The invention comprises a method and apparatus for treating a tumor of a patient with positively charged particles, comprising the steps of: (1) transporting the positively charged particles sequentially from an accelerator, through a beam transport line, through a nozzle, and toward a position of the tumor; (2) treating the tumor with first particles, of the positively charged particles, where at least fifty percent of the first particles pass through a patient position, from the nozzle, to a post-patient position; and (3) detecting a beam position of the first particles in the post-patient position with a detector. The flash treatment preferably delivers the first particles at a rate exceeding one MHz.