The cross-section, position and/or direction of an electron bundle generated by an electron generator is detected w.r.t. a target. A device with at least one conductor in the region of the target is provided such that a signal can be diverted under the influence of the electron bundle. The conductor is made of a material with a core charge number less than that of tungsten so that no unwanted radiation occurs under the alternating effect of the electrons with the conductor. The conductor is made of carbon fibre. An evaluation device generates an output signal dependent on the cross-section, position and/or direction of the electron bundle.
