Radiation detection apparatus and radiation detection method

Patent metadata

Field	Value
Publication number	US-9927536-B2
Application number	US-201414496081-A
Country	US
Kind code	B2
Filing date	Sep 25, 2014
Priority date	Sep 30, 2013
Publication date	Mar 27, 2018
Grant date	Mar 27, 2018

Abstract

A radiation detection apparatus includes a selecting unit that allows a light having a light emission wavelength and a polarization direction to pass thorough the selecting unit, an optical system that forms an image of the light, a photon detecting unit that observes the image formed by the optical system, and detects the photon in whole range of the entire image, a counting unit that calculates the number of the alpha rays based on a result of counting the photons derived from the light emission of gas excited by the alpha rays, whereby it is possible to sufficiently eliminate background light (noise light) even if background light is strong, and therefore observe weak light emission.

First claim

What is claimed is:

1. A radiation detection apparatus comprising:
a wavelength selecting unit configured to pass light having a selected wavelength when a light emission is produced by excitation of a gas by an alpha ray;
a first polarization selecting unit configured to receive the light from the wavelength selecting unit, to select a polarization direction, and to pass light of the selected polarization direction;
an optical system configured to form an image of the light passed through the wavelength selecting unit and the first polarization selecting unit;
a photon detecting unit configured to detect photons in the image formed by the optical system;
a counting unit configured to identify each of the photons detected by the photon detecting unit that are larger than a threshold value as a photon derived from the light emission of gas excited by the alpha ray count the identified photons, and calculate the number of the alpha rays based on a result of counting the identified photons; and
a polarized light projecting unit configured to project polarized light having a polarization direction perpendicular to the polarization direction selected by the first polarization selecting unit.

2. The radiation detection apparatus according to claim 1 , wherein the first polarization selecting unit is configured to select a first polarization direction and a second polarization direction,
wherein the optical system is configured to form a first image in a first case where the first polarization selecting unit selects the first polarization direction and a second image in a second case where the first polarization selecting unit selects the second polarization direction,
wherein the photon detecting unit is configured to detect the photons in the first image and the photons in the second image, and
wherein the counting unit is configured to use a difference value as the value obtained from the result of counting the detected photons, the difference value being between the number of the detected photons in the first image and the number of the detected photons in the second image.

3. The radiation detection apparatus according to claim 1 , further comprising an angle setting unit configured to adjust and fix an angle between the optical system and the photon detecting unit to desired angle value by rotating or moving at least one of the optical system and the photon detecting unit.

4. The radiation detection apparatus according to claim 1 , wherein the polarized light projecting unit includes a polarized light source configured to radiate the polarized light.

5. The radiation detection apparatus according to claim 1 , wherein the polarized light projecting unit includes a light source configured to radiate a non-polarized light, and a second polarization selecting unit configured to allow a light in a predetermined direction to pass through the second polarization selecting unit, the predetermined direction being perpendicular to both the polarization direction selected by the first polarization selecting unit and a propagating direction of the non-polarized light radiated from the light source.

6. The radiation detection apparatus according to claim 1 , wherein the photon detecting unit comprises an optical sensing element configured to detect the photons in a matrix.

7. The radiation detection apparatus according to claim 6 , wherein the optical sensing element is selected at least one type from a CCD that has cooling function, an EMCCD that has electron multiplying function, an ICCD, a back side illumination type image sensor, and a MPPC.

8. The radiation detection apparatus according to claim 6 , wherein the optical sensing element is selected at least one type from the photodetector selected from a photomultiplier tube, a PIN photodiode, and an avalanche photodiode.

9. A radiation detection method comprising:
selecting a wavelength associated with light emitted when a gas is excited by an alpha ray;
selecting a first polarization direction;
forming an image of a light having the selected wavelength and the selected polarization direction selected from the light emitted by the excited gas;
detecting at least one photon in the image formed;
identifying each of said at least one photon detected in the detecting step having an intensity larger than a threshold value as a photon derived from the light emitted by the excited gas;
counting each of the identified photons;
calculating the number of the alpha ray based on a result of the counting each of the identified photons; and
further comprising projecting a polarized light to a region in which the light is emitted by the excited gas,
wherein the polarization direction includes a first polarization direction, and
wherein the polarized light has a second polarization direction which is perpendicular to both a propagating direction of the polarized light and the first polarization direction.

10. The radiation detection method according to claim 9 , further comprises selecting a second polarization direction, and wherein the value obtained from a result of counting each of the detected photons is a difference between the number of the detected photons when the first polarization direction is selected and the number of the detected photons when the second polarization direction is selected.

11. The radiation detection method according to claim 9 , wherein the polarized light projecting step includes projecting a non-polarized light from a light source and allowing a light component in a second polarization direction of the non-polarized light to pass through a polarization selecting unit that selects the second polarization direction, thereby obtaining the polarized light of which polarization direction is the second polarization direction from the non-polarized light.

Assignees

• Toshiba Kk

Inventors

• Kuroda Hidehiko
• Nakayama Kunihiko
• Takakura Kei
• Izumi Mikio
• Kume Naoto

Classifications

• G01T1/205

  the detector being a gas · CPC title

• G01J1/42

  using electric radiation detectors (optical or mechanical part G01J1/04; by comparison with a reference light or electric value G01J1/10) · CPC title

• G01T1/169 Primary

  Exploration, location of contaminated surface areas · CPC title

• G01T1/2006

  using a combination of a scintillator and photodetector which measures the means radiation intensity · CPC title

• G01T1/2002 Primary

  Optical details, e.g. reflecting or diffusing layers · CPC title