A particle accelerator system, including apparatuses and methods, that is configurable through repositioning of shorting devices therein to operate at different charged particle beam currents while maintaining optimum transfer of electromagnetic power from electromagnetic waves to one or more accelerating sections thereof, and reducing or eliminating reflections of electromagnetic waves. The particle accelerator system includes at least two accelerating sections and an electromagnetic drive subsystem with portions of the electromagnetic drive subsystem being interposed physically between the accelerating sections, thereby making the particle accelerator system compact. The electromagnetic drive subsystem includes, among other components, a 3 dB waveguide hybrid junction having a coupling window in a narrow wall thereof which is shared by the junction's rectangular-shaped waveguides. By virtue of the coupling window being positioned in a narrow wall rather than a wide wall, the maximal power of the 3 dB waveguide hybrid junction is increased significantly.