Space-charge effects and ion distribution in plasma source mass spectrometry

✍ Scribed by Gangqiang Li; Yixiang Duan; Gary M. Hieftje

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 847 KB
• Volume: 30
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.1190300609

✦ Synopsis

Abstract

Space‐charge effects appear to be key in understanding ion‐transport processes in plasma‐source mass spectrometry. Both theoretical calculations and experimental measurements demonstrate that space charge influences ion transport between the plasma source and mass analyzer. In a theoretical analysis, both drift space and accelerating space in the interface have been considered and preliminary conclusions have been drawn concerning space‐charge repulsion and ion‐beam divergence in those regions. In the experimental work, spatial patterns of sample deposition on the third stage vacuum orifice plate were recorded while using a microwave plasma source. To measure these patterns, a stainless‐steel target was used to cover the orifice and both x‐ray fluorescence microanalysis and scanning electron microscopy (SEM) were used to examine the sample material deposited on it. The resulting spatial maps show that analyte deposition is somewhat element‐dependent in a way that is correlated with analyte atomic mass. These findings can be explained on the basis of space‐charge theory.