CN104169741A - Composite gamma-neutron detection system - Google Patents
Composite gamma-neutron detection system Download PDFInfo
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- CN104169741A CN104169741A CN201380014938.2A CN201380014938A CN104169741A CN 104169741 A CN104169741 A CN 104169741A CN 201380014938 A CN201380014938 A CN 201380014938A CN 104169741 A CN104169741 A CN 104169741A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T3/00—Measuring neutron radiation
- G01T3/06—Measuring neutron radiation with scintillation detectors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/16—Measuring radiation intensity
- G01T1/20—Measuring radiation intensity with scintillation detectors
- G01T1/2008—Measuring radiation intensity with scintillation detectors using a combination of different types of scintillation detectors, e.g. phoswich
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T3/00—Measuring neutron radiation
- G01T3/008—Measuring neutron radiation using an ionisation chamber filled with a gas, liquid or solid, e.g. frozen liquid, dielectric
Abstract
The present invention provides a gamma-neutron detector based on mixtures of thermal neutron absorbers that produce heavy-particle emission following thermal capture. In one configuration, B-10 based detector is used in a parallel electrode plate geometry that integrates neutron moderating sheets, such as polyethylene, on the back of the electrode plates to thermalize the neutrons and then detect them with high efficiency. The moderator can also be replaced with plastic scintillator sheets viewed with a large area photomultiplier tube to detect gamma-rays as well. The detector can be used in several scanning configurations including portal, drive-through, drive-by, handheld and backpack, etc.
Description
The cross reference of related application
The application be for right of priority based on Dec 20th, 2009 submit to title identical the 61/289th, No. 207 U.S. Provisional Patent Application on Dec 22nd, 2010 submit to name be called " Composite Gama Neutron Detection System " the 12/976th, the part continuation application of No. 861 U.S. Patent applications.
In addition, the application be for right of priority based on June 11st, 2008 submit to No. 0810638.7 UK Patent Application and be on June 11st, 2009 submit to PCT/GB2009/001444 national phase application, for right of priority on Dec 10th, 2010 submit to name be called " Photomultiplier and Detection System " the 12/997th, the part continuation application of No. 251 U.S. Patent applications.
The application also for right of priority based on February 4th, 2012 submit to the 61/595th, No. 044 U.S. Provisional Patent Application.
Quote and be incorporated to above-mentioned whole application by entirety at this.
Technical field
The application relates in general to radioactive material detection field, specifically, relate to the system and the technology that detect neutron and gamma ray, and more particularly, relate to the cost benefit detection system based on neutron and gamma ray and method high, small-sized and that easily manufactured by Available Material.
Background technology
The physical transportation of material, the transport that comprises mailbag, goods, starting material and other commodity is the ingredient of any economy.Conventionally, with the mode transporting material of cask or counter.This container or cupboard comprise the intermodal container that semitrailer, truck and train and container ship or airfreighter can carry.But this freight container or cargo container can be used in the contraband goods of illegal transport such as nuclear material and radioactive material.Detect these threaten require particularly on national boundaries or state circle and such as the reloading point at airport and harbour for determine exist hiding nuclear material fast, safety and checking system accurately.
Current, adopt passive and active detection technique to carry out the nuclear material of detection of concealed.Passive detection technology is sent gamma ray based on nuclear threat or radioactivity threat, and in some cases, sends the neutron that can detect, the principle of radiation.Although passive detection system is easily used, but they exist many shortcomings, comprise because such as the inhibition of the natural background of the vehicle just scanning and interior thing thereof, because such as the variation of the natural background frequency spectrum of the non-malignant goods of roof clay tile, fertilizer etc. and to have false positive rate and false detection rate that the goods that is arranged in or approaches the gamma ray of pernicious line exists the inevitable factor of emitting isotope to cause high.In addition, many gamma ray sources be self-shileding and/or from outside screen easily, make like this them be difficult to detect, because radiation sucks in shielding.In addition, conventionally, gamma detecting device makes neutron detector bad luck, and good neutron detector is usually bad gamma detecting device.
Other detection techniques adopt uncharged particle, carry out the suspicious container of irradiation such as neutron and photon (gamma ray).Uncharged particle can pass highly dense object, thereby identifies interested element-specific, therefore, some pick-up unit because with the object of positive test in the element-specific that exists react to each other and utilize absorption and/or the scatter graph of neutron or photon.The 5th, 006, No. 299 and the 5th, 114, No. 662 and the 5th, 076, in No. 993 United States Patent (USP)s, can find the example of this device, the 5th, 006, No. 299 and the 5th, 114, No. 662 United States Patent (USP) adopts thermal neutron analysis technology (TNA) to scan explosive luggage, and the 5th, 076, No. 993 United States Patent (USP) has been described the contraband detection system of analyzing (PFNA) based on pulsed rapid neutron.Be incorporated to by reference above-mentioned all patents at this.
Such as differential decay analyze (DDA) and after neutron or photon induced fission the active detection technique the measurement of transfer delay gamma ray and neutron can be used in to detect and have fissioner.Preferably utilize the insensitive neutron of mutual radiation and gamma detector measuring radiation.Postpone the detection of neutron and be even in the case of exist hide (respectively) shielding body of nuclear material and compared with postponing gamma ray background still little, the reliable method of detection fissioner.Because postpone the quantity of neutron than few two orders of magnitude of quantity that postpone gamma ray, so require efficient large area detecting device the most responsive in neutron detection.
Above-described each detection system defectiveness.Particularly, these devices adopt the accelerator that produces the high-energy neutron with wide spectrum energy conventionally.Absorption/the scattering of the neutron moving with particular energy is difficult to detect by given a large amount of neutrons of object in the situation that not reacting to each other.Therefore, " fingerprint " that device produces is minimum, is difficult to analyze, and conventionally causes very a large amount of false positives or false negative testing result.
In addition, known prior art detection system has limitation, and its design and method hinder it to realize low radiation dose, and this constitutes a threat to the human and environment in inspection, also hinders and produces high-quality image, and high-quality image is the condition precedent of commercial acceptance.
Although wish to use passive and active detection technique simultaneously, needs be that cost benefit is high, small-sized and by the detection system based on neutron and gamma ray and the method for Available Material manufacture neutron detector.
The neutron detector the most often adopting is He-3 gas ratio chamber.At this, He-3 and neutron cross reaction, to produce He-4 ion.In the electric field of detecting device, make this ion accelerate to enough high-octane degree, thereby make other gas atom ionization.If carefully control, can make γ-ray emission avalanche breakdown, thereby cause the measured current impulse of the output that is positioned at detecting device.By to gas boosting, the probability reacting to each other can be brought up to reasonable level by thermal neutron in gas.But He-3 is more rare material, and occurring in nature does not exist.Make like this availability and provide this detecting device to there is certain uncertainty in the future.In addition, transport pressurization He-3 pipe requires special license, may have like this trouble and may have problems.
The most general passive radioactive material detecting device that the whole world adopts adopts moderation of neutrons body 105 on top, this moderation of neutrons body 105 has: the multiple He-3 that embed in it detect organ pipe 116, and this He-3 detects organ pipe 116 and covered by lead shield 108; And bottom, this bottom comprises that plastic scintillator and PMT (photomultiplier) embed the slow body 110 in it, as shown in Figure 1A.But this detector configurations still adopts rare He-3.In addition, Figure 1B illustrates another detecting device conventionally adopting that gamma ray separates with neutron detector.As shown in Figure 1B, layout adjacent with plastic scintillator 110 comprises that multiple He-3 detect the moderation of neutrons body 105 of organ pipe 116, and this plastic scintillator 110 comprises PMT115 and lead shield 108.But this detector configurations still adopts rare He-3, and present larger footprint.
Be useful on the several alternative detecting device of replacing He-3 detecting device.But the many detecting devices in these detecting devices are also to gamma ray sensitivity, in the application that neutron and gamma ray must be differentiated, this is unacceptable.
