Flexible graphite as beam dumping material in the TDE blocks of the Large Hadron Collider

The Large Hadron Collider (LHC) is a high energy particle collider at the European Laboratory for Particle Physics (CERN) in Geneva, Switzerland. The LHC Beam Dumping System (LBDS) is composed by different equipment employed to extract and absorb the LHC circulating beam in case of need. At the end of the LBDS resides the LHC main dump (so called TDE, which stands for Target Dump External). The TDE block is constituted by several graphite blocks with different densities enclosed in a 318L stainless steel jacket. Among the different type of carbon-based materials, the flexible graphite is the one owning the lowest density (1-1.2 g/cm3). It differs from typical graphite forms such as polycrystalline and pyrolytic graphite in that no binder is added during the production process. The bonding frictional forces due to particle asperities give the typical flexibility to the material and contribute to the deformation mechanism. In order to predict the thermo-mechanical response to the proton beam-induced sudden energy deposition, the material behavior needs to be investigated in-depth in a wide range of temperature and strain-rates. In this preliminary work, the static properties of a commercial flexible graphite (Sigraflex® from SGL Carbon) have been observed at room temperature in the in-plane direction. Two sides DIC technique has been employed in order to get a reliable measurement of the strain on both front and edge specimen surfaces; the crosshead displacement-rate was varied between 0.01-10 mm/min. Finally, a discussion about the stress-strain behavior and the deformation mechanism has been given.