Techniques for commensurate cusp-field for effective ion beam neutralization are disclosed. In one particular exemplary embodiment, the techniques may be realized as a charged particle injection system comprising a beamguide configured to transport an ion beam through a dipole field. The charged particle injection system may also comprise a first array of magnets and a second array of magnets configured to generate a multi-cusp magnetic field, positioned along at least a portion of an ion beam path, the first array of magnets being on a first side of the ion beam path and the second array of magnets being on a second side of the ion beam path. The charged particle injection system may further comprise a charged particle source having one or more apertures configured to inject charged particles into the ion beam path. The charged particle injection system may furthermore align the one or more apertures with at least one of the first array of magnets and the second array of magnets to align the injected charged particles from the charged particle source with one or more magnetic regions for an effective charged particle diffusion into the ion beam path.