Embodiments of the invention provide an apparatus, method, and program product to control a lamp system. The apparatus comprises a plasma lamp bulb (20) and a microwave generator (12) operable to generate a microwave energy field to excite the plasma lamp bulb (20) to emit ultraviolet light (24). The apparatus further comprises a sensor (70) to measure the intensity of the ultraviolet light (24) and a reflector (42) positioned between the plasma lamp bulb (20) and the sensor (70) The reflector (42) is operable to reflect at least a portion of the ultraviolet light (24) generated by the plasma lamp bulb (20). The method comprises receiving a target intensity for the ultraviolet light (24) and measuring an intensity of the ultraviolet light (24) using a sensor (70). The method further comprises comparing the target intensity to the measured intensity and, in response to the comparison, adjusting power to a microwave generator (12) to adjust the intensity of the ultraviolet light (24).