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Flatness measurement on CuCD block 5 (left), picture of the block (right). The white arrows highlight the trace of the beam.
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The LHC collimation system must adopt materials with excellent thermal shock resistance, high electrical conductivity, geometrical stability, and radiation hardness. Two novel composites, Molybdenum–Carbide–Graphite and Copper–Diamond, are proposed for the LHC collimation upgrade. A postirradiation examination was performed to assess the status of...
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... measurements were performed in the metrology lab at CERN with the optical machine ZEISS O- INSPECT 863. Figure 7 shows an example of the results obtained on the fifth block, the most damaged. As visible, the effect of the beam is quite evident on the middle part of block, between ±5 mm from the central axis, where all the pulses focused. ...
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... the maximum value of the total energy do not coincide perfectly with the maximum measured flat- ness variation. Although the cumulative damage induced during the experiment in the CuCD jaw is significant as seen in Figure 7, the functioning of the collimator could be guaran- teed thanks to the 5th axis. By moving vertically the jaw of ±10 mm from the damaged area, it would be possible to expose to the beam a fresh surface of the absorber with Other interesting measurements were carried out to quantify dimension and position of the localized damages both on the free surface of each block and on the lateral faces. ...
Citations
... The area showing a change of color was analysed with the topography and no peel-off of the coating was observed, thus the mark is probably related to copper melting. These observations are in line with the findings of previous HiRadMat experiments [9][16] [17], where the same materials and similar loading conditions were tested. Thus, for TCSPM, on top of the LS2 solution, another option was validated: the Cu-coated graphite blocks with Cu-coated tapering. ...
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.
... Other important aspects concerned the evaluation of which quantities and properties it was possible or necessary to measure and which are the most suitable measuring systems to catch the evolution of the phenomena. The postprocessing phases of many of those experiments are still in progress, in continuous development, and under evaluation to setup new experiments [27,[47][48][49]. ...
The investigation of wave propagation in solids requires the development of reliable methods for the prediction of such dynamic events in which the involved materials cover wide ranges of different possible states, governed by plasticity, equation of state, and failure. In the present study, the wave propagation in metals generated by the interaction of high-energy proton beams with solids was considered. In this condition, axisymmetric waves were generated, and, depending on the amount of the delivered energy, different regimes (elastic, plastic, or shock) can be reached. Nonlinear numerical analyses were performed to investigate the material response. The starting point was the energy map delivered into the component as the consequence of the beam impact. The evolution of both hydrodynamic and mechanical quantities was followed starting from the impact and the effects induced on the hit component were investigated. The results showed the portion of the component close to the beam experiences pressure and temperature increase during the deposition phase. The remaining part of the component is traversed by the generated shockwave, which induces high values of strain in a short time or even the failure of the component.
... Regarding collimator composition, advanced carbonbased materials such as copper diamond [55,56], carbon fiber [57], and carbon composites [58] may offer better performance than other low-Z, low-density materials such as aluminum. We were given a sample of molybdenum carbide graphite (MoGr) [58] by colleagues at the CERN LHC in September 2019. ...
The Advanced Photon Source (APS) team is building a fourth-generation storage ring (4GSR), replacing the present double-bend achromat lattice with a multibend achromat system thereby allowing the production of ultrabright x-ray beams. The new lattice enables a 2-order-of-magnitude reduction in horizontal beam emittance and a factor of two increase in beam current. The result is an electron beam of very high energy and power densities. Initial predictions suggest many common ultrahigh-vacuum-compatible materials struck by the full-intensity electron beam will be damaged. Two experimental beam abort studies have been conducted on collimator test pieces in the present APS SR to inform the design of a fully-functional machine protection system for APS 4GSR operations at 200 mA. A comprehensive suite of diagnostics was utilized during the studies. The diagnostics used in these experiments are not new, but employed in different ways to obtain unique data sets. With these sets now in hand, we are developing new numerical tools to guide collimator design using pelegant [M. Borland, elegant: A flexible SDDS-compliant code for accelerator simulation, Technical Report No. LS-287, Advanced Photon Source, 2000; Y. Wang and M. Borland, Implementation and performance of parallelized elegant, in Proceedings of the 2007 Particle Accelerator Conference, http://cern.ch/AccelConf/p07/PAPERS/THPAN095.PDF, pp. 3444–3446], mars [N. V. Mokhov and S. I. Striganov, Fermilab-conf-07/008-ad, AIP Conf. Proc. 896, 50 (2007)], and flash [B. Fryxell et al., flash: An adaptive mesh hydrodynamics code for modeling astrophysical thermonuclear flashes, Astrophys. J. Suppl. Ser. 131, 273 (2000)APJSA21538-436510.1086/317361; P. Tzeferacos et al., Laboratory evidence of dynamo amplification of magnetic fields in a turbulent plasma, Nat. Commun. 9, 591 (2018)NCAOBW2041-1723].
