X-ray sources and production of X-rays, in particular, producing monochromatic x-rays is provided. More specifically, a method for producing X-rays and the use of the X-ray source for x-raying bodies (for example human bodies). An aerogel, for example in the form of a rod, may be provided in a housing as a target. Said target may be bombarded with an electron beam, the aerogel being vaporized due to the extreme low density and the high energy. As a result, the target is guided by means of a roller such that an unused target for producing, in particular, the monochromatic X-rays, is always available.