A fast magnet switching method and apparatus used to rapidly redirect cations, such as H+ or C6+, in a beam path, such as during or between treatment of individual volumes or voxels of a tumor of the patient, is described. Switching means include rapidly increasing or decreasing applied current to a coil about a magnet, which rapidly alters a magnetic field crossing the charged particle path and redirects a charged particle beam away from the patient, such as to a charged particle beam stop. Means to rapidly induce the current change include: (1) using a separate high voltage power supply and/or (2) opening a switch to redirect current through a resistor. In both cases, the rapid current change to the coil yields a rapid change the magnetic field and a corresponding rapid change in direction of the charged particles in the charged particle cancer therapy system.
