Status of Nb3Sn accelerator magnet R&D

Excellent mechanical and electrical properties of multifilamentary NbTi have made it the conductor of choice in superconducting accelerators starting from the Tevatron. However, the LHC operating field of 8.33 T is close to limit for NbTi technology. In order to advance to higher fields, a superconductor with higher upper critical field is needed. At present, Nb₃Sn is the most suitable material in terms of properties, availability, and cost. In contrast to NbTi, Nb₃Sn is brittle and strain sensitive. Magnet R&D programs are underway worldwide to develop technologies that can take advantage of Nb₃Sn properties while coping with the associated challenges. Status and accomplishments of the different programs are reviewed in the context of the requirements of next-generation accelerator facilities and possible upgrades to present ones.