Method and system for detecting ionizing radiation

• US 6,806,474 B2
• Filed: 08/07/2002
• Issued: 10/19/2004
• Est. Priority Date: 04/14/2000
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: McGregor, Douglas S., Kearfott, Kimberlee J.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gabor, Otilia
• Application Number:
  US10/214,000
• Publication Number:
  US 20030042426A1
• Time in Patent Office: 804 Days
• Field of Search: 250/393, 250/394, 250/363.04, 250/363.1, 250/366, 250/370.07
• US Class Current: 250/393
• CPC Class Codes: G01V 5/02 specially adapted for surface logging, e.g. from aircraft

Abstract

A method and system for detecting ionizing radiation emitted by material located over an extended area are provided. The method and system include a radiation detector disposed within a detector space on a detection axis. An array of collimating louvers is positioned about the radiation detector and is movable between different polar positions or angles relative to the detection axis. A mechanism is provided for moving the array of collimating louvers between the different polar angles to collimate the ionizing radiation from different locations over the area. The detector produces electrical signals as a function of the polar positions of the array of collimating louvers.

Claims

1. A method for detecting ionizing radiation emitted by a material located over an extended area without the need for moving a radiation detector having a detection axis substantially perpendicular to the area and located within a detector space, the method comprising:

allowing ionizing radiation over a first narrow range of polar angles relative to the detection axis to enter the detector space and be detected by the detector while shielding ionizing radiation outside the first narrow range of polar angles from entering the detector space; and

allowing ionizing radiation over at least one other narrow range of polar angles different from the first narrow range of polar angles to enter the detector space and be detected by the detector while shielding ionizing radiation outside the at least one other narrow range of polar angles from entering the detector space until the ionizing radiation emitted by the material over the extended area has been detected.

2. The method as claimed in claim 1, further comprising shielding ionizing radiation outside a first range of acute angles substantially perpendicular to the detector axis during the steps of allowing.

3. The method as claimed in claim 2 further comprising shielding ionizing radiation outside at least one other range of acute angles different from the first range of acute angles during the steps of allowing.

4. The method as claimed in claim 1, wherein each of the steps of allowing allows spaced, parallel planes of ionizing radiation to enter the detector space and be detected by the detector.

5. The method as claimed in claim 1, wherein the ionizing radiation is gamma rays.

6. The method as claimed in claim 1, wherein the detector is a radiation spectrometer.

7. The method as claimed in claim 1, wherein the ionizing radiation includes gamma rays and wherein the detector is a gamma ray spectrometer.

8. The method as claimed in claim 1, wherein the detector includes a semiconductor substrate.

9. A system for detecting ionizing radiation emitted by material located over an extended area, the system comprising:

a support structure having a detector space;

a detector having a detection axis substantially perpendicular to the extended area and disposed within the detector space; and

an assembly located about the detector and including an array of spaced, parallel, collimating louvers movable together between different polar angles relative to the detection axis to allow ionizing radiation over narrow ranges of polar angles relative to the detection axis to enter the detector space and to be detected by the detector while shielding ionizing radiation outside the narrow ranges of polar angles from entering the detector space until ionizing radiation emitted by the material over the extended area has been detected.

10. The system as claimed in claim 9 wherein the assembly includes a movable mechanism for moving the louvers in unison at first ends of the louvers.

11. The system as claimed in claim 10 wherein second ends of the louvers are pivotably connected to the support structure.

12. The system as claimed in claim 10 wherein the mechanism is movable in a direction substantially parallel to the detection axis to move the louvers between the different polar angles.

13. The system as claimed in claim 9 further comprising a partial shield positioned about the detector for movement about the detection axis for shielding ionizing radiation outside selected ranges of acute angles substantially perpendicular to the detection axis.

14. The system as claimed in claim 13 wherein the partial shield is also positioned about the assembly.

15. The system as claimed in claim 9 wherein the array of collimating louvers are cylindrically symmetrical.

16. The system as claimed in claim 9 wherein the detector is a radiation spectrometer.

17. The system as claimed in claim 9 wherein the ionizing radiation includes gamma rays and wherein the detector is a gamma ray spectrometer.

18. The system as claimed in claim 9 wherein the detector includes a semiconductor substrate.