Abstract: The invention relates to a particle accelerator for radiotherapy by means of ion beams (150). The particle accelerator comprises a sixfold synchrotron ring (100) having six rectilinear beam sections (1 to 6) and six curved beam sections (7 to 12). Injection means (43) for introducing a linearly accelerated ion beam into the synchrotron ring (100) are arranged on a first rectilinear beam section (1) of the six rectilinear beam sections (1-6). Along the course of a second rectilinear beam section (5) there is at least one acceleration means (44) for the ion beam. Extraction means (45) for extracting the internal beam highly accelerated after several circulations are provided on a third rectilinear beam section (4). Each curved beam section (7 to 12) comprises a pair of dipole magnets (13/14, 15/16, 17/18, 19/20, 21/22, 23/24).

Abstract: A method for producing planar surfaces having very fine peaks in the micron range or smaller, e.g. planar field emission cathodes, of conductive or semiconductive material, by filling cavities in a matrix. A sheet of the planar dielectric material is irradiated with high energy ions, e.g. from a heavy ion accelerator to form nuclear traces therein, and is subsequently subjected to an etching process to expose the nuclear traces. Thereafter, the hole-like nuclear traces or cavities are filled with conductive or semiconductive material and one surface of the sheet of planar material is covered, at the open ends of the nuclear traces or cavities, with a coating of likewise conductive or semiconductive material. If desired the matrix of planar material may subsequently be removed.