The International Fusion Materials Irradiation Facility – Demo Oriented NEutron Source (IFMIF-DONES) is a single-sited Research Infrastructure for testing, validation and qualification of the materials to be used in future fusion power plants like DEMO (a demonstration fusion reactor prototype). It is based on a unique neutron source with an energy spectrum centred on 14 MeV, typical of fusion reactions. IFMIF-DONES will be a major step towards IFMIF as it will develop a unique high-current high-duty cycle accelerator technology, liquid metal target technology and advanced control systems. Being the central element of the DONES Programme, IFMIF-DONES therefore aims to test and qualify the materials needed for the construction of fusion reactors, and to establish an extensive database on fusion materials. Besides, the facility will also offer unique experimental opportunities in other scientific and technology areas including nuclear physics, astrophysics, medical and industrial applications. For this reason, the DONES user community, encompassing scientists and engineers representing both fusion and non-fusion experiments was created as an international scientific community involved in the design, preparation and execution of scientific activities at the DONES facility, as well as the exploitation of the results obtained in all relevant areas of science and industrial applications. The mission of IFMIF-DONES is to provide a neutron source producing high energy neutrons at sufficient intensity and irradiation volume in order to: Generate materials irradiation test data for design, licensing, construction and safe operation of DEMO, under simulated fusion environment relevant to anticipated needs in radiation resistance for the structural materials in early DEMO; Generate a data base for benchmarking of radiation responses of materials hand in hand with computational material science; Develop a complementary experiments’ work Programme relevant for other scientific and technological areas. Additionally, given the fact that IFMIF-DONES will be available during ITER operation, the possibility that IFMIF-DONES could assist ITER in some aspects of its nuclear operation phase should not be disregarded. Furthermore, it has been identified that IFMIF-DONES may be relevant for other fusion-related technologies (e.g. tritium, breeding blanckets technologies,...). The mission of IFMIF-DONES is translated into the following technical objectives: Neutron spectrum: it should simulate the first wall neutron spectrum of early DEMO as closely as possible to provide the same nuclear response which affects the material behaviour under irradiation in terms of primary recoil spectrum (PKA), important transmutation reactions, and gas production (He, H). This implies the use of a D-Li stripping source. Neutron fluence accumulation in the high flux region: Fluences of 20 NRT dpa in <2.5 years applicable to a 0.3 litre volume and Fluences of 50 NRT dpa in <3 years applicable to a 0.1 litre volume. Temperature range: the high flux region needs to be equipped with temperature controlled test modules that can cover the temperature ranges from at least 250 to 550 °C. Dpa and temperature gradients in high flux region: Over a gauge volume corresponding to standardized miniaturized specimens: dpa gradient <15% and temperature gradient within ±3% with long time stability in the same order. Simultaneous irradiation of several irradiation modules must be feasible.