Method and system for measuring neutron emissions and ionizing radiation, solid state detector for use therein, and imaging system and array of such detectors for use therein

• US 6,921,903 B2
• Filed: 11/05/2002
• Issued: 07/26/2005
• Est. Priority Date: 11/05/2002
• 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.
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): TANINGCO, MARCUS H
• Application Number:
  US10/288,071
• Publication Number:
  US 20040084626A1
• Time in Patent Office: 994 Days
• Field of Search: 250/370.05, 250/390.01, 250/370.13
• US Class Current: 250/370.05
• CPC Class Codes: G01T 3/08 with semiconductor detectors

Abstract

A method and system for measuring neutron emissions and ionizing radiation, such as gamma emissions, solid state detector for use therein, and imaging system and array of such detectors for use therein are provided using Cd- and/or Hg-containing semiconductors or B-based, Li-based or Gd-based semiconductors. The resulting systems and detectors used therein may be not only compact and portable, but also capable of operating at room temperature. The detectors may also be operable as gamma ray spectrometers.

Claims

1. A method for measuring neutron emissions and ionizing radiation, the method comprising:

positioning at least one solid state detector to receive the neutron emissions and ionizing radiation, the at least one solid state detector including;

a first semiconductor active region comprising at least one material having a first concentration sufficient for generating neutron-induced ionizing radiation in response to neutron absorptions and for generating a first electronic signal in response to the neutron absorptions and corresponding ionizing radiation;

a second semiconductor active region comprising the at least one material having a second concentration lower than the first concentration so as to be substantially less responsive to the neutron emissions for generating a second electronic signal in response to neutron-induced radiation emissions; and

a shield positioned to shield the neutron-induced ionizing radiation emitted from the first semiconductor active region so that the second semiconductor active region in unaffected by the ionizing radiation from the first semiconductor active region, and the second electronic signal from the second semiconductor active region is not generated in response to the neutron-induced ionizing radiation from the first semiconductor active region; and

processing the first and second signals to distinguish between the neutron emissions and the ionizing radiation measured by the at least one solid state detector.

2. The method as claimed in claim 1, wherein the first and second semiconductor active regions have substantially the same size and shape.

3. The method as claimed in claim 1, wherein the first and second semiconductor active regions have substantially similar sensitivity to background and surrounding ionizing radiation which primarily includes gamma rays, x-rays, and charged particles, and to radiations released by neutron interactions within the first and second semiconductor active regions.

4. The method as claimed in claim 1, wherein the at least one detector is a room temperature solid state detector.

5. The method as claimed in claim 1, wherein the at least one material is selected from the group consisting of CdTe, CdZnTe, CdS and HgI₂.

6. The method as claimed in claim 1, wherein the at least one material includes isotopes of Cd-113 and wherein concentration of Cd-113 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Cd-113 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

7. The method as claimed in claim 1, wherein the at least one material includes isotopes of Hg-199 and wherein concentration of Hg-199 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Hg-199 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

8. The method as claimed in claim 1, wherein the at least one material includes isotopes of B-10 and wherein concentration of B-10 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of B-10 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

9. The method as claimed in claim 1, wherein the at least one material includes isotopes of Li-6 and wherein concentration of Li-6 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle radiation emissions and concentration of Li-6 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

10. The method as claimed in claim 1, wherein the at least one material includes isotopes of Gd-157 or Gd-155 and wherein concentration of Gd-157 or Gd-155 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of Gd-157 or Gd-155 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

11. The method as claimed in claim 1, wherein each of the semiconductor active regions comprises a detector capable of detecting charged particles.

12. The method as claimed in claim 1, wherein the neutron-induced ionizing radiation includes gamma ray emissions.

13. The method as claimed in claim 1, wherein the neutron-induced ionizing radiation includes charged particles.

14. The method as claimed in claim 1, wherein each of the semiconductor active regions comprises a gamma ray spectrometer.

