1. An X-ray device for the generation of at least one X-ray pulse, the device comprising: an X-ray tube having a thermionic cathode and an anode; and an X-ray generator comprising a Marx generator for the generation of at least one high-voltage pulse applied to the anode for the generation of the at least one X-ray pulse, and a simmer power supply unit by which a low voltage is continuously applied to the anode wherein the low voltage is at most is sufficient for the generation of low-energy X-radiation and pre-heats the X-ray tube; wherein the simmer power supply unit a voltage source of the Marx generator.