High pressure mercury AC discharge tube exposed to coherent laser: optical, electrical and thermal aspects

Most optical emission line intensities remain unchanged for a mercury HID plasma, exposed to coherent argon ion laser beam Innova 308 C (476.5 nm) in points far from electrodes. Small raise of Hg-546.08 nm line is due to photo-excitation of Ar + ions, followed by excitation transfers through collision processes from excited (Ar + ) * ions to Ar atoms, then from excited (Ar) * to Hg atoms. When the laser beam hits the electrode tip (photoelectric effect), the amount of electrons involved in plasma collisions increases: all characteristic emission spectral lines are intensifying. Electron temperature and concentration were also calculated. Differential Scanning Calorimetry performed in case of tungsten electrode with emissive material (Y 2 O 3 , BaCO 3 , CaCO 3 , WO 3 ), linear and non-isothermally heated (0.17 K s -1 ) in flowing air, from 290.61 to 1603.72 K (platinum crucible), revealed both endothermic (CaCO 3 and of BaCO 3 decompositions) and exothermal (obtaining CaWO 4 , BaWO 4 and Ba 3 WO 6 ) processes. Thermogravimetry Analysis showed a mass decrease of 0.498%, in 290.61−505.15 K temperature range, due to water release. Oxidation of tungsten electrode causes a significant mass increase of 17.292% in 809.15−1183.15 K range. BaWO 4 , Ba 3 WO 6 and WO 3 sublimations gave a mass fall of 6.757% in 1513.15−1603.72 K range. No thermal effects were recorded on heating in argon atmosphere, from 446.15 to 1596.15 K, in alumina crucible.