The invention comprises a beam adjustment method and apparatus used to perform energy adjustments on circulating charged particles in a synchrotron previously accelerated to a starting energy with a traditional accelerator of the synchrotron. The beam adjustment system uses a radio-frequency modulated potential difference applied along a longitudinal path of the circulating charged particles to accelerate or decelerate the circulating charged particles. Optionally, the beam adjustment system phase shifts the applied radio-frequency field to accelerate or decelerate the circulating charged particles while tightening spatial distribution of a grouped bunch of the circulating charged particles. Optionally, the beam adjustment system simultaneously radially focuses the circulating charged particles using two or more gaps with focusing and/or defocusing edges. The beam adjustment system facilitates treating multiple layers or depths of the tumor without hysteresis and/or between the repeating slow steps of reloading the synchrotron.
