Gamma-ray spectrometry

• US 7,202,478 B2
• Filed: 09/02/2005
• Issued: 04/10/2007
• Est. Priority Date: 04/10/2003
• Status: Active Grant

• Current Assignee: Symetrica Limited
• Original Assignee: Symetrica Limited
• Inventors: Ramsden, David, Meng, Ling-Jian, Ignatov, Sergei, Ivanov, Oleg
• Primary Examiner(s): Porta; David
• Assistant Examiner(s): TANINGCO, MARCUS H
• Application Number:
  US11/219,028
• Publication Number:
  US 20060027754A1
• Time in Patent Office: 585 Days
• Field of Search: 250/361.R
• US Class Current: 250/361.00R
• CPC Class Codes: G01T 1/20 with scintillation detectors

Abstract

A scintillation spectrometer provides improved resolution by ensuring that photons generated by scintillation events occurring in different locations within the scintillation material generate similar light profiles on the photo-detector, thereby making the output signal less sensitive to the initial interaction site and enabling more effective de-convolution of raw data. This is achieved in different ways, such as by: limiting the exit window of the scintillation crystal, introducing a spacer between the scintillation crystal and the detector window, or providing a crystal that is longer than necessary to stop gamma rays.

Claims

1. A system, comprising:

a gamma-ray spectrometer, including;

a scintillation body for receiving gamma-rays and creating photons therefrom;

a photon detector having a sensitive area facing the scintillation body so as to receive and detect the photons; and

a processor operable to process energy loss data obtained by the gamma-ray spectrometer by deconvolution using a response function for the gamma-ray spectrometer.

2. The system according to claim 1, wherein the scintillation body has a surface that that is partially curved, and wherein the sensitive area of the photon detector is arranged tangentially to the curved portion of the surface.

3. The system according to claim 2, wherein the scintillation body comprises a generally spherical shape.

4. The system according to claim 1, wherein the photon detector is separated from the scintillation body by a light guiding spacer.

5. The system according to claim 1, wherein the photon detector is based on a semiconductor element.

6. The system according to claim 1, wherein the photon detector comprises a diode selected from a group consisting of (i) a PIN diode, (ii) a drift diode, (iii) a hybrid photodiode, and (iv) an avalanche photodiode.

7. The system according to claim 1, wherein the photon detector comprises a photo-multiplier tube.

8. The system according to claim 1, wherein the scintillation body is packed in a reflective material.

9. The system according to claim 1, further comprising a temperature sensor for measuring the temperature of the scintillation body.

10. A system, comprising:

a gamma-ray spectrometer, comprising;

means for absorbing gamma-rays and creating photons; and

a photon detector arranged to receive and detect photons; and

a processor operable to process energy loss data obtained by the gamma-ray spectrometer by deconvolution using a response function for the gamma-ray spectrometer.

11. The system according to claim 10, further including a light guiding spacer for spreading the photons so that an intensity profile of the photons across the photon detector is substantially uniform, and a length of the light guiding spacer is between 0.5–

10 times a corresponding width of the means for absorbing gamma-rays and creating photons.

12. The system according to claim 11, wherein the light-guiding spacer is packed in a reflective material.

13. A system according to claim 10, further comprising a temperature sensor for measuring a temperature of the means for absorbing gamma-rays and creating photons.

14. A system, comprising:

a gamma-ray spectrometer comprising a scintillation body for absorbing gamma-rays within the scintillation body and creating photons therefrom, and means for receiving and detecting the photons; and

a processor operable to process energy loss data obtained by the gamma-ray spectrometer by deconvolution using a response function for the gamma-ray spectrometer.

15. The system according to claim 14, wherein the scintillation body comprises Cesium Iodide.

16. The system according to claim 14, wherein the scintillation body comprises Sodium Iodide.

17. The system according to claim 14, wherein the scintillation body comprises Lutetium Oxyorthosilicate.

18. The system according to claim 14, wherein the scintillation body comprises Yttrium Aluminum Perovskite.

19. The system according to claim 14, wherein the scintillation body comprises an array of pillars.

20. The system according to claim 19, wherein the pillars are laterally isolated from each other with reflective material.

21. The system according to claim 20, wherein the means for receiving and detecting the photons comprises an array of detection elements.

22. The system according to claim 21, wherein the array of detection elements comprises a diode selected from a group consisting of (i) an array of discrete photodiodes, (ii) a monolithic array of photodiodes, (iii) a multi-pixel hybrid photodiode, and (iv) an electron-bombarded charged coupled detector.

23. The system according to claim 21, further comprising a coded-aperture mask arranged before the scintillation body to allow for imaging across the array of detection elements.

24. The system according to claim 21, further comprising a collimator arranged before the scintillation body to allow for imaging across the array of detection elements.

25. The system according to claim 21, further comprising a pin hole arranged before the scintillation body to allow for imaging across the array of detection elements.

26. The system according to claim 14, further comprising a temperature sensor for measuring a temperature of the scintillation body.

27. A method of gamma-ray spectroscopy, comprising the steps of:

(a) providing an object to be analyzed based on gamma rays;

(b) collecting energy-loss data for the object provided in said step (a) with a gamma-ray spectrometer comprising a scintillation body for receiving gamma-rays and creating photons therefrom, and a photon detector having a sensitive area facing the scintillation body so as to receive and detect the photons; and

(c) processing the energy-loss data collected in said step (b) by deconvolution using a response function computed for the gamma-ray spectrometer.

28. The method according to claim 27, wherein the energy loss-data collected in said step (b) is collected with temperature data indicating the temperature of the scintillation body, and the processing in said step (c) compensates the energy-loss data in respect of temperature using the temperature data.

29. The method according to claim 27, wherein the sensitive area of the photon detector is not more than 10% of a surface area of the scintillation body.

30. A method of gamma-ray spectroscopy, comprising:

(a) providing an object to be analyzed based on gamma rays of at. least a first energy;

(b) collecting energy-loss data for the object provided in said step (a) with a gamma-ray spectrometer comprising a scintillation body for absorbing the gamma-rays and creating photons therefrom, and a photon detector arranged to receive and detect the photons; and

(c) processing the energy-loss data collected in said step (b) by deconvolution using a response function computed for the gamma-ray spectrometer.

31. The method according to claim 30, wherein the energy loss-data collected in said step (b) contains temperature data indicating a temperature of the scintillation body, and the processing in said step (c) compensates the energy-loss data in respect of temperature using the temperature data.

32. The method according to claim 30, wherein the scintillation body is dimensioned to have a length of at least twice an attenuation length of gamma rays in order to spread the photons so that they more uniformly illuminate the photon detector.