Lifetime investigation of excimer UV sources

The principle underlying the operation of excimer lamps relies on the radia tive decomposition of excimer states created by a dielectric barrier discha rge in a rare gas or a mixture of rare gas-halogen In excimer lamp technolo gy, no electrodes are in direct contact with the discharge gases, thus avoi ding any reaction between the discharge and the electrodes or contamination of the gas with evaporated electrode material, as well as electrode corros ion which can occur in conventional lamps leading to short operational life times. Therefore, an investigation of the lifetime of these lamps is of vit al importance before any industrial application can be seriously considered . In this paper the detailed lifetime of 172, 222, and 308 nm excimer lamps as well as overall efficiency. stability, and any output fluctuations, hav e been investigated. It was found that efficiency increased as input power decreased. It was noted however that colour centres were formed within the first 60 h of operation for 172 nm excimer lamps which reduced their output intensity during their time. By contrast, 100% of the original UV intensit y output by the 222 and 308 nm lamps was still maintained after up to 4000 h operating time. These results are compared with the lifetime of conventio nal mercury lamps. (C) 2000 Elsevier Science B.V. All rights reserved.