... For example, the HL-LHC upgrade is going to double the energy stored in the particle beam [12], and hence the C-C carbon composite actually used in the primary and secondary collimators will be limiting the capacities of the LHC [13]. In this challenging context, the CERN has launched a significative R&D program to search for novel materials with the purpose of taking advantage of the mechanical and thermal properties of graphite matrices [14][15][16] and comparing them with some adopted high temperature resistance metals [17][18][19][20][21]. In the last years, the materials that might be exposed to particle beams irradiation, which are usually referred to as Beam Intercepting Devices (BID), have been routinely tested in dedicated facilities such as the HiRadMat [22,23]. ...
The development of particle accelerators with ever increasing energies is raising the standards of the structures which could interact with the particle beams. These structures could be subjected to strong shockwaves in accidental scenarios. In order to test materials in such conditions, one of the most promising techniques is the impact with high-power lasers. In view of the setting up of future experimental campaigns within the Petawatt High-Energy Laser for Heavy Ion Experiments (PHELIX), the present work aims at the development of a numerical approach for the simulation of graphite impacted by laser beams. In particular, the focus is on the spallation damage caused by shockwave reflection: a sufficiently intense laser beam could ablate the matter until plasma conditions, hence producing a shockwave which could travel inside the material and reach a free surface. A numerical model to properly describe the spall fragmentation of graphite has been calibrated on the basis of literature-available experimental data. The numerical approach is a 'two-step' procedure: the first step is the definition of the laser-matter interaction and the second one concerns the description of the shockwave evolution into matter. The simulations satisfactorily reproduce the dynamic response of graphite impacted by two different laser sources with various intensities, despite the difficulties of characterising a phenomenon which is extremely fast and chaotic.
... Furthermore, the large variations in density, the sensitivity to micro-and mesostructure, and the brittleness of graphite make numerical simulations unreliable for the identification of failure limits. In this context, irradiation experiments were already conducted to assess the performance of implicit and explicit numerical models with respect to prototype BIDs [11,12]. But, catastrophic failure of graphite materials by beam-induced dynamic mechanical loads has yet to be observed. ...
... Simulation of Sample #1 SGL R6650 at 1 × 10 11 ppp. ...
Various graphite targets with a tantalum core were exposed to 440 GeV pulsed proton beams at the HiRadMat facility at CERN. The dynamic response was investigated by monitoring the surface velocity of the samples by laser Doppler vibrometry. The study comprises different graphite grades, such as polycrystalline, expanded and carbon-fiber reinforced graphite, and low-density graphitic foams, all candidates for beam-intercepting devices in high-power accelerators. The purpose of the tantalum core is to concentrate the large energy deposition in this high-density material that withstands the localized beam-induced temperature spike. The generated pressure waves are estimated to result in stresses of several hundred MPa which subsequently couple with the surrounding graphite materials where they are damped. Spatial energy deposition profiles were obtained by the Monte Carlo code FLUKA and the dynamic response was modelled using the implicit code ANSYS. Using advanced post-processing techniques, such as fast Fourier transformation and continuous wavelet transformation, different pressure wave components are identified and their contribution to the overall dynamic response of a two-body target and their failure mode are discussed. We show that selected low-intensity beam impacts can be simulated using straight-forward transient coupled thermal/structural implicit simulations. Carbon-fiber reinforced graphites exhibit large (macroscopic) mechanical strength, while their low-strength graphite matrix is identified as a potential source of failure. The dynamic response of low-density graphitic foams is surprisingly favourable, indicating promising properties for the application as high-power beam dump material.
