Patent ID: 7227130
Filing Date: 2007-06-05
Classification: H01J

Abstract:
1. A method of operating a mass spectrometer having an elongated rod set, the rod set having an entrance end, an exit end, a plurality of A rods and a plurality of B rods; the method comprising: (a) providing a first group of ions within the rod set; (b) providing a second group of ions within the rod set, the second group of ions being opposite in polarity to the first group of ions; (c) providing a first RF signal to the plurality of A rods and a second RF signal to the plurality of B rods to provide a RF drive voltage to the rod set to radially confine the first group of ions and the second group of ions in the rod set; and, (d) providing an entrance auxiliary RF voltage to the entrance end and an exit auxiliary RF voltage to the exit end relative to the RF drive voltage, to trap both the first group of ions and the second group of ions in the rod set, wherein the entrance auxiliary RF voltage applied to the entrance end and the exit auxiliary RF voltage applied to the exit end are derived from the RF drive voltage, and step (d) comprises providing a capacitive dividing network between the first RF signal and a ground to derive an auxiliary RF voltage from the first RF signal, the auxiliary RF voltage being one of the entrance auxiliary RF voltage applied to the entrance end and the exit auxiliary RF voltage applied to the exit end.