| Paper | Title | Page |
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| MOPOST024 | A Local Modification of HL-LHC Optics for Improved Performance of the Alice Fixed-Target Layout | 108 |
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Funding: This project has received funding from the European Union’s Horizon 2020 research and innovation programme, grant agreement number 101003442 - FIXEDTARGETLAND. The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) is the world’s largest and most powerful particle accelerator colliding beams of protons and lead ions at energies up to 7 TeV and 2.76 TeV, respectively. ALICE is one of the detector experiments optimised for heavy-ion collisions. A fixed-target experiment in ALICE is considered to collide a portion of the beam halo, split using a bent crystal, with an internal target placed a few meters upstream of the detector. Fixed-target collisions offer many physics opportunities related to hadronic matter and the quark-gluon plasma to extend the research potential of the CERN accelerator complex. Production of physics events depends on the particle flux on target. The machine layout for the fixed-target experiment is being developed to provide a flux of particles on a target high enough to exploit the full capabilities of the ALICE detector acquisition system. In this paper, we discuss a method of increasing the system’s performance by applying a local modification of optics to set the crystal at the optimal betatron phase. marcin.patecki@pw.edu.pl |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOST024 | |
| About • | Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 01 July 2022 | |
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| MOPOST043 | Testing the Global Diffusive Behaviour of Beam-Halo Dynamics at the CERN LHC Using Collimator Scans | 172 |
| SUSPMF063 | use link to see paper's listing under its alternate paper code | |
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| In superconducting circular particle accelerators, controlling beam losses is of paramount importance for ensuring optimal machine performance and an efficient operation. To achieve the required level of understanding of the mechanisms underlying beam losses, models based on global diffusion processes have recently been studied and proposed to investigate the beam-halo dynamics. In these models, the building block of the analytical form of the diffusion coefficient is the stability-time estimate of the Nekhoroshev theorem. In this paper, the developed models are applied to data acquired during collimation scans at the CERN LHC. In these measurements, the collimators are moved in steps and the tail population is re-constructed from the observed losses. This allows an estimate of the diffusion coefficient. The results of the analyses performed are presented and discussed in detail. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOST043 | |
| About • | Received ※ 07 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 17 June 2022 | |
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| MOPOST045 | A Novel Tool for Beam Dynamics Studies with Hollow Electron Lenses | 176 |
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| Hollow Electron Lenses (HELs) are crucial components of the CERN LHC High Luminosity Upgrade (HL-LHC), serving the purpose of actively controlling the population of the transverse beam halo to reduce particle losses on the collimation system. Symplectic particle tracking simulations are required to optimize the efficiency and study potentially undesired beam dynamics effects with the HELs. With the relevant time scales in the collider in the order of several minutes, tracking simulations require considerable computing resources. A new tracking tool, Xsuite, developed at CERN since 2021, offers the possibility of performing such tracking simulations using graphics processing units (GPUs), with promising perspectives for the simulation of hadron beam dynamics with HELs. In this contribution, we present the implementation of HEL physics effects in the new tracking framework. We compare the performance with previous tools and show simulation results obtained using known and newly established simulation setups. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOST045 | |
| About • | Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 22 June 2022 — Issue date ※ 08 July 2022 | |
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| TUPOTK060 | Simulations of Miscut Effects on the Efficiency of a Crystal Collimation System | 1358 |
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Funding: Research supported by the HL-LHC project. The concept of crystal collimation relies on the use of bent crystals which can coherently deflect high-energy halo particles at angles orders of magnitude larger than what is obtained from scattering with conventional materials. Crystal collimation is studied to further improve the collimation efficiency at the High Luminosity Large Hadron Collider (HL-LHC). In order to reproduce the main experimental results of crystal collimation tests and to predict the performance of such a system, a simulation routine capable of modeling interactions of beam particles with crystal collimators was developed and recently integrated into the latest release of the single-particle tracking code SixTrack. A new treatment of the miscut angle, i.e. the angle between crystalline planes and crystal edges, was implemented to study the effects of this manufacturing imperfection on the efficiency of a crystal collimation system. In this paper, the updated miscut angle model is described and simulation results on the cleaning efficiency are presented, using configurations tested during Run 2 of the LHC as a case study. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK060 | |
| About • | Received ※ 07 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 04 July 2022 | |
