Patent ID: 9230790
Filing Date: 2016-01-05
CPC Classification: H01J

Claim Text:
1. An apparatus for focusing dispersed ions, comprising: a plurality of electrodes spaced apart from one another, each of said electrodes having the same thickness and having an aperture for passage of ions therethrough, wherein said apertures collectively define an interior volume extending between an ion inlet and an ion outlet through which the ions can traverse; and a controller configured to apply a DC electric potential to each of said electrodes without applying an RF potential to any of the electrodes, so as to exert a focusing force on ions passing through each of said apertures towards a central axis of said volume; wherein one or more openings are formed between the plurality of electrodes through which gas can escape said volume; wherein the controller applies a DC potential to each of the plurality of electrodes that is opposite in polarity to a DC potential applied to the immediately-preceding electrode, if any, in the ion inlet direction; and wherein the change in DC potential between two adjacent electrodes alternates between an increasing change and a decreasing change as the electrodes extend from the ion inlet to the ion outlet and wherein, if it is assumed that the plurality of electrodes are numbered with consecutive positive integers from the ion inlet to the ion outlet, then: the controller applies a DC potential to each even-numbered electrode that is less than a DC potential applied to any preceding electrodes in the ion inlet direction; and for each odd-numbered electrode for which an immediately-preceding even-numbered electrode and an immediately-preceding odd-numbered electrode exist in the ion inlet direction, the controller applies a DC potential to the odd-numbered electrode that is greater than a DC potential applied to the immediately-preceding even-numbered electrode and that is less than a DC potential applied to the immediately-preceding odd-numbered electrode.