The proposed accelerator complex consists of

1) 400-MeV (mega-electron volts) normal-conducting Linac,
2) 600-MeV superconducting Linac to increase the energy from the 400 to 600 MeV,
3) 3-GeV Proton Synchrotron (PS), and
4) 50-GeV PS.

The 400-MeV protons are partly injected into the 3-GeV PS and partly into the 600-MeV Linac. The 600-MeV proton beam will be used for the basic research for nuclear waste transmutation converting long-lived radioactive nuclides into short-lived or non-radioactive nuclides. The main part of the 3-GeV proton beam will be delivered to the neutron/meson facility where extensive research programs on nuclear/particle physics, condensed matter physics, material sciences and structural biology will be carried out by using beams of muon and neutron. A part of the 3-GeV beam will be transferred to the 50-GeV PS. At the 50-GeV PS, nuclear/particle physics experiments using kaon beams, anti-proton beam, neutrino beams, and primary proton beams are planned.

Japan is expected to take a significant leadership role in accelerator science in the 21st century using this facility; the present neutron source facility will be one of three major centers (Asia/Pacific rim, Europe, and North America) in the world, which were strongly recommended for immediate construction by the OECD Mega Science Forum for neutron sources. The OECD Mega Science Forum for nuclear physics also emphasized the scientific importance of the 50-GeV PS as a world center for future hadron physics.

Phase 1 of the Joint Project was approved very recently including construction of 400-MeV Linac, 3-GeV PS, 50-GeV PS, major part of the 3-GeV neutron/meson facility, and a portion of the 50-GeV experimental facility. We plan to complete it within 6 years.

	The author of this article, Professor Shoji NAGAMIYA, is the project director of the Joint Project.