Apparatus, systems, and methods for processing workpieces are provided. An arc lamp can include a tube. The arc lamp can include one or more inlets configured to receive water to be circulated through the arc lamp during operation as a water wall, the water wall configured to cool the arc lamp. The arc lamp can include a plurality of electrodes configured to generate a plasma in a forming gas introduced into the arc lamp via the one or more inlets. The forming gas can be or can include a mixture of a hydrogen gas and an inert gas, the hydrogen gas in the mixture having a concentration less than 4% by volume. The hydrogen gas can be introduced into the arc lamp prior to generating the plasma. The arc lamp may be used for processing workpieces.