Method for Obtaining Information about a Radiation Source or a Material Interacting with a Radiation Source and a Measurement Setup for Performing the Method

• US 20130204578A1
• Filed: 06/23/2010
• Published: 08/08/2013
• Est. Priority Date: 06/23/2010
• Status: Active Grant

• Current Assignee: Arktis Radiation Detectors Ltd.
• Original Assignee: Arktis Radiation Detectors Ltd.
• Inventors: Chandrasekharan, Rico, Davatz, Giovanna, Howard, Alexander
• Granted Patent: US 9,651,505 B2
• Time in Patent Office: Days
• US Class Current: 702/180
• CPC Class Codes: G01N 23/06 and measuring the absorption
• CPC Class Codes: G01T 3/00 Measuring neutron radiation G01T5/00 takes precedence
• CPC Class Codes: G01V 5/20 Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
• CPC Class Codes: G06F 17/18 for evaluating statistical data , e.g. average values, frequency distributions, probability functions, regression analysis forecasting specially adapted for a specific administrative, business or logistic context G06Q10/04

Abstract

A method for obtaining information about an unknown neutron source or an unknown material interacting with a known neutron source comprises the steps of: (a) providing a radiation detector capable of delivering a neutron energy information allowing the production of response histogram(s) as a function of neutron energy, (b) measuring with said radiation detector neutrons being emitted from said unknown neutron source or from said unknown material, (c) deriving from said measured neutrons a neutron energy spectrum, especially in form of a histogram, (d) normalizing said energy spectrum or histogram relative to a parameter or set of parameters derived from the measurement of a different variable, (e) comparing said normalized energy spectrum or histogram with known energy spectra or histograms, and (f) drawing conclusions on the basis of said comparison about the nature of the unknown neutron source or unknown material.

Claims

1. A method for obtaining information about a radiation source or a material interacting with radiation from a radiation source, said method comprising the steps of:

(a) providing a radiation detector capable of delivering neutron energy information allowing the production of response histogram(s) as a function of energy (E);

(b) measuring with said radiation detector neutrons being emitted from said radiation source or from said material;

(c) deriving from said measured neutrons a neutron energy spectrum, especially in form of a response histogram;

(d) normalizing said energy spectrum or response histogram relative to a parameter or set of parameters derived from the measurement of a different variable;

(e) comparing said normalized energy spectrum or histogram with known energy spectra or histograms; and

(f) drawing conclusions on the basis of said comparison about the nature of the radiation source or material, or both.

2. The method according to claim 1, wherein said known histograms are taken from a database, and said comparing step is made automatically by using a respective comparing means.

3. The method according to claim 1, wherein the parameter or set of parameters used for normalization is derived from one or more other measured values, thereby introducing an energy dependence into the normalization.

4. The method according to claim 3, wherein the parameter or set of parameters used for normalization is derived from at least one measurement of an intensity of electromagnetic radiation within a predetermined energy range of electromagnetic radiation, such as gamma, infrared, visible or UV radiation.

5. The method according to claim 1, wherein the parameter used for normalization is provided by said radiation detector.

6. The method according to claim 1, wherein said radiation detector is a detector based on He-3, He-4, Ar-40, Xe-131 or an organic scintillation material.

7. The method according to claim 1, wherein said radiation source comprises a plurality of different radiation sources, especially located at different positions in space, and the information gained is used to reject or subtract one or more of said plurality of different radiation sources, especially ambient background radiation, to thereby achieve higher sensitivity for the remaining sources of radiation.

8. The method according to claim 1, wherein said radiation source or said material comprises a nuclear material.

9. The method according to claim 1, wherein further information, especially in form of timing or directional information, is used for drawing conclusions about the nature of the radiation source or material.

10. The method according to claim 1, wherein said energy spectrum or histogram is additionally processed prior to step (e), said additional processing preferably involving a spectral deconvolution, template matching, fitting and/or extrapolation to higher or lower energies based on a set of plausible assumptions.

11. The method according to claim 1, wherein, in step (f), an energy dependent weighting factor is obtained to define the radiation dose of a radiation field for health physics, dosimetric, or monitoring purposes.

12. The method according to claim 1, wherein said conclusions are used for diagnostic purposes in processes involving nuclear fission or fusion.

13. The method according to claim 4, wherein the parameter or set of parameters used for normalization is derived from at least one measurement of gamma radiation, and there is a gamma source independent of the radiation source.

14. The method according to claim 1, wherein, in step (f), the radiation source is classified as being an industrial source, an alpha-n neutron source, a fission source, a cosmic source, an ambient source, or a specific isotope.

15. The method according to claim 1, wherein the radiation source emits coincident particles including neutrons, gammas or fission fragments from fission decays, and said coincident particles are measured to assess the Poissonian character of said neutron source.

16. The method according to claim 1, wherein said material is placed between the radiation source and the radiation detector, such that the material moderates the neutron radiation.

17. The method according to claim 1, wherein said material scatters radiation from the radiation source into the radiation detector.

18. The method according to claim 1, wherein a gamma and neutron radiation source as well as gamma and neutron detectors are used, and the information from the detectors is used to gain information regarding an object between the source and the detector or in a position where radiation from the source passes through the object prior to arriving at the detector, and said conclusion is drawn from comparing the ratio of detected neutron to detected gamma radiation as a function of energy.

19. A measurement setup for performing the method according to claim 1, comprising:

a radiation detector for detecting fast neutron radiation as well as gamma radiation and providing at its output a neutron energy spectrum of the detected fast neutrons and a gamma count rate of the detected gamma radiation or a total count rate as the sum of gamma count rate and other count rates;

normalizing means for normalizing the neutron energy spectrum delivered by the radiation detector by means of the gamma count rate or total count rate as the sum of gamma count rate and other count rates delivered by the radiation detector; and

comparing means for comparing the normalized neutron energy spectrum delivered by the normalizing means with a known spectrum.

20. The measurement setup according to claim 19, wherein the radiation detector uses the scintillation of a noble gas as a detecting means.

21. The measurement setup according to claim 19, wherein the known spectrum for the comparing means is taken from a database which is connected to the comparing means.