The D33 small‐angle neutron scattering (SANS) instrument at the Institut Laue–Langevin (ILL) is the most recent SANS instrument to be built at the ILL. In a project beginning in 2005 and lasting ...seven years, the concept has been developed, and the instrument designed, manufactured and installed. D33 was commissioned with neutrons during the second half of 2012, fully entering the ILL user programme in 2013. The scientific case required that D33 should provide a wide dynamic range of measured scattering vector magnitude q, flexibility with regard to the instrument resolution, and the provision of polarized neutrons and 3He spin analysis to facilitate and expand studies in magnetism. In monochromatic mode, a velocity selector and a flexible system of inter‐collimation apertures define the neutron beam. A double‐chopper system enables a time‐of‐flight (TOF) mode of operation, allowing an enhanced dynamic q range (qmax/qmin) and a flexible wavelength resolution. Two large multitube detectors extend the dynamic q range further, giving qmax/qmin ≃ 25 in monochromatic mode and a very large qmax/qmin > 1000 in TOF mode. The sample zone is large and flexible in configuration, accommodating complex and bulky sample environments, while the position of D33 is such as to allow high magnetic fields at the sample position. The instrument is of general purpose with a performance rivalling that of D22, and is well adapted for SANS studies in scientific disciplines as diverse as solution scattering in biology and soft matter and studies of physics, materials science and magnetism. This article provides a detailed technical description of D33 and its performance and characterization of the individual components, and serves as a technical reference for users of the instrument.
This article provides a detailed technical description of the D33 small‐angle neutron scattering instrument at the ILL and serves as a technical reference for users of the instrument.
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.
Abstract
Two 6 t beam dumps, made of a graphite core encapsulated in
a stainless steel vessel, are used to absorb the energy of the two
Large Hadron Collider (LHC) intense proton beams during ...operation of
the accelerator. Operational issues started to appear in 2015 during
LHC Run 2 (2014–2018) as a consequence of the progressive increase
of the LHC beam kinetic energy, necessitating technical
interventions in the highly radioactive areas around the
dumps. Nitrogen gas leaks appeared after highly energetic beam
impacts and instrumentation measurements indicated an initially
unforeseen movement of the dumps. A computer modelling analysis
campaign was launched to understand the origin of these issues,
including both Monte Carlo simulations to model the proton beam
interaction as well as advanced thermo-mechanical analyses. The main
findings were that the amount of instantaneous energy deposited in
the dump vessel leads to a strong dynamic response of the whole dump
and high accelerations (above 200 g). Based on these findings, an
upgraded design, including a new support system and beam windows,
was implemented to ensure the dumps' compatibility with the more
intense beams foreseen during LHC Run 3 (2022–2025) of 539 MJ per
beam. In this paper an integral overview of the operational
behaviour of the dumps and the upgraded configurations are
discussed.
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.
Malalignment is the main cause of tibial component loosening. Implants that migrate rapidly in the first two post-operative years are likely to present aseptic loosening. It has been suggested that ...cancellous bone stresses can be correlated with tibial component migration. A recent study has shown that patient-specific finite element (FE) models have the power to predict the short-term behavior of tibial trays. The stresses generated within the implanted tibia are dependent on the kinematics of the joint; however, previous studies have ignored the kinematics and only applied static loads. Using explicit FE, it is possible to simultaneously predict the kinematics and stresses during a gait cycle. The aim of this study was to examine the cancellous bone strains during the stance phase of the gait cycle, for varying degrees of varus/valgus eccentric loading using explicit FE. A patient-specific model of a proximal tibia was created from CT scan images, including heterogeneous bone properties. The proximal tibia was implanted with a commercial total knee replacement (TKR) model. The stance phase of gait was simulated and the applied loads and boundary conditions were based on those used for the Stanmore knee simulator. Eccentric loading was simulated. As well as examining the tibial bone strains (minimum and maximum principal strain), the kinematics of the bone-implant construct are also reported. The maximum anterior-posterior displacements and internal-external rotations were produced by the model with 20 mm offset. The peak minimum and maximum principal strain values increased as the load was shifted laterally, reaching a maximum magnitude for -20 mm offset. This suggests that when in varus, the load transferred to the bone is shifted medially, and as the bone supporting this load is stiffer, the resulting peak bone strains are lower than when the load is shifted laterally (valgus). For this particular patient, the TKR design analyzed produced the highest cancellous bone strains when in valgus. This study has provided an insight in the variations produced in bone strain distribution when the axial load is applied eccentrically. To the authors' knowledge, this is the first time that the bone strain distribution of a proximal implanted tibia has been examined, also accounting for the kinematics of the tibio-femoral joint as part of the simulation. This approach gives greater insight into the overall performance of TKR.
