CN101019042B

CN101019042B - Object examination by dual energy radiation scanning and delayed neutron detection

Info

Publication number: CN101019042B
Application number: CN2005800067918A
Authority: CN
Inventors: 詹姆斯·E·克莱顿; 保罗·比约克尔霍尔姆
Original assignee: Varian Medical Systems Inc
Current assignee: Varian Medical Systems Inc; Varian Medical Systems Technologies Inc
Priority date: 2004-03-01
Filing date: 2005-02-28
Publication date: 2010-05-12
Anticipated expiration: 2025-02-28
Also published as: CN101019042A; CN101048653B; CN101048653A

Abstract

In one embodiment, a method of examining contents of an object comprising scanning an object at first and second radiation energies, detecting radiation at the first and second energies, and calculating a first function of the radiation detected at the first and second energies, for corresponding pixels. A pixel is a projection of radiation through the object onto the detector. The first functions of a plurality of pixels are grouped and a second function of the group is analyzed to determine whether the object at least potentially contains material having an atomic number greater than the predetermined atomic number. The second function may be compared to a third function, which may be a threshold having a value based, at least in part, on material having a predetermined atomic number. Delayed neutrons may be detected to determine whether the material is nuclear material. Systems are also disclosed.

Description

Check object by dual energy radiation scanning and deferred neutron detection

The application requires the temporary patent application No.60/549 of submission on March 1st, 2004, the temporary patent application No.60/568 that on May 5th, 093 and 2004 submitted to, and 541 rights and interests, they have been transferred to assignee of the present invention and have been introduced into by reference at this.

Technical field

To comprising that the object (object) as the big object of freight transportation instrument and so on carries out radiation scanning (radiation scanning), with the identification contraband goods.

Background technology

Radiation generally is used for non-invasion ground and checks content such as objects such as luggage, sack, briefcase, cargo containers, so as for example on the airport, the contraband goods hidden of harbour and public building identification.For example, contraband goods can comprise hiding rifle, cutter, explosive release, illegal drug and weapons of mass desturction, as nuclear or " dirty " radioactivity bomb.A kind of common check system is line scanner (line scanner), wherein transmits the object that will check between radiation source fixing as X-radiation and so on and fixing detector.Radiation is calibrated (collimation) and is fan beam or pencil beam (pencil beam).The radiation that sees through object is decayed in various degree by the content of object.The decay of radiation is the function of the density of the material that passes through of beam.Survey and measure the radiation of transmission.Can produce the radiation image of object content, be used for checking.Image has shown shape, size and the different densities of content.

The about typically 160KeV of employed fixedly radiation source is to the x-ray radiation source of about 450KeV in the common check system.For example, x-ray source can be tough causing (Bremsstrahlung) radiation source.X-ray source in this energy range can be an X-ray tube.The X-radiation of 450KeV can not penetrate the big object as cargo container and so on fully.The cargo container of standard typically is 20～50 feet long (6.1～15.2 meters), 8 feet high (2.4 meters), 6～9 feet wide (1.8～2.7 meters).The size (long, high, wide) that is used to hold the aviation cargo container that will leave many interior luggage of airframe or other goods in can change up to about 240 * 118 * 96 inches (6.1 * 3.0 * 2.4 meters) from about 35 * 21 * 21 inches (0.89 * 0.53 * 0.53 meters).On cargo pallet (pallet), also can support the object of raft, as many luggage.Can there be the cargo pallet of supporting side walls may have the comparable size that must go up cargo container, and uses term " freight transportation instrument " to contain cargo container and cargo pallet.

To take on the aircraft smuggling in handbag and the luggage to be current well-known concerned issue though rifle, explosive and other contraband goods be contained in, but it is less open but also serious threat is to utilize ship transnational smuggling contraband goods in big freight transportation instrument.Transporting to ship in 1,000 7 hundred ten thousand containers of the U.S. has only 2%～10% to be examined." inspection post action of terror (Checkpoint Terror) ", US News and world's report (U.S.News andWorld Report), on February 11st, 2002, the 52nd page.

