Determination of the absolute intensity of barium lines during dimming operation in the vicinity of fluorescent lamp electrodes
Résumé
In this work the intensity of barium lines during dimming operation in the vicinity of fluorescent lamp electrodes is investigated using the high-sensitivity method of Atomic emission spectroscopy. Investigations of fluorescent lamps (FL) are often focused on the electrodes, since the lifetime of the lamps is typically limited by the electrode lifetime and durability. During steady state operation, the work function lowering emitter material, in particular, barium, is lost. Greater barium losses occur under dimming conditions, in which reduced discharge currents lead to increased cathode falls, the result of the otherwise diminished heating of the electrode by the bombarding plasma ions. From these measurements we infer barium loss for a range of discharge currents and auxiliary coil heating currents. We show that the Ba loss can very easily be reduced by moderate auxiliary coil heating.