Embodiments of the present disclosure relate to an oxygen cleaning chamber with UV radiation generator temperature control and a method of atomic oxygen cleaning a substrate. The atomic oxygen cleaning chamber includes a process chamber and a cooling chamber coupled to the process chamber and a divider sealingly separating the process chamber from the cooling chamber. An ultraviolet (UV) radiation generator is disposed in the cooling chamber and provides UV radiation through the divider into the process chamber. A gas distribution assembly distributes ozone over an upper surface of a pedestal in the process chamber and a coolant distribution assembly distributes cooling gas into the cooling chamber to cool the UV radiation generator. By actively cooling the UV radiation generator, a higher intensity UV radiation at a stable wavelength is produced, i.e., without wavelength drift normally associated with high power UV radiation generator outputs.