||In 2001-2 GE superseded its Lucalox HO High Output lamps by the XO range, with still higher performance. Both these classes of lamps feature high xenon pressure, to achieve increased luminous flux and maintenance, as well as longer life due to reduced loss of electrode and emitter materials.
The XO lamp replaced the former ignition antenna mounted on bi-metal strips with a track of cermet sintered into the arc tube surface - similar to the PIA design introduced by Philips in 1997. The antenna is always oriented in-line with the support frame to minimise shadowing. In an unusual move for GE, its tradtional external amalgam reservoir has also been eliminated, in favour internal amalgam but uniquely, located at only one end of the arc tube. An intentional cold spot has been created behind one electrode by applying a heat shield around the other. Deleterious reactions between amalgam and the seals are avoided by the similarly unique 2-piece ceramic arc tube - at the amalgam end the diameter has been reduced by a co-moulded end plug without any join. The niobium seal is made to a thin wire instead of the usual tube, which maintains a greater distance to the amalgam.
Less evident is the mechanically polished arc tube surface(see detail photo) which increases transmission. The ceramic is believed to be NGK's G-40 zirconium-doped alumina, which achieves superior sodium resistance and allows a life increase. The traditional barium getter of the outer bulb has also been replaced by a zirconium-iron alloy, having superior sorption for hydrogen. All together, these multiple design innovations make the Lucalox XO lamps some of the most reliable and highly performing lamps in their class.