Abstract: The invention concerns an x-ray tube having a thermionic emitter and a warning means, which exhibits means for measuring as least one electrical property of the thermionic emitter and produces a signal during analysis of the measured electrical property, if the measured electrical property shows a value indicating an impending failure of the thermionic emitter.

Abstract: A directly thermionic flat emitter is presented whose emitting surface contains meandering conductor tracks. The conductor tracks are formed by slots in the emitting surface. The slots are arranged as claimed in a pattern of cuts which comprises a multiplicity of straight slots (3; 8, 9) which run at least transverse to the course of the main current direction and are arranged in a plurality of rows offset from one another. Meandering current paths (4) are thereby produced.

Abstract: An X-ray tube has a vacuum housing that accepts a cathode and an anode and that is provided with an electrically conductive beam exit window. During operation of the X-ray tube, the beam exit window lies at a negative potential and is electrically conductively connected via a resistance to a potential that is positive relative to the negative potential, this resistance being dimensioned such that, during operation of the X-ray tube, the difference in potential between the negative potential of the beam exit window and the positive potential lies on the order of magnitude of a few kilovolts.