Space charge dosimeters for extremely low power measurements of radiation in shipping containers

• US 20050248456A1
• Filed: 05/06/2004
• Published: 11/10/2005
• Est. Priority Date: 05/06/2004
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Hanson, Gregory R., Buckner, Mark A., Britton, Charles L. Jr., Bryan, William L.
• Granted Patent: US 7,525,431 B2
• Time in Patent Office: Days
• US Class Current: 340/539.290
• CPC Class Codes: G06Q 10/08 Logistics, e.g. warehousing, loading or distribution; Inventory or stock management
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 21/12 responsive to undesired emission of substances, e.g. pollution alarms
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

Methods and apparatus are described for space charge dosimeters for extremely low power measurements of radiation in shipping containers. A method includes insitu polling a suite of passive integrating ionizing radiation sensors including reading-out dosimetric data from a first passive integrating ionizing radiation sensor and a second passive integrating ionizing radiation sensor, where the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor remain situated where the dosimetric data was integrated while reading-out. Another method includes arranging a plurality of ionizing radiation sensors in a spatially dispersed array; determining a relative position of each of the plurality of ionizing radiation sensors to define a volume of interest; collecting ionizing radiation data from at least a subset of the plurality of ionizing radiation sensors; and triggering an alarm condition when a dose level of an ionizing radiation source is calculated to exceed a threshold.

Claims

1. A method, comprising insitu polling a suite of passive integrating ionizing radiation sensors including reading-out dosimetric data from a first passive integrating ionizing radiation sensor and a second passive integrating ionizing radiation sensor, wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor remain situated where the dosimetric data was integrated while reading-out.

2. The method of claim 1, wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor are powered only during reading-out dosimetric data.

3. The method of claim 1, wherein reading-out dosimetric data from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor includes reading-out to a communications circuit having a radio frequency transmitter that modulates a radio frequency signal as a function of dosimetric data read-out from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

4. The method of claim 3, wherein the communications circuit is located within a radio frequency tag that transmits environmental state sensor data including dosimetric data read-out from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

5. The method of claim 4, wherein the radio frequency tag modulates the radio frequency signal using at least one modulation technique selected from the group consisting of hybrid spread spectrum, direct sequence spread spectrum, frequency hopping, time hopping, time division multiplexing, orthogonal frequency division multiplexing and infrared.

6. The method of claim 1, wherein i) dosimetric data from the first passive integrating ionizing radiation sensor is a function of a first filter having a first admittance and ii) dosimetric data from the second passive integrating ionizing radiation sensor is a function of a second filter having a second admittance that is substantially different from the first admittance.

7. The method of claim 1, further comprising insitu temperature compensating of read-out dosimetric data from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

8. The method of claim 1, further comprising insitu calibrating the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

9. A method of measuring ionizing radiation proximate a shipping container, comprising the method of claim 1.

10. An apparatus, comprising:

a first passive integrating ionizing radiation sensor;

a second passive integrating ionizing radiation sensor coupled to the first passive integrating ionizing radiation sensor; and

a communications circuit coupled to the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor,

wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor read-out dosimetric data to the communications circuit.

11. The apparatus of claim 10, wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor are powered only during reading-out dosimetric data.

12. The apparatus of claim 10, wherein the communications circuit includes a radio frequency transmitter that modulates a radio frequency signal as a function of dosimetric data read-out from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

13. The apparatus of claim 12, wherein the first passive integrating ionizing radiation sensor, the second passive integrating ionizing radiation sensor and the communications circuit define a radio frequency tag that transmits environmental state sensor data as a function of dosimetric data read-out from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

14. The apparatus of claim 12, wherein the radio frequency tag modulates the radio frequency signal using at least one modulation technique selected from the group consisting of hybrid spread spectrum, direct sequence spread spectrum, frequency hopping, time hopping, time division multiplexing, orthogonal frequency division multiplexing and infrared.

15. The apparatus of claim 10, wherein the first passive integrating ionizing radiation sensor includes a first filter having a first admittance and the second passive integrating ionizing radiation sensor includes a second filter having a second admittance that is substantially different from the first admittance.

16. The apparatus of claim 10, wherein at a least one sensor selected from the group consisting of the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor includes a metal oxide silicon field effect transistor space charge dosimeter.

17. The apparatus of claim 10, wherein at a least one sensor selected from the group consisting of the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor includes an electret ion chamber space charge dosimeter.

18. The apparatus of claim 10, wherein at a least one sensor selected from the group consisting of the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor includes a microcantilever space charge dosimeter.

19. The apparatus of claim 10, further comprising a temperature compensation circuit coupled to the communications circuit, wherein the temperature compensation circuit insitu temperature compensates read-out dosimetric data from the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

20. The apparatus of claim 10, further comprising a calibration circuit coupled to the communications circuit, wherein the calibration circuit insitu calibrates the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

21. A shipping container, comprising the apparatus of claim 10.

22. A method, comprising:

arranging a plurality of ionizing radiation sensors in a spatially dispersed array;

determining a relative position of each of the plurality of ionizing radiation sensors to define a volume of interest;

collecting ionizing radiation data from at least a subset of the plurality of ionizing radiation sensors; and

triggering an alarm condition when a dose level of an ionizing radiation source is calculated to exceed a threshold.

23. The method of claim 22, wherein the spatially dispersed configuration defines an at least partially occupied array.

24. The method of claim 22, further comprising calculating a local statistical background ionizing radiation level.

25. The method of claim 22, further comprising calculating at least one surface characterizing a substantially constant ionizing radiation flux density to localize a position of the ionizing radiation source.

