J-PARC is a research-facility complex covering a variety of research programs. Proton accelerators form the basis of this complex. Two fundamental parameters specifying the performance of a proton beam are the beam energy and the beam intensity.

Beam power, which is given by the product of these two parameters, is another important parameter for the practical use of proton beams. The figure below shows an energy-intensity graph, in which the performances of proton-beam facilities in the world (in operation, under construction and proposed) are plotted. Since both axes of the graph are in logarithmic scale, points on a straight line (from upper left to lower right) correspond to the same beam power.

The J-PARC accelerator complex consists of
■ A linear accelerator, mainly used as an injector
■ the Rapid-Cycling Synchrotron (RCS, 3 GeV)
■ the Main Ring (MR, a synchrotron with energy of 50 GeV max.)

The above components constitute an experimental facility for researching into material and biological science, and nuclear and particle physics.

Power map of worldwide proton Accelerators

From this graph, one can see that the power of the beam provided by J-PARC for nuclear and particle physics is higher than that of existing machines by an order of magnitude, and that for the material and biological science is one of the highes in the world.