Systems for generating a proton beam include an electromagnetic radiation beam (e.g., a laser) that is directed onto an ion-generating target by optics to form the proton beam. At least one processor is configured to control the source of the electromagnetic radiation and the optics to alter the energy, polarization, spatial profile, and/or the temporal profile of the electromagnetic radiation beam, and to adjust the flux and/or energy of the proton beam. In some instances the system may adjust the proton beam energy while holding the proton beam flux substantially constant, or alternatively adjust the proton beam flux while holding the proton beam energy substantially constant. In other instances the system may adjust the proton beam energy while varying the proton beam flux, and/or adjust the proton beam flux while varying the proton beam energy.
