss the expected performance of the overall system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB158
About •	paper received ※ 04 June 2021 paper accepted ※ 02 July 2021 issue date ※ 26 August 2021
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THPAB176	Studies on Beam Collimation System for the ESSnuSB Accumulator	scattering, proton, linac, simulation	4107
	Y. Zou, M. Olvegård Uppsala University, Uppsala, Sweden
	Funding: This work is supported by the European Union Horizon 2020 research and innovation program under grant agreement No 777419. The ESSnuSB, a neutrino facility based on the European Spallation Source, aims at measuring, with precision, the charge-parity (CP) violating lepton phase at the 2nd oscillation maximum. The ESS linac will have to be upgraded to provide an additional 5 MW beam for the ESSnuSB to produce an unprecedented high-intensity neutrino beam. An accumulator ring is employed to compress the 2.86 ms long pulse from the linac to around 1.5 µs in order to satisfy the target requirements and improve the physics performance. In the operation of a high-intensity proton accumulator, the most important issue is to minimize the uncontrolled beam loss to reduce component activation to make hands-on maintenance possible. For this purpose, a two-stage collimation system is designed, which consists of a thin scraper to scatter halo particles and secondary collimators to absorb those scattered particles. Phase advances between scraper and secondary collimators, together with the material, the thickness of collimators, have been detailed studied and numerical simulations have been performed to evaluate the performance of the collimation system. This paper presents the design of the collimation system.
	Poster THPAB176 [5.022 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB176
About •	paper received ※ 11 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021
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THPAB235	Detailed Electromagnetic Characterisation of HL-LHC Low Impedance Collimators	impedance, simulation, operation, factory	4258
	A. Kurtulus, C. Accentura, N. Biancacci, F. Carra, F. Caspers, N. Chitnis, F. Giordano, R. Illan Fiastre, S. Joly, I. Lamas Garcia, L. Mourier, E. Métral, S. Redaelli, B. Salvant, W. Vollenberg, C. Vollinger, C. Zannini CERN, Geneva, Switzerland
	The High Luminosity Large Hadron Collider (HL-LHC) project will upgrade the LHC machine to allow operation with increased luminosity for the experiments. In order to achieve this goal, different operational parameters of the machine need to be pushed beyond the present design values, including the stored beam energy. One of the main challenges related to the achievement of the upgraded performance is the beam collimation system and its contribution to the overall machine impedance budget. In this perspective, new low impedance collimators have been designed, fabricated, and installed in the LHC. In this study, we will present their detailed electromagnetic (EM) characterization by means of radio frequency (RF) measurements and EM simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB235
About •	paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 10 August 2021
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THPAB307	Behaviour of Ironless Inductive Position Sensors in Close Proximity to Each Other	simulation, ECR, FEM, site	4390
	N.J. Sammut, A. Grima University of Malta, Information and Communication Technology, Msida, Malta M. Di Castro, A. Masi CERN, Meyrin, Switzerland
	Funding: CERN - The European Organisation for Nuclear Research UM - The University of Malta Safety critical systems like the collimators of the Large Hadron Collider require transducers which are immune to interference from their surroundings. The ironless inductive position sensor is used to measure the position of collimator jaws with respect to the beam and is designed to be immune to external DC or slowly changing magnetic fields. In this paper we investigate whether frequency separation is required when multiple ironless inductive position sensors are used and whether two or more sensors at the same frequency results in cross-talk. Numerical simulations and experiments are conducted to study the magnetic field behaviour of the sensors, their interference with each other and the impact of this interference on the position reading. Finally, this paper defines guidelines on safe operation of the ironless inductive position sensor in the aforementioned conditions.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB307
About •	paper received ※ 17 May 2021 paper accepted ※ 02 July 2021 issue date ※ 22 August 2021
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Paper

Title

Other Keywords

Page

Power Deposition in Superconducting Dispersion Suppressor Magnets Downstream of the Betatron Cleaning Insertion for HL-LHC

proton, dipole, simulation, operation

37

A. Waets, C. Bahamonde Castro, E. Belli, R. Bruce, N. Fuster-Martínez, A. Lechner, A. Mereghetti, S. Redaelli, M. Sabaté-Gilarte, E. Skordis
CERN, Meyrin, Switzerland

Funding: Research supported by the HL-LHC project
The power deposited in dispersion suppressor magnets downstream of the Large Hadron Collider (LHC) betatron cleaning insertion is governed by off-momentum particles scattered out of the primary collimators. In order to mitigate the risk of magnet quenches during periods of short beam lifetime in future High-Luminosity (HL-LHC) operation, new dispersion suppressor (DS) collimators are considered for installation (one per beam). In this paper, we present FLUKA simulations for both protons and Pb ions at 7 TeV, predicting the power deposition in the DS magnets, including the new higher-field dipoles 11T which are needed to integrate the collimator in the cold region next to the cleaning insertion. The simulated power deposition levels for the adopted HL-LHC collimator configuration and settings are used to assess the quench margin by comparison with the present estimated quench levels.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB001

