US 5,410,156 A · High energy x-y neutron detector and radiographic/tomographic device

Abstract

An improved fast neutron x-y detector and radiographic/tomographic device utilizing a white neutron probe (4). The invention includes a multiple scattering filter (44), radiographic and tomographic imaging of the number densities of atoms in small volume increments through a sample 32 and the atomic, chemical and physical structure of a sample, (32), and neural net analysis techniques, where the neural net is trained through use of simulated volume increments. The invention detects fast neutrons over a two dimensional plane, measures the energy of the neutrons, and discriminates against gamma rays. In a preferred embodiment, the detector face is constructed by stacking separate bundles (6) of scintillating fiber optic strands (20) one on top of the other. The first x-y coordinate is determined by which bundle (6) the neutron strikes. The other x-y coordinate is calculated by measuring the difference in time of flight for the scintillation photon to travel to the opposite ends of the fiber optic strand 20. In another embodiment, the detector is constructed of discrete scintillator sections (48) connected to fiber optic strands (52) by couplers (50) functioning as lens. The fiber optic strands (52) are connected to a multi-anode photomultiplier (100) tube (56). The x-y coordinate of a neutron interaction is determined by the row and column of the affected scintillation section (48). Neutron energy for both detectors is calculated by measuring the flight time of a neutron from a point source (2) to the detector face.

Claims15

Dependent claims

A method for analyzing neutrons of multiple energies which have passed through a sample to determine the presence or absence of certain atoms in specified number densities and ratios, for purposes of explosives detection or analysis of a sample, comprising the steps of:

producing a white neutron beam ( a beam of neutrons of multiple energies);
determining the neutron attenuation of the white neutron beam without a sample in the path of the beam;
directing the white neutron beam through the sample;
reducing the multiple scattering of said neutrons;
measuring the attenuation of the neutrons which travel through the sample without scattering;
comparing the baseline white neutron beam directed onto the sample with the unscattered neutrons passing through the sample, and determining neutron attenuation as a function of neutron energy;
comparing the resulting attenuation with known neutron cross-sections;
creating a radiographic or tomographic image showing the number densities and ratios of atoms throughout volume increments of the sample through such comparison;
and
determining whether an explosive or other specific substance is present in any such volume increment by comparing the resulting number densities and ratios of atoms in said volume increments of the sample to known number densities and ratios of atoms in explosives or other substance sought to be identified.

7 more elements

Apparatus for producing a radiographic/tomographic view of a sample showing the number densities of atoms in volume increments through a sample, consisting of a first means for producing a beam of white neutrons and directing said beam;

a second means for conveying samples into place for exposure to the beam;
a third means for directing the beam through the sample;
a fourth means for reducing the multiple scattering of neutrons by the sample;
a fifth means of detecting neutrons;
a sixth means of determining the location in the sample through which such neutrons pass;
a seventh means of measuring the intensity of neutrons both before and after the sample is placed in the neutron beam;
an eighth means of comparing the neutrons intensities which reach the detector means without a sample in the neutron beam path with the neutrons passing through the sample;
a ninth means of determining the number densities or ratios of atoms, atomic, chemical or physical structure of the sample through such comparison;
a tenth means of creating a tomographic image of the number densities or ratios of atoms, atomic, chemical or physical structure of the sample;
and an eleventh means of comparing said samples with a database of samples with known features for features sought to be identified in the unknown samples.

7 more elements

Dependencies are inferred from the claim text.

High energy x-y neutron detector and radiographic/tomographic device

Life of this patent

High energy x-y neutron detector and radiographic/tomographic device

Life of this patent

Abstract

Claims15