A method of removing contaminants from a double-ended arc discharge tube includes the steps of providing at least one capillary channel at each end of the tube, where the ends of the tube are sealed closed except at the capillary channels, and introducing a flushing gas into the tube through one capillary channel at one end of the tube and removing the flushing gas and contaminants through another capillary channel at another end of the tube. During manufacture, the double-ended arc discharge tube has a sealed electrode and an open capillary channel at each end of the tube.