Utilizing traditional bomb to scatter the atomic bomb of radioactive material and " dirty bomb " at wide geographic area is can be at the example of freight transportation instrument and the nuclear device of more smuggling in the wisp. similar, also can in these objects, smuggle the radioactivity that can be used for making atomic facility, fissible, easily fission and fertile material. as uranium-235, the easy fissioner of uranium-233 and plutonium-239, can experience fission by catching slow (heat) neutron. fissile material comprises easy fissioner, and can experience the material of fission by catching fast neutron, can be transformed into easy fissioner by catching slow (heat) neutron as uranium-238. fertile material. for example, uranium-238 for example can be transformed into plutonium-239., and it is fissible that thorium-232 can be transformed into uranium-233., easily fission and fertile material are referred to herein as " nuclear material ".

It is too slow for conventional purposes that the content of the object by manual examination (check) such as freight transportation instrument and so on is discerned nuclear device, nuclear material and radioactive material (may not be nuclear material).By discerning radioactive material as the passive check system of radiation detector and nuclear device is faster, but difficult.For example, radiation detector can be placed along the path of object.Because nuclear material is normally fine and close, and their absorb the great majority in the photon that they launch.Also can be used for the effusion of block radiation as the shielding material of iron, lead, tungsten or palladium, stoped detection radiation.In addition, though some easy fissioner as uranium-233, uranium-235 and plutonium-239 has radioactivity, has the extremely long half life period (10 ⁴～10 ⁸The order of magnitude in year).For this material, too slow from the counting rate of spontaneous decay, make passive detection unreliable.And more a spot of radioactive material can be arranged in big goods means of transport.And, be difficult to other the fine and close thing that is equipped with in nuclear device and nuclear material and the object be distinguished by standard X-ray scanning.

Can utilize such radiation beam to strengthen the material composition information of the object content that can obtain by X-ray scanning: the power spectrum of this radiation beam has and differently interactional two the different-energy end points of object content (peak energy).It is relevant with material to interact.For example, can provide two X-ray beams with power spectrum by having the x-ray source of 6MeV and 9MeV or higher accelerating potential, this x-ray source produces the X-radiation bundle with 6MeV and 9MeV peak energy respectively.For the X-ray beam with 6MeV peak energy, X-radiation will mainly be decayed by Compton (Compton) scattering.On most of power spectrum, there are not a lot of electron pairs to produce.For having the 9MeV or the X-ray beam of high peak energies more, brought out more electron pair and produced.Compton scattering has also taken place.The ratio of surveying under two energy end points that sees through radiation can be indicated the atomicity (automic number) of the material that radiation beam passes through.Though electron pair begins to produce at 1.022MeV, Compton scattering plays a major role, till reaching higher peak energy.

For example, U.S. Patent No. 5,524,133 disclose the scanning system that is used for as the big object or the goods on the delivery vehicle of container.In one embodiment, provide two fixing x-ray radiation sources, each radiation source all sends and is calibrated (collimation) and is the beam of fan beam.Emitter surface is to the sides adjacent of goods, and fan beam is vertical mutually.The offside that the fixed detector array is placed on goods is relative with each radiation source, so that receive the radiation that sees through goods.In addition, each radiation source all sends the X-radiation of two kinds of different-energies.A kind of energy is much higher than another kind of energy.For example, can use the energy of 1MeV and 5MeV or 6MeV.Determine the ratio (ratio) of the average X ray number that detector array integral body is surveyed at each energy end points each detector of the ratio of the average X ray number of each Layer Detection or detector array under each energy end points, and itself and look-up table compared, with the identification average atom number corresponding with this ratio.Determine the material content of goods thus.

