Research Of Ion Mobility Spectrometer Based On Positive Pulse Corona Discharge Ion Source

As a superior technology of trace gaseous material detection, ion mobility spectrometry (IMS) is widely used in airport security, chemical and biological warfare agent detection and environmental monitoring, etc. Radioactive ion source 63Ni is favored for use in traditional IMS analyzers because of its stable and reliable operation with ionization chemistry and independent ability without an external power supply. However, radioactive elements in miniaturized portable IMS would pose a potential health threat to users, which is not easy to be promoted and widely accepted. Therefore, with the consideration of health and environmental protection, the development of alternative ion source is imperative.Positive pulse corona discharge with non-radioactive characteristic and low power consumption and high efficiency is employed as the ion source of IMS in our research. Meanwhile, it can be easily manufactured by MEMS technology and the structure of corresponding drift tube is simple, which contributes to the miniaturization of ion mobility spectrometer as well.After sufficient and comprehensive review on the research background of this subject, the principle and structure of IMS was discussed in detail. Utilizing "needle-grid" asymmetric electrode structure, lots of experiments were carried out to analyze the character of DC and pulse corona discharge in positive mode. The number of positive ions generated by single pulse discharge and its relationship with electrode parameters was measured via the experimental system, providing data support for the design of pulse corona discharge ion source directly. Then, the main structure of IMS based on pulse corona discharge ion source was designed and manufactured, and the reactant ion mobility spectrometry in the air was detected successfully, which confirms the feasibility of positive pulse corona discharge as the ion source of IMS. Effect of water vapor on the signal obtained from ion mobility spectrometry was analyzed through experiment results. By detecting the relationship between ion migration rate and electric field and measuring the reproducibility of ion mobility spectrometry, the performance of the main structure of IMS was verified.