Dipolar Excitation in the Third Stability Region

Quadrupole mass filters are normally operated as narrow band pass filters by appropriate choices of rf and DC voltages corresponding to Mathieu a and q values near the apex of the first stability region. We add an auxiliary quadrupole excitation potential to the main drive voltage. As a result, stability islands appear on the ([Formula: see text]) plane. The method of the islands mapping on the ([Formula: see text]) plane is discussed in detail. The DC electric field's effect responsible for removing “shadowing” islands has been studied using a combination of analytic theory and computer modeling. We call a narrow stability region elongated along an iso-[Formula: see text] line an X-island. Two such stability islands were found where operation is possible without mass spectra interference when the DC potential is used. Those islands are formed by quadrupole potentials with relative excitation frequencies [Formula: see text] and [Formula: see text], where [Formula: see text] Many other stability X-islands are presented in detail and illustrated by their transmission contours. This data is necessary for experimental testing of the separation mode at those islands. The study demonstrates how to use X-islands to achieve relatively high resolution 4000-12,000 at the transmission of about 28-15%, respectively.

Section: Direct Current Excitation In Y Directionmentioning

confidence: 99%

Stable X-islands of quadrupole mass filter

Konenkov

Seregin

Makhmudov

et al. 2019

“…The study shows that strong dipole resonances occur at frequencies 0.25em ω = β Ω / 2, where β = 0,1, 2 … are the boundary values of the parameter β for the joint stability zones of the Mathieu equation. 15,17 The dipole excitation along the stability diagram boundaries creates instability bands. The width of an instability band increases nonlinearly with the increase of the dipole potential amplitude.…”

Section: Discussionmentioning

confidence: 99%

Modeling dipolar excitation for quadrupole mass filter

Konenkov

Сысоев

2022

The results of modeling AC and DC dipole excitation of ion oscillations in a quadrupole mass filter are presented. The simulation is done by numerical integration of the ion motion equations, ions’ initial coordinates and velocities are distributed normally. For AC dipole excitation the instability bands on the ( a, q) stability diagram follow along the isolines [Formula: see text] and [Formula: see text], creating regular dips on the transmission contour. We show that AC excitation at frequency Ω/2 makes it possible to control the resolution of the mass filter by either changing the AC amplitude or phase. Instability bands can be used for mass selective excitation in a linear ion trap. Options for the joint use of DC and AC dipole excitation to form the mass peak shape are considered.

“…The possibility of using additional DE for mass analysis of the linear quadrupole is considered in. [51][52][53][54][55][56][57] The QMF with DE is described in the patent [(a)]. The idea of the method is to change the stability boundaries of the first region by removing the stable boundary by DE.…”

Section: Quadrupole Mass Filter With Dipole Excitationmentioning

confidence: 99%

“…Round rods with r / r 0 = 1.130. 52 the stability bands following along the isolines β y . As a result, harmful peaks (Figure 41(b), DC y = 0) appear when the scanning line a = 2λq crosses this Y stability band.…”

Section: Stability Islands and Dipole Excitationmentioning

confidence: 99%

Dipole and quadrupole resonance excitation in linear quadrupoles

Konenkov

2023

In the development of commercial quadrupole mass spectrometers, there is an interest in improving the performance characteristics such as transmission, resolution, and mass range. In particular, parametric and dipolar resonance excitation of trapping ions are used for linear quadrupole mass filters. Theoretical methods and numerical simulation of ion trajectories were applied for study of ion-optical properties. The review is devoted to description of different excitation methods to improve QMF performance and consists of three parts. The first part presents the results of a linear ion trap simulation for various operating conditions and excitation methods. The second part considers the effects of dipole excitation (DE) on the performance of the quadrupole mass filter. The last part analyzes the formation of stability islands by different methods of quadrupole excitation. To date conditions of mass separation in quadrupole mass filters with sin wave supply were described for stability islands of the first and third stability regions formed by quadrupole and DE. By complicating the electronics such methods allow to overcome the destructive influence of electric field distortions and obtain a resolving power and ion transmission efficiency comparable with commercial devices. At quadrupole resonance excitation by a two-frequency signal, it is possible to reduce the length of electrodes three times without losses in resolution and transmission, which reduces the cost of rod set production with micrometer accuracy. Dipole resonance excitation allows controlling the shape of the mass peak by changing amplitude and phase of the auxiliary AC signal. The main factors affecting the resolving power of a linear ion trap are described theoretically. The numerical modeling results are confirmed by experiment.