A light source includes a rotatable drum, an exhaust tube coupled to the rotatable drum to exhaust nitrogen gas from an interior of the rotatable drum, a feed tube situated within the exhaust tube to provide liquid nitrogen to the interior of the rotatable drum, and a casing to surround at least a portion of the exhaust tube. The light source also includes a rotary air bearing between the exhaust tube and the casing, to allow the exhaust tube to rotate with the rotatable drum.