Radiation detecting apparatus

Abstract

In a radiation detecting apparatus, an α ray and a β ray are transmitted through a light shielding film but an incident light is shielded. A first light is emitted from a first scintillator by the α ray transmitted through the light shielding film. The first scintillator has an emission center wavelength based on the α ray. A second light is emitted in a second scintillator by the β ray transmitted through the light shielding film. The second scintillator has an emission center wavelength based on the β ray. The first and second lights are detected by two photo-detectors, respectively. The first emission center wavelength and the second emission center wavelength are different from each other.

What is claimed is:  
     
         1 . A radiation detecting apparatus comprising: 
 a light shielding film for transmitting therethrough first and second radiations while shielding an incidence of light;    a first scintillator for emitting a first light by the first radiation transmitted through the light shielding film, said first scintillator having an emission center wavelength based on the first radiation;    a second scintillator for emitting a second light by the second radiation transmitted through the light shielding film, said second scintillator having an emission center wavelength based on the second radiation; and    detection means having at least one photo-detector for detecting the first light emitted from the first scintillator and the second light emitted in the second scintillator,    said first emission center wavelength and said second emission center wavelength being different from each other.    
     
     
         2 . A radiation detecting apparatus according to  claim 1 , wherein said first emission center wavelength is a wavelength of the first light emitted in the first scintillator and having a peak emission intensity in an emission wavelength band of the first scintillator, and said second emission center wavelength is a wavelength of the second light emitted in the second scintillator and having a peak emission intensity in an emission wavelength band of the second scintillator.  
     
     
         3 . A radiation detecting apparatus according to  claim 2 , wherein said first scintillator and second scintillator are arranged in parallel to each other so that the second scintillator is located away from the first scintillator at a predetermined distance, further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means; and an air layer interposed between the first and second scintillators, 
 said first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.    
     
     
         4 . A radiation detecting apparatus according to  claim 2 , further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein said first scintillator and second scintillator are closely optically adhered with each other, 
 said first emission center wavelength of the first scintillator being set shorter than the second emission center wavelength of the second scintillator.    
     
     
         5 . A radiation detecting apparatus according to  claim 2 , further comprising means for condensing the first light emitted from the first scintillator and the second light emitted in the second scintillator on the detection means, wherein said first scintillator and second scintillator are closely optically adhered with each other, 
 said first emission center wavelength of the first scintillator being set longer than the second emission center wavelength of the second scintillator.    
     
     
         6 . A radiation detecting apparatus according to  claim 2 , further comprising a condensing box for condensing the first and second lights on the detection means, said condensing box having an inner surface for diffusely reflecting the first and second lights and a side surface, said light shielding film being mounted on the side surface on which the first and second radiations incident, said first and second scintillators being arranged inside the light shielding film, and wherein said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, 
 said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,    said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.    
     
     
         7 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, 
 said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,    said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and    wherein said first filter and the second filter are closely optically adhered on the back surface of the second scintillator.    
     
     
         8 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has a substantially rectangular shape, and wherein said first photo-detector and the second photo-detector are adjacently arranged so that a line is crossed to a longitudinal direction of the second scintillator, said line connecting a center point of the sensitive surface of the first photo-detector and that of the sensitive surface of the second photo-detector.  
     
     
         9 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has a substantially rectangular shape, and wherein said first photo-detector and the second photo-detector are arranged on both lateral sides of the second scintillator so that the first photo-detector is the most distant from the second photo-detector.  
     
     
         10 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, 
 said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,    said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and    wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval so that an air layer is interposed between the back surface of the second scintillator and the first filter, and said second filter is closely optically adhered on the back surface of the second scintillator.    
     
     
         11 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, 
 said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,    said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator, and    wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and said second filter is closely optically adhered on the back surface of the second scintillator, further comprising a surrounding box having an inner surface portion for surrounding a back surface side of the second scintillator so as to form a closed space therein, said back surface of the second scintillator and said first filter forming parts of the inner surface portion of the surrounding box, said inner surface portion of the surrounding box except for the back surface of the second scintillator and the first filter being processed to totally internally reflect diffusely the first light emitted from the first scintillator.    
     
     
         12 . A radiation detecting apparatus according to  claim 11 , wherein said inner surface portion comprises a plurality of inner surfaces, each of said inner surfaces is inclined so that the diffusely reflecting directions on average of the first light on the inner surfaces of the surrounding box are substantially directed to a position of the second scintillator at which a center axis of the sensitive surface of the first photo-detector is crossed.  
     
