The cathode system includes an electron emitter (3) and electrodes between the emitter and anode (1) of the x-ray tube. The electrodes can be switched on by a switching arrangement (8,9) with a pulse/pause ratio dependent tube current. The electrodes are switched to a potential (Uw,UH) which varies from that of the electron emitter. The electrodes include an anode (5) switched to a positive potential (UH) by the switching arrangement (9). The duration of the switching cycle of the switching arrangement (8,9) is approximately 10 microseconds. The anode has an opening for the emitted electron beam (E).
