Design report of M-arena at the north-counter hall

A intense proton accelerator consisting of a basic equipment in Japanese Hadron plan is composed of a group of three accelerators such as a 200 MeV proton linear accelerator, a 3 GeV proton synchrotron and a 50 GeV proton synchrotron. Among them, the 200 MeV proton linear accelerator is an injector of 3 GeV ring. The GeV ring is a synchrotron with 25 Hz revolution frequency, which can accelerate 200 μA in mean current and realize 0.6 MW in beam power. And the 50 GeV ring is an intense proton synchrotron with about 1,500 m in all periphery and has 10 μA in mean current. These accelerators are planned to construct at northern area of the High Energy Accelerator Research Organization. So as to be able to construct effectively and economically by applying the present facility at the best condition, M-arena is planned to install at north-counter hall executing 12 GeV PS at present. Its design work is promoted under an aim to introduce a proton beam with 3 GeV/200 μA at the north-counter hall, to set a pion forming target on the proton beam line, and to develop a high quality pulse muon channel with the highest intensity without any report. (G.K.)