Two-Dimensional Detection System for Neutron Radiation in the Field of Neutron Scattering Spectrometry

Abstract

A two-dimensional detection system for neutron radiation is disclosed. The detection system includes a means ( 1 ) for emitting a neutron beam ( 10 ), a support means ( 2 ) adapted for receiving a sample ( 3 ), a photoemission means ( 5 ) adapted for being activated by a neutron radiation, and a cooled low light level charge-coupled detection device ( 7 ). The emission means ( 1 ) emits a monochromatic neutron beam ( 10 ). The system further includes a filter means ( 4 ), the filter means ( 4 ) being located between the support means ( 2 ) and the photoemission means ( 5 ) and being adapted for trapping at least a substantial part of the monochromatic neutron beam transmitted ( 12 ) by the sample ( 3 ), and an amplification means ( 6 ) located upstream the charge-coupled detection device ( 7 ) and coupled with the charge-coupled detection device ( 7 ).

1 . Two-dimensional detection system for neutron radiation comprising a means for emitting a neutron beam, a support means adapted for receiving a sample, a photoemission means adapted for being activated by a neutron radiation, a cooled low light level charge-coupled detection device, wherein the emission means emits a monochromatic neutron beam and in that the system further comprises:
 a filter means, the filter means being located between the support means and the photoemission means and being adapted for trapping at least a substantial part of the monochromatic neutron beam transmitted by the sample; and   an amplification means located upstream the charge-coupled detection device and coupled with the charge-coupled detection device.   
   
   
       2 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the filter means traps the entire monochromatic neutron beam transmitted by the sample. 
   
   
       3 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the photoemission means emits alpha radiation originating from a single nuclear reaction. 
   
   
       4 . Two-dimensional detection system for neutron radiation according to  claim 3 , wherein the photoemission means is a lithium-based scintillator. 
   
   
       5 . Two-dimensional detection system for neutron radiation according to  claim 4 , wherein the lithium-based scintillator is a composite material based on lithium sulphide. 
   
   
       6 . Two-dimensional detection system for neutron radiation according to  claim 4 , wherein the lithium-based scintillator is a composite material based on lithium fluoride. 
   
   
       7 . Two-dimensional detection system for neutron radiation according  claim 1 , wherein the photoemission means is in the form of a plate with a length of between 5 and 100 cm, a width of between 5 and 100 cm and a thickness of less than or equal to 1.2 mm. 
   
   
       8 . Two-dimensional detection system for neutron radiation according to  claim 3 , wherein the photoemission means is plane. 
   
   
       9 . Two-dimensional detection system for neutron radiation according to  claim 3 , wherein the photoemission means is curved, defined by a portion of cylinder delimited by a plane with dimensions varying from 5 to 100 cm in length and in width. 
   
   
       10 . Two-dimensional detection system for neutron radiation according to  claim 3 , wherein the photoemission means is curved, defined by a portion of sphere. 
   
   
       11 . Two-dimensional detection system for neutron radiation according to  claim 3 , wherein the photoemission means is lined with a surface opaque to light and transparent to neutron radiation, and located on the inlet of the photoemission means. 
   
   
       12 . Two-dimensional detection system for neutron radiation according to  claim 11 , wherein the opaque surface is formed from a rigid material adapted for holding the photoemission means in place. 
   
   
       13 . Two-dimensional detection system for neutron radiation according to  claim 11 , wherein the opaque surface is an aluminum plate. 
   
   
       14 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the charge-coupled detection device enables coding on at least 12 bits. 
   
   
       15 . Two-dimensional detection system for neutron radiation according to  claim 14 , wherein the charge-coupled detection device enables coding on 16 bits. 
   
   
       16 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the charge-coupled detection device is a camera adapted for variable pause times. 
   
   
       17 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the photoemission means, the amplification means and the charge-coupled detection device are enclosed in a box designed such that no light radiation other than that emitted by the photoemission means can penetrate inside. 
   
   
       18 . Two-dimensional detection system for neutron radiation according to  claim 17 , wherein the photoemission means and the charge-coupled detection device coupled with the amplification means respectively form the inlet end and outlet end of the box. 
   
   
       19 . Two-dimensional detection system for neutron radiation according to  claim 18 , wherein the system further comprises a protection means capable of reducing the influence of parasite radiation between support means for the sample and the photoemission means. 
   
   
       20 . Two-dimensional detection system for neutron radiation according to  claim 19 , wherein the protection means is a conical or pyramid shaped element, having the photoemission means as its base and being located between the support means for the sample and the photoemission means. 
   
   
       21 . Two-dimensional detection system for neutron radiation according to  claim 19 , wherein the protection means is a casing comprising a cylindrical part and a tapered end part, and surrounding the box. 
   
   
       22 . Two-dimensional detection system for neutron radiation according to  claim 19 , the protection means includes sidewalls adapted for absorbing parasite radiation not originating from the sample. 
   
   
       23 . Two-dimensional detection system for neutron radiation according to  claim 19 , wherein the protection means contains an inert gas or a primary vacuum. 
   
   
       24 . Two-dimensional detection system for neutron radiation according to  claim 23 , wherein the inert gas is helium. 
   
   
       25 . Two-dimensional detection system for neutron radiation according to  claim 23 , wherein the inert gas is argon. 
   
   
       26 . Two-dimensional detection system for neutron radiation according to  claim 23 , wherein the inert gas is nitrogen. 
   
   
       27 . Two-dimensional detection system for neutron radiation according to  claim 17 , wherein the box comprises inside walls adapted for absorbing neutron and gamma radiation. 
   
   
       28 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the system further comprises a mirror adapted for reflecting only light radiation emitted by the photoemission means towards the amplification means. 
   
   
       29 . Two-dimensional detection system for neutron radiation according to  claim 28 , wherein the mirror is made from aluminized quartz and is less than or equal to 10 mm thick. 
   
   
       30 . Two-dimensional detection system for neutron radiation according to  claim 28 , wherein the mirror is plane. 
   
   
       31 . Two-dimensional detection system for neutron radiation according to  claim 28 , wherein the mirror is curved. 
   
   
       32 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the system further comprises a means for absorbing neutron and gamma radiation, this absorption means being arranged at the outlet of the photoemission means. 
   
   
       33 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the amplification means and the charge-coupled detection device are surrounded by a shield for stopping gamma radiation. 
   
   
       34 . Two-dimensional detection system for neutron radiation according to  claim 33 , wherein the shield is a metal with a thickness and a density such that the product of the thickness and the density is greater than or equal to 34. 
   
   
       35 . Two-dimensional detection system for neutron radiation according to  claim 33 , wherein the shield is made of tungsten with a thickness of about 2 cm. 
   
   
       36 . Two-dimensional detection system for neutron radiation according to  claim 1 , wherein the system further comprises a collimation device arranged between the emission means and the support means, and outputting an output neutron beam with a diameter of between 0.5 and 15 mm. 
   
   
       37 . Two-dimensional detection method for neutron radiation comprising the steps of:
 emitting a neutron beam towards a sample,   transforming the neutron beam output from the sample into photons,   detecting the photons emitted by a cooled low light level charge transfer detection device,   
     the method being characterized in that it further comprises the steps consisting of:
 transforming the neutron beam emitted towards the sample into a monochromatic neutron beam, 
 filtering the neutron beam output from the sample so as to trap at least a substantial part of the monochromatic neutron beam transmitted by the sample, 
 amplifying the photon radiation upstream the cooled low light level charge transfer detection device.