A device is used to precisely deliver the treatment plan created by an automatic planning system by positioning a single low energy radiation source, or a plurality of low energy sources connected to each other, in a predetermined parallel, planar, or similar geometry, each source equipped with blocking and attenuation mechanisms, thereby delivering a plurality of parallel overlapping beams indexed on a millimeter or submillimeter grid such that a concentration of dose is achieved at a variable depth in tissue relative to the dose where the radiation first enters the tissue. A plurality of overlapping beams indexed on a millimeter or submillimeter grid can converge on a target volume loaded with gold nanoparticles to deliver a tumorcidal dose of radiation in as little as a single session to tumor cells but not to normal cells or to deliver serial radiosurgical treatments.