Therefore, need a kind of cost benefit high, small-sized and easily manufactured the detection system based on neutron and gamma ray and the method for neutron detector by Available Material.In addition, need a kind of cost-effective small-sized detection system that neutron is separated with gamma detector.
Summary of the invention
In one embodiment, the application has described a kind of flash plating
10b plane ionization chamber neutron detector, can utilize this flash plating
10b plane ionization chamber neutron detector is as working as previous irradiation portal monitor (RPM)
3directly unofficial replacement of He detecting device.
In one embodiment, the detecting device of this instructions comprises the argon gas tagma being clipped between boron spraying anode and cathode electrode plate.
In one embodiment, multiple districts are stacked, to improve the inherent efficiency of detecting device.In one embodiment, detecting device is multilayer, and comprises more than 20 layers.
In one embodiment, " piling up " multiple detector cells district, to realize the area of 1 square metre at the most.In one embodiment, for easy transport, folding large detector cell.
In one embodiment, adopt parallel plate geometry structure, this parallel plate geometry structure is be integrated in the back side of battery lead plate such as poly moderation of neutrons sheet, with thermalized neutron, then with efficient detection they.Optionally, can utilize plastic scintillator sheet to replace slow body, can watch this plastic scintillator sheet with large cathode diameter photomultiplier, also to detect gamma ray except neutron, identical with the situation of existing RPM.
Structure also described by this instructions and manufacture is simple, easy and cellular zone detecting device is proportional, easily adapt to the large area detecting device that various application and cost are low.
In one embodiment, this instructions has been described neutron cellular zone detecting device, and this neutron cellular zone detecting device comprises: ground floor and the second layer, and this ground floor and the second layer comprise tygon, for slowing down rapid neutron; Third and fourth layer, comprise B-10, for catching the rapid neutron of slowing down, wherein third and fourth layer between first and second layers; And gas zone layer is between third and fourth layer, and when catching the middle period of the day from 11 p.m. to 1 a.m, this third and fourth layer is sent charged particle, and this charged particle makes the gas ionization in the layer of gas zone, to produce free electron and ion pair.
In one embodiment, neutron detector comprises multiple cellular zones detecting device, and this cellular zone detecting device is stacking, thereby improves detector efficiency.
In another embodiment, this instructions has been described gamma neutron cellular zone detecting device, and this gamma neutron cellular zone detecting device comprises: ground floor and the second layer, and this ground floor and the second layer comprise the responsive plastic scintillator of gamma, for slowing down rapid neutron, and detect gamma ray; Third and fourth layer, comprise B-10, for catching the rapid neutron of slowing down, wherein third and fourth layer between first and second layers; And gas zone layer is between third and fourth layer, and when catching the middle period of the day from 11 p.m. to 1 a.m, this third and fourth layer is sent charged particle, and this charged particle makes the gas ionization in the layer of gas zone, to produce free electron and ion pair.
In one embodiment, gamma neutron detector comprises multiple cellular zones detecting device, and this cellular zone detecting device is stacking, thereby improves detector efficiency.
In one embodiment, plastic scintillator comprises: be arranged at least one in organic solid scintillator, inoganic solids scintillator or the liquid scintillator between glassy layer.
In another embodiment, this instructions has been described the method for manufacturing use in detecting device scaled, low cost, large area boron substrate, and the method comprises: by thin copper foil sheet as metallic substrates; Copper Foil is attached to rigid layer, to form composite substrate, thereby provides large area structure intensity; By composite substrate is immersed in liquor ferri trichloridi, etching is piled up figure and each electric wire in composite substrate; Composite substrate is arranged on cylinder, for vacuum moulding machine; And boron is deposited on the surface of Copper Foil, to form described boron substrate, wherein utilize mask blocks boron to deposit on electric wire.In one embodiment, the thickness of Copper Foil is in the scope of 50 to 100 μ m.In one embodiment, rigid layer comprises kapton layer.
In one embodiment, the method for manufacture large area boron substrate comprises alternatively by boron substrate layer being stacked in to the step of manufacturing rapid neutron detecting device on polythene strip.
In accompanying drawing, be shown in further detail above-mentioned and other embodiment of the present invention, and more detailed description is provided below.
Brief description of the drawings
In the time studying by reference to the accompanying drawings, by reference to detailed description below, will understand these and other feature and advantage of the present invention, because understand better them.
Figure 1A illustrates the radioactive material detecting device that adopts He-3, comprises the prior art of moderation of neutrons body and plastic scintillator;
Figure 1B illustrates the radioactive material detecting device that adopts He-3, comprises the prior art of moderation of neutrons body and plastic scintillator;
Fig. 1 C illustrates the principle layout of compound according to an embodiment of the invention gamma neutron detector;
Fig. 2 illustrates the typical neutron detector of the potpourri based on silver activation zinc sulphide;
Fig. 3 illustrates the also typical neutron detector for the potpourri based on silver activation zinc sulphide of gamma ray detection by plastic scintillator;
Fig. 4 illustrates the experimental result of utilizing the neutron detector based on silver activation zinc sulphide;
Fig. 5 illustrates respectively for gamma and reacts to each other and the pulse signal of the function of time of reacting to each other of neutron;
Fig. 6 illustrates the difference between gamma ray and neutron measurement signal;
Fig. 7 A illustrates an embodiment in order to improve neutron-sensitive degree with the detecting device of the present invention of multilayer gamma and neutron detector material;
Fig. 7 B illustrates in order to improve neutron detection efficiency to have another embodiment that has the detecting device of the present invention of angle detector plate;
Fig. 8 illustrates the typical sensing circuit for detection system of the present invention;
Fig. 9 illustrates by the typical case of the gamma neutron detector of the present invention of Automobile drive and applies;
Figure 10 illustrates the another kind typical case application of the gamma neutron detector of constructing by scanning of travelling;
Figure 11 illustrates another the typical case's application with the gamma neutron detector combining for generation of the mobile X-ray scanners of compound gamma neutron radioscopic image;
Figure 12 illustrates another embodiment of the combination gamma neutron detector of gate-type or gantry structure and the imaging system based on X ray;
Figure 13 illustrates the gamma neutron detector of portable structure according to an embodiment of the invention;
Figure 14 illustrates boron-10 based on parallel-plate (B-10) detecting device according to an embodiment of the invention;
Figure 15 A illustrates the rapid neutron detecting device geometry in the first embodiment;
Figure 15 B illustrates the rapid neutron detecting device geometry in the second embodiment;
Figure 16 A illustrates the typical way that can realize scalability for the B-10 detecting device of manufacturing this instructions;
Figure 16 B illustrates the typical way that can realize scalability for the B-10 detecting device of manufacturing this instructions;
Figure 16 C illustrates the typical way that can realize scalability for the B-10 detecting device of manufacturing this instructions;
Figure 17 is the curve map that the detection efficiency of the B-10 detecting device of this instructions is shown;
Figure 18 be illustrate with based on
3the differential decay of He is analyzed (DDAA) detecting device and is compared, of the present invention
10the curve map of the rapid neutron detection efficiency of B neutron detector;
Figure 19 A illustrates the first manufacturing step at the bottom of the large area boryl of manufacturing this instructions;
Figure 19 B illustrates the second manufacturing step at the bottom of the large area boryl of manufacturing this instructions;
Figure 19 C illustrates the 3rd manufacturing step at the bottom of the large area boryl of manufacturing this instructions;
Figure 19 D illustrates the 4th manufacturing step at the bottom of the large area boryl of manufacturing this instructions;
Figure 19 E illustrates the 5th manufacturing step at the bottom of the large area boryl of manufacturing this instructions; And
Figure 19 F illustrates the 6th manufacturing step at the bottom of the large area boryl of manufacturing this instructions.
Embodiment
This instructions discloses a kind of in the situation that gamma separates with neutron characteristic remarkable, the system and method that utilizes compound gamma neutron detector detection of radioactive to threaten, can construct this compound gamma neutron detector, so that gamma detection and neutron detection are all had to hypersensitivity.System of the present invention is reported to the police and is realized biggest threat detection with minimal error, and therefore improves handling capacity.
