a rotating anode for an x - ray tube has an anode body composed of composite fiber material , mounted in a bearing system , the anode body having a target surface with a focal ring and including fibers with particularly high heat conductivity in the longitudinal direction . an axis - proximal cooling system is associated with the anode body . the majority of all fibers with high heat conductivity in the longitudinal direction terminate bluntly both at the focal ring and at the cooling system , such that their abutting faces respectively are in direct , heat - conducting contact both with the focal ring and with the cooling system .