The more complicated factor of X-ray scanning is, with the measurement of radiation behind the tested object interaction be on the statistical significance.For example, see through the photon number that the measuring accuracy of the X-radiation of object is used to measure and the restriction of system's intrinsic noise.It is the cluster measured value bunch at center that the duplicate measurements of same amount typically produces with the average.The curve of this bunch measured value typically forms " normal distribution " curve.Discrete (width of normal distribution curve) of single measurement characterizes with standard deviation.Use Poisson statistics in the X-ray scanning that utilizes the homogeneous X-ray bundle, the percentage error of measurement is 1 divided by the square root that is detected photon number except that system noise.When detecting more photon, standard deviation reduces, and measuring accuracy improves.Though can increase the photon number that detects sweep time by increasing, the throughput that slows down the exemplary x-ray scanning system generally is unacceptable.For example, in current market, postponing sack or luggage that the freight transportation instrument passes through harbour or border or postpones the screening passenger on the airport greatly, is unacceptable.

For example, the precision of managing to discern as the scanning system of the material of uranium and so on can be a feature with its " sensitivity " and " selectivity " thereof. and sensitivity is to discern the probability that has uranium in the freight transportation instrument. and the high sensitivity system will be than more true newspaper (true positive) (correctly discerning the existence of uranium) of muting sensitivity system identification and failing to report still less (the leakage detection of uranium).Yet the raising of sensitivity may cause reporting by mistake the increase of quantity, and this may be unacceptable.For example, the selectivity as precision statistics tolerance is that scanning system can correctly be discerned the probability that does not have uranium in the freight transportation instrument.High selectivity system will be than low selectivity system identification wrong report (when not having uranium in the freight transportation instrument, identification uranium) still less.

Not enough photon is collected the measurement that may cause big standard deviation and is distributed.Therefore, the distribution of material of being concerned about as uranium and so on may be overlapping with other distribution of not having threat materials.Therefore, may not know whether special measurement indicates the material of being concerned about, cause wrong report thus.Still need to be used for to survey accurately the nuclear material hidden in freight transportation instrument and other object feasible, efficiently reach non-inbreak method and system.

Summary of the invention

Fissible, easily the fission and fertile material (nuclear material) have high atomicity (being atomic number) (Z).For example, the atomicity (Z) of axle is 92, and the atomicity of plutonium is 94.Be defined as by U.S. Nuclear Regulatory Commission than the special nuclear material (SNM) of the easier experience of other easy fissioner fission and comprise plutonium, uranium-233 and to be rich in isotope uranium-233 or the uranium of uranium-235.Usually shield radioactive material with high atomicity material as plumbous (Z=82), tungsten (Z=74) and palladium (Z=46), the some of them radioactive material may have the atomicity lower than nuclear material (for example the atomicity of cobalt-60 is 27).On the contrary, the iron as the main material of the most of industrial goods that load and transport in the freight transportation instrument has 26 atomicity.Also the agricultural product that can load and transport in the freight transportation instrument have lower atomicity.Agricultural product are mainly by the carbon with lower atomicity (Z=6), nitrogen (Z=7) and water (H ₂O, H (Z=1); O (Z=8)) forms.Embodiments of the invention are checked the content of object, may indicate existing of high atomicity material that nuclear material exists to check.Also can check object self and buried object.

According to the embodiment of the invention, check the object content by the following method: come scanning object with radiation beam with different-energy such as different-energy end points; The function of radiation that calculating is surveyed under two kinds of energy; And determine according to this function whether object comprises the material of atomicity greater than predetermined atomicity at least in part.For example, object can be the freight transportation instrument, and these two energy end points can be greater than 1MeV.For example, the energy end points can be 9MeV and 5MeV.For example, function can be the radiation ratio of surveying under two energy end points.This ratio is referred to herein as transmittance (TR).Atomicity is called as high atomicity material (HANM) greater than the material of predetermined atomicity.Can be with first function and compare based on second function of predetermined atomicity at least in part, to determine.For example, second function can be a threshold value.For example, the threshold value ratio (also being TR) that can be at least in part obtain based on the test material that has predetermined atomicity by scanning under two identical energy end points.Threshold value further can be regulated predetermined integral multiple or non-integral multiple standard deviation.Change standard difference will influence the sensitivity and the selectivity of system usually in the opposite direction.For example, increase the standard difference and can improve selectivity, reduce the wrong report number, but it also can desensitization, reduce the detection of aiming at newspaper.In special applications, need balance selectivity and sensitivity.For example, also can imbed object underground.