... e instrumentation system described in this paper was designed and built for the HRMT-14 experiment, performed in 2012. anks to its very good performance, it was then used as the cornerstone also for other successive experiments, such as HRMT-23 "Jaws" [12] and HRMT-36 "Multimat" [13]. e HRMT-14 2 Shock and Vibration experimental setup consisted of a multimaterial sample holder allowing to test six different materials under hadron beams of different intensity (from 1 × 10 11 to 3 × 10 13 protons) at the energy of 440 GeV. e test-bench was designed and equipped in order to measure in real-time physical quantities necessary to reconstruct the material models, such as axial and hoop strains, radial velocity, and temperature. ...
... e HRMT-14 test also highlighted the strong electromagnetic coupling between the strain gauges and the particle beam, which typically lasts about 20 µs, hindering the first wave signal in the measurement. In successive HiRadMat experiments, such as for example HRMT-23 "Jaws" [12], optical fibres were added to the instrumentation system. In fact, optical fibres are immune to electromagnetic effects, as it has been also confirmed by recent works in harsh environments such as mercury target experiments [30]. ...
In recent years, significant efforts were taken at CERN and other high-energy physics laboratories to study and predict the consequences of particle beam impacts on devices such as collimators, targets, and dumps. The quasi-instantaneous beam impact raises complex dynamic phenomena which may be simulated resorting to implicit codes, for what concerns the elastic or elastoplastic solid regime. However, when the velocity of the produced stress waves surpasses the speed of sound and we enter into the shock regime, highly nonlinear numerical tools, called Hydrocodes, are usually necessary. Such codes, adopting very extensive equations of state, are also able to well reproduce events such as changes of phase, spallation, and explosion of the target. In order to derive or validate constitutive numerical models, experiments were performed in the past years at CERN HiRadMat facility. This work describes the acquisition system appositely developed for such experiments, whose main goal is to verify, mostly in real time, the response of matter when impacted by highly energetic proton beams. Specific focus is given to one of the most comprehensive testing campaigns, named “HRMT-14.” In this experiment, energy densities with peaks up to 20 kJ/cm³ were achieved on targets of different materials (metallic alloys, graphite, and diamond composites), by means of power pulses with a population up to 3 × 1013 p at 450 GeV. The acquisition relied on embarked instrumentation (strain gauges, temperature probes, and vacuum sensors) and on remote acquisition devices (laser Doppler vibrometer and high-speed camera). Several studies have been performed to verify the dynamic behaviour of the standard strain gauges and the related cabling in the chosen range of acquisition frequency (few MHz). The strain gauge measurements were complemented by velocity measurements performed using a customised long-range laser Doppler vibrometer (LDV) operating in the amplitude range of 24 m/s; the LDV, together with the high-speed video camera (HSVC), has been placed at a distance of 40 m from the target to minimize radiation damage. In addition, due to the large number of measuring points, a radiation-hard multiplexer switch has been used during the experiment: this system was designed to fulfil the multiple requirements in terms of bandwidth, contact resistances, high channel reduction, and radiation resistance. Shockwave measurements and intense proton pulse effects on the instrumentation are described, and a brief overlook of the comparison of the results of the acquisition devices with simulations, performed with the finite element tool Autodyn, is given. Generally, the main goal of such experiments is to benchmark and improve material models adopted on the tested materials in explicit simulations of particle beam impact, a design scenario in particle accelerators, performed by means of Autodyn. Simulations based on simplified strain-dependent models, such as Johnson–Cook, are run prior to the experiment. The model parameters are then updated in order to fit the experimental response, under a number of load cases to ensure repeatability of the model. This paper, on the other hand, mostly focuses on the development of the DAQ for HiRadMat experiments, and in particular for HRMT-14. Such development, together with the test design and run, as well as postmortem examination, spanned over two years, and its fundamental results, mostly in terms of dedicated instrumentation, have been used in all successive HiRadMat experiments as of 2014. This experimental method can also find applications for materials undergoing similarly high strain rates and temperature changes (up to 106 s-1 and 10.000 K, respectively), for example, in the case of experiments involving fast and intense loadings on materials and structures.
