Grant: Subatomic Physics Envelope - Project

Our objective is to investigate the feasibility of a novel magnetic inflector for the beam injection into a cyclotron. Conventionally, the axial injection from an external ion source into a cyclotron is through an electrostatic spiral inflector, and also starts along the magnetic axis of the cyclotron. We propose to break this rule, and inject beams with large angles with respect to the magnetic axis. This allows the injection structure to be almost entirely magnetic, with only a short electrostatic deflector for the final deflection into the median plane. As opposed to the electrostatic inflectors, which are complicated spiral--shaped electrodes, the proposed magnetic inflector takes the form of a void inside the central part of the cyclotron yoke.  This relative simplicity opens up a possibility of using multiple magnetic inflectors in a single cyclotron. In principle a cyclotron could host as many injection ports as the RF system periodicity permits, implying that multiple beams could be simultaneously injected into the same cyclotron, multiplying its current output. These simultaneously injected beams would come from different external ion sources. These beams, for the most part, would not overlap throughout the acceleration process, occupying several times more volume in the real space than a single beam. Even though the neighboring beams would interact with each other via the Coulomb force, the space charge force would be significantly smaller than if the same amount of charge was concentrated into a single beam. This would constitute an elegant way to push further the intensity limit of high intensity cyclotrons. Such a cyclotron would have to use charge exchange extraction, as the multiple turns stacked beam would not separate radially. The present proposal will be to understand how to overcome several potential obstacles to the implementation of this novel concept: (1) The off--axis injection path will complicate the design of injection line that connects the ion source to the magnetic inflector. (2) Maintaining sufficient focusing along the injection channel is not a trivial task, and may require extensive numerical modelling and beam dynamics simulations. (3) Matching of the injection orbit becomes more difficult by the need of using symmetric RF structure, to allow multiple beam injection. (4) Accurate simulation of beam dynamics in the center region will require taking into account the space charge effect, considering neighboring turns and boundary conditions. The proposed research is to study in depth these potential obstacles, which have to be  overcome through investigations in the present study. Pursuing this research would allow TRIUMF to maintain its reputation for excellence in research on cyclotrons. The success of this research project would impact the long term planning of subatomic physics research in Canada, by providing an affordable and reliable means to produce high intensity driver beams.