     
         13 . A radiation detecting apparatus according to  claim 2 , further comprising a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, said light guide being adapted to condense the first and second lights on the detection means, and wherein said detection means comprises first and second photo-detectors each having a sensitive surface sensitive to each of the first and second lights; a first filter mounted on the sensitive surface of the first photo-detector; and a second filter mounted on the sensitive surface of the second photo-detector, 
 said first filter being adapted to transmit therethrough only the first light emitted from the first scintillator,    said second filter being adapted to transmit therethrough only the second light emitted in the second scintillator.    
     
     
         14 . A radiation detecting apparatus according to  claim 13 , wherein said first filter is arranged to be away from the back surface of the second scintillator at a predetermined interval, and said second filter is closely optically adhered on the back surface of the second scintillator, and wherein said light guide has an opening surface opposite to the back surface of the second scintillator, said light guide being arranged so that the opening surface thereof being away from the back surface of the second scintillator at a predetermined interval so as to interpose an air layer between the opening surface of the light guide and the back surface of the second scintillator, said opening surface thereof having an area which is larger than that of the first filter.  
     
     
         15 . A radiation detecting apparatus according to  claim 2 , further comprising a light guide connecting the at least one photo-detector to an edge portion of the second scintillator, said light guide being adapted to convert the second light to a fluorescent light.  
     
     
         16 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, said fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a light guide adapted to condense the converted fluorescent light on the at least one photo-detector, said converted fluorescent light being emitted from a surface of the fluorescent screen, said at least one photo-detector detecting the condensed fluorescent light.  
     
     
         17 . A radiation detecting apparatus according to  claim 2 , wherein said second scintillator has an incident surface on which the first and second radiations are incident and a back surface opposite to the incident surface, further comprising a fluorescent screen arranged on a back surface side of the second scintillator and opposite through an air layer to the back surface thereof, said fluorescent screen being adapted to convert the first light emitted from the first scintillator to a fluorescent light; and a second light guide having a fluorescent substance adapted to absorb the converted fluorescent light so as to emit a fluorescent light, said converted fluorescent light by the fluorescent screen being emitted from an edge portion of the fluorescent screen, said fluorescent light emitted from the light guide having a wavelength which is longer than that of the converted fluorescent light by the fluorescent screen, said at least one photo-detector detecting the fluorescent light emitted from the second light guide.  
     
     
         18 . A radiation detecting apparatus according to  claim 2 , further comprising means for capturing a signal outputted from the detection means so as to recognize a signal having a predetermined pulse height value and over as an optical signal thereby eliminating a signal less than the predetermined pulse height value as a noise, said optical signal corresponding to at least one of the first and second lights emitted from the first and second scintillators.  
     
     
         19 . A radiation detecting apparatus according to  claim 2 , wherein said detection means comprises a plurality of photo-detectors, a first group of the photo-detectors being adapted to detect the first light emitted from the first scintillator, a second group thereof being adapted to detect the second light emitted from the second scintillators, further comprising means for capturing signals outputted each of the first and second groups of the photo-detectors and, in a case of detecting signals outputted from at least one of the first and second groups of the photo-detectors, for recognizing detected signals corresponding to at least one of the first and second lights emitted from the first and second scintillators and, in a case where only one signal is outputted from at least one of the first and second groups of the photo-detectors, for eliminating the only one signal as a noise.  
     
     
         20 . A radiation detecting apparatus according to  claim 2 , further comprising an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, said optical attenuation filter being interposed between the first and second scintillators; a condensing box for condensing the first and second lights on the detection means, said condensing box having an inner surface for diffusely reflecting the first and second lights; and means for inputting signals detected by the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.  
     
     
         21 . A radiation detecting apparatus according to  claim 2 , further comprising an optical attenuation filter for transmitting therethrough the first and second radiations and attenuating an intensity of the first light emitted from the first scintillator, said optical attenuation filter being interposed between the first and second scintillators; a light guide in which the first light emitted from the first scintillator and the second light emitted in the second scintillator are incident, said light guide being adapted to condense the first and second lights on the detection means; and means for inputting signals outputted from the detection means so as to discriminate, according to a difference of waveforms of the inputted signals, between an optical signal corresponding to the first light emitted from the first scintillator and an optical signal corresponding to the second light emitted from the second scintillator.