Ponente
Descripción
Fine- and medium-grained nuclear grade graphite materials have been used as low-Z secondary particle production targets in large-scale neutrino experiments. Irradiation induced dimensional change as well as thermo-mechanical changes in these materials have been identified as a limiting factor in their lifetime. Therefore, it is essential to develop a mechanistic understanding of irradiation damage and its correlation with bulk properties to inform future target material selection. This sets the horizon of this PhD work. Specifically, a set of preliminary neutron diffraction measurements at the ENGINX beamline (ISIS Neutron & Muon Source) have been carried out on an ex-service unfractured NT02 POCO-ZXF5Q to acquire the distribution of strains as a function of irradiation damage. The position and broadening of the basal plane diffraction peaks have been analysed and will be reported. A follow-up experiment has been planned to collect spectra with better signal to noise ratio and to investigate areas away from the proton beam centre, i.e., subject to less beam damage. In addition, for accelerated irradiation experiment on next generation graphite target materials, He+ ion irradiation capabilities have been identified at Surrey Ion Beam Centre. HOPG, POCO, together with IG510U, IG430U, IG110 and G347A will be irradiated with 2 MeV He+ at 500oC for three fluences: 4.5×1017 ions/cm2, 7.5×1016 ions/cm2 and 2.3×1016 ions/cm2. These materials will subsequently be studied by Transmission electron microscopy (TEM), nanoindentation and Time-domain Thermo-reflectance (TDTR); the results will be correlated with Raman and XRD measurements of crystalline differences between irradiated and unirradiated graphite.
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