Investigation of the cathodic region of a fluorescent lamp

Z. Tlais, D. Buso, S. Bhosle, G. Zissis
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引用次数: 1

Abstract

In this work the absolute intensity of barium lines during dimming operation in the vicinity of fluorescent lamp electrodes is investigated using the 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. In general, a commercial electrode system consists of a tungsten coil coated with a work function reducing emitter mix of alkali oxides, such as BaO, SrO and CaO. One of the main issues with dimming is a reduction in lamp life when the additional heating of the electrodes is not optimal, causing not-optimal electrode temperatures. There is a need for design rules for dimming to reach "good" lamp life, based on "good" additional heating. Such dimming design rules can be derived from measurements of the absolute intensities of both neutral (Ba I) and ionised (Ba II) barium lines, as these are key parameters to describe the evaporation and the sputtering of the emitter material. During steady state operation free barium is produced, which transports to the surface by diffusion through the coating mass. Barium escapes from the emitter during the course of lamp operation due to sputtering (primarily during starting and dimming), where the discharge is sustained by secondary electron emission from the (cold) electrode, and due to evaporation (primarily during steady-state), where the discharge is sustained by thermionic emission from the (hot) electrode. In the first type of experiment, the atomic emission diagnostic is used for the detection and measurement the intensities of the neutral (Bal-553.5 nm) and ionised (Ball-455.4n m) barium. The FL is dimmed for a range of discharge currents and auxiliary coil heating currents. It is seen that there is a threshold discharge current in which the behaviour of barium intensity with respect to current is markedly different. In a second type of experiment, we can estimate the relative intensities for Ba I and Ba II from the relative area under their line of absolute intensities. From these two measurements we show that the Ba loss can very easily be reduced by appropriate auxiliary coil heating.
荧光灯阴极区域的研究
本文用原子发射光谱法研究了荧光灯电极附近调光过程中钡谱线的绝对强度。荧光灯(FL)的研究通常集中在电极上,因为灯的寿命通常受到电极寿命和耐久性的限制。一般来说,一个商业电极系统由一个钨线圈组成,涂有一层功函数降低发射极的碱氧化物混合物,如BaO, SrO和CaO。调光的主要问题之一是当电极的额外加热不是最佳时,会减少灯的寿命,导致非最佳电极温度。有必要设计规则调光,以达到“良好”的灯寿命,基于“良好”的额外加热。这种调光设计规则可以从测量中性(Ba I)和电离(Ba II)钡线的绝对强度中得出,因为这些是描述发射极材料蒸发和溅射的关键参数。在稳态运行过程中产生游离钡,通过涂层扩散输送到表面。在灯工作过程中,由于溅射(主要是在启动和调光期间)和蒸发(主要是在稳态期间),钡从发射器中逸出,其中放电由(冷)电极的二次电子发射维持,其中放电由(热)电极的热离子发射维持。在第一类实验中,原子发射诊断用于检测和测量中性(ball -553.5 nm)和电离(Ball-455.4n m)钡的强度。FL在放电电流和辅助线圈加热电流范围内变暗。可以看出,存在一个阈值放电电流,其中钡强度相对于电流的行为显着不同。在第二种类型的实验中,我们可以从Ba I和Ba II的绝对强度线下的相对面积来估计它们的相对强度。从这两个测量我们表明,Ba损耗可以很容易地减少适当的辅助线圈加热。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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