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paper received ※ 19 May 2021 paper accepted ※ 07 July 2021 issue date ※ 16 August 2021

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MOPAB002

Risk of Halo-Induced Magnet Quenches in the HL-LHC Beam Dump Insertion

proton, insertion, betatron, operation

41

J.B. Potoine, A. Apollonio, E. Belli, C. Bracco, R. Bruce, M. D’Andrea, R. García Alía, A. Lechner, G. Lerner, S. Morales Vigo, S. Redaelli, V. Rizzoglio, E. Skordis, A. Waets
CERN, Meyrin, Switzerland
F. Wrobel
IES, Montpellier, France

Funding: Research supported by the HL-LHC project
After the High Luminosity (HL-LHC) upgrade, the LHC will be exposed to a higher risk of magnet quenches during periods of short beam lifetime. Collimators in the extraction region (IR6) assure the protection of magnets against asynchronous beam dumps, but they also intercept a fraction of the beam halo leaking from the betatron cleaning insertion. In this paper, we assess the risk of quenching nearby quadrupoles during beam lifetime drops. In particular, we present an empirical analysis of halo losses in IR6 using LHC Run 2 (2015-2018) beam loss monitor measurements. Based on these results, the halo-induced power density in magnet coils expected in HL-LHC is estimated using FLUKA Monte Carlo shower simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB002

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paper received ※ 19 May 2021 paper accepted ※ 13 July 2021 issue date ※ 22 August 2021

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MOPAB006

Optics Configurations for Improved Machine Impedance and Cleaning Performance of a Multi-Stage Collimation Insertion

optics, impedance, collider, scattering

57

R. Bruce, R. De Maria, M. Giovannozzi, N. Mounet, S. Redaelli
CERN, Geneva, Switzerland

For a two-stage collimation system, the betatron phase advance between the primary and secondary stages is usually set to maximise the absorption of secondary particles outscattered from the primary. Another constraint is the contribution to the ring impedance of the collimation system, which can be decreased through an optimized insertion optics, featuring large values of the beta functions. In this article we report on first studies of such an optics for the CERN LHC. In addition to a gain in impedance, we show that the cleaning efficiency can be improved thanks to the large beta functions, even though the phase advance is not set at the theoretical optimum.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB006

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paper received ※ 17 May 2021 paper accepted ※ 28 May 2021 issue date ※ 11 August 2021

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MOPAB283

Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring

electron, simulation, HOM, GUI

898

O. Sedláček, N. Kumar, A. Salehilashkajani, C.P. Welsch, H.D. Zhang
The University of Liverpool, Liverpool, United Kingdom
P. Forck, S. Udrea
GSI, Darmstadt, Germany
N. Kumar, A. Salehilashkajani, O. Sedláček, C.P. Welsch, H.D. Zhang
Cockcroft Institute, Warrington, Cheshire, United Kingdom
S. Mazzoni, O. Sedláček
CERN, Geneva, Switzerland

Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beam’s transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB283

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paper received ※ 18 May 2021 paper accepted ※ 28 July 2021 issue date ※ 19 August 2021

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TUPAB192

Studies on Momentum Collimation for CSNS-RCS Upgrades

bunching, betatron, space-charge, emittance

1855

Y.W. An, J. Chen, S.Y. Xu, Y. Yuan
IHEP, Beijing, People’s Republic of China
X.H. Lu, J.B. Yu
IHEP CSNS, Guangdong Province, People’s Republic of China

The CSNS project was a high intensity pulsed facility, and achieved the the design goal of 100kW in 2020. The upgrades of the CSNS are proposed, and the momentum collimator is a component of the upgrades. This paper will show the design scheme of the momentum collimator and the simulation results are also presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB192

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paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 28 August 2021

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TUPAB194

Operation Status of CSNS/RCS Transverse Collimation System

shielding, radiation, radioactivity, monitoring

1862

J.B. Yu, J.X. Chen, L. Liu, X.J. Nie, C.J. Ning, G.Y. Wang, A.X. Wang, J.S. Zhang
IHEP CSNS, Guangdong Province, People’s Republic of China
L. Kang, Q.B. Wu, S.Y. Xu
IHEP, Beijing, People’s Republic of China

