There is a global consensus among materials scientists and engineers that thequalification of materials in an appropriate test environment isindispensable for the design, construction and safe operation ofdemonstration fusion reactors as well as for the calibration of data generated from fission reactor and accelerator irradiations. In anevaluation process based on a series of technical workshops it wasconcluded that an accelerator driven D-Li stripping source would bethe best choice to fulfil the requirements within a realistic timeframe. In response to this need, an international design team withmembers from the European Union, Japan, the United States of America and the Russian Federation has developed, under theauspices of the International Energy Agency during a conceptual design activity phase(1994-1996), a suitable and feasible concept for an accelerator drivenD-Li stripping source. This reference design for the InternationalFusion Materials Irradiation Facility (IFMIF) is based onconservative linac technology and two parallel operating 125 mA,40 MeV deuteron beams that are focused onto a common liquid Litarget with a beam footprint of 50 mm by 200 mm. The materialstesting volume behind the Li target is subdivided into different fluxregions: the high flux test region (0.5 L, 20-55 dpa/full poweryear), the medium flux test region (6 L, 1-20 dpa/full power year), and the lowflux test region (>100 L, <1 dpa/full power year). The design developed was the basis for the conceptual design evaluation phase(1997-1998) and for subsequent engineering oriented activities. On the basis ofcomprehensive neutron transport calculations, an evaluation of theirradiation parameters and the available testing volumes has shown thatthe users' requirements can be fulfilled. Major engineering effortshave been undertaken to establish an IFMIF design that is based onavailable and already proven technologies. The design developedis based on extensive reliability, availability, maintainability andsafety studies and is conceived for long term operation with atotal annual facility availability of at least 70%.