Status of the Spallation Neutron Source with focus on target materials

Abstract

An overview of the design and construction of the Spallation Neutron Source (SNS) is presented. Key facility performance parameters are summarized and plans for initial operation are described. Early efforts produced a conceptual design in 1997; the project itself was initiated in 1999, with the official groundbreaking taking place in December of 1999. As of April 2005 building construction was complete and the overall project was more than 90% complete. The design of the target and surrounds are finished and the first target was installed in June 2005. First beam on target is expected in June, 2006. The engineering design of the target region is described. The key systems comprise the mercury target, moderator and reflector assemblies, remote handling systems, utilities and shielding. Through interactions with the 1 GeV proton beam, the target, moderators and reflectors produce short pulse neutrons in thermal energy ranges, which are transported to a variety of neutron scattering instruments. The mercury target module itself is described in more detail. Materials issues are expected to govern the overall lifetime and have influenced the design, fabrication and planned operation. A wide range of materials research and development has been carried out to provide experimental data and analyses to ensure the satisfactory performance of the target and to set initial design conditions. Materials R&D concentrated mainly on cavitation erosion, radiation effects, and mercury compatibility issues, including investigations of the mechanical properties during exposure to mercury. Questions that would require future materials research are discussed.