Optimization and Analysis on Ion Mobility Spectrometer Based on a Laser Ionization Source

Both drift distance and drift voltage are important parameters of ion mobility spectrometer, because they have significant impact on improving the sensitivity and resolution of apparatus. Some phenomenas were observed when we optimized the ion mobility spectrometer based on a 248 nm KrF excimer laser: the entire apparatus has a good stability, and the signal intensity is decreased with the increase of drift distance and the decline of drift voltage. The reasons are deduced that the electric field is not completely uniform, therefore fewer ions are received with the longer drift distance, and more ions are received with the faster speed in the horizontal direction owing to the elevation of drift voltage. The drift distance can be set to 100 mm taking account of resolution. These conclusions are confirmed through the analysis of signal current and waveform.