The invention comprises a method and apparatus for using a turning magnet of an accelerator of a cancer therapy system, the accelerator comprising first magnet coils and second correction coils wound about a magnet core where: (1) at a first time, the second correction coils are used to correct a magnetic field, resultant from the first magnet coils, used to turn cations and (2) at a second time, after reversing polarity of the correction coils, the correction coils are used to turn anions and/or electrons, the cations and electrons used to treat a tumor of a patient positioned in a treatment position relative to a treatment beam from the accelerator during the first and second time periods.
