Improvement of reflectron time-of-flight mass spectrometer for better convergence of ion beam

Abstract

Reflectron time-of-flight mass spectrometer (RTOF-MS) is a powerful tool to achieve high resolution in mass analysis of various ions. As it is often supposed that analyte ions are generated in a small volume in the ion-extraction region, its performance is not optimized for ions spread over a large volume. Not only the mass resolution is degraded due to incomplete space and energy focusing, but also the ion beam is subject to significant divergence of ion trajectories after it is reflected from an ion reflector. Here we present a novel design of RTOF-MS equipped with an additional electrostatic lens in front of a conventional grid-less ion reflector for improving convergence of an ion beam. The performance is examined by mass analysis of Ag3+ ions extracted from a volume of 6.3 cm3, i.e., a cylinder with 20-mm length and 20-mm diameter. The improved convergence of an ion beam is demonstrated by a two-dimensional image of ions on the ion detector. Mass resolution is evaluated as well.