Funding: Natural Science Foundation of Guangdong Province 2018A030313959
In order to meet the requirements of daily maintenance of CSNS/RCS, the transverse collimation system was designed to concentrate the uncontrollable beam loss in this region. Based on physical parameters, considering the processing technology, the area was rationally arranged; combined with the requirements of physical and radiation protection, under the premise of meeting the use requirements, fully consider the limit switch, mechanical hard limit and other components, increasing the output control signals of rotary encoder and displacement sensor, the movement of the absorbers were monitored. At present, the beam collimation system has been running with no mechanical failure for two years on CSNS, and it plays an active role in beam power boost and beam loss control, which proves that the structural design of the system is reasonable.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB194

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paper received ※ 17 May 2021 paper accepted ※ 11 June 2021 issue date ※ 17 August 2021

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WEPAB023

Crystal Collimation of 20 MJ Heavy-Ion Beams at the HL-LHC

operation, hadron, collider, luminosity

2644

M. D’Andrea, R. Bruce, M. Di Castro, I. Lamas Garcia, A. Masi, D. Mirarchi, S. Redaelli, R. Rossi, B. Salvachua, W. Scandale
CERN, Geneva, Switzerland
F. Galluccio
INFN-Napoli, Napoli, Italy
L.J. Nevay
Royal Holloway, University of London, Surrey, United Kingdom

The concept of crystal collimation at the Large Hadron Collider (LHC) relies on the use of bent crystals that can deflect halo particles by a much larger angle than the standard multi-stage collimation system. Following an extensive campaign of studies and performance validations, a number of crystal collimation tests with Pb ion beams were performed in 2018 at energies up to 6.37 Z TeV. This paper describes the procedure and outcomes of these tests, the most important of which being the demonstration of the capability of crystal collimation to improve the cleaning efficiency of the machine. These results led to the inclusion of crystal collimation into the LHC baseline for operation with ion beams in Run 3 as well as for the HL-LHC era. A first set of operational settings was defined.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB023

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 27 August 2021

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WEPAB024

Release of Crystal Routine for Multi-Turn Proton Simulations within SixTrack v5

simulation, proton, collider, hadron

2648

M. D’Andrea, A. Mereghetti, D. Mirarchi, V.K.B. Olsen, S. Redaelli
CERN, Geneva, Switzerland

Crystal collimation is studied as a possible scheme to further improve the efficiency of ion collimation at the High Luminosity Large Hadron Collider (HL-LHC), as well as for possible applications in the CERN program of Physics Beyond Colliders. This concept relies on the use of bent crystals that can deflect high-energy halo particles at large angles, of the order of tens of urad. In order to reproduce key experimental results of crystal collimation tests and predict the performance of this system when applied to present and future machines, a dedicated simulation routine was developed. This routine is capable of modeling both coherent and incoherent interactions of beam particles with crystal collimators, and is fully integrated into the magnetic tracking and collimator modeling provided by the single-particle tracking code SixTrack. This paper describes the implementation of the routine in the latest version of SixTrack and its most recent improvements, in particular regarding the treatment of the crystal miscut angle.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB024

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paper received ※ 19 May 2021 paper accepted ※ 23 June 2021 issue date ※ 14 August 2021

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WEPAB360

Future Prospective for Bent Crystals in Accelerators

lattice, scattering, experiment, SRF

3545

M. Romagnoni
INFN-Ferrara, Ferrara, Italy
M. Romagnoni
Universita’ degli Studi di Milano, Milano, Italy

Super magnet dipoles employed to steer high energy particle beams are massive instruments requiring cryogenic cooling and featuring large energy consumption. A bent crystal has the potential in a few millimeters to deflect 100-1000 GeV particle beams as much as an hundreds-tesla magnetic dipole. Indeed, within the lattice of a crystal, large electric fields up to several GeV/cm are present. Positive charged particles can be efficiently channeled between two adjacent lattice planes, thus following their curvature. These features and the possibility to selectively affect only the portion of the beam intercepting the crystal led to the proposal of exploiting bent crystals for several purposes, such as the collimation of ions at LHC. In this scheme, the particles on the beam halo instead of being scattered by tens-centimeters long collimators are directly separated from the beam using a 4 mm long silicon crystal. The production of a bent crystal suitable for installation in the LHC beamline requires strict control over lattice features and bending apparatus. The results obtained by the years long research of the INFN research team in Ferrara are presented in this work.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB360

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paper received ※ 14 May 2021 paper accepted ※ 28 July 2021 issue date ※ 18 August 2021

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THPAB158

BEAM COLLIMATION IN THE PIP-II LINAC TO BOOSTER TRANSFER LINE

injection, booster, linac, proton

4068

D.E. Johnson, V.V. Kapin, J.-F. Ostiguy, V.I. Sidorov, M. Xiao
Fermilab, Batavia, Illinois, USA
D.G. Georgobiani
FRIB, East Lansing, Michigan, USA

