| Paper | Title | Page |
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| TUPMW025 | Machine Protection from Fast Crab Cavity Failures in the High Luminosity LHC | 1485 |
| SUPSS005 | use link to see paper's listing under its alternate paper code | |
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| The time constant of a crab cavity (CC) failure can be faster than the reaction time of the active protection system. In such a scenario, the beams cannot be immediately extracted, making the the protection of the machine rely on the passive protection devices. At the same time, the energy stored in the High Luminosity (HL) LHC beams will be doubled with respect to the LHC to more than 700 MJ, which increases the risk of damaging the machine and the experiments in a failure scenario. In this study we estimate the impact that different CC failures have on the collimation system. We also give a first quantitative estimate of the effect of these failures on the elements near the experiments based on FLUKA simulations, using an updated HL-LHC baseline. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW025 | |
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| WEPMW028 | First Attempts at using Active Halo Control at the LHC | 2486 |
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Funding: Research supported by the High Luminosity LHC project. The beam halo population is a non-negligible factor for the performance of the LHC collimation system and the machine protection. In particular this could become crucial for aiming at stored beam energies of 700 MJ in the High Luminosity (HL-LHC) project, in order to avoid beam dumps caused by orbit jitter and to ensure safety during a crab cavity failure. Therefore several techniques to safely deplete the halo, i.e. active halo control, are under development. In a first attempt a novel way for safe halo depletion was tested with particle narrow-band excitation employing the LHC Transverse Damper (ADT). At an energy of 450 GeV a bunch selective beam tail scraping without affecting the core distribution was attempted. This paper presents the first measurement results, as well as a simple simulation to model the underlying dynamics. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW028 | |
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| WEPOY046 | Beam Delivery Simulation: BDSIM - Automatic Geant4 Models of Accelerators | 3098 |
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| Beam Delivery Simulation (BDSIM) is a program that uses a suite of high energy physics software including Geant4, CLHEP & ROOT, that seamlessly tracks particles through accelerators and detectors utilising the full range of particles and physics processes from Geant4. BDSIM has been used to simulate linear colliders such as the International Linear Collider (ILC) and more recently, circular colliders such as the Large Hadron Collider (LHC). The latest developments including improved geometry modelling; external geometry support; process biasing; and a new event display are presented. A significantly revised and improved accompanying tool chain is presented comprising of a series of Python utilities that allow efficient and automatic preparation of models. Furthermore, a library for both ROOT and Python that provides powerful analysis and event viewing after simulation is demonstrated. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY046 | |
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| WEPOY047 | LHC Collimation and Energy Deposition Studies Using Beam Delivery Simulation (BDSIM) | 3101 |
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| Beam Delivery Simulation (BDSIM) is a program that uses a suite of high energy physics software including Geant4, CLHEP & ROOT, that seamlessly tracks particles through accelerators and detectors utilising the full range of particles and physics processes from Geant4. A comparison of the collimator cleaning efficiency and energy deposition throughout the full length of the Large Hadron Collider (LHC) with the established SixTrack simulations of the CERN collimation group is presented. The propagation of the full hadronic showers from collimators provides unparalleled detail in energy deposition maps and these are compared with the data from beam loss monitors that measure radiation outside the magnet body. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY047 | |
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| TUPMW014 | Improved Aperture Measurements at the LHC and Results from their Application in 2015 | 1446 |
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| A good knowledge of the available aperture in the LHC is essential for a safe operation due to the risk of magnet quenches or even damage in case of uncontrolled beam losses. Experimental validations of the available aperture are therefore crucial and were in the past carried out by either a collimator scan combined with beam excitations or through the use of local orbit bumps. In this paper, we show a first comparison of these methods in the same machine configuration, as well as a new very fast method based on a beam-based collimator alignment and a new faster variant of the collimator scan method. The methods are applied to the LHC operational configuration for 2015 at injection and with squeezed beams and the measured apertures are presented. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMW014 | |
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| WEPMW007 | Validation of Off-momentum Cleaning Performance of the LHC Collimation System | 2427 |
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| The LHC collimation system is designed to provide effective cleaning against losses coming from off-momentum particles, either due to un-captured beam or to an unexpected RF frequency change. For this reason the LHC is equipped with a hierarchy of collimators in IR3: primary, secondary and absorber collimators. After every collimator alignment or change of machine configuration the off-momentum cleaning efficiency is validated with loss maps at low intensity. We describe here the improved technique used in 2015 to generate such loss maps without completely dumping the beam into the collimators. The achieved performance of the collimation system for momentum cleaning is reviewed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW007 | |
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| WEPMW030 | Cleaning Performance of the Collimation System of the High Luminosity Large Hadron Collider | 2494 |
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| Different upgrades of the LHC will be carried out in the framework of the High Luminosity project (HL-LHC), where the total stored energy in the machine will increase up to about 700 MJ. This unprecedented stored energy poses serious challenges for the collimation system, which was designed to handle safely up to about 360 MJ. In this paper the baseline collimation layout for HL-LHC is described, with main focus on upgrades related to the cleaning of halo and physics debris, and its expected performance is discussed. The main upgrade items include the presence of new collimators in the dispersion suppressor of the betatron cleaning insertion installed between two 11 T dipoles, and two additional collimators for an improved local protection of triplet magnets. Thus, optimized settings for the entire and upgraded collimation chain were conceived and are shown here together with the resulting cleaning performance. Moreover, the cleaning performance taking into account crab cavities it is also discussed. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMW030 | |
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| THPOY043 | Time Scale of Crab Cavity Failures Relevant for High Luminosity LHC | 4196 |
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Funding: Research supported by the High Luminosity LHC project A good knowledge of the effects of the crab cavities, required for the baseline High Luminosity LHC (HL-LHC), is needed before the results of the first tests of crab cavity prototypes in the SPS, planned for 2018, will be available. In case of crab cavity failures, we have to make sure that time scales are long enough so that the beams can be cleanly dumped before damage by beam loss occurs. We discuss our present knowledge and modeling of crab cavity induced beam losses, combined with mechanical deformation. We discuss lower limits on the time scales required for safe operation, and possible failure mitigation methods. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY043 | |
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