In addition, to have described cost benefit high, small-sized and easily manufactured the compound gamma neutron detection system and method for neutron detector by Available Material for this instructions.
This instructions has been described multiple embodiment.In order to make person of ordinary skill in the field implement the present invention, provide following disclosure.The general negation that should be not any one specific embodiment by the language understanding using in this instructions, can not be used for exceeding meaning restriction claims of the term that used here.General Principle in this definition can be applied to other embodiment and application, and does not depart from essential scope of the present invention.In addition, the term using and term are in order to describe exemplary embodiments, and not should be understood to limited significance.Therefore, give the scope of maximum of the present invention, comprise that meeting the many of principle disclosed herein and feature substitutes, revises and be equal to.For the sake of clarity, do not describe in detail and the details that known technologic material is relevant in the technical field of the invention, thereby can hinder necessarily the present invention.
Several atomic nucleus have heavy in section, for detection of caloic.These atomic nucleus comprise: He, Gd, Cd and two king-sized heavy in section atomic nucleus: Li-6 and B-10.In all cases, after heavy in section atomic nucleus and thermal neutron react to each other, result is energetic ion and secondary high energy charged particles.
For example, utilize the equation below can characterization neutron and B-10 is nuclear reacts to each other:
Equation 1:n+B-10 → Li-7+He-4 (945 targets, Q=4.79MeV)
At this, cross section shown in bracket and Q value, Q value is the energy that reacts to each other and discharge.
Equation characterization neutron equally, below and Li-6 is nuclear reacts to each other:
Equation 2:n+Li-6 → H-3+He-4 (3840 targets, Q=2.79MeV)
Known charged particle and heavy ion have little moving range in condensed matter, conventionally only move several microns from the point reacting to each other.Therefore, high around the Rate of energy deposition reacting to each other a little.The molecular mixing of scintillation response is provided when in the present invention, containing nuclear molecule that neutron cross section is large and excited by energy deposition.Therefore,, in the time mutually mixing with scintillation material, reacting to each other of neutron and Li-6 or B-10 for example causes flashing.If this light propagates into photoelectric detector by medium, light signal can be converted to electronic signal, this electronic signal represents the amount of the energy depositing during neutron reacts to each other.
In addition, such as the material of Cd, Gd with do not send heavy particle and the other materials with high heat capture cross section produces the low-yield internal conversion electron, Auger electron, X ray and the gamma ray that substantially send simultaneously, energy range is from several keV to several MeV.Therefore, in the time mixing or in the time manufacturing, will produce light (particle that may be heavier is few) such as these materials of one deck of oxygen gadolinium sulfide (GOS) and cadmium tungstate (CWO) in scintillator matrix in scintillator.GOS with two catalyzer, causes decaying at a slow speed (the 1ms order of magnitude) and quick (the 5 μ s order of magnitude) conventionally.CWO has disintegration constant faster.According to gross energy, very large part energy will be deposited in this layer, and some electronics are deposited in scintillator around energy simultaneously.In addition in a large amount of X ray that, heat produces after catching and gamma ray scintillator around, react to each other.Therefore, neutron reacts to each other and will cause disintegration constant and the fast event of disintegration constant at a slow speed.In many cases, neutron signal comprises the signal (being called " coincidence ") with slow component and quick component, because electronics interweaves in this layer and gamma ray reacts to each other in scintillator around.
Can be tuning to surrounding the scintillation response of Li-6 or the nuclear material of B-10, make this light can be by thering is the secondary fluor in order only gamma radiation to be made the characteristic that response selects, such as the plastic scintillator in an embodiment.In another embodiment, the material that surrounds Li-6 or B-10 is not scintillator, but only to the transparent non-flicker plastics that produce in neutron-sensitive detecting device.
Therefore, plastic scintillator is all responsive to neutron and gamma.When the H thermalization in detecting device and then catch the middle period of the day from 11 p.m. to 1 a.m, send and conventionally can detect 2.22MeV gamma ray.Like this, the present invention realizes the compound gamma neutron detector that can detect with hypersensitivity neutron and gamma radiation.In addition, composite detector of the present invention also provides the good separation of gamma characteristic and middle subcharacter.It should be noted that except charged particle at this, B-10 produces gamma ray.Therefore, utilize neutron capture to produce the material of gamma ray afterwards, result is similar gamma ray to be detected.But great majority application all wishes to detect neutron; Therefore, the advantage of detecting device of the present invention is also to detect neutron.
Fig. 1 C illustrates the principle layout of compound according to an embodiment of the invention gamma neutron detector 100.With reference to figure 1C, this detector design adopts the flicker plate (gamma detecting device) 101 and 102 of two gamma sensitivities to surround single neutron detector 103.Neutron detector 103 also comprises the single flat board of the compound scintillator of neutron-sensitive, in this compound scintillator, mixes with the scintillation material such as ZnS such as the atomic nucleus of the neutron-sensitive material of Li-6 or B-10.In one embodiment, in keeping by the effective scintillation response of ZnS, for neutron-sensitive material (such as Li-6), can realize the density of by volume calculating 20-30%.
In one embodiment, gamma detector plates is by manufacturing such as the solid scintillation material that is still not limited to organic scintillator and inorganic scintillator, this organic scintillator (for example comprises solid plastic scintillator, NE102) and anthracene, this inorganic scintillator comprises NaI (T1), CsI (T1), CsI (Na) and BaF
2.
In another embodiment, can between glass plate, arrange that liquid scintillator is used as gamma detecting device.The organic solvent that these usually adopt using anthracene molecule as solvent and organometallics forms, to strengthen scintillation efficiency and therefore generally speaking more easily to use than solid scintillator.
In one embodiment, neutron detector can comprise binder molecule, is dissolved in the styrene as basic substrate in appropriate solvent such as being still not limited to.Because solvent evaporation, once the plastic membrane forming after dry is highly stable and have from supporting.The element-specific (, Gd, Li, B) of scintillation material (for example, ZnS) and neutron was mixed mutually with solvent and bonding agent before solvent evaporation.Because solvent evaporation, mixes so form the homogeneous of whole three kinds of components.
In variant embodiment, Gd, Li, B filler liquid scintillator (the anthracene molecule based on having suitable organometallics improves scintillation efficiency conventionally) can be sealed in the gap between gamma flicker plate.Advantageously, thin glass baffle plate is arranged between neutron scintilator and gamma detecting device, to prevent, between two scintillator materials, chemical reaction occurs.
In one embodiment, for the manual application of large fixing field erected maximum 2m × 1m, typical board size is in the scope of 0.1m × 0.1m.If be greater than this full-size, light collection starts to become problem, because physical treatment and be encapsulated into problem.If be less than this full-size, detection efficiency starts to be reduced to lower than level of significance, causes progressively extending Measuring Time.
In one embodiment, gamma detecting device is thicker than neutron detector.Advantageously, for large fixing fielded system, the thickness of gamma detecting device is not less than 0.01m (for manual application) to 0.2m.Compared with rear gamma detecting device, front gamma detecting device can be optimized for to different thickness, so that whole gamma and neutron detection efficiency are brought up to the highest.For example, the front gamma detecting device of 0.05m and the rear gamma detecting device of 0.1m can be applied to large fixing fielded system.For the probability that gamma is reacted to each other is reduced to minimumly, and the chance that light leaves scintillator to be brought up to the highest, neutron detector is conventionally thin.Typical neutron detector based on solid screen flicker body is in the thickness range of 0.5-1mm, and liquid neutron scintilator can be in 0.01 to 0.05m thickness range.
One or more photoelectric detector of optical signals from gamma detecting device 101,102 and neutron detector 103 is read, and in one embodiment, photoelectric detector is photomultiplier (PMT) 104.Therefore, light signal is converted to electronic signal, then, pulse processor 105 is processed these electronic signals, this pulse processor 105 specify respectively due to gamma and neutron react to each other 106 and 107 cause react to each other.
