Method and apparatus for injection of ions into an electrostatic ion trap

Patent metadata

Field	Value
Publication number	US-10170292-B2
Application number	US-201715782797-A
Country	US
Kind code	B2
Filing date	Oct 12, 2017
Priority date	May 5, 2015
Publication date	Jan 1, 2019
Grant date	Jan 1, 2019

Abstract

A method of injecting ions into an electrostatic trap, comprising: generating ions in an ion source; transporting the ions from the ion source to an ion store downstream of the ion source; releasing the ions from the ion store to an ion guide downstream of the ion store; and accelerating the ions from the ion guide as a pulse into an orbital electrostatic trap for mass analysis, wherein the average velocity of the ions as the ions exit from the ion guide is substantially higher than the average velocity of the ions as they exit from the ion store, wherein there is a delay between releasing the ions from the ion store and accelerating the ions from the ion guide. Also an apparatus suitable for the method.

First claim

The invention claimed is:

1. An apparatus for injecting ions into an electrostatic trap, comprising:
an ion source for generating ions;
an ion store downstream of the ion source for receiving ions that have been generated in the ion source;
a non-trapping ion guide downstream of the ion store for receiving ions that have been released by the ion store and for accelerating the received ions into an orbital electrostatic trap downstream of the ion guide; and
a pulser configured to provide a voltage pulse in the ion guide for increasing the average velocity of the ions at the exit of the ion guide from the average velocity of the ions at the entrance to the ion guide, wherein a delay is arranged between releasing the ions from the ion store and providing the voltage pulse to the ion guide such that for ions of the same m/z forming an ion packet, the duration of the ion packet as it enters the electrostatic trap is substantially shorter than when the ion packet enters the ion guide from the ion store.

2. The apparatus as claimed in claim 1 configured such that in operation the electrostatic trap separates the ions along a direction z according to their mass-to-charge ratio; and the initial velocity of the ions in the ion guide in the direction z prior to acceleration is substantially smaller than the velocity of the ions in the direction z during ion detection in the electrostatic trap.

3. The apparatus as claimed in claim 1 further comprising at least one ion optical device located between the ion source and the ion store for transporting ions from the ion source to the ion store.

4. The apparatus as claimed in claim 1 further comprising a mass filter or an ion mobility separator upstream of the ion store.

5. The apparatus as claimed in claim 1 wherein the ion store is a linear or 3D RF ion trap.

6. The apparatus as claimed in claim 1 wherein the ion store is gas-filled, optionally to a pressure 1×10 −3 mbar to 5×10 −3 mbar.

7. The apparatus as claimed in claim 1 wherein the ion store is configured such that the ions are slowly released from the ion store to the ion guide with energies less than 1V.

8. The apparatus as claimed in claim 1 wherein the ion store is configured such that the ions are released from the ion store over a period of 10 to 100 microseconds.

9. The apparatus as claimed in claim 1 wherein the ion store is configured such that ions are released from the ion store by applying a DC voltage pulse to generate an axial field gradient in the ion store.

10. The apparatus as claimed in claim 1 wherein the ion guide is gas-free, optionally wherein the pressure is less than or equal to 10 −3 mbar.

11. The apparatus as claimed in claim 1 configured such that the ions are accelerated from the ion guide by applying a DC voltage pulse to generate an axial field gradient in the ion guide, whereby an energy increase of the ions depends on their initial position within the guide.

12. The apparatus as claimed in claim 1 further comprising auxiliary electrodes external to the ion guide for applying a pulsed DC axial field gradient in the ion guide.

13. The apparatus as claimed in claim 1 wherein the ion guide is configured with segmented electrodes for applying a pulsed DC axial field gradient in the ion guide.

14. The apparatus as claimed in claim 1 configured such that the energy range of the accelerated ions is 1% to 30% of the final energy of the ions in the electrostatic trap.

15. The apparatus as claimed in claim 1 configured such that at the same time as applying the axial field gradient, any RF field in the ion guide is switched off.

16. The apparatus as claimed in claim 1 configured such that the energy spread of the ions accelerated by the ion guide is significantly smaller than the final energy of the ions within the electrostatic trap, optionally wherein the energy spread of the ions is not more than 30% or not more than 20% or not than 10%, of the final energy of the ions within the electrostatic trap.

17. The apparatus as claimed in claim 1 configured such that the ion guide focuses the ions at a focal point within the electrostatic trap and wherein the ions are focused into ion packets that are sufficiently narrow in the z-direction of the electrostatic trap when they pass near one or more detection electrodes of the electrostatic trap so as to maintain coherence of the ion packets during detection.

18. The apparatus as claimed in claim 17 further comprising an ion lens located downstream of the ion guide for adjusting the position of the focal point of the accelerated ions.

19. The apparatus as claimed in claim 1 wherein the ion guide is a linear RF multipole ion guide, optionally wherein the ion guide axis is substantially orthogonally to the direction z of mass separation in the electrostatic trap.

20. A mass spectrometer for mass analysing ions comprising the apparatus for injecting ions as claimed in claim 1 and an electrostatic trap for receiving and mass analysing the ions accelerated by the ion guide.

21. An apparatus for injecting ions into an electrostatic trap, comprising:
an ion source for generating ions;
an ion store downstream of the ion source for receiving ions that have been generated in the ion source;
a non-trapping ion guide downstream of the ion store for receiving ions that have been released by the ion store and for accelerating the received ions into an electrostatic trap downstream of the ion guide; and
a pulser configured to provide a voltage pulse in the ion guide for increasing the average velocity of the ions at the exit of the ion guide compared to the average velocity of the ions at the entrance to the ion guide, wherein a delay is arranged between releasing the ions from the ion store and providing the voltage pulse to the ion guide such that for ions of the same m/z forming an ion packet, the duration of the ion packet as it enters the electrostatic trap is substantially shorter than when the ion packet enters the ion guide from the ion store;
wherein accelerating the ions into the electrostatic trap takes place in the same direction as the release of ions from the ion store, which is substantially orthogonal to a direction of mass separation, z, in the electrostatic trap.

22. An apparatus for injecting ions into an electrostatic trap, comprising:
an ion source for generating ions;
an ion store downstream of the ion source for receiving ions that have been generated in the ion source; and a
a helical trajectory ion guide downstream of the ion store for receiving ions that have been released by the ion store and for accelerating the received ions into an electrostatic trap downstream of the ion guide;
wherein accelerating the ions into the electrostatic trap takes place substantially orthogonally to the direction of the release of ions from the ion store and substantially parallel to a direction of mass separation, z, in the electrostatic trap.

23. The apparatus as claimed in claim 22 further comprising a pulser for accelerating the ions configured to provide a voltage pulse in the ion guide for increasing the average velocity of the ions at the exit of the ion guide compared to the average velocity of the ions at the entrance to the ion guide.

24. The apparatus as claimed in claim 22 wherein a delay is arranged between releasing the ions from the ion store and accelerating the ions from the ion guide.

25. The apparatus as claimed in claim 22 c

Assignees

• Thermo Fisher Scient Bremen Gmbh

Inventors

• Makarov Alexander A

Classifications

• H01J49/4295

  Storage methods · CPC title

• H01J49/062

  Ion guides (linear ion traps performing mass selection H01J49/4225, mass filters H01J49/421) · CPC title

• H01J49/4245 Primary

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

• H01J49/426

  Methods for controlling ions · CPC title

• H01J49/425 Primary

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