26. The method of claim 25, wherein calculating includes normalizing ionizing radiation data from at least one of the plurality of ionizing radiation sensors as a function of absorbing structure located within the volume of interest.

27. A method of monitoring shipping containers, comprising the method of claim 22.

28. An apparatus, comprising:

a plurality of ionizing radiation sensors arranged in a spatially dispersed configuration where a relative position of each of the plurality of sensors array is determined to define a volume of interest;

a data collection circuit coupled to the plurality of ionizing radiation sensors to collect ionizing radiation data from at least a subset of the plurality of ionizing radiation sensors; and

a computer coupled to the data collection circuit to i) calculate a dose level of an ionizing radiation source and compare the dose level to a threshold and ii) trigger an alarm when the dose level is equal to or greater than the threshold.

29. The apparatus of claim 28, wherein the spatially dispersed configuration defines an at least partially occupied array.

30. The apparatus of claim 28, wherein each of the plurality of ionizing radiation sensors includes a passive integrating ionizing radiation sensor.

31. A vehicle, comprising the apparatus of claim 28.

32. A method, comprising:

arranging a plurality of passive integrating ionizing radiation sensors in a spatially dispersed array;

determining a relative position of each of the plurality of passive integrating ionizing radiation sensors to define a volume of interest;

collecting ionizing radiation data from at least a subset of the plurality of passive integrating ionizing radiation sensors; and

triggering an alarm condition when collected ionizing radiation data from the subset of the plurality of passive integrating ionizing radiation sensors meets a predetermined spatial pattern criterion.

33. The method of claim 32, wherein the predetermined spatial pattern criterion includes a plurality of alternative patterns.

34. The method of claim 32, wherein the predetermined spatial pattern criterion includes a dosimetric data pattern defined by a function that includes a cube root of a radius from an approximate location of an ionizing radiation source.

35. An apparatus, comprising:

a first insulated gate field effect transistor including a first source, a first drain and a first insulated gate;

a second insulated gate field effect transistor including a second source, a second drain and a second insulated gate, the second source coupled to the first source;

a first conductor coupled to the second gate;

a first active region connected to the first conductor, the first active region accumulating dosimetric data from incident ionizing radiation;

a second conductor connected to the first active region;

a second active region coupled to the second conductor, the second active region accumulating dosimetric data from incident ionizing radiation; and

a third conductor coupled between the second active region and the first gate,

wherein the second conductor is coupled to both the first source and the second source.

36. The apparatus of claim 35, further comprising a third insulated gate field effect transistor that provides temperature compensation data.

37. A method, comprising insitu polling a suite of passive integrating ionizing radiation sensors including reading-out dosimetric data from a first passive integrating ionizing radiation sensor and a second passive integrating ionizing radiation sensor,

wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor remain situated where the dosimetric data was integrated while reading-out dosimetric data and

wherein the first passive integrating radiation sensor and the second integrating radiation sensor are connected to read-out circuits presenting extremely high impedance while in a passive integration mode and while in an active read-out mode, without destruction of integrated dosimetric data allowing continuous integration of ionizing radiation to a maximum extent of the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor.

38. The apparatus of claim 37, wherein the read-out circuits present impedance of from approximately 10¹¹ ohms to approximately 10¹⁵ ohms.

39. A method, comprising insitu polling a suite of passive integrating ionizing radiation sensors including reading-out dosimetric data from a first passive integrating ionizing radiation sensor and a second passive integrating ionizing radiation sensor,

wherein the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor remain situated where the dosimetric data was integrated while reading-out and

wherein the first passive integrating radiation sensor and the second integrating radiation sensor are connected to read-out circuits presenting extremely high impedance while in passive integration mode and during active read-out of dosimetric data without destruction of integrated dosimetric data allowing continuous integration of ionizing radiation to the maximum extent of the sensors and upon sensing the attainment of maximum integration limits, readout circuits will reset passive integrating radiation sensors and accumulate in a non-volatile manner the number of sensor reset cycles.

40. The apparatus of claim 39, wherein the read-out circuits present impedance of from approximately 10¹¹ ohms to approximately 10¹⁵ ohms.

41. An apparatus comprising:

a first passive integrating ionizing radiation sensor;

a second passive integrating ionizing radiation sensor;

a read-out circuit coupled to both the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor, the read-out circuit presenting an extremely high impedance to both the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor both while the read-out circuit is in a passive integration mode and while the read-out circuit is in an active read-out mode; and

a communication circuit coupled to the read-out circuit,

wherein read-out dosimetric data from both the first passive integrating radiation sensor and the second passive integrating radiation sensor is presented to the communications circuit.

42. The apparatus of claim 41, wherein at least one sensor selected from the group consisting of the first passive integrating ionizing radiation sensor and the second passive integrating ionizing radiation sensor includes a thick oxide insulated gate field effect transistor space charge dosimeter.

43. The apparatus of claim 41, wherein the read-out circuits present impedance of from approximately 10¹¹ ohms to approximately 10¹⁵ ohms.

44. An apparatus, comprising:

a thick oxide dosimeter; and

a readout circuit coupled to the thick oxide dosimeter,

wherein both the thick oxide dosimeter and the readout circuit are constructed on a single high impedance and low leakage substrate.

45. The apparatus of claim 44, wherein the thick oxide dosimeter includes a thick oxide insulated gate field effect transistor space charge dosimeter.

46. The apparatus of claim 44, wherein the single high impedance and low leakage substrate includes at least one construction selected from the group consisting of silicon on sapphire, silicon on insulator and transmutated high resistivity silicon.

47. The apparatus of claim 44, wherein the read-out circuits present impedance of from approximately 10¹¹ ohms to approximately 10¹⁵ ohms.