An X-ray source is proposed having a rotating piston tube (2) which is mounted such that it can rotate, in which a stationary guide body (12), which at least partially surrounds the tube, is provided for cooling the anode plate (4). The guide body (12) is designed such that a liquid coolant, which is supplied to the tube (2) from a reservoir (15) concentrically with respect to the anode-bearing shaft (17), is initially positively guided along the tube outside of the anode plate (4) and along the beam outlet window (20) of the tube forming narrow gaps (18, 19), and is then passed out radially via at least one baffle plate (21) which is arranged on the tube (2) and engages in a correspondingly designed gap in the guide body (12). The high-voltage parts have an insulating gas applied to them, which is physically not separated from the liquid coolant in the source housing (1).