Injection of ions into an ion storage device

Abstract

A method of injecting ions into an ion storage device, comprising: providing an RF trapping field in the ion storage device that defines a trapping volume in the ion storage device by applying one or more RF voltages to one or more trapping electrodes; providing a gas in the trapping volume; injecting ions into the trapping volume through an aperture in an end electrode located at a first end of the ion storage device, the end electrode having a DC voltage applied thereto; reflecting the injected ions at a second end of the ion storage device, opposite to the first end, thereby returning the ions to the first end; and ramping the DC voltage applied to the end electrode during the period between injecting the ions through the aperture and the return of the ions to the first end, such that by the time the ions return to the first end for a first time a potential barrier is established by the ramped DC voltage that prevents returning ions from striking the end electrode. Also an apparatus for injecting ions into an ion storage device, which comprises a controller for ramping a first DC voltage applied to an end electrode of the device having an entrance aperture during a period between injection of ions through the entrance aperture and a return of the injected ions to the aperture so as to establish a potential barrier that prevents returning ions from striking the end electrode.