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The new PIP-II superconducting linac will deliver a 2 mA average H^- beam to the existing Booster synchrotron. The injected beam is accumulated by charge exchange over approximately 300 turns; phase space painting is used to mitigate space charge effects. To limit the power load on the internal waste beam absorber from the transverse tails of the H⁻ distribution missing the foil, the beam will be collimated in both planes in the linac to Booster transfer line using compact collimators of a novel design. Both the number of parasitic hits and the fraction of the beam missing the foil are sensitive functions of the H⁻ beam centroid position with respect to the edge of the foil. The positioning of the collimation is constrained by the availability of suitable space in the transfer line lattice, by specifics of the collimator design, by the phase space orientation at the collimator, and by the betatron phase advance to the foil needed to achieve proper orientation of the spatial distribution at the injection point. In this contribution, we describe the procedure by which collimator positions were optimized. We then discuss the expected performance of the overall system.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB158

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paper received ※ 04 June 2021 paper accepted ※ 02 July 2021 issue date ※ 26 August 2021

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THPAB176

Studies on Beam Collimation System for the ESSnuSB Accumulator

scattering, proton, linac, simulation

4107

Y. Zou, M. Olvegård
Uppsala University, Uppsala, Sweden

Funding: This work is supported by the European Union Horizon 2020 research and innovation program under grant agreement No 777419.
The ESSnuSB, a neutrino facility based on the European Spallation Source, aims at measuring, with precision, the charge-parity (CP) violating lepton phase at the 2nd oscillation maximum. The ESS linac will have to be upgraded to provide an additional 5 MW beam for the ESSnuSB to produce an unprecedented high-intensity neutrino beam. An accumulator ring is employed to compress the 2.86 ms long pulse from the linac to around 1.5 µs in order to satisfy the target requirements and improve the physics performance. In the operation of a high-intensity proton accumulator, the most important issue is to minimize the uncontrolled beam loss to reduce component activation to make hands-on maintenance possible. For this purpose, a two-stage collimation system is designed, which consists of a thin scraper to scatter halo particles and secondary collimators to absorb those scattered particles. Phase advances between scraper and secondary collimators, together with the material, the thickness of collimators, have been detailed studied and numerical simulations have been performed to evaluate the performance of the collimation system. This paper presents the design of the collimation system.

Poster THPAB176 [5.022 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB176

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paper received ※ 11 May 2021 paper accepted ※ 21 June 2021 issue date ※ 01 September 2021

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THPAB235

Detailed Electromagnetic Characterisation of HL-LHC Low Impedance Collimators

impedance, simulation, operation, factory

4258

A. Kurtulus, C. Accentura, N. Biancacci, F. Carra, F. Caspers, N. Chitnis, F. Giordano, R. Illan Fiastre, S. Joly, I. Lamas Garcia, L. Mourier, E. Métral, S. Redaelli, B. Salvant, W. Vollenberg, C. Vollinger, C. Zannini
CERN, Geneva, Switzerland

The High Luminosity Large Hadron Collider (HL-LHC) project will upgrade the LHC machine to allow operation with increased luminosity for the experiments. In order to achieve this goal, different operational parameters of the machine need to be pushed beyond the present design values, including the stored beam energy. One of the main challenges related to the achievement of the upgraded performance is the beam collimation system and its contribution to the overall machine impedance budget. In this perspective, new low impedance collimators have been designed, fabricated, and installed in the LHC. In this study, we will present their detailed electromagnetic (EM) characterization by means of radio frequency (RF) measurements and EM simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB235

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paper received ※ 19 May 2021 paper accepted ※ 19 July 2021 issue date ※ 10 August 2021

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THPAB307

Behaviour of Ironless Inductive Position Sensors in Close Proximity to Each Other

simulation, ECR, FEM, site

4390

N.J. Sammut, A. Grima
University of Malta, Information and Communication Technology, Msida, Malta
M. Di Castro, A. Masi
CERN, Meyrin, Switzerland

Funding: CERN - The European Organisation for Nuclear Research UM - The University of Malta
Safety critical systems like the collimators of the Large Hadron Collider require transducers which are immune to interference from their surroundings. The ironless inductive position sensor is used to measure the position of collimator jaws with respect to the beam and is designed to be immune to external DC or slowly changing magnetic fields. In this paper we investigate whether frequency separation is required when multiple ironless inductive position sensors are used and whether two or more sensors at the same frequency results in cross-talk. Numerical simulations and experiments are conducted to study the magnetic field behaviour of the sensors, their interference with each other and the impact of this interference on the position reading. Finally, this paper defines guidelines on safe operation of the ironless inductive position sensor in the aforementioned conditions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB307

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paper received ※ 17 May 2021 paper accepted ※ 02 July 2021 issue date ※ 22 August 2021

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