15. The method as claimed in claim 1, wherein the at least one material includes either Cd or Hg.

16. The method as claimed in claim 1, wherein the at least one material is B-based, Li-based or Gd-based.

17. A system for measuring neutron emissions and ionizing radiation, the system comprising:

at least one solid state detector including;

a first semiconductor active region comprising at least one material having a first concentration sufficient for generating neutron-induced ionizing radiation in response to neutron absorptions and for generating a first electronic signal in response to the neutron absorptions and corresponding ionizing radiation;

a second semiconductor active region comprising the at least one material having a second concentration lower than the first concentration so as to be substantially less responsive to the neutron emissions for generating a second electronic signal in response to neutron-induced radiation emissions; and

a shield positioned to shield the neutron-induced ionizing radiation emitted from the first semiconductor active region so that the second semiconductor active region in unaffected by the ionizing radiation from the fist semiconductor active region, and the second electronic signal from the second semiconductor active region is not generated in response to the neutron-induced ionizing radiation from the first semiconductor active region; and

a signal processor for processing the first and second signals to distinguish between the neutron emissions and corresponding ionizing radiation measured by the at least one solid state detector.

18. The system as claimed in claim 17, wherein the first and second semiconductor active regions have substantially the same size and shape.

19. The system as claimed in claim 17, wherein the first and second semiconductor active regions have substantially similar sensitivity to background and surrounding ionizing radiation which primarily includes gamma rays, x-rays, and charged particles, and to radiations released by neutron interactions within the first and second semiconductor active regions.

20. The system as claimed in claim 17, wherein the at least one detector is a room temperature solid state detector.

21. The system as claimed in claim 17, wherein the at least one material is selected from the group consisting of CdTe, CdZnTe, CdS and HgI₂.

22. The system as claimed in claim 17, wherein each of the semiconductor active regions comprises a gamma ray spectrometer.

23. The system as claimed in claim 17, wherein the at least one material includes either Cd or Hg.

24. The system as claimed in claim 17, wherein the at least one material includes isotopes of Cd-113 and wherein concentration of Cd-113 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Cd-113 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

25. The system as claimed in claim 17, wherein the at least one material includes isotopes of Hg-199 and wherein concentration of Hg-199 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Hg-199 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

26. The system as claimed in claim 17, wherein the at least one material includes isotopes of B-10 and wherein concentration of B-10 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of B-10 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

27. The system as claimed in claim 17, wherein the at least one material includes isotopes of Li-6 and wherein concentration of Li-6 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle radiation emissions and concentration of Li-6 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

28. The system as claimed in claim 17, wherein the at least one material includes isotopes of Gd-157 or Gd-155 and wherein concentration of Gd-157 or Gd-155 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of Gd-157 or Gd-155 in the second semiconductor active region is reduced such that it is less sensitive to the neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

29. The system as claimed in claim 17, wherein each of the semiconductor active regions comprises a detector capable of detecting charged particles.

30. The system as claimed in claim 17, wherein the neutron-induced ionizing radiation includes gamma ray emissions.

31. The system as claimed in claim 17, wherein the neutron-induced ionizing radiation includes charged particles.

32. The system as claimed in claim 17, wherein the at least one material is B-based, Li-based or Gd-based.

33. A solid state detector for measuring neutron emissions and ionizing radiation, the detector comprising:

a first semiconductor active region comprising at least one material having a first concentration sufficient for generating neutron-induced ionizing radiation in response to neutron absorptions and for generating a first electronic signal in response to the neutron absorptions and corresponding ionizing radiation;

a second semiconductor active region comprising the at least one material having a second concentration lower than the first concentration so as to be substantially less responsive to the neutron emissions for generating a second electronic signal in response to neutron-induced radiation emissions; and

a shield positioned to shield the neutron-induced ionizing radiation emitted from the first semiconductor active region so that the second semiconductor active region in unaffected by the ionizing radiation from the fist semiconductor active region, and the second electronic signal from the second semiconductor active region is not generated in response to the neutron-induced ionizing radiation from the first semiconductor active region.

34. The detector as claimed in claim 33, wherein the first and second semiconductor active regions have substantially the same size and shape.

