The "Multimat" experiment at CERN HiRadMat facility: advanced testing of novel materials and instrumentation for HL-LHC collimators

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

Design, construction, and beam tests of a rotatable collimator prototype for high-intensity and high-energy hadron accelerators

A rotatable-jaw collimator design was conceived as a solution to recover from catastrophic beam impacts which would damage a collimator at the Large Hadron Collider (LHC) or its High-Luminosity upgrade (HL-LHC). One such rotatable collimator prototype was designed and built at SLAC and delivered to CERN for tests with LHC-type circulating beams in the Super Proton Synchrotron (SPS). This was followed by destructive tests at the dedicated High Radiation to Materials (HiRadMat) facility to validate the design and rotation functionality. An overview of the collimator design, together with results from tests without and with beam are presented

FIRST RESULTS OF AN EXPERIMENT ON ADVANCED COLLIMATOR MATERIALS AT CERN HIRADMAT FACILITY

A comprehensive, first-of-its-kind experiment (HRMT-14) has been recently carried out at CERN HiRadMat facility on six different materials of interest for Beam Intercepting Devices (collimators, targets, dumps). Both traditional materials (Mo, W and Cu alloys) as well as advanced metal/diamond and metal/graphite composites were tested under extreme conditions as to pressure, density and temperature, leading to the development of highly dynamic phenomena as shock-waves, spallation, explosions. Experimental data were acquired, mostly in real time, relying on extensive integrated instrumentation (strain gauges, temperature and vacuum sensors) and on remote acquisition devices (laser Doppler vibrometer and high-speed camera). The experiment was a success under all points of view in spite of the technological challenges and harsh environment. First measurements are in good agreement with results of complex simulations, confirming the effectiveness of the acquisition system and the reliability of advanced numerical methods when material constitutive models are completely available. Valuable information has been collected as to thermalshock robustness of tested materials

Investigation on AlN epitaxial growth and related etching phenomenon at high temperature using high temperature chemical vapor deposition process.

International audienceThick MN layers were grown by high temperature chemical vapor deposition (HTCVD) on 8 degrees off-axis (0 0 0 1) 4H-SiC, on-axis (0 0 0 1) 6H-SiC and on-axis (0 0 0 1) AlN templates between 900 degrees C and 1600 degrees C. The experimental set-up consists of a vertical cold-wall reactor working at low pressure in which the reactions take place on a graphite susceptor heated by induction. The reactants used are ammonia (NH(3)) and aluminum chlorides (AlCl(x)) species in situ formed via Cl(2) reaction with high purity aluminum wire. As-grown AlN layers have been characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Optical Profilometry, Atomic Force Microscopy (AFM) and Raman spectroscopy. In this study, the influence of the deposition temperature and the N/Al ratio in the gas phase is studied in order to stabilize epitaxial growth. The epitaxy on AlN template is favored using a low N/Al ratio in the gas phase and a high temperature above 1400 degrees C. The crystalline quality of epitaxial AlN layers is found to increase with increasing deposition temperature from 1400 to 1500 degrees C. Growth rates up to 14 mu m h(-1) have been reached for epitaxial AlN layers. An important etching phenomenon is also observed at high temperature: apparition of pin holes certainly around threading dislocations at 1400-1500 degrees C and substrate etching at 1600 degrees C. (C) 2011 Elsevier B.V. All rights reserved

Undoped TiO2 and nitrogen-doped TiO2 thin films deposited by atomic layer deposition on planar and architectured surfaces for photovoltaic applications

International audienceUndoped and nitrogen doped TiO2 thin films were deposited by atomic layer deposition on planar substrates. Deposition on 3D-architecture substrates made of metallic foams was also investigated to propose architectured photovoltaic stack fabrication. All the films were deposited at 265 degrees C and nitrogen incorporation was achieved by using titanium isopropoxide, NH3 and/or N2O as precursors. The maximum nitrogen incorporation level obtained in this study was 2.9 at. %, resulting in films exhibiting a resistivity of 115 Omega cm (+/-10 Omega cm) combined with an average total transmittance of 60% in the 400-1000 nm wavelength range. Eventually, TiO2 thin films were deposited on the 3D metallic foam template

Developments of TaN ALD Process for 3D Conformal Coatings

International audienceThere is a growing interest in producing tantalum nitride (TaN) thin films for various industrial applications. For example, in microelectronics, the development of IC technology is driven by the need to increase both performance and functionality while reducing power and cost. This goal can be achieved by several solutions among which the introduction of architecture enhancements such as 3D integration. The most challenging step is the deposition of a conformal, continuous, and adherent diffusion barrier. In this work, atomic layer deposition (ALD) of TaN thin films is explored using the combination between the thermodynamical behavior of the precursor, mass transfer in the reactor, and the operating conditions. TaN thin film deposition on very complex shape substrates, such as nanodots, TSV, silicon nanowires, and carbon nanotubes, has been evaluated