A modular beam amplifier for use in generating high power beams of particles in systems such as a spacecraft propulsion engine, comprising a distributed DC power generator including a plurality of DC generator cells connected in series to each other and a plurality of power taps at different points between the DC generator cells, an ion injector producing a particle beam and a plurality of amplifier modules in series with each other and coaxial with the particle beam. Each amplifier module in the plurality of amplifier modules includes a focus lens and a plurality of annular amplifier plates. Each amplifier plate pairs with and connects to a power tap. The plurality of DC generator cells is physically arranged in a serpentine arrangement of connected rows to minimize the physical length of the distributed DC power generator.