Computer simulations of a new three rods ion optic (TRIPOLE) with high focusing and mass filtering capabilities

Abstract

A novel three rod (tripole) ion optic to which three AC voltages with symmetrically delayed phase shifts were applied to each electrode. We studied its ion guiding, focusing, and mass filtering capabilities by SIMION ver. 7.0 computer simulations. An electric field mathematical model was developed to calculate the pseudopotential of the tripole radial AC force. The tripole showed stable ion guiding for wide ranges of AC amplitude; better collisional focusing than hexapole and octapole and similar focusing as quadrupole (rod pole). Also, the ion optic clearly showed interesting mass filtering potential when the phase shift was asymmetrically delayed. The symmetric shape of the pseudopotential field explained the tripole ion guiding and focusing capabilities. For mass filtering, the pseudopotential was asymmetric and its effect was balanced with DC voltage to separate the ions, depending in their masses. The resolution was much lower than quadrupole but useful when rough filtering was required. (J Am Soc Mass Spectrom 2007, 18, 413-421)

The tripole linear ion trap with highly efficient orthogonal ion ejection designed by computer simulations

“…The radio‐frequency (RF) potentials created by the phase‐shifted RF voltages (Fig. 3(a)) were overlapped by the superposition principle as explained elsewhere 13. By symmetry, the other two electrodes have the same normalized potential if the angle coordinate value is rotated 120° from electrode ‘1’ to electrode ‘2’ and −120° to electrode ‘3’.…”

“…In short, the pseudopotential well showed concentric circular patterns with non‐null value at the center, similar to the referenced work 13. This fact demonstrates theoretically the ion‐guiding capability of the tripole; thus, this device has the potential to be also an LIT.…”

“…In previous work,12, 13 we introduced a new ion guide with three rods (tripole) and phase‐shifted AC voltages. In this work by computer simulations we will study the tripole designed as a linear ion trap (tLIT), its trapping efficiency, its novel orthogonal ejecting capabilities and its compatibility with a time‐of‐flight (TOF) analyzer.…”

Comparative performance of tripole and quadrupole ion guides at elevated pressure

“…A tripole ion guide requires three RF voltages with relative phase shifts of 2π/3 for its operation: A · cos( ω t), A · cos( ω t + 2π/3) and A · cos( ω t + 4π/3),14 where A is the amplitude of the RF and ω is its angular frequency. The electric field in the tripole of the infinite length which electrodes are distant enough from the other conductors is not changed if one adds an arbitrary potential to all the rods.…”

“…Only recently tripole transmission properties have been evaluated by numerical simulations 12 and experimentally. 13 In this paper, we demonstrate for the first time the operational tripole RF ion guide 14 in the intermediate pressure region, and compare its performance to that of the quadrupole ion guide.…”