1. Introduction
The introduction in past years of extremely energetic particle accelerators such as the Large Hadron Collider (LHC) [1] brought about the need for advanced cleaning and protection systems in order to safely increase the energy and intensity of particle beams to unprecedented levels [2]. A key element of the cleaning and protection system is constituted by collimators [3], which are designed to intercept and absorb beam particles and to shield other components from the catastrophic consequences of beam orbit errors [4]. Furthermore, recent ambitious programs for the development of accelerator facilities aimed at the massive production of elusive particles, such as neutrinos or muons, relying on target systems submitted to the impact of proton beams at unprecedented intensities (impact power up to 5 MW) [5]. Therefore, it is paramount to assess the response to such potentially destructive events of materials presently used, or being developed for future use, in collimators and other beam intercepting devices (targets, dumps, absorbers, spoilers, windows, etc.).
1.1. Physical Phenomenon and Numerical Simulations
Complex numerical methods have been developed in the last years to study dynamic phenomena, such as phase transitions, density changes, shockwave propagation, explosions, and fragment projections, generated in matter when it is impacted by highly energetic particle beams. These effects, triggered by the thermomechanical load acting on the target, completely hinder second-order effects such as radiation damage which, for single particle beam pulses, are associated to a negligible amount of displacements per atom (dpa) [6]. Unfortunately, material models required to perform such simulations, at the extreme conditions as to temperature, pressure, and density induced by beam impacts, are hardly available in the scientific literature; besides, most of the existing information is often classified as it is drawn from military research. Finally, very few data can be found for nonconventional alloys and compounds. Figure 1 shows an example of numerical simulation of particle beam impact on an LHC collimator, performed with the explicit tool Autodyn. The simulation is compared with an experimental result observed at the CERN HiRadMat facility [8].
(a)
... Reviews of recent developments that are already being implemented for the upgrade of the LHC can be found in [236]. Promising results were achieved recently that identified valid solutions for a new generation of secondary collimators for the HL-LHC made of a novel Molybdenum-Graphite composite [274], possibly Mo-coated, as well as for metallic composites suitable for tertiary collimators, but about 15 times more robust against beam impact than the tungsten alloy used presently at the LHC [275,276] (Fig. 8.90). Z X p + Y 1 m graphite block Fig. 8.90 Example of an energy deposition result as obtained with FLUKA [258,262]. ...
Magnets are at the core of both circular and linear accelerators. The main function of a magnet is to guide the charged particle beam by virtue of the Lorentz force, given by the following expression:where q is the electrical charge of the particle, v its velocity, and B the magnetic field induction. The trajectory of a particle in the field depends hence on the particle velocity and on the space distribution of the field. The simplest case is that of a uniform magnetic field with a single component and velocity v normal to it, in which case the particle trajectory is a circle. A uniform field has thus a pure bending effect on a charged particle, and the magnet that generates it is generally referred to as a dipole.
... In order to validate the mechanical design and the material choices, two experiments were performed in 2015 and 2017 at CERN HiRadMat facility [7]. During the first experiment, named "Jaws" [8], two full scale HL LHC collimator jaws in MoGr and CuCD were built, largely instrumented and installed in a vacuum chamber together with a standard LHC collimator in CFC ( Figure 2). The test aimed at assessing the thermomechanical response under beam impact of the key elements such as absorbing blocks, taperings, BPMs and cooling circuit. ...
... This is possible thanks to the so called 5 th axis, which can be activated in a collimator in case of accidental impact during operation. Comparing this result with those observed on a standard tertiary collimator during HiRadMat tests in 2013 [13], a factor ~14 of increase in robustness, when moving from Inermet180 to CuCD, could be estimated [8]. ...
... This is a result of the multiple impacts at or above the design scenario. Assuming a linear contribution of each pulse above thresholds, the jaw deflection provoked by one pulse at nominal design intensity is estimated in 5 to 15 µm [8]. ...