In one embodiment, advantageously, gamma sensitive plate 101 and 102 is manufactured by the fast plastic scintillator of fall time, such as the fall time that is shorter than 0.1 μ s.In addition, advantageously, the Li-6 of neutron detector 103 or the B-10 atomic nucleus scintillation material such as ZnS slower with fall time mixes.In one embodiment, the fall time of scintillation material is greater than 1 μ s.The difference of the fall time of the scintillator in fall time and the neutron detector of the scintillator in gamma detecting device contributes to realize remarkable separation between gamma characteristic 106 and middle subcharacter 107.Conventionally, wish to select the scintillation material that atomic weight is low to cause the direct excitation probability that passes through gamma ray that strengthens the repulsion of gamma neutron to be reduced to minimum.
In another embodiment, Li-6 or B-10 mix with the material of response very fast (～10ns) and by the material encirclement of response speed low (～1ns).
Note that if surrounding the material that Li-6 uses is unusual fast scintillator, particularly ought not utilize scintillator to surround at that time, detecting device can be with very high radiant intensity measurement neutron.
Person of ordinary skill in the field understands such as the scintillation material of ZnS can absorb its oneself light, and therefore, restricted to the thickness based on scintillator detecting device of ZnS.Note that this thickness only has several millimeters conventionally.In addition, owing to sending light there is isotropy when each scintillation event, so effectively can form scintillator from the two-layer wide area screen of catching the light sending of screen simultaneously.Therefore, in one embodiment, be designed to the wide screen of area based on scintillator neutron detector 103, make to gather light from the both sides of screen with high-level efficiency.
Note that the detection efficiency of the detection efficiency of the Li-6/ZnS screen that 1mm is thick and the pressurization He-3 gas ratio pipe that diameter is several centimetres is in same order.,, for very little size, compared with pressurization He-3 flue, the neutron detector based on Li-6/ZnS of the present invention has and is equal to or higher detection efficiency.
Therefore, in one embodiment, the potpourri of neutron detector based on silver activation zinc sulphide, this potpourri contain there is high thermal neutron capture cross section, send such as
6li or
10the material of the heavy particle of B., this potpourri is included in heat and catches the thermal neutron absorber that sends heavy particle afterwards.Fig. 2 illustrates a this typical neutron detector 200.With reference to figure 2, detecting device 200 comprises one or more thin screen 201, and this one or more thin screen 201 comprises the potpourri based on ZnS (Ag), as mentioned above.In one embodiment, screen 201 has the thickness of about 0.5mm, and embeds in transparent hydrogeneous photoconductive tube 202.Photoconductive tube 202 is also as moderation of neutrons body.Neutron in ZnS (Ag) the phosphorus screen light producing that reacts to each other enters the photoelectric detector such as photomultiplier (PMT) 203 by photoconductive tube 202, and this photoelectric detector produces and utilizes its signal to neutron counting by counter 204.
Utilize identical basic electronic component, also can realize above-mentioned technology with synchronous gamma ray detection.Therefore, detecting device 200 also comprises plastic scintillator 205, and this plastic scintillator 205 is as gamma detector and slow body.Plastic scintillator can be made up of known other suitable plastic scintillator materials in polyvinyl toluene or PVT or affiliated technical field.Gamma ray in scintillator 205 light producing that reacts to each other is detected by another PMT206, and this PMT206 produces and utilizes its signal to gamma ray event count by counter 207.In one embodiment, counter 207 is multichannel analyzers (MCA) of the frequency spectrum for measuring gamma ray.
Reflection foil 208 is arranged between plastic scintillator 205 and (respectively) screen 201, pollutes mutually preventing from the light signal of neutron and gamma test material.Therefore, utilize reverberator to prevent that the light of gamma ray generation and the light that neutron produces from being gathered by same PMT.Prevent so the wrong neutron counting being caused by gamma ray.Due to the cause of reverberator 208, the neutron in screen react to each other produce some light will be returned photoconductive tube.
The design of Fig. 2 provides a kind of small-sized gamma ray/neutron detector, and it has advantages of standard electronic part and very high gamma ray inhibition.A small amount of gamma ray will react to each other with Li-6 plate, and produce the low signal of intensity.By threshold value being set taking some neutron detection as cost, can eliminate this signal.In one embodiment, in middle subchannel 204, can adopt pulse shape discriminator to strengthen gamma ray inhibition.
Fig. 3 illustrates another typical detectors 300 of simultaneously carrying out neutron and gamma ray detection.In this case, light-guide material is replaced by plastic scintillator 301, and this plastic scintillator 301 is as gamma detector, slow body and photoconductive tube.Detecting device 300 also comprises screen 302, and preferably, this screen 302 is thin, and is used for neutron detection by the potpourri manufacture based on ZnS (Ag).Between ZnS (Ag) and the pulse 304 of plastic scintillator (PVT) generation, utilize pulse shape discriminator (PSD) circuit 303 that neutron is separated with gamma ray event.In addition because the neutron in screen reacts to each other the light that produces with PVT the fall time based on identical and being eliminated by PSD, so realize gamma ray inhibition.The light producing propagates into photomultiplier (PMT) 305 by transparent neutron degradation medium 301, and at photomultiplier 305, light being converted to can measuring-signal, to measure gamma and neutron event.The advantage of mixing neutron/gamma detector is to adopt same PMT to measure neutron and gamma event.
Fig. 4 illustrates to have in the photoconductive tube of embedding to have twice
6the performance of the typical detectors of LiF:ZnS (Ag) screen of LiF concentration and thickness.Presentation of results weight ratio shown in Fig. 4 is 1:2 and signal that screen thickness is 0.45mm.Adopt 1,2 and 3 LiF:ZnS (Ag) screen embedding in tygon to obtain similar results simultaneously, and realize approximately 12% to 22% detection efficiency.Technician in affiliated technical field understands three row of this efficiency and compact package
3the top efficiency that He detecting device can be realized is suitable, and this top efficiency is about 25%.
Signal distributions explanation in Fig. 4 does not absorb all particle energys to be all converted to light, and some light are absorbed by screen.This explanation needs complex optimum, in this complex optimum, obtains correct
6li concentration to realize high neutron-absorbing, still has sufficiently high reacting to each other simultaneously in scintillator, to produce quite high light output.The thickness of the organic slow body of quantity of screen thickness, screen is also important Optimal Parameters.
For the application for neutron detection, the major advantage of ZnS (Ag) phosphorus is, a large amount of light outputs for heavy particle that react to each other compared with the electronics producing with gamma ray.In addition, because the thickness of screen is little, so the detection efficiency of gamma ray is low.In addition, due to ZnS (Ag) screen in the light of electron production similar, the time decay of PVT light is～3ns, so PSD also suppresses gamma ray reacting to each other in PVT.
Technician in affiliated technical field is clear, and the neutron that radioactive material interested produces has an energy range, and along with the energy of the neutron reacting to each other reduces, the efficiency remarkable rising conventionally that reacts to each other of the neutron in detecting device.Because this reason, most of He-3 detecting devices are all arranged in Fu Qing deceleration material, and such as tygon, its function is to promote high-energy neutron scattering, improve the detection probability in He-3 gas proportional counter thereby make them lose large energy.In the present invention, advantageously, design gamma detecting device, to realize the difunctional of gamma detection and neutron degradation, thereby further improves neutron detection efficiency.Plastic scintillator material is very effective slow body, because this feature is included in whole detector design.
Fig. 5 illustrates pulse signal, and this pulse signal is the function that the gamma in time and composite detector of the present invention reacts to each other and neutron reacts to each other.With reference to figure 5, the blinking characteristic curve 502 of neutron-sensitive scintillator is significantly different from the family curve 501 of gamma sensitive detectors around.Can also be tuning to these two characteristic signals 501 and 502, to present remarkable difference.This can utilize suitable pulse waveform discrimination method to realize.Therefore, in one embodiment of the invention, determine the gross energy depositing in detecting device and the type reacting to each other.In the time gross energy can being determined by the peak amplitude of analyzing pulse signal, by analyzing the decay rate of scintillation pulse, determine the type reacting to each other.
