Proton irradiation effects in Molybdenum-Carbide-Graphite composites

Abstract The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) has prompted the investigation of novel materials for beam-intercepting devices, and in particular for the collimators responsible for protecting the machine from beam losses. The HL-LHC collimation system will inevitably experience increased levels of radiation damage and undergo changes in their crucial physio-mechanical properties. Graphite-matrix composite materials containing molybdenum carbide particles, along with small amounts of titanium carbide, were developed with the objective of enhanced in-beam performance and tested under proton irradiation. The physical degradation observed in early grades of molybdenum carbide compounds, even after modest proton fluences, has prompted the development of advanced compounds. In this work, we examine the effects of proton irradiation on the microstructural and thermophysical properties of new grades of Molybdenum-carbide-graphite compounds up to fluences of ~2 × 1020 p/cm2. We employ a combination of precision dilatometry and high-energy X-ray diffraction to quantify the dimensional stability and crystallographic phase evolution both pre- and post-irradiation. Our results reveal that these new compounds exhibit superior resilience to radiation damage than their predecessors.