A radiation therapy system includes an accelerator and beam transport system that generates a beam of particles. The accelerator and beam transport system guides the beam on a path and into a nozzle that is operable for aiming the beam toward an object. The nozzle includes a scanning magnet operable for steering the beam toward different locations within the object, and also includes a beam energy adjuster configured to adjust the beam by, for example, placing different thicknesses of material in the path of the beam to affect the energies of the particles in the beam.
