NOBLE GAS DISCHARGES Raphael Mehlich 21.Juni.2010 IdIndex History of noble gases Properties of noble gases High pressure discharge lamps Glow lamps Noble gas excimer Raphael Mehlich 21.Juni.2010 His tory of noble gases 1868: Jules Janssen and Norman Lockler discov ered Helium 1892: Luigi Palmieri verified Helium 1894: LdLord RlihRayleigh has discovere d Argon 1898: Lord Rayleigh and Morris William Travers verified Neon, Xenon and KtKrypton by ftilfractional dis tilla tion of air 1900: Friedrich Ernst Dorn discovered Radon 2006: UnunoctUiium was made byb theInstIiitute for NucNllear Research and the Lawrence Livermore National Laboratory Raphael Mehlich 21.Juni.2010 PtiProperties of noble gases All noble gases are odorless, colorless, nontoxic, incombustible under normal conditions and are stable in a non‐molecular state Raphael Mehlich 21.Juni.2010 Hig h Pressure Disc harge Lamps • Pressure of noble (Xe) gas 5‐20 bar during operation 12‐100 bar • Ignition voltage 20‐30 kV operating voltage 30 V • Distance of electrodes 0,2mm to several mm • Quantum efficiency 40 lm/Watt • Comparable to solar spectrum color temperature ~ 6000 K Raphael Mehlich 21.Juni.2010 AlitiApplication for Disc harge Lamp • Vis‐Spectroscopy (400‐800 nm) • Projector • Spotlight • Purification of water • Pros: ‐ bright light ‐ homogeneous spectrum (400‐800nm) • Cons: ‐ formation of ozone ‐ short lifetime (several 1000h) ‐ high technical effort ‐ safety requirement Raphael Mehlich 21.Juni.2010 Glow Disc harge Lamps • Pressure of noble gas (Xe) less than 10‐2mbar • Operating voltage < 100V • Color depends on applied noble gas • Cold bulb Raphael Mehlich 21.Juni.2010 AlitiApplications • Adv ertisement • Phase checker • Pros: ‐ cold bulb ‐ pure color s Raphael Mehlich 21.Juni.2010 EiExcimers • Excimer = excited dimers • Dimer: two noble gas atoms (Xe2*,Ar2*,…) or noble gas halides (XeF*,KrCl*) • EEixcimer are only stable in exciidted state • R* + R R2* R+ + X‐ + M RX* + M R* + X2 RX* + X Raphael Mehlich 21.Juni.2010 AlitiApplications of EiExcimer Disc harges Light Screens (Planon® ) Excimer Laser High power Cold UV Excimer System Planon® Raphael Mehlich 21.Juni.2010 Plasma TV Noble gases Xe for 148 and 172 nm Ne for orange range Excitation of Xe atoms by electron collision UV Radiation is converted by phosphor into visible light Raphael Mehlich 21.Juni.2010 Sources Hans‐Jörg Bullinger – Technologieführer, Springer Verlag, Berlin (2007) Dieter Meschede – Gerthsen Physik, Springer Verlag, Berlin (2006) Erwin Riedel –AnorganischeChemie, Walter de Gruyter Verlag, Berlin (2004) Wolfgang Demtröder – Experimentalphysik 3, Springer Verlag, Berlin (2010) Joachim Staab ‐ Industriele Gasanalyse, Oldenbourg Verlag, München (1994) http://www. elektronikinfo.de/strom/thermischelampen .htm http://www.uni‐muenster.de/Physik.TD/gasentladungslampen.html http://www.heraeus‐noblelight.com http://www.newport.com http://www.uni‐protokolle.de Raphael Mehlich 21.Juni.2010.