The part of radiation beam that sees through the special part of object as the projection on the detector, is called as " pixel " on the surface.For respective pixel, calculate the function between the radiation of surveying under every kind of energy.Respective pixel preferably overlapping at least half, but this is optional.Respective pixel projection from the teeth outwards is called as " synthetic (resultant) " pixel or abbreviates pixel as.

The synthetic pixel that satisfies test philosophy is indicated at least potentially and is existed HANM. to improve to conclude selectivity and the sensitivity that has HANM in the related object position, embodiments of the invention are analyzed dissimilar synthetic group pixels by different way. and can form grouping (grouping) on every side in each suspicious synthetic pixel (satisfying the synthetic pixel of test condition), perhaps can form a plurality of groupings to surround all pixels in the array. can carry out multinomial test.

According to the embodiment of the invention, a kind of method of checking the object content is disclosed, this method comprises: with the first of the first radiation beam scanning object of first energy; And survey first radiation after first radiation beam and first interact.This method further comprises: with the second portion of the second radiation beam scanning object; And survey second radiation after second radiation beam and second portion interact.This method further comprises: first and second pixels of correspondence are calculated first function of the radiation of surveying under first and second energy, and first function of a plurality of respective pixel is grouped at least one group.This method further comprises: first function according at least some pixels in a plurality of pixels in this at least one group, calculate second function; And, determine whether object comprises the atomicity high atomicity material bigger than predetermined atomicity at least potentially at least in part according to this second function of at least one group.

According to related embodiment, a kind of method of checking the object content is disclosed, this method comprise with above the same, come scanning object with first and second radiation beams of first and second energy.This method further comprises, surveys first and second radiation that see through object under first and second energy.Then, this method further comprises: then right to each of many first and second pixels to correspondence, and calculate the ratio between first function of radiation and second function of radiation, and each ratio is stored in the array that comprises the row and column corresponding with synthetic pixel.This method further comprises: each ratio and threshold value as the function of being scheduled to atomicity are compared, and select at least one to comprise the inspection hatch of multirow and multiple row ratio.This method further comprises: basis at least in part, whether satisfy each ratio predetermined number about the criterion of each ratio and threshold value in each of at least one inspection hatch greater than predetermined number, determine whether object comprises atomicity at least potentially greater than the material of being scheduled to atomicity.

According to another related embodiment, a kind of method of checking the object content is disclosed, wherein also compare with above the same scanning object, probe radiation, ratio calculated and with ratio and the threshold value of being calculated.This method further comprises: to a plurality of synthetic group pixels; Calculate the function of the ratio of grouping; And this function and threshold value compared.This method further comprises: at least in part according to the function of grouping ratio and the comparison between the threshold value, determine whether object comprises the material of atomicity greater than predetermined atomicity at least potentially.

According to another related embodiment, a kind of system that checks the object content is disclosed, this system comprises at least one radiation source, at least a portion that is used to utilize first and second radiation beams of first and second emittance to come scanning object.Place at least one detector, with the radiation under first and second emittance behind detection and the object interaction.At least one processor is connected to detector.This at least one processor is programmed to: to first and second pixels of correspondence, calculate first function of the radiation of surveying under first and second energy; First function of a plurality of respective pixel is grouped at least one group; And second function that calculates first function of a plurality of pixels in this at least one group.This at least one processor further is programmed, so that: at least in part according to this second function of at least one group, determine whether object comprises the high atomicity material of atomicity greater than predetermined atomicity at least potentially.

Because be concerned about very much the identification that nuclear material (fissible, easily fission or fertile material) is existed, thus if there is nuclear material at least potentially in the first test indication, then carry out special for this reason and the test of design will be favourable.According to a further aspect of the invention, the delayed neutron after scanning with enough high-energy exist can with in one of this discussion or multinomial test or other test together, be used for determining whether comprise nuclear material in the object.Nuclear material can be special nuclear material (SNM), and current being defined as by U.S. Nuclear Regulatory Commission of SNM comprises plutonium, uranium-233 or be rich in isotope uranium-233 or the uranium of uranium-235.In an example,, then can carry out delayed neutron and survey if the existence of HANM is discerned in first test at least potentially.