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| TUPOTK061 | Prospects to Apply Machine Learning to Optimize the Operation of the Crystal Collimation System at the LHC | 1362 |
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Funding: Research supported by the HL-LHC project. Crystal collimation relies on the use of bent crystals to coherently deflect halo particles onto dedicated collimator absorbers. This scheme is planned to be used at the LHC to improve the betatron cleaning efficiency with high-intensity ion beams. Only particles with impinging angles below 2.5 urad relative to the crystalline planes can be efficiently channeled at the LHC nominal top energy of 7 Z TeV. For this reason, crystals must be kept in optimal alignment with respect to the circulating beam envelope to maximize the efficiency of the channeling process. Given the small angular acceptance, achieving optimal channeling conditions is particularly challenging. Furthermore, the different phases of the LHC operational cycle involve important dynamic changes of the local orbit and optics, requiring an optimized control of position and angle of the crystals relative to the beam. To this end, the possibility to apply machine learning to the alignment of the crystals, in a dedicated setup and in standard operation, is considered. In this paper, possible solutions for automatic adaptation to the changing beam parameters are highlighted and plans for the LHC ion runs starting in 2022 are discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK061 | |
| About • | Received ※ 07 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 24 June 2022 | |
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| TUPOTK062 | Settings for Improved Betatron Collimation in the First Run of the High Luminosity LHC | 1366 |
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Funding: This work was supported by the High Luminosity LHC project The current betatron collimation system in the LHC is not optimized to absorb off-momentum particles scattered out from the primary collimators. The highest losses are concentrated in the downstream dispersion suppressor (DS). Given the increased beam intensity in the High Luminosity LHC (HL-LHC), there is concern that these losses could risk quenching the superconducting DS magnets. Consequently, a dedicated upgrade of the DS has been studied. However, at this stage, the deployment for the startup of the HL-LHC is uncertain due to delays in the availability of high-field magnets needed to integrate new collimators into the DS. In this paper, we describe the expected collimation setup for the first run of the HL-LHC and explore various techniques to improve the collimation cleaning. These include exploiting the asymmetric response of the two jaws of each primary collimator and adjusting the locally generated dispersion in the collimation insertion. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK062 | |
| About • | Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 23 June 2022 | |
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| WEPOST016 | Development of Collimation Simulations for the FCC-ee | 1718 |
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| A collimation system is under study for the FCC-ee to protect the machine from the multi-MJ electron and positron beams and limit the backgrounds to the detectors. One of the key aspects of the collimation system design is the setup of simulation studies combining particle tracking and scattering in the collimators. The tracking must include effects important for electron beam single-particle dynamics in the FCC-ee, such as synchrotron radiation. For collimation, an aperture model and particle-matter interactions for electrons are required. There are currently no established simulation frameworks that include all the required features. The latest developments of an integrated framework for multi-turn collimation studies in the FCC-ee are presented. The framework is based on an interface between tracking codes, pyAT and Xtrack, and a particle-matter interaction code, BDSIM, based on Geant4. Promising alternative simulation codes and frameworks are also discussed. The challenges are outlined, and the first results are presented, including preliminary loss maps for the FCC-ee. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST016 | |
| About • | Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022 | |
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| WEPOST018 | Power Deposition Studies for Crystal-Based Heavy Ion Collimation in the LHC | 1726 |
| SUSPMF007 | use link to see paper's listing under its alternate paper code | |
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| The LHC heavy-ion program with 208Pb82+ beams is foreseen to benefit from a significant intensity upgrade in 2022. A performance limitation may arise from ion fragments scattered out of the collimators in the betatron cleaning insertion, which risk quenching superconducting magnets during periods of short beam lifetime. In order to mitigate this risk, an alternative collimation technique, relying on bent crystals as primary collimators, will be used in future heavy-ion runs. In this paper, we study the power deposition in superconducting magnets by means of FLUKA shower simulations, comparing the standard collimation system against the crystal-based one. The studies focus on the dispersion suppressor regions downstream of the betatron cleaning insertion, where the ion fragment losses are the highest. Based on these studies, we quantify the expected quench margin expected in future runs with 208Pb82+ beams. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST018 | |
| About • | Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 03 July 2022 | |
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| WEPOST019 | Benchmarks of Energy Deposition Studies for Heavy-Ion Collimation Losses at the LHC | 1730 |
