Ion injection to an electrostatic trap

Patent metadata

Field	Value
Publication number	US-2017352530-A1
Application number	US-201715600996-A
Country	US
Kind code	A1
Filing date	May 22, 2017
Priority date	May 23, 2016
Publication date	Dec 7, 2017
Grant date	—

Abstract

Ions are injected into an orbital electrostatic trap. An ejection potential is applied to an ion storage device, to cause ions stored in the ion storage device to be ejected towards the orbital electrostatic trap. Synchronous injection potentials are applied to a central electrode of the orbital electrostatic trap and a deflector electrode associated with the orbital electrostatic trap, to cause the ions ejected from the ion storage device to be captured by the electrostatic trap such that they orbit the central electrode. Application of the ejection potential and application of the synchronous injection potentials are each started at respective different times, the difference in times being selected based on desired values of mass-to-charge ratios of ions to be captured by the orbital electrostatic trap.

First claim

1 . A method of injecting ions into an orbital electrostatic trap, comprising:
applying an ejection potential to an ion storage device, to cause ions stored in the ion storage device to be ejected towards the orbital electrostatic trap; and applying synchronous injection potentials to a central electrode of the orbital electrostatic trap and a deflector electrode associated with the orbital electrostatic trap, to cause the ions ejected from the ion storage device to be captured by the electrostatic trap such that they orbit the central electrode; wherein the steps of applying the ejection potential and applying the synchronous injection potentials are each started at respective different times, the difference in times being selected based on desired values of mass-to-charge ratios of ions to be captured by the orbital electrostatic trap.

2 . The method of claim 1 , wherein one or both of a magnitude and a direction of the difference between the time at which the step of applying the ejection potential is started and the time at which the step of applying the synchronous injection potentials is started is or are selected based on the desired values of mass-to-charge ratios of ions to be captured by the orbital electrostatic trap.

3 . The method of claim 1 , wherein the desired values of mass-to-charge ratios of ions to be captured by the orbital electrostatic trap includes values lower than a threshold mass-to-charge ratio, the difference in times being selected such that the start of the step of applying the synchronous injection potentials precedes the start of the step of applying the ejection potential.

4 . The method of claim 3 , wherein the threshold mass-to-charge ratio is 100 Thomsons.

5 . The method of claim 1 , wherein the desired values of mass-to-charge ratios of ions to be captured by the electrostatic trap includes values higher than a limit mass-to-charge ratio, the difference in times being selected such that start of the step of applying the ejection potential precedes the start of the step of applying the synchronous injection potentials.

6 . The method of claim 5 , wherein the limit mass-to-charge ratio is 8000 Thomsons.

7 . The method of claim 1 , wherein the magnitude of the difference between the time at which the step of applying the ejection potential is started and the time at which the step of applying the synchronous injection potentials is started is one of: at least 3 μs; at least 10 μs; at least 15 μs; at least 20 μs; and at least 25 μs.

8 . The method of claim 1 , wherein the magnitude of the difference between the time at which the step of applying the ejection potential is started and the time at which the step of applying the synchronous injection potentials is started is based on one or more of: a time period associated with the ejection potential; a time period associated with the synchronous injection potentials; and a time period associated with a flight time for ions between the ion storage device and the electrostatic trap.

9 . The method of claim 8 , wherein the magnitude of the difference is at least 3 times an induction period associated with the synchronous injection potentials.

10 . The method of claim 8 , wherein the magnitude of the difference is based on: a discharge time constant associated with the synchronous injection potentials; and/or a flight time for ions between the ion storage device and the orbital electrostatic trap.

11 . The method of claim 10 , wherein the magnitude of the difference is greater than the flight time for ions between the ion storage device and the orbital electrostatic trap but less than the sum of the flight time for ions between the ion storage device and the orbital electrostatic trap and the discharge time constant associated with the synchronous injection potentials.

12 . The method of claim 10 , wherein the discharge time constant associated with the synchronous injection potentials is dependent on at least one respective resistance and at least one respective capacitance associated with each of the central electrode and the deflector electrode to which the synchronous injection potentials are applied.

13 . The method of claim 10 , wherein the discharge time constant associated with the synchronous injection waveforms is programmable or adjustable using digital circuitry.

14 . The method of claim 1 , wherein the orbital electrostatic trap comprises the central electrode and a co-axial outer electrode and wherein the step of applying synchronous injection potentials comprises applying a trapping injection potential to the central electrode.

15 . The method of claim 14 , wherein the trapping injection potential is a ramping potential from a first injection potential level to a second, lower injection potential level.

16 . The method of claim 1 , wherein an ion deflector comprising the deflector electrode is provided between the ion storage device and the orbital electrostatic trap and wherein the step of applying synchronous injection potentials comprises applying a deflecting injection potential to the ion deflector, to cause the ions to travel towards the orbital electrostatic trap.

17 . The method of claim 1 , wherein the step of applying the ejection potential comprises reducing a magnitude of a potential applied to one or more electrodes of the ion storage device, such that the ions stored in the ion storage device are ejected towards the orbital electrostatic trap.

18 . The method of claim 17 , wherein the step of applying the ejection potential comprises switching off an RF potential applied to one or more electrodes of the ion storage device, and applying a DC extraction potential to one or more electrodes of the ion storage device, such that the ions stored in the ion storage device are ejected towards the orbital electrostatic trap.

19 . The method of claim 1 , wherein the ion storage device is a curved linear trap.

20 . The method of claim 1 , wherein the step of applying an ejection potential is started by applying an ejection trigger signal to an ejection switch controlling application of the ejection potential and/or wherein the step of applying synchronous injection potentials is started by applying one or more injection trigger signals to at least one injection switch controlling application of the synchronous injection potentials.

21 . The method of claim 1 , wherein an RF potential with a predetermined frequency is generated and the difference between respective start times of the steps of applying the ejection potential and applying the synchronous injection potentials is measured using the predetermined frequency of the RF potential.

22 . A mass spectrometer, comprising:
an ion storage device, configured to receive ions for analysis, store the received ions and eject the stored ions; an orbital electrostatic trap, having a central electrode and an associated deflector electrode and being arranged to receive the ions ejected from the ion storage device; and a controller, configured to perform steps of:
applying an ejection potential to the ion storage device, to cause ions stored in the ion storage device to be ejected towards the orbital electrostatic trap; and
applying synchronous injection potentials to the central electrode of the orbital electrostatic trap and a deflector electrode associated with the orbital electrostatic trap, to cause the ions ejected from the ion storage device to be captured by the electrostatic trap such that they orbit the central elec

Assignees

• Thermo Fisher Scient (Bremen) Gmbh

Inventors

• Belov Mikhail
• Denisov Eduard
• Quiring Gregor
• Grinfeld Dmitry

Classifications

• H01J49/061

  Ion deflecting means, e.g. ion gates · CPC title

• H01J49/426

  Methods for controlling ions · CPC title

• H01J49/425 Primary

  with a logarithmic radial electric potential, e.g. orbitraps · CPC title

• H01J49/4245 Primary

  Electrostatic ion traps (H01J49/422 takes precedence) · CPC title

• H01J49/4295

  Storage methods · CPC title