| Paper | Title | Page |
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| MOPMP037 | Updated High-Energy LHC Design | 524 |
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Funding: This work was supported in part by the European Commission under the HORIZON 2020 project ARIES no.730871, and by the Swiss Accelerator Research and Technology collaboration CHART. We present updated design parameters for a future High-Energy LHC. A more realistic turnaround time has led to a revision of the target peak luminosity, as well as a choice of a larger IP beta function, and longer physics fills. Pushed parameters of the Nb3Sn superconducting cable together with a modified layout of the 16 T dipole magnets resulted in revised field errors, updated dynamic-aperture simulations, and an associated re-evaluation of injector options. Collimators in the dispersion suppressors help achieve satisfactory cleaning performance. Longitudinal beam parameters ensure beam stability throughout the cycle. Intrabeam scattering rates and Touschek lifetime appear benign. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP037 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| MOPRB052 | Gamma Factory at CERN: Design of a Proof-of-Principle Experiment | 685 |
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| The Gamma Factory (GF) initiative proposes to create novel research tools at CERN by producing, accelerating and storing highly relativistic partially stripped ion beams in the LHC rings and by exciting their atomic degrees of freedom by lasers, to produce high-energy photon beams. Their intensity would be several orders of magnitude higher than those of the presently operating light sources in the particularly interesting gamma-ray energy domain reaching up to 400 MeV. In this energy domain, the high-intensity photon beams can be used to produce secondary beams of polarized electrons, polarized positrons, polarized muons, neutrinos, neutrons and radioactive ions. Over the years 2017-2018 we have demonstrated that these partially stripped ion beams can be successfully produced, accelerated and stored in the CERN accelerator complex, including the LHC. The next step of the project is to build a proof of principle experiment in the SPS to validate the principal GF concepts. This contribution will present the initial conceptual design of this experiment along with its main challenge - the demonstration of the fast cooling method of partially stripped ion beams. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB052 | |
| About • | paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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| TUPMP035 | Design of the Vacuum System of the FCC-ee Electron-Positron Collider | 1319 |
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| The Future Circular Collider (FCC) Design Study includes the twin storage ring (FCC-ee) where electrons and positrons are stored and made to collide inside two detectors. The vacuum system of FCC-ee must be designed in order to deal with a lower-energy (45.6 GeV), high-current (1390 mA) Z-pole machine and at a later stage with a higher-energy (182.5 GeV) low-current (5.4 mA). The former machine is the most challenging one from the point of view of vacuum, since the photon-stimulated desorption (PSD) generated by the copious synchrotron radiation (SR) fans is quite large. While several concepts have been considered at the beginning, the design retained for the Conceptual Design Report (CDR) is one where the cross-section of the vacuum chamber (VC) in the arcs is a scaled-down version of the one implemented in the SUPERKEKB collider. Contrary to SUPERKEKB tough, the SR fans are absorbed by many short absorbers, with average spacing of 5.8 m. This allow a localization of the PSD gas load and to place lumped pumps in front of the SR absorbers, to maximize the pumping efficiency. The VC design is compatible with the design of the common-yoke dipoles and quadrupoles. The VC material is copper alloy. Optimization of the pressure profiles has been carried out by means of extensive coupled montecarlo simulations, for SR and molecular flow. For the higher energy versions of the machine, for which the SR spectra are characterized by critical energies well above the Compton edge, the localized absorbers facilitate also shielding the tunnel and any radiation-sensitive machine components from X-ray photon damage, by installing short high-Z material around the absorbers. The major features of the CDR relevant for vacuum will be highlighted in the paper. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP035 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPMP036 | Results on the FCC-hh Beam Screen Sawtooth at the Kit Electron Storage Ring Kararesults on the Fcc-Hh Beam Screen Sawtooth at the Kit Electron Storage Ring Kara | 1323 |
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Funding: * The European Circular Energy-Frontier Collider Study (EuroCirCol) project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 654305. In the framework of the EuroCirCol collaboration (work package 4 "Cryogenic Beam Vacuum System"), the fabrication of the FCC-hh beam screen (BS) prototype has been carried out with the aim of testing it at room temperature on the Karlsruhe Institute of Technology (KIT) 2.5 GeV electron storage ring KARA (KArlsruhe Research Accelerator) light source. The BS prototype was tested on a beamline installed by the collaboration, named as BEam Screen TEstbench EXperiment (BESTEX). KARA has been chosen because its synchrotron radiation (SR) spectrum, photon flux and power match quite well the one foreseen for the 50+50 TeV FCC-hh proton collider. The BS prototype (2 m in length) was manufactured according to the base line design (BD) of the FCC-hh BS. It implements a saw-tooth profile designed to absorb the SR generated at the bending magnets. Also, a laser-ablated anti-electron cloud surface texturing [2] was applied at the BS inner walls. We present here the results obtained at BESTEX and the comparison of the results obtained during irradiation of the saw-tooth profile at different geometric configurations. This activity has been carried out in the framework of the EuroCirCol* collaboration (work package 4 "Cryogenic Beam Vacuum System"). |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP036 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | |
