Abstract
In view of the High-Luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN, different materials were investigated for the upgrade of the LHC collimation system. A key objective was ...to determine how the jaws of the new collimators could be manufactured to meet the demanding requirements of HL-LHC, such as thermo-mechanical robustness and stability, beam coupling impedance, Ultra-High Vacuum (UHV), etc. During the Long-Shutdown 2 (LS2), five primary and ten secondary low-impedance collimators were already produced using novel materials. For LS3, in addition to more secondary collimators, the production and installation of other types of devices, including tertiaries and physics-debris collimators, is planned. This paper details the final mate-rial choices and rationale for each collimator family.
A prototype of a luminometer, designed for a future
e
+
e
-
collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this ...beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Molière radius has been determined to be 24.0 ± 0.6 (stat.) ± 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
In 2017, a proton-impact test on HL-LHC collimator materials was carried out in the HiRadMat facility at CERN. The experiment, called “
MultiMat
”, enabled the testing of uncoated and coated ...material composites and alloys, in most of the cases developed at CERN, for different beam collimation functionalities. Manufacturing of these materials was then passed to industry, leading to a series production for use in the collimators installed in the LHC during Long Shutdown 2 (LS2). The industrial versions of bulk and coating materials were tested in HiRadMat in 2021 in the “
MultiMat-2
” experiment, that efficiently re-used the same experimental test bench as for “
MultiMat
”. This new experiment demonstrated the reliability of the absorbers installed in LS2, and confirmed the possible use of alternative materials and coatings for the next LS3 collimator production. This paper describes the preparation and beam parameters of “
MultiMat-2
”, the experimental setup and the main results of the experiment.
Flexible graphite (FG) with ρ = 1 g/cm3 density is a type of highly porous and anisotropic graphite, mainly used for gaskets and sealing applications, but also suitable for energy absorption, such as ...in the beam dumping devices of the Large Hadron Collider (see Heredia 2021 1). Knowledge of its microstructure and mechanical properties needs to be developed for the selection of an adequate material model able accurately predict stresses and failure in FG components. Here, the FG microstructure properties available in literature are reviewed, followed by Focused Ion Beam - Scanning Electron Microscopy investigation and compression tests. Specifically, a single 100 μm × 150 μm cross section was obtained, and the 2D pore sizes and shapes were quantified using image segmentation. Monotonic and cyclic out-of-plane compression tests were performed in single and stacked configuration. Stress-strain curves showed three domains: the initial toe, the transition and the densification domain. The cyclic tangent modulus was also calculated from the cyclic tests. Many observations suggested that FG behaves similarly to crushable foams, crumpled materials and compacted powders, and that both crystalline microstructure and crumpled mesostructure play a predominant role in the deformation mechanism.
•FIB-SEM has proven effective for extracting quantitative information from the microstructure of flexible graphite.•The characteristic pore size obtained from 2D image analysis follows a log-normal distribution with overall expected value of 0.13 μm.•The out-of-plane compression response of flexible graphite shows remarkable similarities with the response of crumpled materials.•The parallel contributions of aligned and misaligned microsheets govern the out-of-plane compression response of flexible graphite.
The new generation internal beam dump of the Super Proton Synchrotron (SPS) at CERN will have to dissipate approximately 270 kW of thermal power, deposited by the primary proton beam. For this ...purpose, it is essential that the cooling system features a very efficient heat evacuation. Diffusion bonding assisted by hot isostatic pressing (HIP) was identified as a promising method of joining the cooling circuits and the materials of the dumps core in order to maximize the heat transfer efficiency. This paper presents the investigation of HIP assisted diffusion bonding between two CuCr1Zr blanks enclosing SS 316L tubes and the realization of a real size prototype of one of the dump’s cooling plates, as well as the assessments of its cooling performance under the dump’s most critical operational scenarios. Energy-dispersive x-ray spectroscopy, microstructural analyses, measurements of thermal conductivity, and mechanical strength were performed to characterize the HIP diffusion bonded interfaces (CuCr1Zr-CuCr1Zr and CuCr1Zr-SS 316L). A test bench allowed to assess the cooling performance of the real size prototype. At the bonded interface, the presence of typical diffusional phenomena was observed. Moreover, measured tensile strength and thermal conductivity were at least equivalent to the lowest ones of the materials assembled and comparable to its bulk properties, meaning that a good bonding quality was achieved. Finally, the real size prototype was successfully tested with an ad hoc thermal test bench and with the highest operational thermal power expected in the new generation SPS internal beam dump. These results demonstrated the possibility to use HIP as a manufacturing technique for the cooling plates of the new generation SPS internal beam dump, but they also open up the way for further investigations on its exploitability to improve the cooling performance of any future high intensity beam intercepting device or in general devices requiring very efficient heat evacuation systems.
