An Advanced High Efficiency Non-Radiogenic Ion Source for Ion Mobility Spectrometry

Abstract

During the last decade, the Denton Research Group has made significant advancements in the field of real time direct vapor detection of low volatile explosives under ambient conditions. An ion source plays a crucial role in the sensitive detection of traces of compounds in gas phase by ion mobility spectrometry, but, all the current ionization techniques have significant drawbacks and do not fully satisfy all needs. To overcome the limitations associated with either hazards from a radiogenic ion source or poor reliability from the current non-radiogenic ion sources, the author of this dissertation has undertaken the development of an entirely new ion source based on dielectric barrier discharge technologies. This dissertation describes the development, characterization, and applications of novel dielectric barrier discharge (DBD) ion sources for ion mobility spectrometry. The sources under investigation are non-radiogenic, highly reliable, and provide a high yield of ions. The difficulty of extracting ion current from a traditional dielectric barrier discharge was solved by using an array of tiny discharges formed at the crossing points of two crossed sets of glass coated wires. The relationship of the excitation voltage, frequency, and extraction field for AC excitation on the extracted ion current were studied. The dielectric barrier discharge ion source were also excited in pulse mode by fast-rising and fast-falling high voltage pulses. A high voltage switch using serial MOSFETs was specially designed for driving the dielectric barrier discharge ion source in pulse mode. Application of this dielectric barrier discharge ion source to ion mobility spectrometry was demonstrated with the measurement of limit of detection and direct vapor detection of explosives.