According to another embodiment of the present invention, a kind of method of checking the object content is disclosed, this method comprises: object is carried out first check, if and there is questionable material in the first inspection indication, then check the detection of delayed neutron. this method further comprises: according to the inspection that delayed neutron is surveyed, determine whether object comprises nuclear material at least in part.

According to another embodiment of the present invention, a kind of method of checking the object content is disclosed, this method comprises: determine whether object comprises the material of atomicity greater than predetermined atomicity at least potentially, and if like this, just determine whether object comprises nuclear material.

According to another embodiment of the present invention, a kind of system that checks the object content is disclosed, this system comprises: at least one radiation source; First detector, be used to survey with object interaction afterwards from the radiation of this at least one radiation source; And second detector, be used for detected neutron.This system further comprises at least one processor that is connected to first and second detectors.This processor is programmed, so that: handle data, to determine whether object comprises questionable material at least potentially from first detector; And processing is from the data of second detector, to determine whether object comprises nuclear material.

According to another embodiment of the present invention, a kind of system that checks the object content is disclosed, this system comprises the device that is used for first and second emittance scanning object at least a portion, wherein first emittance is different from second emittance.This system further comprises: be used to survey with object interaction after the device of radiation photon under first and second radiation, and the device that is used for detected neutron.Also provide the radiation that is used for surveying under first and second energy according to first detector at least in part to determine whether object comprises the device of atomicity greater than the material of predetermined atomicity at least potentially.This system also comprises and is used for determining according to the data of receiving from second detector whether object comprises the device of nuclear material at least in part.

Term " emittance (radiation energy) " refers to the energy feature of radiation beam.For example, feature can be the energy end points or the peak energy of beam.Emittance also can refer to the average or nominal value of beam energy.Also can use other beam energy feature.

Description of drawings

Fig. 1 a is for multiple material, the curve map of measuring as the transmitted radiation function of transmitted radiation under the 9MeV, under 9MeV and the 5MeV;

Fig. 1 b shows the surface curve of the ratio of the radiation that sees through the radiation of the iron block adjacent with lead and see through this iron block under 9MeV under 5MeV;

Fig. 1 c has shown 5 curves, and this 5 curves representative is as the ratio of the transmitted radiation analogue measurement function of the transmitted radiation under the 9MeV, by being identified material under 9MeV and 5MeV;

Fig. 2 is the synoptic diagram of example of the radioscopic image part of freight transportation instrument;

Fig. 3 is at the example of a plurality of pixels through the value array (array) of the 9MeV X-radiation of a freight transportation instrument part;

Fig. 4 is at the example of a plurality of pixels through the value array of the X-radiation of the 5MeV of the freight transportation instrument part of Fig. 6;

Fig. 5 is the example that is combined into transmittance (TR) array of pixel (resultant pixel) according to the embodiment of the invention based on one of the X-radiation of measuring in Fig. 3 and 4;

Fig. 6 a is the process flow diagram for the example of the TR computing method of the usefulness of the embodiment of the invention;

Fig. 6 b is the process flow diagram that is used to regulate through the example of the method for the probe radiation of background image dense area;

Fig. 7 be in the embodiment of the invention for the inspection of various sizes and various standard deviation are realized ten thousand/ the bar chart of the required minimum TR pixel count of false alarm rate;

Fig. 8 is the process flow diagram according to the example of " the inspection hatch test " of the embodiment of Fig. 7;

Fig. 9 is the process flow diagram that is used for providing to the operator example of the method for checking output according to the embodiment of the invention;

Figure 10 is the process flow diagram of example of " in abutting connection with test (contiguitytest) " according to another embodiment of the present invention;

Figure 11 is for the usefulness of the embodiment of the invention, represents the example of TR array of one group of pixel of a cargo container part;

Figure 12 is the process flow diagram according to the example of " the matrix test " of the embodiment of Figure 11;

Figure 13 is the process flow diagram according to the example of the threshold value calculation method of the embodiment of the invention;

