Method and system for detecting an explosive

• US 7,847,265 B2
• Filed: 07/22/2010
• Issued: 12/07/2010
• Est. Priority Date: 04/06/2005
• Status: Expired due to Fees

• Current Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute)
• Original Assignee: Battelle Energy Alliance LLC (Battelle Memorial Institute)
• Inventors: Rohde, Kenneth W., Blackwood, Larry G., Reber, Edward L.
• Primary Examiner(s): Porta; David P
• Assistant Examiner(s): Taningco; Marcus H
• Application Number:
  US12/841,857
• Publication Number:
  US 20100286943A1
• Time in Patent Office: 138 Days
• Field of Search: 250/252.1, 250/339.07, 250/370.01, 250/370.05, 250/390.01, 702/85, 702/179
• US Class Current: 250/390.01
• CPC Class Codes: G01V 5/20 Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
• CPC Class Codes: G01V 5/234 Measuring induced radiation, e.g. thermal neutron activation analysis

Abstract

A method and system for detecting at least one explosive in a vehicle using a neutron generator and a plurality of NaI detectors. Spectra read from the detectors is calibrated by performing Gaussian peak fitting to define peak regions, locating a Na peak and an annihilation peak doublet, assigning a predetermined energy level to one peak in the doublet, and predicting a hydrogen peak location based on a location of at least one peak of the doublet. The spectra are gain shifted to a common calibration, summed for respective groups of NaI detectors, and nitrogen detection analysis performed on the summed spectra for each group.

Claims

1. A method of determining a presence of at least one explosive in a vehicle, the method comprising:

directing energy at a vehicle using a neutron generator;

reading spectra from a plurality of NaI detectors arranged adjacent the vehicle in a plurality of groups comprising different combination of NaI detectors;

calibrating the spectra, comprising;

performing Gaussian peak fitting to define peak regions;

locating a Na peak and an annihilation peak doublet;

assigning a predetermined energy level to one peak in the doublet; and

predicting a hydrogen peak location based on a location of at least one peak of the doublet;

gain shifting the spectra to a common calibration;

summing the spectra for respective groups of NaI detectors; and

performing Nitrogen detection analysis on the summed spectra for each group.

2. The method of claim 1, further comprising performing Gaussian peak fitting to find a peak in a region surrounding the predicted hydrogen peak location.

3. The method of claim 2, further comprising predicting a Na peak location based on the location of the annihilation peak and the peak found in the region surrounding the predicted hydrogen peak.

4. The method of claim 2, further comprising predicting a Na peak location using a linear fit to the location of the annihilation peak and the location of the hydrogen peak.

5. The method of claim 2, further comprising predicting a Na peak location using a linear fit to the location of the annihilation peak and the location of the hydrogen peak and then applying a nonlinearity adjustment.

6. The method of claim 5, further comprising providing a library of spectra with known calibrations and using the library to develop a prediction equation for locating the hydrogen peak and developing the nonlinearity adjustment.

7. The method of claim 5, further comprising providing a library of spectra with known calibrations and using the library to develop the nonlinearity adjustment.

8. The method of claim 5, further comprising performing Gaussian peak fitting to find a peak in a region surrounding the predicted Na peak location.

9. The method of claim 8, further comprising fitting a quadratic equation to the annihilation peak, the hydrogen peak, and the Na peak to produce an energy calibration equation.

10. A system for determining a presence of at least one explosive in a vehicle, the system comprising:

a neutron generator located and oriented to direct energy at a vehicle location;

a plurality of NaI detectors adjacent the vehicle location, comprising a plurality of groups containing different combinations of the NaI detectors; and

a control system configured to;

read spectra from the plurality of NaI detectors;

calibrate the spectra, comprising;

performing Gaussian peak fitting to define peak regions;

locating a Na peak and an annihilation peak doublet;

assigning a predetermined energy level to one peak in the doublet; and

predicting a hydrogen peak location based on the location of at least one peak of the doublet;

gain shift the spectra to a common calibration;

sum the spectra for respective groups of NaI detectors; and

perform nitrogen detection analysis on the summed spectra for each group.

11. The system of claim 10, wherein the control system is further configured to perform Gaussian peak fitting to find a peak in a region surrounding the predicted hydrogen peak location.

12. The system of claim 11, wherein the control system is further configured to predict a Na peak location based on the location of the annihilation peak and the peak found in the region surrounding the predicted hydrogen peak location.

13. The system of claim 11, wherein the control system is further configured to predict a Na peak location using a linear fit to the location of the annihilation peak and the location of the hydrogen peak.

14. The system of claim 11, wherein the control system is further configured to predict a Na peak location using a linear fit to the location of the annihilation peak and the location of the hydrogen peak and then applying a nonlinearity adjustment.

15. The system of claim 14, further comprising a library of spectra with known calibrations, and wherein the control system is configured to use the library to develop a prediction equation for locating the hydrogen peak and to develop the nonlinearity adjustment.

16. The system of claim 14, further comprising a library of spectra with known calibrations, and wherein the control system is configured to use the library to develop the nonlinearity adjustment.

17. The system of claim 14, wherein the control system is further configured to perform Gaussian peak fitting to find a peak in a region surrounding the predicted Na peak location.

18. The system of claim 17, wherein the control system is further configured to fit a quadratic equation to the annihilation peak, the hydrogen peak, and the Na peak to produce an energy calibration equation.