Patent ID: 7141789
Filing Date: 2006-11-28
Classification: H01J

Abstract:
1. A quadrupole electrode system for connection to a voltage supply means for providing an at least partially-AC potential difference within the quadrupole electrode system, the quadrupole electrode system comprising: (a) a quadrupole axis; (b) a first pair of rods, wherein each rod in the first pair of rods is spaced from and extends alongside the quadrupole axis; (c) a second pair of rods, wherein each rod in the second pair of rods is spaced from and extends alongside the quadrupole axis; and (d) a voltage connection means for connecting at least one pair of the first pair of rods and the second pair of rods to the voltage supply means to provide the at least partially-AC potential difference between the first pair of rods and the second pair of rods; such that in use the first pair of rods and the second pair of rods are operable, when the at least partially-AC potential difference is provided by the voltage supply means and the voltage connection means to at least one of the first pair of rods and the second pair of rods, to generate a two-dimensional substantially quadrupole field having a quadrupole harmonic with amplitude A 2 and a hexapole harmonic with amplitude A 3 wherein the magnitude of A 3 is greater than 0.1% of the magnitude of A 2 .