Figure 14 is the process flow diagram of example of selecting the method for threshold value according to another embodiment of the present invention based on the content of freight transportation instrument;

Figure 15 a is to be the example that nuclear material is checked the method for object according to another embodiment of the present invention;

Figure 15 b is to be the example that nuclear material is checked the other method of object according to another embodiment of the present invention;

Figure 16 is programmed so that implement the front elevation of the goods scanning system of the embodiment of the invention;

Figure 17 be similar to Figure 15 system demonstration the top view of a part of goods scanning system of two adjacent x-ray radiation sources;

Figure 18 is the perspective diagram that can implement another X-ray scanning system of the embodiment of the invention; And

Figure 19 is the rear view of Figure 18 system.

Embodiment

According to the embodiment of the invention, the transmission of utilization radiation by object under two kinds of different-energies or the function of decay, come article (item) or position in object or the object are categorized as high atomicity material (HANM), this HANM can be nuclear material or the material that shields this material.Function can be a ratio.This ratio or other this function can be compared with the transmission of the radiation by known atomicity test material under two kinds of identical energy or the same functions of decay.If material has the atomicity higher than test material, can be HANM then with this materials classification.Test material can be any material of atomicity less than the atomicity of care material.For example, test material can be an iron.For example, object can be the freight transportation instrument.And, according to the embodiment of the invention, can determine with the statistical confidence of expectation.

The atomicity of iron (Z) is 26.Because the typical articles in the freight transportation instrument comprises iron and atomicity other material less than iron, so atomicity all is suspicious greater than the existence of any material of iron.Therefore, be enough to sieve HANM and need not discern special material (although this is a kind of option).Though some HANM may not be a nuclear material, as plumbous (Pb, Z=82), tungsten (W, Z=74) and bismuth (Bi, non-nuclear HANM Z=83) can be used for the shielded nucleus material, so also is questionable material.Seldom there is legal HANM in the freight transportation instrument etc., and when having legal HANM, should on the detailed list of goods of freight transportation instrument, identifies them.For example, (Ag Z=47) has medical treatment, industry and photography purposes to silver.If for this legal purposes is transported silver, then should on detailed list of goods, identify silver.In addition, can come nuclear material and other HANM are distinguished by the transmission of nuclear material and the nuclear material shape in the image.Therefore, check detailed list of goods and check that visually the radioscopic image of freight transportation instrument can avoid HANM is identified as nuclear material, reduce the wrong report incidence thus.

For demonstration transmission specific energy by different materials under different-energy is HANM with materials classification, utilization has 9MeV and (measures half-value layer (HVL) 1.16 inches, 2.95cm) and 5MeV (1.04 inches of HVL, 2.64cm) radiation beam of nominal energy scans the sample of iron, lead, lucite (Lucite) and tungsten.Utilization can be from innovation medical system company limited (Varian Medical Systems, Inc., Palo Alto, the M9 that California) obtains of California Palo Alto

Linear accelerator provides radiation beam, this M9 Linear accelerator is set as to be operated under 8.5MeV and the 4.5MeV. M9 can be switched to another energy end points from an energy end points. scanning each sample and collect data under an energy end points, each sample of scanning and collect data under the second energy end points then. utilize along the central shaft of radiation source place about 2 meters apart from radiation source 4030 gadolinium oxides (GdO) scintillation crystal is surveyed the radiation through each sample.The electronics part of detector is covered by plumbous.For the 8.5MeV data acquisition, detector is operated with 300 pulse per seconds (pps), and detector is operated with 1.5 frame per seconds (fps).For the 4.5MeV data acquisition, radiation source is operated with 200pps, and detector is operated with 3fps.128 frames are added up to image.

The sample of iron, lead and the lucite of variable thickness is placed on separately between radiation source and the detector.Different-thickness causes different transmission amounts.For each sample, obtain two width of cloth images and store with the .viv form.Every width of cloth image is carried out standardization, with tuning detector heterogeneity and storage.In addition, and then the sample of different materials is placed mutually.For example, tungsten and iron are placed on respectively after the lead.And, can the sample of multiple material be placed one by one along the direction of beam.For example, tungsten and lead are placed on respectively after the iron.

