Medical application of the KEK booster synchrotron

A 12 GeV proton synchrotron facility is being built at KEK (National Laboratory for High Energy Physics), Tsukuba, Ibaraki, Japan. The facility consists of a Cockcroft Walton's apparatus, a linear accelerator, a booster (a 500 MeV proton synchrotron), and the main ring. This report is described on the projected medical application of the booster together with brief review of the whole facility. Besides medical use, the booster is scheduled to be used for the study of neutron physics and meson experiments. Because the primary objective of this facility is the experimental study on elementary particles, a cooperative committee has been organized for the utilization of the booster for many other fields of applications. As for the medical use, diagnostical applications of the method of proton radiography based on proton absorption, and the method of pen drawing or line drawing based on the difference of multiple scattering are explained. The concrete facilities such as energy degrador, energy absorber, bending magnet, flattening filter, pipe collimater, and focusing magnet are explained. The neutron therapy based on the spallation reaction is also considered. The associated apparatuses such as neutron collimater, gamma-ray shutter, neutron monitor, and switching magnet are briefly explained. Finally, the application of π-mesons to the basic study of medical and biological sciences is discussed as future possibilities. (Aoki, K.)