A 150 MeV FFAG synchrotron with "Return-Yoke Free" magnet

The 150 MeV proton FFAG (Fixed Field Alternating Gradient) synchrotron is under construction at KEK to investigate the possibilities of various applications such as proton beam therapy after the success of the POP FFAG synchrotron. One of distinguished features of this machine compared with the PoP FFAG is to use a new type of magnet, "Return-Yoke Free" magnet. Because there is no return-yoke in the median plane in this magnet, the beam injection and extraction become easier.