A pulsed-discharge radiation source includes a gas chamber, a window, and a conduit system. The conduit system includes a refill path and a conduit. The pulsed-discharge radiation source generates radiation. The gas chamber confines a gas and contaminants produced during the generation of radiation. The window isolates the gas from an environment external to the gas chamber and allows the radiation to travel between the gas chamber and the environment. The refill path allows a replacement of the gas. The conduit circulates the gas to or from the gas chamber during the generating. The conduit system directs a flow of one of a refill gas, the gas, or the refill gas and the gas at least during a refill operation to prevent the contaminant from contacting the window, whereby the conduit system increases the usable lifetime of at least the window.