Systems and methods for reducing contamination of one or more arc lamps are provided. One example implementation is directed to a millisecond anneal system. The millisecond anneal system includes a processing chamber for thermally treating a substrate using a millisecond anneal process. The system further includes one or more arc lamps. Each of the one or more arc lamps is coupled to a water loop for circulating water through the arc lamp during operation of the arc lamp. The system includes a reagent injection source configured to introduce a reagent, such as nitrogen gas, into water circulating through the arc lamp during operation of the arc lamp.