微波等离子体炬耦合方式的研究

A Study of the Coupling Position of the Microwave Plasma Torch

采用气动雾化连续进样、端视观测法 ,考察了微波等离子体炬原子发射光谱法中等离子体Ar线的背景发射以及Al,Mg ,V等元素的信号发射强度随天线耦合连接点位置的不同而发生的变化 .结果表明 ,当天线位于炬管顶端 ,即天线距离活塞 3λ/4和λ/4时均能获得较好的等离子体 ,λ/4略好 ,信号发射强度和信背也较大 ,只是精密度略差一些 .初步探讨了MPT炬管的电磁场结构 .

The microwave plasma torch(MPT) possesses a configuration with three concentric metal tubes. The microwave energy is coupled into the plasmavia a cylindrical antenna that surrounds the intermediate tube. The effects of the antenna position on MPT discharge and performance of the plasma were studied. An end-on viewed MPT was used in this research, and a pneumatic nebulizer was used for sampling. Four emission lines of Ar were studied to find the effect of the coupling position on the plasma background emission. At the same time, the signal intensities and the signal-background ratios of three elements(Al, Mg and V) were also studied, and RSD was investigated also. From the research, it could be found that the analytical performance was better when the antenna position wasλ/4 than 3λ/4, except of a little poorer repeatability. The structure of electromagnetic field of the MPT was discussed also.