# US 2010/0163744 A1 · Long Range Neutron-Gamma Point Source Detection and Imaging Using Rotating Detector

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- Number: US 2010/0163744 A1
- Document ID: US20100163744A1
- Status: Published application
- Kind: A1
- Application number: 12/483,771
- Filed: 2009-06-12
- Published: 2010-07-01
- Earliest claimed: 2008-06-16
- Assignees: Proportional Technologies, Inc.
- Inventors: Jeffrey Lacy
- Web page: https://patentgrep.com/patent/US20100163744A1

## CPC

- G01T 1/18: with counting-tube arrangements, e.g. with Geiger counters (tubes H01J47/08; {with alarm provision G01T7/125})
- G01T 1/2907: {Angle determination; Directional detectors; Telescopes (prospecting by the use of nuclear radiation, e.g. of natural or induced radioactivity G01V5/00)}
- G01T 3/008: {using an ionisation chamber filled with a gas, liquid or solid, e.g. frozen liquid, dielectric (G01T3/006 takes precedence)}
- G01V 5/26: Passive interrogation, i.e. by measuring radiation emitted by objects or goods
- G01T: MEASUREMENT OF NUCLEAR OR X-RADIATION (radiation analysis of materials, mass spectrometry G01N23/00; tubes for determining the presence, intensity, density or energy of radiation or particles H01J47/00)
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)

## Abstract

This application relates to radiation detection, and more particularly, to a method and device for the remote detection and localization of nuclear materials in an unknown background. A method and apparatus for long range neutron and gamma ray detection and imaging is disclosed wherein a panel of thin walled tube detectors are rotated to enhance detection performance. The method and apparatus have particular applicability to portable monitoring and homeland security.

## Claims

### Claim 1

A method of detecting radiation comprising the steps of:
(a) providing a panel monitor comprising a plurality of detector modules stacked vertically;
(b) rotating the panel monitor around a vertical axis;
(c) recording gamma and/or neutron counts at intervals while the panel rotates;
(d) processing information regarding the counts and rotation angle using an algorithm to deduce a radiation source size and direction.

### Claim 2 (depends on 1)

The method of claim 1, wherein the algorithm used for gamma rays comprises:
(a) recording the monitor rotation angle θi, and gamma count rate yi, at time ti, with i taking integer values from 1 to N, where N is the desired number of measurements over the course of a single rotation;
(b) finding parameters a and b that minimize the function χ2=Σ(yi−fi(θi,a,b))2/yi, where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b; and
(c) once a0 and b0 for which χ2(a0,b0)=min(χ2) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(yi)−a0)/30;
and the source direction angle as b0.

### Claim 3 (depends on 1)

The method of claim 1, wherein the algorithm used for neutrons comprises:
(a) recording the monitor rotation angle θi, and neutron count rate yi, at time ti, with i taking integer values from 1 to N, where N is the desired number of measurements over the course of a single rotation;
(b) finding parameters a and b that minimize the function −ln(L)=−ln (Πe−fi·fiyi/yi!), where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi)−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b; and
(c) once a0 and b0 for which −ln(L)(a0,b0)=min(−ln(L)) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(yi)−a0)/30;
and the source direction angle as b0.

### Claim 4 (depends on 1)

The method of claim 1, wherein the panel monitor rotated about the axis at up to 5 revolutions per minute.

### Claim 5 (depends on 1)

The method of claim 1, wherein the panel monitor rotated about the axis at about one revolutions per minute.

### Claim 6 (depends on 1)

The method of claim 1, wherein the gamma ray counts are recorded at between about 0.1 and 10 second intervals.

### Claim 7 (depends on 1)

The method of claim 1, wherein the gamma ray counts are recorded at between about one second intervals.

### Claim 8 (depends on 1)

The method of claim 1, wherein the neutron counts are recorded at between about 0.1 and 10 second intervals.

### Claim 9 (depends on 1)

The method of claim 1, wherein the neutron counts are recorded at between about one second intervals.

### Claim 10 (depends on 1)

The method of claim 1, wherein the panel monitor is rotated about a vertical axis proximate to the center of the panel monitor.

### Claim 11 (depends on 1)

The method of claim 1, wherein said detector modules comprise:
a sealed detector core, said sealed detector core comprising a close-packed array of small-diameter, thin walled tubes;
a neutron collimator; and
a housing for said sealed detector core and collimator.

