[en] As a method for the fabrication of technical separation nozzle elements with extremely small characteristic dimensions, the Institut fuer Kernverfahrenstechnik of the University and the Nuclear Research Centre of Karlsruhe in co-operation with the Siemens AG, Munich, and the Fraunhofer Institute for Solid-State Technology, Munich, are developping the LIGA-process. In this process, poly(methylmethacrylate) layers of an approximate thickness of 0.5 mm are structured by means of X-ray depth-lithography using synchrotron radiation. Subsequently, the nozzle structures are electroformed with nickel using the PMMA-layers as a mould. The manufacturing precision which can be obtained by X-ray depth-lithography was investigated by means of computer simulation of both the irradiation and the development step. In the first step the precision is limited by diffraction, photoelectrons, and beam divergency, respectively. It is shown, that under appropriate conditions each of these effects contributes only some 0.1 μm to errors at the structure edges. The simulation of the development step is based on experiments on the dissolution properties of both irradiated and unirradiated PMMA in a special developing agent. From the results of the computer simulation it can be seen, that the ratio of the slit length to the smallest width which is required for the fabrication of separation nozzles and the required precision are already obtainable in the one-step lithographic process at a characteristic wavelength of 0.2 nm. If an extreme structure height in combination with high precision is required or if a radiation source with a longer characteristic wavelength has to be used, the multi-step process can be applied. The calculations may easily be adapted to different manufacturing parameters concerning the radiation source or the developer characteristic. (orig.)