35. The detector as claimed in claim 33, wherein the first and second semiconductor active regions have substantially similar sensitivity to background and surrounding ionizing radiation which primarily includes gamma rays, x-rays, and charged particles, and to radiations released by neutron interactions within the first and second semiconductor active regions.

36. The detector as claimed in claim 33, wherein the detector is a room temperature solid state detector.

37. The detector as claimed in claim 33, wherein the at least one material is selected from the group consisting of CdTe, CdZnTe, CdS and HgI₂.

38. The detector as claimed in claim 33, wherein each of the semiconductor active regions comprises a gamma ray spectrometer.

39. The detector as claimed in claim 33, wherein the at least one material includes either Cd or Hg.

40. The detector as claimed in claim 33, wherein the at least one material includes isotopes of Cd-113 and wherein concentration of Cd-113 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Cd-113 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

41. The detector as claimed in claim 33, wherein the at least one material includes isotopes of Hg-199 and wherein concentration of Hg-199 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Hg-199 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

42. The detector as claimed in claim 33, wherein the at least one material includes isotopes of B-10 and wherein concentration of B-10 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of B-10 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

43. The detector as claimed in claim 33, wherein the at least one material includes isotopes of Li-6 and wherein concentration of Li-6 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle radiation emissions and concentration of Li-6 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

44. The detector as claimed in claim 33, wherein the at least one material includes isotopes of Gd-157 or Gd-155 and wherein concentration of Gd-157 or Gd-155 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of Gd-157 or Gd-155 in the second semiconductor active region is reduced such that it is less sensitive to the neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

45. The detector as claimed in claim 33, wherein each of the semiconductor active regions comprises a detector capable of detecting charged particles.

46. The detector as claimed in claim 33, wherein the neutron-induced ionizing radiation includes gamma ray emissions.

47. The detector as claimed in claim 33, wherein the neutron-induced ionizing radiation includes charged particles.

48. The detector as claimed in claim 33, wherein the at least one material is B-based, Li-based or Gd-based.

49. An array of solid state detectors for measuring neutron emissions and ionizing radiation, each of the detectors comprising:

a first semiconductor active region comprising at least one material having a first concentration sufficient for generating neutron-induced ionizing radiation in response to neutron absorptions and for generating a first electronic signal in response to the neutron absorptions and corresponding ionizing radiation;

a second semiconductor active region comprising the at least one material having a second concentration lower than the first concentration so as to be substantially less responsive to the neutron emissions for generating a second electronic signal in response to neutron-induced radiation emissions; and

a shield positioned to shield the neutron-induced ionizing radiation emitted from the first semiconductor active region so that the second semiconductor active region in unaffected by the ionizing radiation from the fist semiconductor active region, and the second electronic signal from the second semiconductor active region is not generated in response to the neutron-induced ionizing radiation from the first semiconductor active region.

50. The array as claimed in claim 49, wherein the first and second semiconductor active regions have substantially the same size and shape.

51. The array as claimed in claim 49, wherein the first and second semiconductor active regions have substantially similar sensitivity to background and surrounding ionizing radiation which primarily includes gamma rays, x-rays, and charged particles, and to radiations released by neutron interactions within the first and second semiconductor active regions.

52. The array as claimed in claim 49, wherein each of the detectors is a room temperature solid state detector.

53. The array as claimed in claim 49, wherein the at least one material is selected from the group consisting of CdTe, CdZnTe, CdS and HgI₂.

54. The array as claimed in claim 49, wherein each of the semiconductor active regions comprises a gamma ray spectrometer.

55. The array as claimed in claim 49, wherein the at least one material includes either Cd or Hg.

56. The array as claimed in claim 49, wherein the at least one material includes isotopes of Cd-113 and wherein concentration of Cd-113 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Cd-113 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

57. The array as claimed in claim 49, wherein the at least one material includes isotopes of Hg-199 and wherein concentration of Hg-199 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Hg-199 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

58. The array as claimed in claim 49, wherein the at least one material includes isotopes of B-10 and wherein concentration of B-10 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of B-10 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

59. The array as claimed in claim 49, wherein the at least one material includes isotopes of Li-6 and wherein concentration of Li-6 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle radiation emissions and concentration of Li-6 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

60. The array as claimed in claim 49, wherein the at least one material includes isotopes of Gd-157 or Gd-155 and wherein concentration of Gd-157 or Gd-155 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of Gd-157 or Gd-155 in the second semiconductor active region is reduced such that it is less sensitive to the neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

61. The array as claimed in claim 49, wherein each of the semiconductor active regions comprises a detector capable of detecting charged particles.