A new beam dump has been designed, built, installed and operated to withstand the future proton beam extracted from the proton synchrotron booster (PSB) in the framework of the LHC Injector Upgrade ...(LIU) Project at CERN. The future proton beam consists of up to1×1014 protons per pulse at 2 GeV and is foreseen after the machine upgrades planned for CERN’s Long Shutdown 2 (2019-2020). In order to be able to efficiently dissipate the heat deposited by the primary beam, the new dump was designed as a cylindrical block assembly, made out of a copper alloy and cooled by forced airflow. In order to determine the energy density distribution deposited by the beam in the dump, Monte Carlo simulations were performed using the fluka code, and thermomechanical analyses were carried out by importing the energy density into ANSYS. In addition, computational fluid dynamics (CFD) simulations of the airflow were performed in order to accurately estimate the heat transfer convection coefficient on the surface of the dump. This paper describes the design process, highlights the constraints and challenges of integrating a new dump for increased beam power into the existing facility and provides data on the operation of the dump.
An overview of the HIE-ISOLDE Design Study Catherall, R.; Augustin, M.; Babcock, C. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317
Journal Article
Recenzirano
•Design Study within the HIE-ISOLDE project.•Issues associated with an increase in energy and intensity of primary proton beam.•Secondary ion beam quality improvements.
The On-Line Isotope Mass ...Separator ISOLDE 1 is a facility dedicated to the production of a large variety of radioactive ion beams (RIB) for a great number of different experiments. Over 1000 radioactive nuclides from 70 elements can be produced in thick high-temperature targets via spallation, fission or fragmentation reactions with the PS-Booster pulsed proton-beam. With the arrival of CERN’s new linear accelerator Linac 4 2,3, ISOLDE will have the possibility to exploit a factor of 3 increase in proton-beam intensity and a possible proton-beam energy increase from 1.4GeV to 2GeV 4.
After 20years of successful ISOLDE operation at the PS-Booster, a major upgrade of the facility, the HIE-ISOLDE (High Intensity and Energy ISOLDE) project was launched in 2010. It is divided into three parts; a staged upgrade of the REX post-accelerator to increase the beam energy from 3.3MeV/u to 10MeV/u using a super-conducting Linac, an evaluation of the critical issues associated with an increase in proton-beam intensity and a machine design for an improvement in RIB quality. The latter two will be addressed within the HIE-ISOLDE Design Study. This paper gives an overview of the Design Study and will outline the critical issues to be addressed concerning the intensity upgrade and will propose solutions and improvements to be implemented. It will also give an insight to the propositions being studied in order to improve secondary beam characteristics essential to accomplish a more demanding physics program.
Abstract
Beam Intercepting Devices (BIDs) are essential protection elements for the operation of the Large Hadron Collider (LHC) complex. The LHC internal beam dump (LHC Target Dump Injection or LHC ...TDI) is the main protection BID of the LHC injection system; its main function is to protect LHC equipment in the event of a malfunction of the injection kicker magnets during beam transfer from the SPS to the LHC. Several issues with the TDI were encountered during LHC operation, most of them due to outgassing from its core components induced by electron cloud effects, which led to limitations of the injector intensity and hence had an impact on LHC availability. The absorbing cores of the TDIs, and of beam intercepting devices in general, need to deal with high thermo-mechanical loads induced by the high intensity particle beams. In addition, devices such as the TDI — where the absorbing materials are installed close to the beam, are important contributors to the accelerator impedance budget. To reduce impedance, the absorbing materials that make up the core must be typically coated with high electrical conductivity metals. Beam impact testing of the coated absorbers is a crucial element of development work to ensure their correct operation.
In the work covered by this paper, the behaviour of several metal-coated absorber materials was investigated when exposed to high intensity and high energy proton beams in the HiRadMat facility at CERN. Different coating configurations based on copper and molybdenum, and absorbing materials such as isostatic graphite, Carbon Fibre Composite (CfC) and Silicon Carbide reinforced with Silicon Carbide fibres (SiC-SiC), were tested in the facility to assess the TDI's performance and to extract information for other BIDs using these materials. In addition to beam impact tests and an extensive Post Irradiation Examination (PIE) campaign to assess the performance of the coatings and the structural integrity of the substrates, extensive numerical simulations were carried out.
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.
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