For example, the free software program ImageJ-that utilization can obtain from National Inst. of Health (National Institute of Health) of http://rsb.info.nih.gov/ij/ handles every width of cloth image with Flame Image Process and routine analyzer that Java writes.Also can use known other image processing software in this technical field.The institute that fixed position in every width of cloth image obtains image is concerned about the histogram in zone, and record is from the average and the standard deviation of the be concerned about data of regional collection.In some cases, when and then two kinds of different materials are placed mutually, must be with hand rather than with grand (macro), select be concerned about regional.Therefore, the correspondence position of the sample that scans under two kinds of energy is incomplete same.Position indicator among the ImageJ makes that the position can be at least very approaching.

Histogram average by making image is calculated the energy transmission of every width of cloth image, so that image is carried out standardization divided by the image histogram average that obtains with identical energy under the situation that does not have sample.Then, the energy transmission under calculating and the record 8.5MeV and the ratio of the energy transmission under the 4.5MeV.Also write down the transmission under the 8.5MeV.

Fig. 1 a has shown the result, and Fig. 1 a is that transmission along the radiation beam of the 9MeV nominal energy of Y-axis is with the ratio of the transmission of the radiation beam of 4.5MeV nominal energy, to the curve map along transmission under the 8.5MeV of X-axis.X-axis is the semilog axle.Curve A guides our eyes to connect the different transmittance of the iron that is calculated, and it is corresponding to the different-thickness of sample.Curve B connects the different transmittance of the lead that is calculated.Curve C connects the different transmittance of the lucite that is calculated.Point D has shown the transmittance that is right after the iron after tungsten.Point E has shown the transmittance that is right after the lead after iron.Point F has shown the transmittance by 1.5 inches (38.1mm) tungsten of 3 inches (76.2mm) iron back.Point G has shown the transmittance of 1.5 inches (38.1mm) tungsten of 3 inches (76.2mm) iron back in different images.Point H has shown 3 inches (76.2mm) plumbous transmittance of 3 inches (76.2mm) iron back.

Curve among Fig. 1 a and point have shown at the good separation degree between the material under the low transmission (high decay).About 0.1 and littler transmission under, can clearly distinguish iron, lead and lucite, also be such for the tungsten and the lead of iron back.In addition, in this example, the relative position of curve demonstrates, and along with atomicity increases, the transmittance of material will reduce.Therefore, can be HANM with materials classification for example according to the comparison of the transmittance of the transmittance of every kind of material and each transmittance and iron.Notice that when near transmission (X=1) fully, curve is assembled.For example in optimization system,, and there is less scattering if survey more photon, then also may be in definite degree of separation under the higher transmission (less decay).

Fig. 1 b be under 8.5MeV and 4.5MeV by with the surface curve of the ratio image of the transmission of 1.5 inches (38.1mm) plumbous adjacent 3 inches (76.2mm) steel (iron). use different thickness, make identical by the transmission of two kinds of materials. the I of image partly is the image of steel (iron), and the J of image partly is plumbous image. under 8.5MeV, steel (iron) has approximately identical energy transmission with lead, as utilize detector measured. ratio is different greatly. and the statistics variations that each surperficial roughness is measured by ratio causes. can easily distinguish this two kinds of materials, a plurality of standard deviations because their ratio is separated by. under the lower situation of transmission, standard deviation will be bigger, ratio will be close together, and will need more complicated statistical study.

In above-mentioned experiment, radiation source and detector are close together, and need wide radiation beam, and this has reduced the homogeneity of incident radiation.In addition, scattering does not reduce, and detector efficiency is low.Fig. 1 c has shown 5 curves, these 5 curve descriptions according to there not being simulation under these problem conditions to simulate, seeing through the radiation of 5 kinds of different materials under the 9MeV and under 5MeV, seeing through the ratio of the radiation of these 5 kinds of different materials as the function of transmission potential under the 9MeV.Detector comprises 30mm cadmium tungstate (CdWO ₄).In simulation, to compare with above actual test, scattering has reduced, and radiation source and detector have further separated (about 13 meters).Material is water (H ₂O), aluminium, iron, uranium and gold, as shown in the figure.The above test of curve ratio is more level and smooth, and when the transmission under the 9MeV increased, curve was assembled.As mentioned above, under the height decay (low transmission) of incident radiation, there is big degree of separation between the different materials.Reduce the degree of separation that (decay increase) increase with transmission and demonstrate the atomicity correlativity.In addition, in this example, ratio increases with atomicity and reduces.If more low-yieldly come ratio calculated divided by higher-energy by making, then ratio will increase and increase with atomicity.

