X-ray tube comprising an exit window

An electron-optical system directs an electron beam which emanates, for example from a line-shaped or annular emissive cathode element, onto an anode target face in a collimated fashion so that a large part of reflected electrons is incident on the target face again, thus contributing to the generating of X-rays. The construction of the electron-optical system and the high degree of re-incidence of scattered electrons allows for a minimum distance between the anode target face and the exit window. A filament of the cathode may be constructed so as to achieve an optimally uniform operating temperature over a comparatively large part of its length.