Multi-reflection mass spectrometer

Patent metadata

Field	Value
Publication number	US-10964520-B2
Application number	US-201916697329-A
Country	US
Kind code	B2
Filing date	Nov 27, 2019
Priority date	Dec 21, 2018
Publication date	Mar 30, 2021
Grant date	Mar 30, 2021

Abstract

A multi-reflection mass spectrometer comprising two ion mirrors spaced apart and opposing each other in a direction X, each mirror elongated generally along a drift direction Y, the drift direction Y being orthogonal to the direction X, a pulsed ion injector for injecting pulses of ions into the space between the ion mirrors, the ions entering the space at a non-zero inclination angle to the X direction, the ions thereby forming an ion beam that follows a zigzag ion path having N reflections between the ion mirrors in the direction X whilst drifting along the drift direction Y, a detector for detecting ions after completing the same number N of reflections between the ion mirrors, and an ion focusing arrangement at least partly located between the opposing ion mirrors and configured to provide focusing of the ion beam in the drift direction Y, such that a spatial spread of the ion beam in the drift direction Y passes through a single minimum at or immediately after a reflection having a number between 0.25N and 0.75N, wherein all detected ions are detected after completing the same number N of reflections between the ion mirrors.

First claim

The invention claimed is:

1. A multi-reflection mass spectrometer comprising:
two ion mirrors spaced apart and opposing each other in a direction X, each mirror elongated generally along a drift direction Y, the drift direction Y being orthogonal to the direction X;
a pulsed ion injector for injecting pulses of ions into the space between the ion mirrors, the ions entering the space at a non-zero inclination angle to the X direction, the ions thereby forming an ion beam that follows a zigzag ion path having N reflections between the ion mirrors in the direction X whilst drifting along the drift direction Y;
a detector for detecting ions after completing the same number N of reflections between the ion mirrors; and
an ion focusing arrangement at least partly located between the opposing ion mirrors and configured to provide focusing of the ion beam in the drift direction Y, such that a spatial spread of the ion beam in the drift direction Y passes through a single minimum at or immediately after a reflection having a number between 0.25N and 0.75N, wherein all detected ions are detected after completing the same number N of reflections between the ion mirrors.

2. The multi-reflection mass spectrometer of claim 1 wherein the spatial spread of the ion beam in the drift direction on the first reflection is substantially the same as the spatial spread of the ion beam in the drift direction on the N-th reflection.

3. The multi-reflection mass spectrometer of claim 1 wherein the spatial spread of the ion beam in the drift direction Y passes through a single minimum that is substantially halfway along the ion path between the ion focusing arrangement and the detector.

4. The multi-reflection mass spectrometer of claim 1 wherein the ion focusing arrangement comprises a drift focusing lens or pair of drift focusing lenses for focusing the ions in the drift direction Y.

5. The multi-reflection mass spectrometer of claim 4 wherein at least one drift focusing lens is a converging lens.

6. The multi-reflection mass spectrometer of claim 5 wherein the converging lens focuses the ions such that the spatial spread of the ion beam in the drift direction Y has a maximum at the converging lens that is 1.2-1.6 times, or about √2 times, the spatial spread at the minimum.

7. The multi-reflection mass spectrometer of claim 5 wherein the spatial spread of the ion beam in the drift direction Y has a maximum at the converging lens that is in the range 2× to 20× an initial spatial spread of the ion beam in the drift direction Y at the ion injector.

8. The multi-reflection mass spectrometer of claim 1 wherein the ion beam undergoes K oscillations between the ion mirrors from the ion injector to the ion detector and K is a value within a range that is +/−50%, or +/−40%, or +/−30%, or +/−20%, or +/−10% around an optimum value, K (opt) given by:

K
⁡

(
opt
)

=

(

D
L
2

4
⁢

⁢
Π
⁢

⁢
W

)

1
/
3

wherein D L is the drift length travelled by the ion beam in the drift direction Y, Π is the phase volume wherein Π=δα i ·δx i and δα i is the initial angular spread and δx i is the initial spatial spread of the ion beam at the ion injector, and W is the distance between the ion mirrors in the X direction.

9. The multi-reflection mass spectrometer of claim 1 wherein the angular spread of the ion beam, δα, after focusing by the ion focusing arrangement is within a range that is +/−50%, or +/−40%, or +/−30%, or +/−20%, or +/−10% around an optimum value, δα (opt) given by:

δ
⁢

⁢

α
⁡

(
opt
)

=

2
⁢

⁢
Π

W
⁢

⁢

K
⁡

(
opt
)

.

10. The multi-reflection mass spectrometer of claim 1 wherein the ion focusing arrangement is located before a reflection having a number less than 0.25N in the ion mirrors.

11. The multi-reflection mass spectrometer of claim 1 wherein the initial spatial spread of the ion beam in the drift direction Y at the ion injector, δx i , is 0.25-10 mm or 0.5-5 mm.

12. The multi-reflection mass spectrometer of claim 1 wherein the ion focusing arrangement comprises a drift focusing lens positioned after a first reflection and before a fifth reflection in the ion mirrors.

13. The multi-reflection mass spectrometer of claim 12 wherein the ion focusing arrangement comprises a drift focusing lens positioned after a first reflection in the ion mirrors and before a second reflection in the ion mirrors.

14. A multi-reflection mass spectrometer of claim 12 wherein the drift focusing lens is the only drift focusing lens positioned between the first reflection and the ion detector.

15. The multi-reflection mass spectrometer of claim 12 wherein the drift focusing lens comprises a trans-axial lens, wherein the trans-axial lens comprises a pair of opposing lens electrodes positioned either side of the beam in a direction Z, wherein direction Z is perpendicular to directions X and Y.

16. The multi-reflection mass spectrometer of claim 15 wherein each of the opposing lens electrodes comprises a circular, elliptical, quasi-elliptical or arc-shaped electrode.

17. The multi-reflection mass spectrometer of claim 15 to wherein each of the pair of opposing lens electrodes comprises an array of electrodes separated by a resistor chain to mimic a field curvature created by an electrode having a curved edge.

18. The multi-reflection mass spectrometer of claim 15 wherein the drift focusing lens comprises a multipole rod assembly or an Einzel lens.

Assignees

• Thermo Fisher Scient Bremen Gmbh

Inventors

• Stewart Hamish
• Grinfeld Dmitry E
• Makarov Alexander A

Classifications

• H01J49/406 Primary

  with multiple reflections · CPC title

• H01J49/4245

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

• H01J49/0031

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

• H01J49/004

  Combinations of spectrometers, tandem spectrometers, e.g. MS/MS, MSn · CPC title

• H01J49/061

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