Patent ID: 6576893
Filing Date: 2003-06-10
Classification: H01J

Abstract:
A method of trapping ions in an ion trapping device having a ring electrode and two end-cap electrodes, the method comprising:(a) forming sample ions in an ion source external to said ion trapping device, (b) introducing said ions into said ion trapping device through a hole at the centre of a first said end-cap electrode, (c) retarding said ions by applying to a second said end-cap electrode a retarding voltage relative to said first end-cap electrode and said ring electrode, said retarding voltage being applied before said ions have entered the ion trapping device through said hole, (d) removing said retarding voltage when said ions are about to change their direction of motion towards said first end-cap electrode, and (e) establishing an ion trapping field quickly by abruptly applying a radio frequency voltage between said ring electrode and said end-cap electrodes after said ions have been introduced into the ion trapping device.