An evacuable outer housing having at least one X-ray-permeable beam exit window, an electron source, an anode and a collector for catching electrons which penetrate the anode are included as an X-ray source. The collector is part of an electrical current circuit for applying a negative potential to the anode, and the radiation window is disposed such that X-ray radiation which exits from the anode at an angle of 130 degrees to 230 degrees to the electron beam direction can be coupled out through the radiation window. An imaging system includes such an X-ray, an arrangement to accommodate an object to be examined, and an X-ray detector.