Two new absorbing materials were developed as collimator inserts to fulfil the requirements of HL-LHC higher brightness beams: molybdenum-carbide graphite (MoGr) and copper-diamond (CuCD). These materials were tested under intense beam impacts at CERN HiRadMat facility in 2015, when full jaw prototypes were irradiated. Additional tests in HiRadMat were performed in 2017 on another series of material samples, including also improved grades of MoGr and CuCD, and different coating solutions. This paper summarizes the main results of the two experiments, with a main focus on the behaviour of the novel composite blocks, the metallic housing, as well as the cooling circuit. The experimental campaign confirmed the final choice for the materials and the design solutions for HL-LHC collimators, and constituted a unique chance of benchmarking numerical models. In particular, the tests validated the selection of MoGr for primary and secondary collimators, and CuCD as a valid solution for robust tertiary collimators.
... Results confirmed the precision of the numerical results when the material models match reasonably well the extreme conditions induced by particle beam impacts [15,16]. In 2015, the HRMT23 (also named "Jaws") [17] experiment validated the design of the jaws made of novel metal-diamond and ceramic-graphite composites designed for HL-LHC collimators, achieving energy densities exceeding those expected for HL-LHC. In 2017, the HRMT21 experiment saw the testing of a low-impedance secondary collimator featuring a faceted rotatable jaw [18], made of a dispersion-strengthened copper, with 20 collimating surfaces to be successively used in case of beam damage. ...
... One of the main elements of novelty of MultiMat with respect to previous experiments was the adoption of slender rods as targets for the beam impacts. This was meant to allow reaching values of deposited energy per cross-section exceeding those achieved in impacts on full collimators jaws [5,9,17,18] or on targets featuring larger cross-sections [11], in spite of the lower pulse intensity. In fact, the total amount of energy deposited over a cross-section is, as it will be shown, a key driver of the material response. ...
... This second scenario entails less energy on the target than the BIE. In Table 5, the parameters of the HL-LHC accidental scenarios and those of another experiment, HRMT23 [17], are reported. The HL-LHC scenarios leads to the most intense peaks of energy density U max in bare materials, while with grazing pulses, with a smaller σ of 0.25 mm, even higher U max values were achieved in MultiMat. ...
The introduction at CERN of new extremely energetic particle accelerators, such as the high-luminosity large hadron collider (HL-LHC) or the proposed future circular collider (FCC), will increase the energy stored in the circulating particle beams by almost a factor of two (from 360 to 680 MJ) and of more than 20 (up to 8500 MJ), respectively. In this scenario, it is paramount to assess the dynamic thermomechanical response of materials presently used, or being developed for future use, in beam intercepting devices (such as collimators, targets, dumps, absorbers, spoilers, windows, etc.) exposed to potentially destructive events caused by the impact of energetic particle beams. For this reason, a new HiRadMat experiment, named “MultiMat”, was carried out in October 2017, with the goal of assessing the behaviour of samples exposed to high-intensity, high-energy proton pulses, made of a broad range of materials relevant for collimators and beam intercepting devices, thin-film coatings and advanced equipment. This paper describes the experiment and its main results, collected online thanks to an extensive acquisition system and after the irradiation by non-destructive examination, as well as the numerical simulations performed to benchmark experimental data and extend materials constitutive models.
The Large Hadron Collider (LHC) Long Shutdown 2 (2019–2021), following LHC Run 2, was primarily dedicated to the upgrade of the LHC Injectors but it included also a significant amount of activities aimed at consolidation of the LHC machine components, removal of known limitations and initial upgrades in view of the High-Luminosity LHC (HL-LHC) to favour the intensity ramp-up during Run 3 (2022–2025). An overview of the major modifications to the accelerator and its systems is followed by a summary of the results of the superconducting magnet training campaign to increase the LHC operation energy beyond the maximum value of 6.5 TeV reached during Run 2. The LHC configuration and the scenarios for proton and ion operation for Run 3 are presented considering the expected performance of the upgraded LHC Injectors and the proton beam intensity limitations resulting from the heat load on the cryogenic system due to beam-induced electron cloud and impedance.
