Aerosol hazard characterization and early warning network

• US 6,490,530 B1
• Filed: 05/23/2000
• Issued: 12/03/2002
• Est. Priority Date: 05/23/2000
• Status: Expired due to Term

• Current Assignee: Wyatt Technology Corporation
• Original Assignee: Wyatt Technology Corporation
• Inventors: Wyatt, Philip J.
• Primary Examiner(s): Hilten, John S.
• Assistant Examiner(s): Cherry, Stephen J.
• Application Number:
  US09/577,108
• Time in Patent Office: 924 Days
• Field of Search: 702/24, 702/23, 702/26
• US Class Current: 702/24
• CPC Class Codes: G01N 1/2202 involving separation of sample components during sampling
• CPC Class Codes: G01N 15/0211 Investigating a scatter or diffraction pattern
• CPC Class Codes: G01N 15/1459 the analysis being performed on a sample stream
• CPC Class Codes: G01N 2001/022 sampling for security purposes, e.g. contraband, warfare agents
• CPC Class Codes: G01N 2001/2223 aerosol sampling devices
• CPC Class Codes: G01N 2015/019 Biological contaminants; Fouling
• CPC Class Codes: G01N 2015/0238 Single particle scatter
• CPC Class Codes: G08B 21/14 Toxic gas alarms G08B21/16 takes precedence

Abstract

An aerosol hazard classification and early warning network is composed of a large number of detector and analysis units, called “detector stations,” which are deployed throughout a region to be warned of a potentially hazardous aerosol intrusion. Such aerosol threats may originate from fires, volcanic eruptions, or overt releases of biological and chemical agents dispersed in aerosol form. Among the former are the characteristic toxic aerosols released during refinery fires or explosions. The latter biological agents include bacterial spores, lyophilized bacterial cells, and virus preparations, whereas chemical agents might include various forms of nerve gasses and other anti-personnel gasses such as mustard, all commonly deployed in aerosol form. Each detector station contains an aerosol handling unit that samples and transfers ambient aerosol particles one-at-a-time through a light scattering chamber where each such particle is constrained to pass through a fine laser beam producing, thereby, an outgoing scattered light wave. The scattering chamber contains a plurality of scattered light detectors arranged to accept light scattered into different angular locations. The signals detected at each detector position are processed by a corresponding digital signal processing chip with the resulting set of digitized signals being transferred to an on-board central processing unit. The CPU analyzes the set of light scattering signals and identifies or otherwise characterizes each particle. The classification/identification data are then stored and, on preprogrammed command, telemetered to a remote “central station” by means of an on-board telemetry unit. The central station analyzes the sets of data received from all the detector stations and then instructs, as necessary, selected detector stations via telemetric means to change their sampling and telemetry rates. As soon as sufficient data are available, the central determines the presence, threat, extent, and progress of the aerosol cloud. These factors are then telemetrically transmitted by means of alarms and warnings sent to potentially threatened regions.

Claims

1. An aerosol hazard characterization and early warning network comprising

A) a plurality of detector stations positioned throughout the physical region to be protected thereby where each detector station is comprised of

i) a light scattering chamber module containing

(a) an aerosol sampling and handling module;

(b) a plurality of scattered light detectors;

(c) a light source producing a monochromatic collimated beam of light traversing a central plane of said chamber;

ii) electronic circuitry converting analog signals produced by said detectors into digital representations thereof;

iii) a central processing unit containing memory and processing means together with controlling and processing software that

(a) controls said aerosol sampling and handling system;

(b) stores digital data produced from each particle light scattering event occurring as said aerosol particle crosses said collimated beam of light;

(c) analyzes said data to characterize each aerosol particle from said particle'"'"'s set of stored digitized light scattering signals;

(d) processes and stores the ensemble of said analyses of said characterized particles for subsequent transmission;

iv) a telemetry communication system that

(a) sends processed data analyses to a central station;

(b) receives modifying control, processing, and transmission instructions from a central station;

