Systems and methods of operation of linear ion traps in dual balanced AC/unbalanced RF mode for 2D mass spectrometry

Patent metadata

Field	Value
Publication number	US-11004672-B2
Application number	US-201916552614-A
Country	US
Kind code	B2
Filing date	Aug 27, 2019
Priority date	Aug 27, 2019
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

A mass selective ion trapping device includes a linear ion trap and a RF control circuitry. The ion trap includes a plurality of trap electrodes configured for generating a quadrupolar trapping field in a trap interior and for mass selective ejection of ions from the trap interior. The RF control circuitry is configured to apply a balanced AC voltage to the trap electrodes during a first period of time such that an AC voltage applied to a first pair of trap electrodes is of the same magnitude and of opposite sign to an AC voltage applied to a second pair of trap electrodes; apply unbalanced RF voltage to the second pair of trap electrodes during a second period of time; ramp the balanced AC voltage down and the unbalanced RF voltage up during a transition period; and eject ions from the linear ion trap after the second period of time.

First claim

What is claimed is:

1. A mass selective ion trapping device comprising:
a linear ion trap including:
a plurality of trap electrodes spaced apart from each other and surrounding a trap interior, the plurality of trap electrodes including a first pair of trap electrodes and a second pair of trap electrodes, at least a first trap electrode of the first pair of trap electrodes including a trap exit aperture, the trap electrodes configured for generating a quadrupolar trapping field in the trap interior and for mass selective ejection of ions from the trap interior;

an RF control circuitry configured to:
during a first period of time, apply a balanced AC voltage to the trap electrodes such that a first AC voltage applied to the first pair of trap electrodes is of opposite sign to a second AC voltage to the second pair of trap electrodes, the first and second AC voltages being of substantially the same magnitude;
during a second period of time, apply unbalanced RF voltage to the second pair of trap electrodes;
during a transition period between the first period of time and the second period of time, ramp the balanced AC voltage down and the unbalanced RF voltage up; and
eject ions from the linear ion trap after the second period of time.

2. The mass selective ion trapping device of claim 1 wherein ions enter the trap during the first period of time.

3. The mass selective ion trapping device of claim 1 wherein a kinetic energy spread of ions before ejection from the linear ion trap is less than about 5.0 eV.

4. The mass selective ion trapping device of claim 1 wherein an electric field on a centerline of the linear ion trap is near zero during the first period of time.

5. The mass selective ion trapping device of claim 1 wherein the AC voltage is in a frequency range of between about 100 kHz and about 600 kHz.

6. The mass selective ion trapping device of claim 1 wherein the AC voltage is less than about 400 V 0-P .

7. The mass selective ion trapping device of claim 6 wherein the AC voltage is less than about 200 V 0-p .

8. The mass selective ion trapping device of claim 1 wherein the RF voltage is in a frequency range of between about 750 kHz and about 1500 kHz.

9. The mass selective ion trapping device of claim 1 wherein during the transition period, a ramp down time for the AC voltage is less than about 1.5 ms and a ramp up time for the RF voltage between about 0.8 ms and about 2.5 ms.

10. The mass selective ion trapping device of claim 1 wherein the balanced AC voltage is applied as a digital waveform.

Assignees

• Thermo Finnigan Llc

Inventors

• Kovtoun Viatcheslav V

Classifications

• H01J49/4265

  Controlling the number of trapped ions; preventing space charge effects · CPC title

• H01J49/4225 Primary

  Multipole linear ion traps, e.g. quadrupoles, hexapoles · CPC title

• H01J49/0031

  Step by step routines describing the use of the apparatus (H01J49/0081 takes precedence) · CPC title

• H01J49/423

  with radial ejection · CPC title

• H01J49/022

  Circuit arrangements, e.g. for generating deviation currents or voltages (regulating electric or magnetic variables in general, e.g. current, magnetic field G05F); Components associated with high voltage supply (high voltage supply per se H02M) · CPC title