Fig. 6 illustrates when analog pulse waveform is differentiated and is applied to when gamma ray is separated with neutron event, differentiates gamma ray and neutron for 252Cf and 60Co radioactive source.Curve 601 represents the measurement of the gamma ray to being sent by 60Co, and curve 602 represents the measurement of the neutron to being sent by 252Cf.Technician in affiliated technical field is clear, and in one embodiment, these two curves separate and can differently distinguish out.
In one embodiment, by deduct the calibrator quantity of gamma ray from the neutron number of measuring, improve gamma ray inhibition.
In one embodiment, advantageously, in the direct combine digital burst process of output of detecting device.Because data rate can be quite high, so the processing of detecting device contributes to this data filtering to low bandwidth, to be transferred to other disposal systems.The radioactivity amount that can utilize this data monitoring to detect, and utilize some devices to produce and suitably report to the police and/or show data.
In another aspect of the present invention, the reaction that note that neutron also may produce relevant gamma ray radiation.For example, in the neutron reaction of Gd-157, the Gd-158 atomic nucleus exciting decays along with sending of gamma ray.In the finite time reacting to each other at neutron, produce this gamma ray, and therefore, can utilize pulse waveform to differentiate the principle relevant to time domain, respond in conjunction with neutron scintilator, be included in the gamma response of measuring in gamma detecting device around, to produce composite signal.
Although Fig. 1 C illustrates the typical construction of composite detector, can set up modification detector configurations, thereby further strengthen neutron and gamma detection efficiency.Two exemplary variation structures are shown in Fig. 7 A and Fig. 7 B.As shown in Figure 7 A, first is configured in the direction that is substantially perpendicular to incident radiation 705 arrival directions, the responsive scintillator sheet 701 of arranging multiplayer gamma alternate with each other and neutron-sensitive scintillator panel 702.In this structure, the efficiency of gamma neutron detector is directly proportional to the quantity of the plate of detector plates material; But reduced like this effect because with detector back layer compared with, preferential absorption radiation in the ground floor of detecting device.In the time arranging detector plates with this structure, significantly strengthen neutron-sensitive.
In another structure shown in Fig. 7 B, the multilayer of layout gamma detector material 710 alternate with each other and neutron detector material 720, and their orientation and the direction that enters radiation 715 are tilted., layer 710 and 720 is not parallel to the direction that enters radiation 715.This detector configurations that detector plates tilts significantly improves neutron detection efficiency.This is because neutron in this case or the photon path by sensitive detectors plate is longer, compared with the layout of the plate shown in Fig. 7 A, contributes to like this to improve detection efficiency.But the detecting device manufacture of this structure is also more expensive, and require larger sensing circuit.
Under technician in technical field understand there are other structures of scintillator material and photoelectric detector, and according to it applicability to application, can select any structure.Therefore, be not limited to the plastic scintillator gamma detecting device with Li-6/ZnS neutron detector with reference to the of the present invention compound gamma neutron detector of figure 1,7A and 7B description.In one embodiment, for example, utilize NaI (T1) to there is the liquid scintillator based on lithium, boron or gadolinium of fall time very fast as gamma detecting device and utilization, can construct composite detector.At this, NaI (T1) gamma detecting device will provide the remarkable pulse height information reacting to each other about gamma ray, and neutron detector will continue to provide the information about incoming neutron flux.
It should be understood that the reflecting coating using with suitable optically-coupled material will improve overall light collection efficiency, and therefore, improve all degree of detector response.Be to be further appreciated that, can also utilize the shape of optical light guide and scintillator material to improve the light collection efficiency of detection system.In addition, be to be further appreciated that, can utilize the radiation shielding material such as lead, tygon and cadmium paper tinsel adding around scintillation material to reduce the response of detection system to spontaneous background radiation.
In yet another embodiment of the present invention, can adopt the neutron scintilator that different pulse shape is provided because quick and thermal neutron react to each other, each pulse waveform is different from the pulse waveform that gamma detecting device is selected.
Fig. 8 illustrates typical detectors sensing circuit architecture.With reference to figure 8, circuit 800 comprises photomultiplier (PMT) 801, and this photomultiplier (PMT) 801 utilizes with ground connection anode 803 and keeps the negative electrode 802 of high negative pressure to work.Anode 803 is by transformer 805 and high-speed sampling analog to digital converter (ADC) 805 AC coupling.ADC805 forms the time-domain sampling from the entering signal of PMT801.In certain embodiments, ADC, to be equal to, or greater than the clock speed work of 100MHz, provides the sampling period of 10ns at the most with the fall time with reducing to accurate measurement amplitude height and rising.In one embodiment, advantageously, filtering circuit is included in PMT801 and between the input of ADC805, to be used as nyquist filter, thereby prevents undesirably aliasing of sampled data.In one embodiment, utilize AC coupling transformer 804 as inductance component, realize LCR multipole filters.
In modified construction, utilize large bandwidth analogue amplifier, PMT801 can DC coupling to the input end of ADC805.Various other Circnit Layouts are apparent for the technician in affiliated technical field.
Advantageously, the numerical data directly ADC being produced is delivered to digital processing circuit, such as field programmable gate array (FPGA) 806.FPGA carries out the processing of high-speed figure pulse waveform, and constructs this FPGA, with the time of arrival of (1) recording impulse; (2) determine the amplitude of this pulse; And (3) determine the rear along the time of pulse, to differentiate that neutron reacts to each other and gamma reacts to each other.Pulse by Pulse data are delivered to random access memory 807, and then, utilize the software program of operation on computing machine 808 to analyze this Pulse by Pulse data, to solve the detection counting rate with respect to dynamic adjustments baseline.Can pass through visual-display screen 809, visual detector, audio frequency acoustical generator or any other appropriate device, operator is indicated to this result, with in the time radiomaterial being detected, send signal.
The various additive methods of realizing pulse waveform discriminating are apparent for the technician in affiliated technical field.
Fig. 9 illustrates the application of the compound gamma neutron detector in mobile system in Automobile drive scanning structure.With reference to figure 9, gamma neutron detector 901 is arranged in vehicle 902.This structure allows to reorientate fast detecting device 901 from any to another point, and this structure also for vehicle along highway by time convert and scans vehicle.In this embodiment, vehicle 902 is driven to the position such as roadside, and start detection system 901.In one embodiment, be positioned at the checking matter that passes through that one or more sensor (not shown) on vehicle 902 determines that existence will scan, such as the vehicle passing through, and automatically connect detection system 901.One scan vehicle, just automatically disconnect gamma neutron detector 901.One completes in given position scanning, just can make vehicle 902 drive to reposition, and visual scanning as requested.This feature provides the ability with rational conversion regime random site scanning.
When there is no source scanning vehicle at scanning scene, utilize and record natural background radiation in the gamma neutron detector of off-state, and utilize this natural background rate to set suitable alarm threshold, while there is alarm threshold, during in on-state, additional radioactivity in the vehicle passing through, detected at scanner.
In Another application, compound gamma neutron detector 901 is arranged in the vehicle 902 that can travel by static target with known speed.Along with vehicle 902 travels, stimulating radiation sends data, has radioactive material to determine in static checking matter.
Figure 10 illustrates the Another application of one or more compound gamma neutron detector of constructing by scanning in travelling.With reference to Figure 10, thering is left side, right side and upside, lorry such as 1004 can travel in the schema construction passing through, and arranges multiple compound gamma neutron detectors 1001,1002 and 1003, passes through system as fixedly travelling.Process the signal of self-detector 1001,1002 and 1003 and result is presented on display 1005.Display is also connected to audio alarm 1006 and visual alarm 1007, in the time that suspection on the vehicle 1004 being scanned has radioactive material, automatically produces audio alarm 1006 and visual alarm 1007.Can utilize the result in display 1005 and warning 1006 and 1007 to determine whether to need further to search vehicle 1004, and this vehicle is transferred to Accreditation Waiting Area, for example, do manual seeking.Travelling shown in Figure 10 also adopts traffic control system 1008 by scanning system, and this traffic control system 1008 is handled and stopped 1009, so that vehicle stop is for inspection.Scanning result one appears on display 1005, just stops and automatically rises.
