Real time gamma-ray signature identifier

• US 8,180,579 B2
• Filed: 03/27/2006
• Issued: 05/15/2012
• Est. Priority Date: 03/25/2005
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Inventors: Rowland, Mark, Ham, Cheryl, Perkins, Dwight, Wong, James, Gosnell, Tom B.
• Primary Examiner(s): TEIXEIRA MOFFAT, JONATHAN CHARLES
• Application Number:
  US11/390,728
• Publication Number:
  US 20070108379A1
• Time in Patent Office: 2,241 Days
• Field of Search: 702/22
• US Class Current: 702/27
• CPC Class Codes: G01T 1/36 Measuring spectral distribution of X-rays or of nuclear radiation spectrometry pulse selection circuits per se H03K; investigation of materials by radiation diffraction G01N23/20; spectrometer tubes H01J49/00

Abstract

A real time gamma-ray signature/source identification method and system using principal components analysis (PCA) for transforming and substantially reducing one or more comprehensive spectral libraries of nuclear materials types and configurations into a corresponding concise representation/signature(s) representing and indexing each individual predetermined spectrum in principal component (PC) space, wherein an unknown gamma-ray signature may be compared against the representative signature to find a match or at least characterize the unknown signature from among all the entries in the library with a single regression or simple projection into the PC space, so as to substantially reduce processing time and computing resources and enable real-time characterization and/or identification.

Claims

1. A real-time method of identifying radioactive materials by their gamma-ray signatures on a computerized gamma-ray signature identification system, comprising:

receiving an unknown gamma-ray spectrum as input into the computerized gamma-ray signature identification system;

providing in the computerized gamma-ray signature identification system at least two libraries of predetermined spectra for various nuclear material types with each library having spectral entries which share a common pre-defined parameter that is different from and independent of other libraries;

in a computer processor of the computerized gamma-ray signature identification system, performing principal component analysis on each of said at least two libraries to produce corresponding transformed basis sets representing the libraries and indexing each spectrum of the libraries in principal component space;

in the computer processor, projecting an unknown spectrum onto the respective principal component space of said at least two libraries; and

in the computer processor, determining a first identity of the unknown spectrum based on the unknown spectrum'"'"'s proximity to clusters of a basis set in the principal component space of a first one of said at least two libraries;

in the computer processor, determining a second identity of the unknown spectrum based on the unknown spectrum'"'"'s proximity to clusters of a basis set in the principal component space of a second one of said at least two libraries; and

presenting the determined identity of the unknown spectrum to a user as the first identity based on the assumption that the unknown spectrum meets the criteria of a first pre-defined parameter and as the second identity based on the assumption that the unknown spectrum meets the criteria of a second pre-defined parameter.

2. The method of claim 1,

wherein the step of providing the at least two libraries of predetermined spectra includes calculating signature variations to avoid the difficulty of measuring for signature variations.

3. The method of claim 1,

wherein the at least two libraries include predetermined spectra for various nuclear material types and associated intrinsic and extrinsic variations.

4. The method of claim 3,

wherein the extrinsic variations include shielding configurations.

5. The method of claim 1,

wherein the at least two libraries are each a comprehensive library having entries representing substantially more than thirty spectral models.

6. The method of claim 1,

wherein the spectral entries of a first one of said libraries share a common characteristic of being unitized.

7. The method of claim 1,

wherein performing principle component analysis includes receiving input for a desired number of principal components to be used for principle component analysis.

8. The method of claim 1,

wherein the respective basis sets index individual spectra of the libraries in the principle component space by means of principal component scores.

9. The method of claim 1,

wherein the step of determining the identity of the unknown spectrum by combining results of the unknown spectrum'"'"'s proximity to clusters of each of the basis sets in the respective principal component spaces of said at least two libraries includes the determination of Mahalanobis distances to nearby cluster of models.

10. A real-time computerized gamma-ray signature identification system comprising:

at least two libraries of predetermined spectra for various nuclear material types and configurations with each library having spectral entries which share a common characteristic pre-defined parameter different from and independent of other libraries;

computer processor means for performing principal component analysis on each of said libraries to transform the libraries into a corresponding basis sets representing the libraries and indexing each spectrum of the libraries in principal component space;

computer processor means for determining the identity of the unknown spectrum as a first identity based on the assumption that the unknown spectrum meets the criteria of a first pre-defined parameter and as a second identity based on the assumption that the unknown spectrum meets the criteria of a second pre-defined parameter by projecting an unknown spectrum onto the respective principal component space of said at least two libraries.

11. A real-time computerized gamma-ray signature identification system comprising:

at least two libraries of predetermined spectra for various nuclear material types and configurations with each library having spectral entries which share a common pre-defined parameter different from and independent of other libraries;

a principal component analysis module adapted to perform principal component analysis on each of said libraries so as to transform the libraries into a corresponding basis sets representing the libraries and indexing each spectrum of the libraries in principal component space;

an input module for receiving an unknown spectrum to be identified;

and computer processor means for determining the identity of the unknown spectrum as a first identity based on the assumption that the unknown spectrum meets the criteria of a first pre-defined parameter and as a second identity based on the assumption that the unknown spectrum meets the criteria of a second pre-defined parameter by projecting the unknown spectrum onto the respective principal component space of said at least two libraries.