ION TRAP

摘要

There is provided a quadruple ion trap (22) of the type including a ring electrode (24) and first and second end cap electrodes (26, 28), which define a trapping volume. The end cap electrodes (26, 28) include central apertures (30) for the injection of ions or electrons into the trapping volume and for the ejection of stored ions during the analysis of a sample. Field faults in the RF trapping field are compensated by addition of a concentric recess or depression in the surface of at least one end cap (26, 28) around the aperture (30). There is also provided an ion trap mass spectrometer employing the ion trap.