B) a central station that receives processed data from each of the detector stations, sends, if deemed necessary, each detector station modified sampling instructions based on said central station analysis of data received therefrom, analyzes data received from said detector stations to establish aerosol source cloud extent and movement, and communicates by telemetric means early warnings of threats posed by said cloud through said region to be protected, said central station is comprised of

i) a telemetric transmitting and receiving module;

ii) a central processing unit, CPU, containing switching and buffering means permitting data transmitted from all detector stations to be received and stored;

iii) analytical software permitting said CPU to analyze and process data so-received and to modify, as required, the sampling and analytical processes performed by each said detector station;

iv) separate telemetric module to transmit appropriate warnings to said protected region of immanent threats based on said analyses and suitable measures suggested to mitigate said threat.

2. The aerosol hazard characterization and early warning network of claim 1 where said monochromatic collimated beam of light is plane polarized.

3. The aerosol hazard characterization and early warning network of claim 1 where said plurality of detectors include some that have been fitted with analyzers placed before them.

4. The aerosol hazard characterization and early warning network of claim 1 where said plurality of detectors lie along great circles with respect to the center of said light scattering chamber.

5. The aerosol hazard characterization and early warning network of claim 1 where said electronic circuitry converting each analog signal produced by each of said detectors into a digital representation thereof consists of a preprogrammed digital signal processing chip.

6. The aerosol hazard characterization and early warning network of claim 1 where said detector stations are powered by an on-board battery source.

7. The aerosol hazard characterization and early warning network of claim 1 where said detector stations are powered by line source with a battery backup source.

8. The battery-powered network of claim 6 where said battery is maintained charged by solar cell charging means.

9. The aerosol hazard characterization and early warning network of claim 4 where said plurality of detectors include some that lie in a plane perpendicular to the plane of polarization of said monochromatic beam of light.

10. The aerosol hazard characterization and early warning network of claim 3 where said analyzers are narrow band pass filters preventing thereby all light from entering said detector to which it is affixed of wavelength different from the wavelength incident upon the scattering particles.

11. The aerosol hazard characterization and early warning network of claim 3 where said analyzers are plane polarizing and are affixed to detectors lying in a plane perpendicular to the plane of polarization of said incident beam.

12. The aerosol hazard characterization and early warning network of claim 1 where said CPU of each said detector station calculates the mean size, size distribution, and changes in said mean size and size distribution of said characterized particles.

13. The aerosol hazard characterization and early warning network of claim 1 where said light source is a laser.

14. The aerosol hazard characterization and early warning network of claim 13 where said laser is a GaAs solid state laser.

15. The aerosol hazard characterization and early warning network of claim 13 where power output of said laser is of the order of 30 mW.

16. The aerosol hazard characterization and early warning network of claim 1 where said aerosol sampling and handling module dilutes said sampled aerosol source cloud and transports individual aerosol particles within a sheath flow through said scattering chamber, said monochromatic light beam, and exiting through an exhaust port.

17. The aerosol hazard characterization and early warning network of claim 1 where said plurality of detectors are high gain transimpedance photodiodes.

18. The aerosol hazard characterization and early warning network of claim 3 where said analyzers include optical waveplates.

19. The aerosol hazard characterization and early warning network of claim 3 where said analyzers include electrically adjustable liquid crystal retarders.

20. The aerosol hazard characterization and early warning network of claim 19 where said processing software permits said detector station CPU to calculate Stokes parameters for each aerosol particle for which digitized detector signals have been collected.

21. The aerosol hazard characterization and early warning network of claim 1 where said light scattering chamber module includes UV light excitation source.

22. The aerosol hazard characterization and early warning network of claim 1 where said detector station scattered light detectors whose digitized signals are to be processed and analyzed by said detector station CPU are placed at polar angles between 5°

and 175° and

azimuthal angles between 0° and

360°

.

45. The aerosol hazard characterization and early warning network of claim 13 where said laser source is a GaAs solid state laser.

