Systems and methods of controlling a proton beam of a proton treatment system

A proton beam delivery system for use in proton therapy, comprising:

• at least one achromatic beamline having a first power setting to direct a proton beam having a first predetermined range of proton beam energies to a target treatment area, a second power setting to direct a proton beam having a second predetermined range of proton beam energies to the target treatment area, and a third power setting to direct a proton beam having a third predetermined range of proton beam energies to the target treatment area;
• and
• a power changing unit configured to control an energy level of the proton beam and a power setting of the at least one achromatic beamline such that the power changing unit changes the power setting of the at least one achromatic beamline between the first power setting and the second power setting based on changes in proton beam energy that occur within the first predetermined range of proton beam energies, and to incrementally change the power setting of the at least one achromatic beamline between the second and third power settings based on changes on proton beam energy that occur within the second predetermined range of proton beam energies.