Novel LHC collimator materials: High-energy Hadron beam impact tests and nondestructive postirradiation examination

Abstract

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 the composites, tested under intense proton beam impacts at the CERN HiRadMat facility. Metrology measurements, computed tomography, and 3D topography allowed to evaluate the localized spallation induced by the beam. This article provides an overview of the thermophysical characterization of the two composites before irradiation and nondestructive postirradiation results.

Dynamic Response of Advanced Materials Impacted by Particle Beams: The MultiMat Experiment

“…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.…”

“…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.…”

“…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.…”

Accelerator Engineering and Technology: Accelerator Technology

“…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).…”

Dynamic Response of Graphitic Targets with Tantalum Cores Impacted by Pulsed 440‐GeV Proton Beams

“…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.…”