Mask for coded aperture systems

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

a position sensitive detector configured to observe a location of emitted high energy radiation, the position sensitive detector comprising a surface comprising a first radiation sensitive material, a surface of the position sensitive detector positioned within a plane; and

an active mask positioned between a source of the high energy radiation and the position sensitive detector, the active mask comprising a plurality of attenuating elements formed from a second radiation sensitive material and a plurality of transparent elements through which the high energy radiation passes for detection by the position sensitive detector, wherein each attenuating element of the plurality of attenuating elements is configured to resolve an energy of the high energy radiation absorbed by the plurality of attenuating elements to identify the source of the high energy radiation.

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

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

4. The detector of claim 1 , wherein at least one of the first radiation sensitive material and the second radiation sensitive material comprises at least one of a scintillation material and a direct detection material, the scintillation material comprising at least one of sodium iodide, cesium iodide, sodium iodide (thallium), gadolinium oxyorthosilicate, bismuth germinate, and lutethium oxyorthosilicate, and the direct detection material comprising at least one of germanium, cadmium zinc telluride, and cadmium telluride.

5. The detector of claim 1 , wherein each attenuating element of the plurality of attenuating elements comprises at least one of a cylindrical shape, a planar shape, a rectangular shape, and a polygonal shape.

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

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

8. The detector of claim 1 , wherein the active mask is configured to increase a photopeak efficiency for a 662 keV gamma-ray by at least about 25%.

9. The detector of claim 1 , wherein the active mask is configured to increase a photopeak efficiency for low-energy gamma-rays by at least about 50%.

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

a detector configured to identify and locate a radioisotope, the detector comprising:

a position sensitive detector configured to observe a location of a high energy radiation source, the position sensitive detector comprising a surface comprising a first radiation sensitive material, a surface of the position sensitive detector positioned within a plane; and

an active mask comprising a plurality of attenuating elements and a plurality of transparent elements positioned between the high energy radiation source and the position sensitive detector, the plurality of attenuating elements comprising a second radiation sensitive material and configured to resolve an energy of high energy radiation absorbed by the plurality of attenuating elements to identify the high energy radiation source.

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

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

13. The system of claim 10 , wherein at least one of the first radiation sensitive material and the second radiation sensitive material comprises at least one of a scintillation material and a direct detection material, the scintillation material comprising at least one of sodium iodide, cesium iodide, sodium iodide (thallium), gadolinium oxyorthosilicate, bismuth germinate, and lutethium oxyorthosilicate, the direct detection material comprising at least one of germanium, cadmium zinc telluride, and cadmium telluride.

14. The system of claim 10 , wherein each element of the plurality of attenuating and transparent elements comprises at least one of a cylindrical shape, a planar shape, a rectangular shape, and a polygonal shape.

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

16. 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.

17. 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.

18. 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 comprising the first radioisotope sensitive material.

19. The system of claim 10 , wherein the detector is configured to produce signals corresponding to an energy and a pattern of the high energy radiation absorbed by the plurality of attenuating elements.

20. The system of claim 10 , further comprising a computer coupled in communication with the detector, the computer configured to provide spectral information regarding an isotope emitting the high energy radiation based on the energy of the high energy radiation resolved by the plurality of attenuating elements.