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| TUPMP037 | Recent Developments of Monte-Carlo Codes Molflow+ and Synrad+ | 1327 |
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Molflow+ and Synrad+ are Monte Carlo simulation tools for ultra-high vacuum and synchrotron radiation, respectively. Over the years they have become a common tool for designing and analysing the vacuum system of particle accelerators. This contribution gives a short summary about new features added since IPAC-14*. Some highlights: In traditional Monte Carlo simulations, one simulated ’virtual’ particle represents a given number of physical molecules or photons. This is a weakness where the pressure or flux of the simulated system spans across multiple orders of magnitude. Synrad now supports low flux mode, a weighed Monte Carlo technique where the represented number of photons is reduced at every reflection, providing significantly better statistics at low flux regions. As for Molflow+, angle maps allow recording the molecules, directional distribution at any point, and then desorb a reduced gas quantity according to the recording. In linear systems, this allows iterative simulations that have been proven to treat systems up to 7 orders of magnitude of pressure difference. Without the new technique the computing time would be prohibitively slow on desktop computers, which is what most users of the two codes use. Both codes now have a built-in geometry builder that allows creating simple models through a set of 3D operations, and modifying those imported from CAD tools. Molflow+ has recently become open source, and it has been made compatible with, and tested on different versions of Linux and macOS. Examples of application of Molflow+ to novel Beam Gas Curtain detector and the design of the FCC-ee vacuum system will be given, alongside with some benchmarking runs against data published in literature.
* M. Ady, R. Kersevan, "Introduction to the Latest Version of the Test-particle Monte Carlo Code Molflow+", Proc. IPAC’14, Dresden, Germany, June 2014, pp. 2348-2350. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP037 | |
| About • | paper received ※ 13 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| TUPMP038 | Summary of Modelling Studies on the Beam Induced Vacuum Effects in the FCC-hh | 1331 |
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Funding: The European Circular Energy-Frontier Collider Study (EuroCirCol) project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 654305. EuroCirCol is a conceptual design study of a Future Circular Collider (FCC-hh) which aims to expand the current energy and luminosity frontiers that the LHC has established. The vacuum chamber of this 50 TeV, 100 km collider, will have to cope with unprecedented levels of synchrotron radiation power for proton colliders, dealing simultaneously with a tighter magnet aperture. Since the high radiation power and photon flux will release large amounts of gas into the system, the difficulty to keep a low level of residual gas density increases considerably compared with the LHC. This article presents a study of the beam induced vacuum effects for the FCC-hh novel conditions, the different phenomena which, owing to the presence of the beam, have an impact on the vacuum level of the accelerator. To achieve this, a novel beam screen has been proposed, featuring specific mitigating measures aimed at dealing with the beam induced effects. It is concluded that thanks to the new beam screen design, the vacuum level in the FCC-hh shall be adequate, allowing to reach the molecular density requirement of better than 1015 H2/m3 with baseline beam parameters within the first months of conditioning. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPMP038 | |
| About • | paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | |
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| WEPGW093 | Commissioning of the Prototype for a New Gas Curtain Beam Profile Monitor Using Beam Induced Fluorescence for HL-LHC | 2709 |
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Funding: This work is supported by the HLLHCUK project and the STFC Cockcroft Institute core grant No. ST/G008248/1. A new supersonic gas-jet curtain based beam profile monitor is under development for minimally invasive simultaneous transverse profile diagnostics of proton and electron beams, at pressures compatible with LHC. The monitor makes use of a thin gas-jet curtain angled at 45 degrees with respect to the charged particle beams. The fluorescence caused by the interaction between the curtain and the beam can then be detected using a dedicated imaging system to determine its transverse profile. This contribution details design features of the monitor, discusses the gas-jet curtain formation and presents various experimental tests, including profile measurements of an electron beam using nitrogen and neon curtains. The gas-jet density was estimated by correlating it with the number of photons detected by the camera. These measurements are then compared with results obtained using a movable pressure gauge. This monitor has been commissioned in collaboration with CERN, GSI and the University of Liverpool. It serves as a first prototype of a final design that will be placed in the LHC beam line to measure the profile of the proton beam. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW093 | |
| About • | paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | |
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