Patent ID: 6914242

Claim:
Apparatus for delivering ions to a mass analyzer comprising: (a) a time of flight ion guide having an entrance end and an exit end; (b) a pulsing device for receiving a continuous ion stream containing ions of different atomic mass and for delivering pulses of ions from said continuous stream of ions into the entrance end of said ion guide so that ions in each of said pulses of ions reach the exit end of said ion guide in ascending order of their atomic mass; and (c) a gating device at the exit end of said ion guide operating in timed sequence with said pulsing device for allowing only ions of a predetermined atomic mass in each of said pulses of ions to pass through said gating device to said mass analyzer, wherein said gating device comprises a first part and a second part, said first part having an aperture, wherein electrical potentials applied to said first part and said second part of said gating device can selectively allow ions to pass through said aperture.