In modified construction, one or more gamma neutron detector of the present invention is provided with the baggage handling system adopting on airport.Like this, also can utilize system of the present invention to detect the radioactive material of standing in luggage by boat.In another modified construction, one or more gamma detecting device of the present invention can be arranged in aviation goods treatment facility and the porch of scrap metal treatment facility.
In yet another embodiment of the present invention, gamma neutron detector and the combination of mobile X-ray scanners, to produce compound gamma neutron radioscopic image.This is shown in Figure 11.With reference to Figure 11, gamma neutron detector 1101 is arranged on mobile X-ray scanners 1100.This moves X-ray scanners 1100 and also comprises the X-ray scanning system 1102 being arranged on vehicle 1103.In this case, in transmitting radioscopic image by X-ray scanning system 1102, obtain the radiated signal from gamma neutron detector 1101.Make like this from the signal of gamma neutron detector 1101 relevant to radioscopic image data, thereby help operator determine inspection goods in there is radioactive material.Can adopt the 10/201st, 503,10/600,629,10/915,687,10/939,986,11/198,919,11/622,560,11/744,411,12/051,910,12/263,160,12/339,481,12/339,591,12/349,534,12/395, in 760 and 12/404, No. 913 U.S. Patent applications, disclosed any mobile system, merges all these U.S. Patent applications by reference at this.
In yet another embodiment, with gate-type or planer-type structure, gamma neutron detector of the present invention and x-ray imaging system combination.With reference to Figure 12, multiple gamma neutron detectors 1201 are together with the X ray transmission system 1202 of arranging with gate-type structure.The checking matter of checking or vehicle can pass through this door or gantry.This mode of operation also makes radiated signal relevant to the radioscopic image of checked checking matter, thereby improves detection efficiency.For example, in radioscopic image, observe and exist a small amount of increase of high decay area gamma ray and/or neutron signal to represent to exist shielding radioactive source lower than threshold value.
Figure 13 illustrates another structure of the gamma neutron detector of portable hand-held structure.With reference to Figure 13, show gamma neutron detection instruments and meters 1300.This instrument comprises master unit 1301 and handle 1302.In one embodiment, the flicker plate of compound gamma neutron detector (not shown) is arranged in master unit 1301, and advantageously, electronic component and battery are arranged in the handle 1302 of instrument.Near the feedback of the radiant quantity of the existence about instrument 1300 is offered operator by embedded indicator 1303.This structure is for random search, and particularly little checking matter, and corner or bight in search vehicle are very useful.
Novel method of the present invention, by neutron scintillation detector and gamma detector combination, mixes gamma neutron detector to form.The method has the bicharacteristic advantage of detection, thereby improves detection efficiency.In addition, utilize pulse waveform discrimination method, system of the present invention also makes neutron signal and gamma signal good separation.According to application, system of the present invention can, in various structures, include but are not limited to:: fixed, travel by gate-type, planer-type, portable and hand-held.Combination detector can be for the Vehicle inspection of carriage of goods by sea inspection and land reloading point and scrap metal treatment facility, for luggage and aviation goods scanning.Combination neutron gamma detecting device of the present invention and/or neutron detector part and/or gamma detector portion also will meet radiation detection ansi standard.
Compared with system based on He-3, system that should be based on He-3 is because the undersupply of He-3 existing problems, and the present invention is not limited to the system using with specific atoms nuclei.As mentioned above, for system of the present invention, may be used to radioactive material such as the hot capture cross section of neutron any suitable material large, that send particle of lithium (LI-6), boron (B-10), cadmium (Cd), gadolinium (Gd) and helium (3-He) and detect.This feature contributes to make cost and supplies with controlled.In addition, compared with system based on He-3, combination gamma neutron detector of the present invention is more small-sized and lighter, because in one embodiment, detecting device of the present invention only uses one group of electronic component, and system based on He-3 adopts many group electronic components.At this, it should be noted that in other embodiments, the present invention can adopt many group electronic components.
Most of gate-type radiological monitors (RPM) of adopting all over the world all by plastic scintillator for detection of gamma ray, and by slowing down
3he detecting device is used for measuring neutron.Importantly, to note that in typical RPM, for the suboptimum slowing down structure in order reducing costs, each module only to be adopted to one or two
3he pipe.Realize like this neutron detection efficiency of a few percent.
The neutron detector of advising can be replaced in gate-type radiological monitor (RPM)
3he detecting device because its neutron detection and gamma ray detection ability with
3the detectability of He is identical.In addition, detecting device of the present invention do not contain deleterious material, commercially available, do not need very firm aspect special transport license, mechanical property and environment and easily produce with rational cost.This detecting device is also applicable to hand-held and backpack detecting device, the efficiency ratio of this hand-held and backpack detecting device
3the efficiency of He is high.Finally, this method is applicable to integrated neutron and gamma detector, because it adopts the single PMT with simple and small electronic component.
As mentioned above, just as
3he,
10b has large thermal neutron capture cross section, and sends two high energy charged particles that can detect, but with
3he difference,
10b is in nature abundance.On the other hand,
3the supply of He reduces rapidly, and therefore,
3he gas is very expensive, and is difficult to obtain.Although in the past, being coated with boron detecting device can use, and for example, is coated with boron detecting device as pile neutron flux monitor, and efficiency is low, has limited its purposes.
Therefore, this instructions described in one embodiment scumbling apply
10b plane ionization chamber neutron detector, it can replace current gate-type radiological monitor (RPM) for directly declining
3he detecting device.In various embodiments, coating
10b has the thickness of 0.1 to 2.0mm scope.In one embodiment, coating
10b means that to enter the energy loss of charged particle of gas compartment by overlay large.Mean that compared with thick overlay to enter the energy loss of charged particle of gas compartment by overlay large.This is unfavorable to signal.But thicker overlay can improve detection efficiency, reach the required number of plies of specific efficiency and reduce.
In one embodiment, the detecting device of this instructions comprises the argon gas tagma between anode and the minus plate that is inserted in coating boron.
In one embodiment, adopt parallel plate geometry structure, this parallel plate geometry structure makes to be combined in such as poly moderation of neutrons sheet the back side of battery lead plate, with thermalized neutron, and then, with efficient detection they.Optionally, replace slow body by the plastic scintillator that utilizes large cathode diameter photomultiplier to observe, also to detect gamma ray except neutron, identical with the situation of existing RPM.
Structure also described by this instructions and manufacture is simple, easy and cellular zone detecting device is proportional, easily adapt to the large area detecting device that various application and cost are low.
In one embodiment, as mentioned above, to based on
10the large area of B
3the exploitation that He replaces detecting device concentrates on the parallel-plate chamber principle of utilizing shown in Figure 14.With reference to Figure 14, the basic geometry of a cellular zone detecting device comprise clip gas zone 1403, by the first boron layer 1401 of high pressure bias voltage and the second boron layer 1402.These two boron layers are caught thermal neutron.When catching the middle period of the day from 11 p.m. to 1 a.m, send two charged particles
7li and Alpha and make gas ionization, thus free ion and electronics produced.The voltage 1405 applying is plundered the electric charge that produces signal.
Equation below illustrates
10the neutron capture reaction of B:
In this reaction, can find out, send with contrary direction
7li and Alpha.A particle makes the gas ionization in gas zone 1403, thereby produces free electron and ion pair.High pressure bias voltage is plundered ion, the pulse signal being directly proportional to produce the quantity right to electrons/ions.Because the multiple of electronics is not depended in this chamber, proportional counter utilizes it to improve signal, so can apply low-voltage.In 94% reaction, Alpha's ion receives Isosorbide-5-Nitrae 7MeV, and in approximately 6% reaction, it receives 1.78MeV.
