Mercury may be removed from discharge lamps and phosphorescent tubes in the following years. The xenon excimer dielectric barrier discharge is a good candidate to be a mercury-free lamp for the generation of effective UV and VUV radiations.
This study concerned a coaxial dielectric barrier discharge lamp excited by sinusoidal or pulse voltage excitation (<3000 V, 20 kHz). The pyrex lamp (dielectric glass) is 120 mm long and have a 10 mm external diameter, thickness is 1mm. The conductive material is aluminum (electrodes) deposited on the external surfaces of the lamp to avoid quick deterioration. The gas mixture in the lamp is a neon xenon 50%-50% at pressure (30-60 mbar). The gas pressure appears as an important parameter for improving VUV production [1] . The use of high xenon pressures in a mixture promotes the possibility of production and excitation of the excimer Xe2* which produced radiation at 147 nm [2]. The optical part is acquired using an OCEAN OPTICS HR 2000+ spectrometer to identify the excited atoms and molecules responsible for the different emissions.
This work presents the evolution of the luminous efficacy of the lamp as a function of the pressure and voltage applied. It will be followed by an analysis of the reaction kinetics to understand the appearance of the species responsible for UV and VUV radiation.
[1] E. Robert, S. Point, S. Dozias, R. Viladrosa, et J. M. Pouvesle, « Study of pulsed neon–xenon VUV radiating low pressure plasmas for mercury free fluorescent sign optimization », Journal of Physics D: Applied Physics, vol. 43, no 13, p. 135202, avr. 2010.
[2] S. Point, E. Robert, S. Dozias, C. Cachoncinlle, et R. Viladrosa, « Effect of mixing pressure on xenon VUV radiation in the case of mercury-free signs excited in electric pulse mode », June 2006 Physics Journal IV (Proceedings) 138(1) DOI: 10.1051/ jp4: 2006138013.