Rotating field mass and velocity analyzer

• US 5,726,448 A
• Filed: 02/21/1997
• Issued: 03/10/1998
• Est. Priority Date: 08/09/1996
• Status: Expired due to Term

• Current Assignee: Zimmer Incorporated (Zimmer Biomet Holdings, Inc.)
• Original Assignee: California Institute of Technology
• Inventors: Smith, Steven Joel, Chutjian, Ara
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/803,331
• Time in Patent Office: 382 Days
• Field of Search: 250/290, 250/291, 250/292, 250/293, 250/294, 250/295
• US Class Current: 250/290
• CPC Class Codes: H01J 49/421 Mass filters, i.e. deviating unwanted ions without trapping

Abstract

A rotating field mass and velocity analyzer having a cell with four walls, time dependent RF potentials that are applied to each wall, and a detector. The time dependent RF potentials create an RF field in the cell which effectively rotates within the cell. An ion beam is accelerated into the cell and the rotating RF field disperses the incident ion beam according to the mass-to-charge (m/e) ratio and velocity distribution present in the ion beam. The ions of the beam either collide with the ion detector or deflect away from the ion detector, depending on the m/e, RF amplitude, and RF frequency. The detector counts the incident ions to determine the m/e and velocity distribution in the ion beam.

Claims

1. A mass analyzer for identifying mass and velocity distributions in an ion beam comprising:

a cell receiving said ion beam;

means for creating a rotating RF field imparting a non-magnetic field within said cell, wherein said cell is a magnetic field free cell; and

a detector located in close proximity to said cell for counting ions in said ion beam.

2. The mass analyzer as set forth in claim 1, wherein said rotating RF field is time dependent.

3. The mass analyzer as set forth in claim 1, wherein said detector is a Faraday cup.

4. The mass analyzer as set forth in claim 1, wherein said detector is a two-dimensional array detector.

5. The mass analyzer as set forth in claim 4, wherein said detector is a resistive anode microchannel plate.

6. The mass analyzer as set forth in claim 4, wherein said detector is a charge coupled device.

7. The mass analyzer as set forth in claim 1, further comprising a second detector located in close proximity to said cell for counting ions in said ion beam.

8. The mass analyzer as set forth in claim 1, further comprising an ionizer for ionizing said ion beam before said ion beam is received by said cell.

9. The mass analyzer as set forth in claim 8, wherein said ionizer is a field emission ionizer.

10. The mass analyzer as set forth in claim 8, wherein said ionizer is a field ionization ionizer.

11. The mass analyzer as set forth in claim 8, wherein said ionizer is an electrospray nozzle ionizer.

12. A mass analyzer for identifying mass and velocity distributions in an ion beam comprising:

a cell comprising at least two walls with time-dependent alternating RF potentials applied to each wall;

a rotating RF field imparting a non-magnetic field and located within the cell, wherein said cell is a magnetic field free cell;

a detector located at an end of said cell for counting ions in said ion beam.

13. The mass analyzer as set forth in claim 12, further comprising a second detector located at a bottom of said cell for counting ions in said ion beam.

14. The mass analyzer as set forth in claim 12, wherein said rotating RF field is time dependent.

15. The mass analyzer as set forth in claim 12, wherein said detector is a charged-particle detector.

16. A mass analyzer for identifying mass and velocity distributions in an ion beam comprising:

first and second consecutive cells, each having two walls orthogonally oriented;

time-dependent alternating RF potentials applied to each wall, wherein said RF potentials create crossed electric fields within each cell to generate a non-magnetic rotating RF field within each cell, wherein said cell is a magnetic field free cell;

a detector located at an end of said cells for counting ions in said ion beam.

17. The mass analyzer as set forth in claim 16, further comprising a second detector located at a bottom of one cell of said cells for counting ions in said ion beam.

18. The mass analyzer as set forth in claim 16, wherein said crossed RF fields are both in phase.

19. The mass analyzer as set forth in claim 16, further comprising a second detector located at a bottom of one cell of said cells for counting ions in said ion beam.

20. The mass analyzer as set forth in claim 16, wherein said rotating RF field is time dependent.

21. The mass analyzer as set forth in claim 16, wherein said detector is a charged-particle detector.

22. A method for identifying mass and velocity distributions in an ion beam projected into a cell with at least two walls, comprising the steps of:

applying time-dependent alternating RF potentials to each wall of the cell to create crossed electric fields in the cell;

generating non-magnetic rotating RF fields within the cell, wherein said cell is a magnetic field free cell;

accelerating the ion beam into the cell;

dispersing the ion beam according to the mass and velocity distribution present in the ion beam by the rotating RF field; and

counting ions in said ion beam.

23. The mass analyzer as set forth in claim 22, wherein the step of dispersing the ion beam further comprises the step of selecting an RF amplitude and a frequency of the RF potentials to thereby force the ions of the ion beam to either collide with the ion detector or to deflect away from the ion detector.

24. The mass analyzer as set forth in claim 22, wherein the step of applying time-dependent alternating RF potentials to each wall of the cell creates crossed RF fields that are both in phase.