For high Z materials,
10b has time the highest thermal neutron capture cross section.Cross section is 3837 targets, and
3he has the cross section of 5333 targets.Because
10b has this large thermal neutron capture cross section, so based on
10the detecting device of B can be realized
3he is equal to efficiency.Not only large area parallel-plate chamber can be designed to pure thermal neutron detecting device, and can design optimization its, to detect rapid neutron.
In many cases, compared with pure thermal neutron detection efficiency, rapid neutron detects more relevant to check-out console, because all neutrons are all " fast " (having the energy that is greater than 0.1MeV) in the time producing.Really, fast-neutron fission neutron is one of most important characteristics of fission event.In one embodiment, the multiple cellular zones detector stack shown in Figure 14 stacks, to improve the inherent efficiency of detecting device.In one embodiment, detecting device is multilayer, and comprises more than 20 layers.
Figure 15 A and 15B illustrate respectively the first and second embodiment of the rapid neutron detecting device geometry that can replace large area gate-type radiological monitor.With reference to figure 15A, cellular zone detecting device comprises: the first polyethylene layer 1501, the first boron plating layer 1503, gas zone layer 1505, the second boron overlay 1507 and the second polyethylene layer 1509.In one embodiment, gas zone layer 1505 comprises argon gas.In operation, polyethylene layer makes rapid neutron slowing down, this neutron of thermalization, and catch this neutron by boron.Therefore, polyethylene layer is for slowing down rapid neutron.
As shown in Figure 15 B, photon detector and neutron detector integrate.At this, replace polyethylene board, plastic scintillator is integrated in detecting device in two-layer 1510 and 1520 mode.Plastic scintillator is for two objects; It can slowing down rapid neutron, and can detect gamma ray, because it is gamma ray scintillation detector.Although the design of Figure 15 A can replace in current RPM
3he module, but the design of Figure 15 B in individual module can be replaced whole gamma ray and the neutron detection module of current RPM.
As mentioned above, utilize parallel-plate chamber principle, can realize the scalability that covers large-area detecting device.Figure 16 A to 16C illustrates three exemplary steps that can realize scalability.Figure 16 A illustrates the Liang Ge stackable unit district detecting device 1601 with reference to figure 15A and 15B description.In one embodiment, stacking detecting device has the size of scope in 10cm × 10cm × 1cm.The stacking detecting device that comprises two cellular zone detecting devices 1601 comprises altogether four boron layers 1605, two argon gas tagmas 1607 and three kapton layers 1609.1609 pairs of thin boron overlay of kapton layer provide rigidity.Technician in affiliated technical field is clear, and other suitable materials also can be for this object.
By adding more boron, or in other words, by adding more multi-layered boron, by stacking more than one cellular zone detecting device, the quantity of the neutron absorber material during increase detecting device is stacking.Utilize more boron, detect neutron and there is higher likelihood, because in the time that neutron passes through detecting device, with at least the interactional chance of one deck boron is higher.Therefore, in one embodiment, multiple cellular zones detector stack stacks, to improve the inherent efficiency of detecting device.In one embodiment, detecting device is multilayer, and comprises more than 20 layers.
Figure 16 B illustrates another embodiment of scaled detecting device of the present invention.In one embodiment, " piling up " cellular zone, to realize 1m at the most
2area.Each square 1605 in detector matrix 1606 represents a cellular zone detecting device, and by having 10 × 10 detecting devices, can realize large area.Each has the separate cord 1607 of feed-in data-acquisition system.Each is separated by the groove 1608 for electrical isolation.
In yet another embodiment, Figure 16 C illustrates the detecting device 1610 of collapsible geometry, by the detecting device of 1m × 1m being installed in encapsulation together with folding mode as shown in Figure 16 B, the detecting device 1610 of this collapsible geometry can reach very large area.Fold and make detecting device have more rodability, in the time launching, this detecting device is realized very large area of detection, thereby improves detection efficiency.
By drawing and 2 inch diameters with 4atm pressure
3it is required that He pipe is realized identical thermal neutron detection efficiency 1702
10the quantity of B layer 1701, Figure 17 illustrates the detection efficiency of B-10 detecting device of the present invention.In a typical case, calculate the thick capturing events quantity of every layer of 1 μ m.Because the size of the 1.47MeV alpha particle in boracic metal is approximately 3.5 μ m, so select this thickness.If boron layer is too thick,, in this layer, charged particle is lost its all energy, and disappears, and signal is not acted on.With reference to Figure 17, can find out, with
3he pipe is realized identical thermal neutron detection efficiency needs 40 1 μ m thick
10b layer, as shown in line 1703, this thermal neutron detection efficiency is about 85%.
Large area
10b thermal neutron detecting device can also be good rapid neutron detecting device.In many active detection technology, detect the rapid neutron that represents to hide weird atom nuclear material.Figure 18 is by of the present invention
10the rapid neutron detection efficiency of B neutron detector with based on
3the differential decay of He is analyzed (DDAA) detecting device and is compared.After the detection source neutron decay of thermalization in detecting device, DDAA technology can detect thermal neutron induction fission neutron.This illustrates because tygon exists
10stratification in B detecting device, and as the function of tygon thickness
10the curve map of the fall time 1801 of B neutron detector and the detection efficiency 1802 of detecting device.
In the situation that detection efficiency is 25%, DDAA detecting device is realized the fall time of 40 μ s.This means, for the fall time identical with DDAA detecting device,
10each polyethylene layer in B neutron detector is necessary for the thickness of 6mm, as shown in curve 1801.Therefore,
10b neutron detector inherent detection efficiency is now about 20%, as shown in curve 1802, very similar with DDAA detecting device.
Figure 19 A to 19F illustrates in one embodiment in step mode, and the area adopting in the time manufacturing cellular zone of the present invention detecting device is about 1m
2the embodiment of production run of large area boron substrate layer.The method of advising is followed existing semiconductor technology, and it is economical and can expand.
As shown in Figure 19 A, in step 1900, in order to have satisfactory electrical conductivity, very thin copper foil 1911 is as metallic substrates.In one embodiment, the thickness of Copper Foil 1911 is in the scope of 50-100 μ m.In one embodiment, copper foil 1901 has 100cm
2area.
As shown in Figure 19 B, in step 1910, Copper Foil 1911 is invested to the more rigid layer 1912 such as kapton layer, realize like this large area structure intensity.Then, copper layer/kapton layer is immersed in liquor ferri trichloridi, with etching 10cm × 10cm block graphics and each electric wire.
Once etching trace, just this layer is installed on reel 1921, carry out vacuum moulding machine, as shown in Figure 19 C, as step 1920.
As shown in Figure 19 D, step 1930 illustrates that boron 1931 is deposited on copper face 1911.In order to deposit, the substrate that invests reel 1933 rotates around spray booth (not shown).In one embodiment, spray booth comprises for B
10c/B
4the magnetron 1934 of C spraying.Utilize linear spraying source 1934, can reduce target substrate distance, and can restrict boron loss in one direction.In addition,, by maximizing magnetron power density and passing ratio method, can improve deposition.In one embodiment, in the time of spraying, in boron target, embed extra electron transmitter.In one embodiment, utilize extra electron to improve stability and the temperature of deposition, realize so more fast and more stable boron film.Authorize Hilliard name be called " Electron-Assisted Deposition Process and Apparatus " the 7th, 931, No. 787 United States Patent (USP) has been described extra electron transmitter, merges the full content of this United States Patent (USP) at this by application.
Because boron conduction, so utilize mask 1935 to stop that boron is deposited on etched electric wire, therefore, prevents wire short-circuiting.
As shown in Figure 19 E, in step 1940, depositing after boron, from vacuum, take out large area boron layer 1941, and be ready to be arranged on detecting device.
As shown in Figure 19 F, in optional step 1950, on this detecting device, manufacture rapid neutron detecting device, wherein boron/copper/kapton layer 1951 is layered on polythene strip 1952.
After having manufactured every layer, as with reference to described in figure 15a and 15b, each independent substrate layer is stacking in this detecting device/stratification, thus improve boron amount, and neutron detection efficiency is brought up to the highest.
