POSITIVE-ION MULTI-TURN INJECTION WITH BI-WAVEFORM FAST ORBIT-BUMP MAGNETS

An injection system for both negative-ion charge- exchange injection and positive-ion multi-turn injection was developed in order to accelerate heavier positive ions in the KEK proton synchrotron. As for positive-ion multi-turn injection, a further device for effective beam injection was also tried in order to suppress the losses of incoming beams to reduce the residual radioactivity. Using this system, helium ions have been successfully accelerated in the KEK 12-GeV proton synchrotron. A charge-exchange injection scheme has been used to inject proton and deuteron beams into the booster synchrotron. This scheme, however, cannot be applied to heavier positive ions, such as helium ions. Therefore, a conventional multi-turn injection scheme for positive ions must take the place of the charge-exchange scheme. For this project a new injection system for both negative-ion charge-exchange injection and positive-ion multi-turn injection was developed (1). Positively charged helium ions are injected into the KEK booster synchrotron by means of a septum magnet and two fast orbit-bump magnets system. In this system, positive-ion beams are gradually injected from the center of the horizontal phase space to the outside by shifting the closed orbit, which is controlled by two fast orbit-bump magnets. To fill the ring acceptance with incoming beams effectively, a nonlinear slope of the fast orbit-bump magnetic field is required. An approximated waveform can be realized by a newly developed bi-waveform power supply system. An outline of effective multi-turn injection using the nonlinear slope of the fast orbit bump magnet and experimental results of positive-beam injection are summarized in this paper.