23. A method for providing early warning of an impending aerosol threat to a designated physical region comprising the steps of

a. placing throughout said physical region a plurality of detector stations where each detector station contains

i. a light scattering chamber module means comprised of

an aerosol sampling and handling means;

2. a plurality of scattered light detector means;

3. a light source producing a monochromatic collimated beam of light traversing a central plane of said chamber;

ii. electronic circuitry means converting analog signals produced by said detectors into digital representations thereof;

iii. central processing unit means containing memory and processing means together with controlling and processing software that

1. controls said aerosol sampling and handling system;

2. stores digital data produced from each particle light scattering event occurring as said aerosol particle crosses said light beam;

3. analyzes said data to characterize each aerosol particle from said particle'"'"'s set of stored digitized light scattering signals;

4. processes and stores the ensemble of said analyses of said characterized particles for subsequent transmission;

iv. a telemetry communication means to

1. send processed data analyses to a central station;

2. receive modifying control, processing, and transmission instructions from a central station;

b. receiving processed data from each of said detector station means at a central station means that would send, if deemed necessary, to each detector station means modified sampling instructions based on said central station means analysis of data received therefrom, to analyze data received from said detector station means to establish aerosol source cloud extent and movement, and to communicate by telemetric means early warnings of threats posed by said cloud through said region to be protected, said central station consists of

i. a telemetric transmitting and receiving means;

ii. a central processing unit means, CPU, containing switching and buffering means permitting data transmitted from all detector stations to be received and stored;

iii. analytical software means permitting said CPU to analyze and process data so-received and to modify, as required, the sampling and analytical processes performed by each said detector station;

iv. separate telemetric means to transmit appropriate warnings to said protected region of immanent threats based on said analyses and suitable measures suggested to mitigate said threat.

24. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said monochromatic beam of light is plane polarized.

25. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said plurality of scattered light detector means include some that have been fitted with analyzers placed before them.

26. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said plurality of scattered light detector means lie along great circles with respect to the center of said light scattering chamber.

27. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said electronic circuitry means converting each analog signal produced by each of said scattered light detector means into a digital representation thereof consists of a preprogrammed digital signal processing means.

28. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said detector station means are powered by an on-board battery means.

29. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said detector station means are powered by line source with a battery backup source.

30. The method of claim 29 where said battery means is maintained charged by solar cell charging means.

31. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 26 where said plurality of scattered light detector means include some that lie in a plane perpendicular to the plane of polarization of said monochromatic light beam.

32. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 25 where said analyzer means are narrow band pass filter means preventing thereby all light from entering said scattered light detector means to which it is affixed of wavelength different from the wavelength incident upon the scattering particles.

33. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 25 where said analyzer means are plane polarizing and are affixed to scattered light detector means lying in a plane perpendicular to the plane of polarization of said incident light beam.

34. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said CPU means of each said scattered light detector station means calculates the mean size, size distribution, and changes in said mean size and size distribution of said characterized particles.

35. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said light source means is a laser.

36. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 35 where said wavelength of light produced by said laser is of the order of 680 nm.

37. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 36 where said power output of said laser is of the order of 30 mW.

38. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said aerosol sampling and handling means provides means to dilute said sampled aerosol source cloud and means to transport individual aerosol particles within a sheath flow means through said scattering chamber means, said light beam, and exiting through an exhaust port means.

39. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said plurality of scattered light detector means are high gain transimpedance photodiode means.

40. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 25 where said analyzer means include optical waveplate means.

41. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 25 where said analyzer means include electrically adjustable liquid crystal retarder means.

42. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 41 where said processing software means permits said detector station CPU means to calculate Stokes parameters for each aerosol particle for which digitized detector signals have been collected.

43. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said light scattering chamber means includes UV light excitation means.

44. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said detector station scattered light detector means whose digitized signals are to be processed and analyzed by said detector station CPU means are placed at polar angles between 5°

and 175° and

azimuthal angles between 0° and

360°

.

46. The method for providing early warning of an impending aerosol threat to a designated physical region of claim 23 where said light source is a laser.