Therefore, cellular zone of the present invention detecting device comprises at least two painting boron metal levels that clip gas zone.In one embodiment, detecting device comprises multiple cellular zones detecting device, and this cellular zone detecting device comprises whole 20 above layers.
For rapid neutron (fission frequency spectrum), most of neutrons need to be before boron be caught generation slowing down.It should be noted that capture cross section raises along with the reduction of neutron energy.Once carry out slowing down, boron just absorbs or catches neutron, sends like this charged particle.Due to 180 degree emitted particles, so only have one by gas zone, generation can detected electrons/ion.If the first tygon or scintillator layers be slowing down rapid neutron not, the second layer does like this, until n layer, thereby improve detection efficiency.Although notice neutron for the first time collision in may lose all energy, this is not normal conditions, therefore, needs to use whole cellular zone detecting device in the each stack layer that comprises attaching polyethylene or scintiphoto.Therefore, multiple layer being appended to this when stacking, the probability that detects multiple neutrons raises.
Above-mentioned example is only for illustrating many application of system of the present invention.Although described several embodiments of the present invention at this, it should be understood that and can implement the present invention with many other particular forms, and do not depart from essential scope of the present invention.Therefore, this example and the present embodiment are regarded as illustrative and nonrestrictive, and within the scope of the appended claims, can be revised the present invention.
Claims (21)
1. a gamma neutron detector, comprising:
The ground floor of the compound scintillator of neutron-sensitive; And
The responsive scintillator of gamma second and the 3rd layer, wherein ground floor is between the second layer and the 3rd layer.
2. gamma neutron detector according to claim 1, wherein, described ground floor comprises in Li-6, B-10, Cd or the Gd mixing with ZnS.
3. gamma neutron detector according to claim 1, wherein, described ground floor comprises that by steam drying one in ZnS in the potpourri of bonding agent and solvent or ZnS (Ag) and Li-6, B-10, Cd or Gd forms.
4. gamma neutron detector according to claim 2, wherein, described Li-6 or B-10 by volume have 20% to 30% concentration with respect to ZnS.
5. gamma neutron detector according to claim 1, wherein, described second and the 3rd layer of one of comprising in organic solid scintillator, inoganic solids scintillator or liquid scintillator.
6. gamma neutron detector according to claim 1, wherein, described second and the 3rd layer comprise the plastic scintillator with quick fall time, and described ground floor comprises the scintillator with slower fall time.
7. gamma neutron detector according to claim 1, wherein, described second and the 3rd layer than described the first bed thickness.
8. gamma neutron detector according to claim 7, wherein, described second and the thickness of the 3rd layer in the scope of 0.01m to 0.20m.
9. gamma neutron detector according to claim 1, wherein, described second and the 3rd layer of front and rear panels that forms respectively different-thickness.
10. gamma neutron detector according to claim 1, wherein, the responsive scintillator of multiple described gammas and the compound scintillator of multiple described neutron-sensitives layout alternate with each other in the direction that is substantially perpendicular to incident radiation direction.
11. gamma neutron detectors according to claim 1, wherein, the responsive scintillators of multiple described gammas and the compound scintillator of multiple described neutron-sensitives layout alternate with each other and with an angle orientation of the direction of incident radiation.
12. 1 kinds of gamma neutron detectors, comprising:
The gamma detecting device of plastic scintillator;
Neutron detector, has at least one screen that comprises the potpourri of in silver activation ZnS and Li-6 or B-10; And
At least one photoelectric detector, for gathering respectively the light of neutron and the generation of gamma detecting device and this light being converted to neutron and gamma event.
13. gamma neutron detectors according to claim 12, also comprise pulse shape discriminator, for differentiating neutron and gamma event; And wherein said at least one screen embeds in plastic scintillator.
14. gamma neutron detectors according to claim 12, also comprise the reflection foil between at least one screen and plastic scintillator; And wherein at least one screen embeds in transparent hydrogeneous photoconductive tube.
15. 1 kinds comprise the detecting device in subarea at least one, described at least one subarea comprise:
First and second layers, comprise B-10, for catching neutron; And
District's floor, comprises gas, between first and second layers, wherein ought catch the middle period of the day from 11 p.m. to 1 a.m, and first and second layers are sent charged particle, and this charged particle makes the gas ionization in district's floor, to produce free electron and ion pair.
16. detecting devices according to claim 15, wherein, described gas is argon gas.
17. detecting devices according to claim 15, wherein, at least one, subarea also comprises that position is first and second layers of betwixt poly the 3rd layer and the 4th layer.
18. detecting devices according to claim 15, wherein, at least one, subarea also comprises that position is third and fourth layer of first and second layers of responsive plastic scintillator of gamma betwixt.
19. detecting devices according to claim 15, wherein, multiple neutrons cellular zone is stacked, thereby improves the efficiency of composite detector.
20. detecting devices according to claim 15, wherein, pile up together multiple neutrons cellular zone, thereby improve area and the efficiency of composite detector.
21. detecting devices according to claim 15, wherein, multiple neutrons cellular zone keeps together with folding geometry.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US201261595044P | 2012-02-04 | 2012-02-04 | |
| US61/595,044 | 2012-02-04 | ||
| PCT/US2013/023684 WO2013116241A1 (en) | 2012-02-04 | 2013-01-29 | Composite gamma-neutron detection system |
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|---|---|
| CN104169741A true CN104169741A (en) | 2014-11-26 |
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| CN201380014938.2A Pending CN104169741A (en) | 2012-02-04 | 2013-01-29 | Composite gamma-neutron detection system |
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| Country | Link |
|---|---|
| EP (1) | EP2810096A4 (en) |
| JP (1) | JP2015510589A (en) |
| KR (1) | KR20140119092A (en) |
| CN (1) | CN104169741A (en) |
| AU (1) | AU2013215286B2 (en) |
| BR (1) | BR112014019120A8 (en) |
| CA (1) | CA2863633C (en) |
| GB (1) | GB2513765A (en) |
| IN (1) | IN2014DN06515A (en) |
| MX (1) | MX350345B (en) |
| WO (1) | WO2013116241A1 (en) |
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- 2013-01-29 BR BR112014019120A patent/BR112014019120A8/en not_active IP Right Cessation
- 2013-01-29 JP JP2014555627A patent/JP2015510589A/en active Pending
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| CN104820233A (en) * | 2015-05-15 | 2015-08-05 | 中国科学院高能物理研究所 | Scintillator array structure, and neutron detector employing same |
| CN109690353A (en) * | 2016-09-13 | 2019-04-26 | 皇家飞利浦有限公司 | Combined imaging detector for X-ray and nuclear imaging |
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| CN110988966A (en) * | 2019-12-17 | 2020-04-10 | 中国人民解放军96901部队23分队 | Neutron and gamma ray compound photography method and system based on CLYC crystal |
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| CN113640853A (en) * | 2021-07-16 | 2021-11-12 | 中国原子能科学研究院 | Target structure for measuring high-fluence thermal neutron fission ionization chamber |
Also Published As
| Publication number | Publication date |
|---|---|
| EP2810096A1 (en) | 2014-12-10 |
| WO2013116241A1 (en) | 2013-08-08 |
| AU2013215286B2 (en) | 2015-08-27 |
| BR112014019120A2 (en) | 2017-06-20 |
| MX2014009411A (en) | 2016-08-26 |
| JP2015510589A (en) | 2015-04-09 |
| AU2013215286A1 (en) | 2014-08-28 |
| EP2810096A4 (en) | 2016-02-17 |
| MX350345B (en) | 2017-09-05 |
| GB2513765A (en) | 2014-11-05 |
| KR20140119092A (en) | 2014-10-08 |
| IN2014DN06515A (en) | 2015-06-12 |
| CA2863633C (en) | 2017-02-21 |
| GB201413624D0 (en) | 2014-09-17 |
| BR112014019120A8 (en) | 2017-07-11 |
| CA2863633A1 (en) | 2013-08-08 |
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