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| During some periods in its second physics run (2015-2018), the LHC has been operated with 208Pb82+ ion beams at an energy of 6.37 ZTeV. The LHC is equipped with a betatron collimation system, which intercepts the transverse beam halo and protects sensitive equipment such as superconducting magnets against beam losses. However, hadronic fragmentation and electromagnetic dissociation of heavy ions in collimators generate off-rigidity particles, which can be lost in the downstream dispersion suppressor, putting the magnets at risk to quench. An accurate modelling of the beam-induced energy deposition in the collimation system and superconducting magnets is important for quantifying possible performance limitations arising from magnet quenches. In this paper, we compare FLUKA shower simulations against beam loss monitor measurements recorded during the 2018 208Pb82+ run. In particular, we investigate fast beam loss events, which lead to recurring beam aborts in 2018 operation. Based on these studies, we assess the ability of the simulation model to reproduce the observed loss patterns in the collimation region and dispersion suppressor. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST019 | |
| About • | Received ※ 08 June 2022 — Revised ※ 10 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 23 June 2022 | |
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| WEPOPT009 | Operational Scenario of First High Luminosity LHC Run | 1846 |
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| A new scenario for the first operational run of the HL-LHC era (Run 4) has been recently developed to accommodate a period of performance ramp-up to achieve an annual integrated luminosity close to the nominal HL-LHC design. The operational scenario in terms of beam parameters and machine settings, as well as the different phases, are described here along with the impact of potential delays on key hardware components. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOPT009 | |
| About • | Received ※ 19 May 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 09 July 2022 | |
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| WEPOTK018 | Simulation of Heavy-Ion Beam Losses with Crystal Collimation* | 2082 |
| SUSPMF048 | use link to see paper's listing under its alternate paper code | |
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With the higher stored energy envisioned for future heavy-ion runs in the LHC and the challenging fragmentation aspect of heavy-ion beams due to interaction with collimator material, the need arises for even more performing collimation systems. One promising solution is crystal channeling, which is used in the HL-LHC baseline and starts with Run III for heavy-ion collimation. To investigate an optimal configuration for the collimation system, a well-tested simulation setup is required. This work shows the simulations of channeling and other coherent effects in the SixTrack-FLUKA Coupling simulation framework and compares simulated loss patterns with data from previous beam tests.
*Research supported by the HL’LHC project |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK018 | |
| About • | Received ※ 07 June 2022 — Accepted ※ 11 June 2022 — Issue date ※ 15 June 2022 | |
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| WEPOTK033 | Layouts for Feasibility Studies of Fixed-Target Experiments at the LHC | 2134 |
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| The Physics Beyond Colliders (PBC) study investigates means of exploiting the potential of the CERN accelerator complex to complement the laboratory’s scientific programme at the main Large Hadron Collider (LHC) experiments. The LHC fixed-target (FT) working group studies new experiments at beam energies up to 7 TeV. One of the proposed experiments is based on a bent crystal, part of the collimation hierarchy, to extract secondary halo particles and steer them onto a target. A second bent crystal immediately downstream of the target is used to study electric and magnetic dipole moments of short-lived baryons. The possibility to install a test stand in the LHC off-momentum collimation Insertion Region (IR3) to demonstrate the feasibility and performance of this challenging scheme is currently under investigation. The integration of a spectrometer magnet into the present layout is particularly critical. In this contribution, we study a possible test setup that could be used in LHC Run 3. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK033 | |
| About • | Received ※ 08 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 28 June 2022 | |
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| WEPOTK034 | LHC Beam Collimation During Extended β*-Levelling in Run 3 | 2138 |
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| During the third operational Run of the Large Hadron Collider at CERN, starting in 2022, the bunch population will be increased to unprecedented levels requiring to deploy β*-levelling of the luminosity over a wide range of values to cope with the limitations imposed by event pile-up at the experiments and heat load on the triplets induced by collision debris. During this levelling, both beam optics and orbit change in various areas of the ring, in particular around the high-luminosity experiments, where several collimators are installed. This requires adapting the collimation system settings adequately, in particular for the tertiary collimators (TCTs) that protect the inner-triplet magnets. To this end, two strategies are considered: keeping collimators at fixed physical openings while shifting their centres following the beam orbit, or varying also the collimator openings. The latter strategy is planned when the larger optics range will be deployed. In this paper, we investigate several loss scenarios at the TCTs in different steps of the levelling, and present the proposed collimator settings during Run 3. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOTK034 | |
| About • | Received ※ 07 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 07 July 2022 | |
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