### Claim 12

A method of detecting radiation comprising the steps of:
(a) providing a panel monitor comprising a plurality of detector modules stacked vertically, the detector module comprising a close-packed array of small-diameter, thin walled tubes;
(b) rotating the panel monitor around a vertical axis at between about 0.01 and 5 revolutions per minute;
(c) recording gamma and/or neutron counts at between about 0.1 and 10 second intervals while the panel rotates;
(d) processing information regarding the counts and rotation angle using an algorithm to deduce a radiation source size and direction, wherein information regarding neutron counts is processed using the following algorithm:
(i) recording the monitor rotation angle θi, and neutron count rate yi, at time ti with i taking integer values from 1 to N, where N is the number of measurements over the course of a single rotation,
(ii) finding parameters a and b that minimize the function −ln(L)=−ln (Πe−fi·fiyi/yi!), where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi)−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b, and
(iii) once a0 and b0 for which −ln(L)(a0,b0)=min(−ln(L)) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(y1)−a0)/30;
and the source direction angle as b0;
and information regarding gamma ray counts is processed using the following algorithm
(i) recording the monitor rotation angle θi, and gamma count rate yi, at time ti, with i taking integer values from 1 to N, where N is the number of measurements over the course of a single rotation,
(ii) finding parameters a and b that minimize the function χ2=Σ(yi-fi(θia,b))2/yi, where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi)−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b, and
(iii) once a0 and b0 for which χ2(a0,b0)=min(χ2) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(y)−a0)/30;
and the source direction angle as b0.

### Claim 13

An apparatus for detection for radiation, comprising:
a panel monitor; said panel monitor comprising a plurality of detector modules stacked vertically and said panel monitor being rotatable about a vertical axis.

### Claim 14 (depends on 13)

The apparatus of claim 13, wherein said panel monitor rotates about a vertical axis proximate to its center.

### Claim 15 (depends on 13)

The apparatus of claim 13, wherein said panel monitor is rotatable about the axis at between about 0.01 and 5 revolutions per minute.

### Claim 16 (depends on 13)

The apparatus of claim 13, wherein said panel monitor is rotatable about the axis at about 1 revolutions per minute.

### Claim 17 (depends on 13)

The apparatus of claim 13, wherein said detector modules comprise:
a sealed detector core, said sealed detector core comprising a close-packed array of small-diameter, thin walled tubes;
a neutron collimator; and
a housing for said sealed detector core and collimator.

### Claim 18 (depends on 13)

The apparatus of claim 13, further comprising:
a preamplifier circuit of a type known as the charge-sensitive configuration;
an analogue shaper;
a discriminator;
and a digital counter.

### Claim 19 (depends on 13)

The apparatus of claim 13, further comprising a processor for processing the count information using a predetermined algorithm.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein the algorithm used for processing information about gamma rays comprises:
(a) recording the monitor rotation angle θi, and gamma count rate yi, at time ti, with i taking integer values from 1 to N, where N is the desired number of measurements over the course of a single rotation;
(b) finding parameters a and b that minimize the function χ2=Σ(yi−fi(θi,a,b))2/yi, where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi)−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b; and
(c) once a0 and b0 for which χ2(a0,b0=min(χ2) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(yi)−a0)/30;
and the source direction angle as b0.

### Claim 21 (depends on 19)

The apparatus of claim 19, wherein the algorithm used for processing information about neutrons comprises:
(a) recording the monitor rotation angle θi, and neutron count rate yi, at time ti, with i taking integer values from 1 to N, where N is the desired number of measurements over the course of a single rotation;
(b) finding parameters a and b that minimize the function −ln(L)=−ln(Πe−fi·fiyi/yi!), where fi is an analytical expression such that fi=a·yti/Σ(yti)+(Σ(yi)−a)·( 1/30), and where yti=yti(θi+b) is the known net angular response of the detector, for each angle θi+b; and
(c) once a0 and b0 for which −ln(L)(a0,b0)=min(−ln(L)) are obtained, computing the following quantities:
the net signal (averaged over all angles) as a0/30;
the background rate as (Σ(yi)−a0)/30;
and the source direction angle as b0.

### Claim 22

An apparatus for detection for radiation, comprising:
a panel monitor; said panel monitor comprising a plurality of detector modules stacked vertically and arranged in a helical pattern.