A cooling apparatus is disclosed that has a first cooling structure (220), in thermal contact with a heat source (210) having a temperature greater than a cool structure (250), comprising a channel through which a cooling fluid is passed, an isolator (230) between the heat source and the cool structure, the isolator in thermal contact with the first cooling structure and comprising a material of low thermal conductivity, and a second cooling (240) structure between the isolator and the cool structure, the second cooling structure comprising a channel through which cooling fluid is passed.