Induced breakdown spectroscopy detector system with controllable delay time

• US 6,034,768 A
• Filed: 07/13/1998
• Issued: 03/07/2000
• Est. Priority Date: 09/26/1997
• Status: Expired due to Term

• Current Assignee: Physical Sciences Incorporated
• Original Assignee: Physical Sciences Incorporated
• Inventors: Holtzclaw, Karl, Hunter, Amy, Piper, Lawrence G., Fraser, Mark E., Davis, Steven J.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Smith, Zandra V.
• Application Number:
  US09/114,147
• Time in Patent Office: 603 Days
• Field of Search: 356/317, 356/318, 356/417, 356/418, 356/316, 356/314, 216/60
• US Class Current: 356/316
• CPC Class Codes: G01N 21/67 using electric arcs or discharges
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma

Abstract

The invention relates to high power, spark induced breakdown spectroscopy (SIBS) detectors with controllable delay time and to spark induced breakdown spectroscopy plasma generators with dual electrodes with specific electrode material, both for use in methods and apparatuses for detecting spectral signatures of atomic emissions, (e.g., from heavy metals such as lead, mercury, chromium, cadmium, arsenic, antimony and beryllium and radioactive materials such as uranium, plutonium, thorium and technetium) for measuring, for example, atomic concentrations of samples such as vapors and airborne particulates.

Claims

1. An induced breakdown spectroscopy system with controllable delay time for detecting a material of interest, the system comprising:

generating means, located near said material of interest, for generating a high energy pulse to create a plasma;

detector means for detecting and measuring a material of interest in the plasma based on spectral emissions of the material of interest;

a processor connected to an output of the detector means, said processor comprising;

filter means to filter out undesirable spectral regions from the detector signal;

wherein said filter means comprise one or more bandpass filters; and

wherein at least one of said one or more bandpass filters is substantially centered to pass spectral emissions that contain at least part of the spectral emissions of said material of interest;

delay means for causing a controllable delay between the time of generation of the plasma and the time of detecting and measuring; and

user control means for controlling the duration of said delay.

2. The system of claim 1 wherein the generating means comprises a spark generating means.

3. The system of claim 1 wherein the high energy pulse is in the range of approximately 0.3-6 Joules.

4. The system of claim 1 wherein the generating means comprises a pair of electrodes for creating the plasma.

5. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to reduce interference with the detection and measuring.

6. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion.

7. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to sputtering.

8. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion and sputtering.

9. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to have a sufficiently high melting point to reduce degradation and sputtering of the at least one electrode.

10. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen have a melting point of about 1900°

C. or higher.

11. The system of claim 1 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen from the group consisting of Re, Ir, Rh and Ta.

12. The system of claim 1 wherein the delay is chosen based at least on the energy level of the pulse generated by the generating means.

13. The system of claim 1 wherein the plasma initially comprises broadband radiation, and the delay is chosen to cause a delay in the detection that is long enough for the broadband radiation to diminish but not longer than the time period for which the spectral emissions of the material of interest persist.

14. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion.

15. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to sputtering.

16. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion and sputtering.

17. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to have a sufficiently high melting point to reduce degradation and sputtering of the at least one electrode.

18. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen have a melting point of about 1900°

C. or higher.

19. The system of claim 13 wherein the generating means comprises at least one electrode, and the at least one electrode comprises a material chosen from the group consisting of Re, Ir, Rh and Ta.

20. The system of claim 1 wherein said processor further comprises integrator means for integrating the detector signal over a variable time period.

21. The system of claim 20 wherein the variable time period of said integrator means is user controllable.

22. The system of claim 1 wherein at least one of said one or more bandpass filters is substantially centered to pass spectral emissions that do not contain the spectral emissions of said material of interest.

23. An induced breakdown spectroscopy system with a user controllable delay time for detecting a material of interest, the system comprising:

means for generating a high energy pulse to create a plasma, said generating means located near said material of interest;

means for detecting and measuring a material of interest in said plasma based on spectral emissions of the material of interest;

means for causing a controllable delay between a time of generation of said plasma and a time of detecting and measuring;

means for controlling a duration of said user controllable delay; and

a processor connected to an output of the detector means, said processor comprising;

one or more bandpass filters to filter out undesirable spectral regions from the detector signal, at least one of said one or more bandpass filters is substantially centered to pass spectral emissions that contain at least part of the spectral emissions of said material of interest.

24. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion.

25. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to sputtering.

26. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to be resistant to corrosion and sputtering.

27. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen to have a sufficiently high melting point to reduce degradation and sputtering of the at least one electrode.

28. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen have a melting point of about 1900°

C. or higher.

29. The system of claim 23 wherein said generating means comprises at least one electrode, and the at least one electrode comprises a material chosen from the group consisting of Re, Ir, Rh and Ta.

30. The system of claim 23 wherein at least one of said one or more bandpass filters is substantially centered to pass spectral emissions that do not contain the spectral emissions of said material of interest.