The invention relates to a drift tube accelerator (1) for the acceleration of ion packets in ion beam acceleration systems, wherein a housing (2) consists of a longitudinally divided three-part vacuum tank (3) having a central unit (4) and a lower half-shell (3) comprising a structured lower steel block (15) and an upper half-shell (6) comprising a structured upper steel block (19). (The cavity arranged between the central unit (4) and the structured steel blocks (15, 19) has at least two acceleration regions (24, 25), between which there is arranged a magnetic focussing device (17), which focuses the ion beam from one region (24) to the next region (25).)The drift tube accelerator (1) according to the invention has such a stable and massive structure that it requires no external supporting aids of any kind in order to obtain alignment, which is reliable and accurate to a few micrometers, of the acceleration components within the drift tube accelerator (1) with respect to the longitudinal axis (7) of ion beam guidance of the central unit (4). The massive structure of the drift tube accelerator (1) according to the invention can be used in general for any linear accelerator.