Spectral Discrimination using Wavelength-Shifting Fiber-Coupled Scintillation Detectors

• US 20170315242A1
• Filed: 04/18/2017
• Published: 11/02/2017
• Est. Priority Date: 02/14/2012
• Status: Active Grant

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Arodzero, Anatoli, Callerame, Joseph, Dinca, Dan-Christian, Sud, Rajen, Grodzins, Lee, Rommel, Martin, Rothschild, Peter, Schubert, Jeffrey
• Granted Patent: US 10,209,372 B2
• Time in Patent Office: Days
• CPC Class Codes: G01T 1/20 with scintillation detectors
• CPC Class Codes: G01T 1/2006 using a combination of a scintillator and photodetector which measures the means radiation intensity
• CPC Class Codes: G01T 1/2008 using a combination of different types of scintillation detectors, e.g. phoswich
• CPC Class Codes: G01T 1/20181 Stacked detectors, e.g. for measuring energy and positional information using a combination of different types of scintillation detectors, e.g. phoswich detectors, G01T1/2008
• CPC Class Codes: G01T 1/20185 Coupling means between the photodiode and the scintillator, e.g. optical couplings using adhesives with wavelength-shifting fibres
• CPC Class Codes: G01T 3/06 with scintillation detectors
• CPC Class Codes: G01T 5/08 Scintillation chambers discharge tubes H01J40/00, H01J47/00; semiconductor devices H01L
• CPC Class Codes: G01T 7/00 Details of radiation-measuring instruments
• CPC Class Codes: G01V 5/0016 Active interrogation, i.e. using an external radiation source, e.g. using pulsed, continuous or cosmic rays
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
• CPC Class Codes: H01L 27/146 Imager structures
• CPC Class Codes: H01L 27/14601 Structural or functional details thereof
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14658 X-ray, gamma-ray or corpuscular radiation imagers measuring X-, gamma- or corpuscular radiation G01T1/00

Abstract

Methods for discriminating among x-ray beams of distinct energy content. A first volume of scintillation medium converts energy of incident penetrating radiation into scintillation light which is extracted from a scintillation light extraction region by a plurality of optical waveguides that convert the scintillation light to light of a longer wavelength. An x-ray beam initially incident upon the first volume of scintillation medium and traversing the first volume is then incident on a second volume of scintillation medium. The first and second scintillation media may be separated by an absorber or one or more further volumes of scintillation medium, and may also have differential spectral sensitivities. Scintillation light from the first and second scintillation volumes is detected in respective detectors and processed to yield a measure of respective low energy and high-energy components of the incident x-ray beam.

Claims

1. A method for discriminating among x-ray beams of distinct energy content, the method comprising:

a. converting energy of an x-ray beam incident upon a first volume of scintillation medium into a first scintillation light;

b. guiding light derived from, and at a first wavelength longer than the first scintillation light via a first plurality of wavelength-shifting optical waveguides;

c. converting energy of x-ray radiation that has traversed the first volume into a second scintillation light in a second volume of scintillation medium;

d. detecting, with a first photodetector, photons at the first wavelength guided by the first plurality of waveguides thereby generating a first detector signal; and

e. detecting, with a second photodetector, photons due to scintillation in the second volume of scintillator material thereby generating a second signal;

f processing the first signal and the second signal to provide a measure of a low energy component and a high-energy component of the x-ray beam incident upon the first volume of scintillation material.

2. A method according to claim 1, further comprising guiding light derived from, and at a second wavelength longer than that of, the second scintillation light via a second plurality of wavelength-shifting optical waveguides to the second photodetector.

3. A method according to claim 1, wherein the first volume of scintillation medium and the second volume of scintillation medium are characterized by distinct spectral sensitivities to an x-ray beam traversing both the first and second volumes of scintillation medium.

4. A method according to claim 1, wherein the second volume of scintillation medium is characterized a higher sensitivity to photons exceeding a specified energy that the first volume of scintillation medium.

5. A method according to claim 1, wherein the second volume of scintillator medium includes plastic scintillator.

6. A method according to claim 1, wherein the first volume of scintillator medium includes a lanthanide-doped barium mixed-halide.

7. A method according to claim 1, further comprising:

g. collecting light produced by scintillation in a third volume of scintillation medium traversed by the incident x-ray beam after transversal of the first volume of scintillation medium and before incidence upon the second volume of scintillation medium;

h. coupling the light produced by scintillation in the third volume into coupled light within a waveguide;

i. converting the light within the waveguide to a light of longer wavelength than the coupled light; and

j. detecting the light of the longer wavelength and producing a third signal for processing in conjunction with the first and second signals.

8. A method according to claim 1, further comprising enhancing a difference between low- and high-energy components of the incident x-ray beam by absorbing energy from the incident x-ray beam after transversal of the first volume of scintillation medium and before incidence upon the second volume of scintillation medium.

9. A method according to claim 5, wherein absorbing energy from the incident x-ray beam after transversal of the first volume of scintillation material includes traversal by the beam of copper intervening between the first volume of scintillation medium and the second volume of scintillation medium.

10. A method according to claim 1, further comprising measuring an average atomic number of material traversed by an x-ray beam on the basis of the measure of the low energy component and the high-energy component of the x-ray beam incident upon the first volume of scintillation medium.