62. The array as claimed in claim 49, wherein the neutron-induced ionizing radiation includes gamma ray emissions.

63. The array as claimed in claim 49, wherein the neutron-induced ionizing radiation includes charged particles.

64. The array as claimed in claim 49, wherein the at least one material is B-based, Li-based or Gd-based.

65. An imaging system for imaging neutron emissions and ionizing radiation, the system comprising:

an array of solid state detectors, each of the detectors including;

a first semiconductor active region comprising at least one material having a first concentration sufficient for generating neutron-induced ionizing radiation in response to neutron absorptions and for generating a first electronic signal in response to the neutron absorptions and corresponding ionizing radiation;

a second semiconductor active region comprising the at least one material having a second concentration lower than the first concentration so as to be substantially less responsive to the neutron emissions for generating a second electronic signal in response to neutron-induced radiation emissions; and

a shield positioned to shield the neutron-induced ionizing radiation emitted from the first semiconductor active region so that the second semiconductor active region in unaffected by the ionizing radiation from the fist semiconductor active region, and the second electronic signal from the second semiconductor active region is not generated in response to the neutron-induced ionizing radiation from the first semiconductor active region; and

an array of sheets of high-density material for separating adjacent solid state detectors.

66. The imaging system as claimed in claim 65, wherein the first and second semiconductor active regions have substantially the same size and shape.

67. The imaging system as claimed in claim 65, wherein the first and second semiconductor active regions have substantially similar sensitivity to background and surrounding ionizing radiation which primarily includes gamma rays, x-rays, and charged particles, and to radiations released by neutron interactions within the first and second semiconductor active regions.

68. The imaging system as claimed in claim 65, wherein each of the detectors is a room temperature solid state detector.

69. The imaging system as claimed in claim 65, wherein the at least one material is selected from the group consisting of CdTe, CdZnTe, CdS and HgI₂.

70. The imaging system as claimed in claim 65, wherein each of the semiconductor active regions comprises a gamma ray spectrometer.

71. The imaging system as claimed in claim 65, wherein the at least one material includes either Cd or Hg.

72. The imaging system as claimed in claim 65, wherein the at least one material includes isotopes of Cd-113 and wherein concentration of Cd-113 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Cd-113 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

73. The imaging system as claimed in claim 65, wherein the at least one material includes isotopes of Hg-199 and wherein concentration of Hg-199 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit gamma rays and concentration of Hg-199 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

74. The imaging system as claimed in claim 65, wherein the at least one material includes isotopes of B-10 and wherein concentration of B-10 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of B-10 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

75. The imaging system as claimed in claim 65, wherein the at least one material includes isotopes of Li-6 and wherein concentration of Li-6 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle radiation emissions and concentration of Li-6 in the second semiconductor active region is reduced such that it is less sensitive to neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

76. The imaging system as claimed in claim 65, wherein the at least one material includes isotopes of Gd-157 or Gd-155 and wherein concentration of Gd-157 or Gd-155 in the first semiconductor active region is sufficient to absorb neutrons and spontaneously emit charged particle and gamma radiation emissions and concentration of Gd-157 or Gd-155 in the second semiconductor active region is reduced such that it is less sensitive to the neutron absorptions and corresponding ionizing radiation than the first semiconductor active region.

77. The imaging system as claimed in claim 65, wherein each of the semiconductor active regions comprises a detector capable of detecting charged particles.

78. The imaging system as claimed in claim 65, wherein the neutron-induced ionizing radiation includes gamma ray emissions.

79. The imaging system as claimed in claim 65, wherein the neutron-induced ionizing radiation includes charged particles.

80. The imaging system as claimed in claim 65, wherein the at least one material is B-based, Li-based or Gd-based.