MASK FOR CODED APERTURE SYSTEMS

• US 20090114824A1
• Filed: 05/16/2008
• Published: 05/07/2009
• Est. Priority Date: 09/12/2007
• Status: Active Grant

• Current Assignee: Morpho Detection (Safran SA)
• Original Assignee: General Electric Company
• Inventors: Gordon, Jeffrey Seymour, Zelakiewicz, Scott Stephen, Jansen, Floribertus Heukensfeldt
• Granted Patent: US 7,915,591 B2
• Time in Patent Office: Days
• US Class Current: 250/363.20
• CPC Class Codes: G01T 1/295 using coded aperture devices, e.g. Fresnel zone plates handling of radiation of particles, e.g. using diaphragms, collimators, diffraction G21K1/00

Abstract

A detector for identification and localization of radioisotopes, comprising a position sensitive detector configured to observe the location of emitted high energy radiation, wherein the position sensitive detector comprises a surface comprised of a first radiation sensitive material; and an active mask disposed in front of the position sensitive detector positioned such that the emitted high energy radiation is detected by the position sensitive detector after passage through the mask, wherein the mask comprises a second radiation sensitive material.

Claims

1. A detector for identification and localization of radioisotopes, comprising:

a position sensitive detector configured to observe the location of emitted high energy radiation, wherein the position sensitive detector comprises a surface comprised of a first radiation sensitive material; and

an active mask disposed in front of the position sensitive detector positioned such that the emitted high energy radiation is detected by the position sensitive detector after passage through the mask, wherein the mask comprises a second radiation sensitive material.

2. The detector of claim 1, wherein the first radiation sensitive material and the second radiation sensitive material are the same.

3. The detector of claim 1, wherein the first radiation sensitive material and the second radiation sensitive material are different.

4. The detector of claim 1, wherein a selected one or both of the first and the second radiation sensitive materials comprise a scintillation material, a direct detection material, or a combination comprising at least one of the foregoing materials;

wherein the scintillation material comprise sodium iodide, cesium iodide, sodium iodide (thallium), gadolinium oxyorthosilicate, bismuth germinate, lutethium oxyorthosilicate, or a combination comprising at least one of the foregoing; and

wherein the direct detection materials comprise germanium, cadmium zinc telluride, cadmium telluride, or a combination comprising at least one of the foregoing.

5. The detector of claim 1, wherein the active mask further comprises a plurality of attenuating elements comprising the second radioisotope sensitive material, wherein each of the plurality of elements comprise a cylindrical shape, a planar shape, a rectangular shape, a polygonal shape, or a combination comprising at least one of the foregoing shapes.

6. The detector of claim 5, wherein each of the plurality of attenuating elements comprises a 3 inch diameter sodium iodide (thallium) cylinder.

7. The detector of claim 1, wherein the active mask increases a photopeak efficiency for a 662 keV gamma-ray by at least about 25%.

8. The detector of claim 1, wherein the active mask increases a photopeak efficiency for low-energy gamma-rays by at least about 50%.

9. The detector of claim 5, wherein the plurality of attenuating elements mask further comprises two or more tiers of the plurality of attenuating elements in a predetermined configuration.

10. A stand-off radiation imaging and detection system, comprising:

a detector configured to identify and locate a radioisotope comprising;

a position sensitive detector configured to observe the location of a high energy radiation source, wherein the position sensitive detector comprises a surface comprised of a first radiation sensitive material; and

an active mask comprising a plurality of attenuating and transparent elements disposed in front of the position sensitive detector, wherein the plurality of attenuating elements are comprised of a second radiation sensitive material and are configured to provide shadowing attenuation to the position sensitive detector energy information for identification of the radioisotope.

11. The system of claim 10, wherein the first radiation sensitive material and the second radiation sensitive material are the same.

12. The system of claim 10, wherein the first radiation sensitive material and the second radiation sensitive material are different.

13. The system of claim 10, wherein a selected one or both of the first and the second radiation sensitive materials comprise a scintillation material, a direct detection material, or a combination comprising at least one of the foregoing materials;

wherein the scintillation material comprise sodium iodide, cesium iodide, sodium iodide (thallium), gadolinium oxyorthosilicate, bismuth germinate, lutethium oxyorthosilicate, or a combination comprising at least one of the foregoing; and

wherein the direct detection materials comprise germanium, cadmium zinc telluride, cadmium telluride, or a combination comprising at least one of the foregoing.

14. The system of claim 10, wherein each of the plurality of attenuating elements comprise a cylindrical shape, a planar shape, a rectangular shape, a polygonal shape, or a combination comprising at least one of the foregoing shapes.

15. The system of claim 14, wherein each of the plurality of attenuating elements comprises a 3 inch diameter sodium iodide (thallium) cylinder.

16. The system of claim 10, wherein the detector comprises a total photopeak efficiency of at least about 60%.

17. The system of claim 10, wherein the detector is configured to detect at least about 35 gammas per second for a 1 milliCurie (mCi) Cesium 137 (¹³⁷Cs) source located 100 meters (m) away.

18. The system of claim 10, wherein the detector is configured to detect at least about 60 gammas per second for a 1 milliCurie (mCi) Cesium 137 (¹³⁷Cs) source located 100 meters (m) away.

19. The system of claim 10, wherein the position sensitive detector comprises a 3-inch thick planar array, wherein the planar array comprises a plurality of elements composed of the first radioisotope sensitive material.

20. A method of detecting a source of radioisotopes comprising:

loading a stand-off radiation imaging and detection system aboard a vehicle, wherein the system is configured to detect the radioisotope source and comprises a detector configured to identify and locate a radioisotope, wherein the detector comprises a position sensitive detector configured to observe the location of a high energy radiation source, wherein the position sensitive detector comprises a surface comprised of a first radiation sensitive material; and

a mask comprising a plurality of attenuating and transparent elements disposed in front of the position sensitive detector, wherein the plurality of attenuating elements are comprised of a second radiation sensitive material;

providing shadowing attenuation to the position sensitive detector with the active mask;

providing energy information for identification of the radioisotope with the second radiation sensitive material of the active mask;

recording detection of the radioisotopes by the system; and

determining the location of the radiation source.