MASS SPECTROMETRY METHOD AND APPARATUS

摘要

A mass spectrometer (10) comprises an ion source (12) which generates nebulized ions which enter an ion cooler (20) via an ion source block (16). Ions within a window of m/z of interest are extracted via a quadrupole mass filter (24) and passed to a linear trap (30). Ions are trapped in a potential well in the linear trap (30) and are bunched at the bottom of the potential well adjacent an exit segment (50). Ions are gated out of the linear trap (30) into an electrostatic ion trap (130) and are detected by a secondary electron multiplier (10). By bunching the ions in the linear trap (30) prior to ejection, and by focussing the ions in time of flight (TOF) upon the entrance of the electrostatic trap (130), the ions arrive at the electrostatic trap (130) as a convolution of short, energetic packets of similar m/z. Such packets are particularly suited to an electrostatic trap because the FWHM of each packet's TOF distribution is less than the period of oscillation of those ions in the electrostatic trap.