Abstract: A cooling system for relatively movable components, such as a rotor seated for rotation with respect to a stationary component, includes a sealed channel in the stationary component disposed between the stationary component and the movable component, and an evaporator disposed within the sealed channel. The channel is filled with coolant, such as alcohol or oil, which is circulated by a pump in a closed circulation path. Heat is thereby conveyed from the system components to be cooled to the evaporator, and from the evaporator to a location where the heat can be dissipated without disturbing operation of the device. The cooling system is suitable for use, for example, in a computer tomograph for cooling the radiation detector.