Patent ID: 8669520

Claim:
An ion trap comprising: a ring electrode; first and second endcap electrodes situated on opposite ends of the ring electrode; and a waveform generator configured to simultaneously vary both frequency and amplitude of an AC voltage waveform applied across the first and second endcap electrodes as a function of time, thereby exciting ions with a band of resonant secular frequencies substantially without exciting ions with adjacent secular frequencies, wherein the AC voltage waveform has a frequency as a function of time t defined as f sup (t)=F c +ΔF cos(2πF m t), and an amplitude as a function of time t defined as A sup (t)=|2πTΔF sin(2πF m t)| 1/2 , where T is waveform duration, F c is the center frequency of a sampling band with half-bandwidth ΔF, and F m is a waveform modulation frequency.