Ion cyclotron resonance cell

• US 5,389,784 A
• Filed: 05/24/1993
• Issued: 02/14/1995
• Est. Priority Date: 05/24/1993
• Status: Expired due to Fees

• Current Assignee: Wnited States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Weller, Robert R.
• Primary Examiner(s): Berman, Jack I.
• Assistant Examiner(s): Beyer, James
• Application Number:
  US08/064,887
• Time in Patent Office: 631 Days
• Field of Search: 250/291, 250/282, 250/290, 250/281, 250/292, 250/288
• US Class Current: 250/291
• CPC Class Codes: G01N 21/6402 Atomic fluorescence; Laser induced fluorescence
• CPC Class Codes: H01J 49/38 Omegatrons ; using ion cyclotron resonance

Abstract

An ion cyclotron resonance cell having two adjacent sections separated by a center trapping plate. The first section is defined by the center trapping plate, a first end trapping plate, and excitation and detector electrodes. The second section includes a second end trapping plate spaced apart from the center plate, a mirror, and an analyzer. The analyzer includes a wavelength-selective light detector, such as a detector incorporating an acousto-optical device (AOD) and a photodetector. One or more ion guides, grounded plates with holes for the ion beam, are positioned within the vacuum chamber of the mass spectrometer between the ion source and the cell. After ions are trapped and analyzed by ion cyclotron resonance techniques in the first section, the ions of interest are selected according to their mass and passed into the second section for optical spectroscopic studies. The trapped ions are excited by light from a laser and caused thereby to fluoresce. The fluorescent light emitted by the excited ions is reflected by the mirror and directed onto the detector. The AOD is scanned, and the photodetector output is recorded and analyzed. The ions remain in the second section for an extended period, enabling multiple studies to be carried out on the same ensemble of ions.

Claims

1. An ion cyclotron resonance cell for analyzing a beam of ions, said cell comprising:

a plurality of electrode plates defining a first volume, said plurality of electrode plates including a pair of opposing trapping plates, said pair of opposing trapping plates each having a hole formed therein through which said beam of ions can move;

an end trapping plate spaced apart from one trapping plate of said pair of trapping plates thereby defining a second volume therebetween and into which said ion beam moves;

means in spaced relation to said second volume for causing said ion beam to fluoresce whereby said ion beam gives off light;

means in spaced relation to said second volume for collecting at least a portion of said light, said collecting means surrounding said second volume; and

means in operating connection with said collecting means for analyzing said at least a portion of said light.

2. The ion cyclotron resonance cell as recited in claim 1, wherein said analyzing means is responsive to the intensity of said at least a portion of said light and produces an output signal related thereto.

3. The ion cyclotron resonance cell as recited in claim 1, wherein said analyzing means further comprises a wavelength-selective light detector.

4. The ion cyclotron resonance cell as recited in claim 1, wherein said analyzing means further comprises an acousto-optical device.

5. The ion cyclotron resonance cell as recited in claim 1, wherein said collecting means is a mirror formed to reflect said at least a portion of said light toward said analyzing means.

6. An ion cyclotron resonance cell for use with a remote source of ions, said cell comprising:

a plurality of electrode plates defining a first section, said first section temporarily confining said ions, at least one of said plurality of electrode plates having a hole formed therein for emitting said ions in a beam;

means for forcing said ions to exit said hole;

an end trapping plate spaced apart from said at least one of said plurality of electrode plates to define a second section, said beam entering said second section through said hole;

means in spaced relation to said second section for causing said beam to give off light; and

means in spaced relation to said second section for collecting at least a portion of said light, said collecting means surrounding said beam; and

means in optical communication with said collecting means for analyzing said at least a portion of said light.

7. The apparatus as recited in claim 6, wherein said collecting means is a mirror in spaced relation to said second section so that said mirror can reflect said light to said analyzing means.

8. The apparatus as recited in claim 6, wherein said analyzing means further comprises a tunable filter, said filter selectively transmitting light of a predetermined wavelength.

9. The apparatus as recited in claim 6, wherein said analyzing means further comprises an acousto-optical device.

10. The apparatus as recited in claim 6, wherein said light-collecting means further comprises a mirror, said mirror positioned and shaped to direct at least a portion of said collected light onto said analyzing means.

11. The apparatus as recited in claim 6, wherein said light-collecting means further comprises a mirror curved about said beam to have a parabolic cross section, said analyzing means laying on the focal point of said mirror so that said mirror can reflect at least a portion of said light onto said analyzing means.

12. The apparatus as recited in claim 6, further comprising means for guiding said ions into said first section.

13. The apparatus as recited in claim 6, further comprising a plurality of guides having holes formed therein, said guides being held at ground potential for guiding said ions into said first section.

14. The ion cyclotron resonance cell as recited in claim 6, wherein said causing means further comprises a laser directed at said ions so that light emitted by said laser excites said ions whereby said ions fluoresce.

15. An ion cyclotron resonance cell for use in a mass spectrometer, said cell having a longitudinal axis, said cell comprising:

a pair of opposing, spaced-apart trapping plates, said trapping plates laying in planes substantially perpendicular to said longitudinal axis;

a plurality of electrode plates, said electrode plates spaced apart from said longitudinal axis whereby the combination of said electrode plates and said pair of trapping plates form a first section, a first plate of said trapping plates having an entrance hole and an opposing, second plate of said trapping plates having an exit hole;

an end trapping plate, said end trapping plate laying in a plane substantially perpendicular to said longitudinal axis, said end trapping plate opposing said second plate and spaced apart therefrom to define a second section, said ions passing through said exit hole into said second section;

means in spaced relation to said first section for guiding ions through said entrance hole;

means in electrical connection with said plurality of electrode plates for mass-analyzing said ions in said first section, said mass-analyzing means analyzing said ions by ion cyclotron resonance methods;

a laser in spaced relation to said second section and adapted for directing laser light on said ions so that said ions are excited and fluoresce, thereby emitting light;

means in spaced relation to said exciting means for receiving at least a portion of said light, said receiving means surrounding said second section; and

means responsive to said receiving means for analyzing said at least a portion of said light.

16. The ion cyclotron resonance cell as recited in claim 15, wherein said analyzing means produces an output signal indicative of the intensity of said at least a portion of said light.

17. The ion cyclotron resonance cell as recited in claim 15, wherein said receiving means further comprises a curved mirror that reflects said at least a portion of said light onto said analyzing means.

18. The ion cyclotron resonance cell as recited in claim 15, wherein said analyzing means further comprises an acousto-optical device.

19. The ion cyclotron resonance cell as recited in claim 15, wherein said receiving means further comprises a curved mirror that reflects said at least a portion of said light onto said analyzing means and said analyzing means further comprises:

a lens positioned to receive said at least a portion of said light;

an acousto-optical device in spaced relation to said lens, said lens focusing said at least a portion of said light onto said device; and

a photodetector positioned to receive light from said acousto-optical device.

20. The ion cyclotron resonance cell as recited in claim 15, wherein said guiding means further comprises at least one plate spaced apart from said first section, held at ground potential with respect to said electrode plates and having a hole formed therethrough for said ions to pass.