Comparative analysis of neutronic features for various specimen payload configurations within the IFMIF-DONES HFTM

The International Fusion Materials Irradiation Facility- DEMO Oriented NEutron Source (IFMIF-DONES) facility is a neutron irradiation facility specifically designed to obtain data on material irradiation for the construction of DEMO (DEMOstration) fusion power plant. The purpose of this study is to investigate and compare the effects of using different realistic models of specimen distribution during the irradiation campaign in the High Flux Test Module (HFTM) in IFMIF-DONES. Parameters such as neutron fluence rate, primary displacement damage rate and gas production have been calculated for two beam footprint sizes: the standard 20×5 cm² and the reduced 10×5 cm². The standard deuteron beam energy is 40 MeV with a current of 125 mA, but other energy values such as 25, 30 and 35 MeV have also been considered to evaluate their impact on the irradiation parameters. As the idea is to reproduce the DEMO conditions, some neutron spectra in the first wall of the DCLL, WCLL and HCPB have also been evaluated to gather reference data and compare the environments of DEMO and IFMIF-DONES. The level of packaging of the specimens impacts directly the neutron fluence rate behaviour and the different specimen distribution models give rise to different primary displacement damage rate distributions, demonstrating their versatility to meet specific needs. With respect to the comparison DEMO values, IFMIF-DONES meets the requirements of primary displacement damage rate and gas production at different beam energies. This study emphasises the essential role of sample distribution in improving the accuracy of measurements made at the IFMIF-DONES facility.