The High Luminosity Large Hadron Collider (HL-LHC) and the LHC-Injection Upgrade (LIU) projects at CERN are upgrading the whole CERN accelerators chain to increase beam brightness and intensity. In ...this scenario, some critical machine components have to be redesigned and rebuilt. Due to the increase in beam intensity, minimizing the electromagnetic interaction between the beam and devices is a crucial design task. Indeed, these interactions could lead to beam instabilities and excessive thermo-mechanical loadings in the device. In this context, this paper presents an example of multi-physics study to investigate the impedance related thermal effects. The analysis is performed on the conceptual design of the new proton synchrotron (PS) internal dump.
New collimators are being produced at CERN in the framework of a large particle accelerator upgrade project to protect beam lines against stray particles. Their movable jaws hold low density ...absorbers with tight geometric requirements, while being able to withstand direct proton beam impacts. Such events induce considerable thermo-mechanical loads, leading to complex structural responses, which make the numerical analysis challenging. Hence, an experiment has been developed to validate the jaw design under representative conditions and to acquire online results to enhance the numerical models. Two jaws have been impacted by high-intensity proton beams in a dedicated facility at CERN and have recreated the worst possible scenario in future operation. The analysis of online results coupled to post-irradiation examinations have demonstrated that the jaw response remains in the elastic domain. However, they have also highlighted how sensitive the jaw geometry is to its mounting support inside the collimator. Proton beam impacts, as well as handling activities, may alter the jaw flatness tolerance value by \(\pm\) 70 \({\mu}\)m, whereas the flatness tolerance requirement is 200 \({\mu}\)m. In spite of having validated the jaw design for this application, the study points out numerical limitations caused by the difficulties in describing complex geometries and boundary conditions with such unprecedented requirements.
Two special calorimeters are foreseen for the instrumentation of the very forward region of an ILC or CLIC detector; a luminometer (LumiCal) designed to measure the rate of low angle Bhabha ...scattering events with a precision better than 10\(^{-3}\) at the ILC and 10\(^{-2}\) at CLIC, and a low polar-angle calorimeter (BeamCal). The latter will be hit by a large amount of beamstrahlung remnants. The intensity and the spatial shape of these depositions will provide a fast luminosity estimate, as well as determination of beam parameters. The sensors of this calorimeter must be radiation-hard. Both devices will improve the e.m. hermeticity of the detector in the search for new particles. Finely segmented and very compact electromagnetic calorimeters will match these requirements. Due to the high occupancy, fast front-end electronics will be needed. Monte Carlo studies were performed to investigate the impact of beam-beam interactions and physics background processes on the luminosity measurement, and of beamstrahlung on the performance of BeamCal, as well as to optimise the design of both calorimeters. Dedicated sensors, front-end and ADC ASICs have been designed for the ILC and prototypes are available. Prototypes of sensor planes fully assembled with readout electronics have been studied in electron beams.
Eur. Phys. J. C 78 (2018) 135 A prototype of a luminometer, designed for a future e+e- collider detector,
and consisting at present of a four-plane module, was tested in the CERN PS
accelerator T9 ...beam. The objective of this beam test was to demonstrate a
multi-plane tungsten/silicon operation, to study the development of the
electromagnetic shower and to compare it with MC simulations. The Moli\`ere
radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using
a parametrization of the shower shape. Very good agreement was found between
data and a detailed Geant4 simulation.
A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam ...test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Molière radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.
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