Abstract
The increase of the stored beam energy in future particle accelerators, such as the HL-LHC and the FCC, calls for a radical upgrade in the design, materials and instrumentation of Beam Intercepting Devices (BID), such as collimators Following successful tests in 2015 that validated new composite materials and a novel jaw design conceived for the HL-LHC collimators, a new HiRadMat experiment, named “HRMT36-MultiMat”, is scheduled for autumn 2017. Its objective is to determine the behaviour under high intensity proton beams of a broad range of materials relevant for collimators and beam intercepting devices, thin-film coatings and advanced equipment. The test bench features 16 separate target stations, each hosting various specimens, allowing the exploration of complex phenomena such as dynamic strength, internal damping, nonlinearities due to anisotropic inelasticity and inhomogeneity, effects of energy deposition and radiation on coatings. This paper details the main technical solutions and engineering calculations for the design of the test bench and of the specimens, the candidate target materials and the instrumentation system.
Highlights
TO THE EXPERIMENTIn the years, the HL-LHC upgrade [1] will increase the energy stored in LHC circulating beams by almost a factor of two
Among the components interacting with the particle beam, the collimators, which are used for beam cleaning and machine protection, are exposed to risks of accidental beam impacts, for example in the case of asynchronous dump or injection error
In 2012, an experiment run in the HiRadMat facility allowed deriving the threshold of damage for tungsten tertiary collimators [6]
Summary
The HL-LHC upgrade [1] will increase the energy stored in LHC circulating beams by almost a factor of two (from 360 to 680 MJ). A new experiment of this kind, named Multimat, is under preparation for tests in autumn 2017 in HiRadMat. The experiment profits of the experience of HRMT14, aiming at testing at HL-LHC energy densities new collimator materials and coatings developed in recent years [14], in addition to novel instrumentation devices for the monitoring and correction of jaw distortion, under design for HL-LHC and FCC. The actuation is currently based on piezo-actuators with a rise time in the order of μs, which is the period of flexural oscillations induced on the collimator jaw in case of beam impact. As similar studies for thermal-induced stress waves are scarce in literature, an analytical model not accounting for radial inertia and a numerical one, including radial dispersive components, material nonlinearities, boundary effects, as Figure 6: Flexural waves under off-centre impact on graphite targets: analytical (left), numerical model (right). To the authors’ knowledge, no dynamic model exists to predict the behaviour under beam impact of thin coatings, here adopted to increase the material electrical conductivity
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