A method for delivering therapeutic light ion radiation to a target volume of a subject, wherein the target volume is located at a predetermined depth from the skin, includes irradiating a surface of the skin with an array of light ion minibeams comprising parallel, spatially distinct minibeams at the surface in an amount and spatially arranged and sized to maintain a tissue-sparing effect from the skin to a proximal side of the target volume, and to merge into a solid beam at a proximal side of the target volume. A gap between the parallel, spatially distinct minibeams at the surface and a species of light ions forming the minibeams are selected such that the array merges into a solid beam at a predetermined beam energy, and across all energies for Bragg-peak spreading, at a proximal side of the target volume.