Be not limited to any particular theory, the relation between ratio and the atomicity of it is believed that is the differentiating effect (differentialeffect) that produces of Compton scattering under the different-energy and electron pair and producing.Under the situation of low atomicity material (as aluminium (Z=13) and water (H2O, H (Z=1), O (Z=8))), under high-energy such as 9MeV, Compton scattering is the mechanism that is in the ascendance.Compton scattering make low atomicity material with the speed of the higher-energy photon that is higher than scattering such as 9MeV photon and so on come scattering such as 5MeV photon and so on than energy photons, this has increased the ratio that sees through radiation of low atomicity material.For higher atomicity material, as silver (Z=47) and uranium (Z=92), electron pair produces the migration that causes high-energy photons, reduces ratio thus.In addition, when energy transmission increased, the variation of ratio was not too responsive to the variation of energy transmission, has caused almost straight curve.

In Fig. 1 a and 1c, if having in the material of generally in the freight transportation instrument, finding the iron of high atomicity (Fe, Z=26) as test material, then the ratio that is calculated less than the ratio of iron just indication have the material of atomicity greater than iron.As mentioned above, the typical articles in the freight transportation instrument comprises iron and atomicity other material less than iron.Therefore, atomicity all is suspicious greater than the existence of any material of iron.

Fig. 1 a and 1c also demonstrate, and when energy transmission increases (because material is thinner), the difference of the ratio of different materials has reduced.Though Fig. 1 a and 1c demonstrate, when energy transmission reduces (for thicker object), the difference of the ratio of different elements and material is bigger, notes, when energy transmission diminished, detectable every pixel light subnumber still less.This may increase the error margin of measuring ratio, reduces the precision that can distinguish material thus.Embodiments of the invention statistics ground illustrates the data of making an uproar.

In the example of the embodiment of the invention, utilization is with transmission or the ratio of decay and relation material atomicity between of two kinds of different-energies by the radiation of material, determine that object comprises the material of atomicity greater than predetermined atomicity at least potentially, this material is considered to HANM.Select predetermined atomicity, make that HANM may be nuclear material or the shielding material that is used for nuclear material.

In an example, utilize at least two kinds of different x-ray energy distribution or power spectrums to come scanning object with different maximum energy levels, maximum energy level is also referred to as end points (endpoint) or peak energy. and the example of operable energy distribution comprises 5MeV and 9MeV, 1MeV and 9MeV and 5MeV and 15MeV. utilize the detecting element of detector array, measure the radiation that under two different-energy end points, sees through object. for example, also can be before object just will enter corresponding radiation beam, after radiation beam sees through air under each energy end points probe radiation, usefulness for standardization. the standardization of air transmission is chosen wantonly. and each detecting element is all along the course of the beam that partly arrives detecting element from x-ray source by object, coming received radiation. the radiation projection from the teeth outwards along every course of the beam transmission is called as " pixel ". and the surface can be corresponding to all or part of of the receiving plane of detector array, for example this surface can be the plane or curved surface, if as this technical field known. each pixel can be corresponding to one or more detecting elements of detector array. produced image, this is optional in an embodiment of the present invention, but optional, then pixel can be corresponding to the pixel of image.

The function of radiation that calculating detects counterpart or pixel under two different-energy end points." correspondence " part or pixel are to be produced by the identical or substantially the same course of the beam by object.Because at the common traversing overshoot bundle of scan period object, so between the scanning under the first and second energy end points, object may move small distance.Therefore, respective pixel may not be to obtain from the identical course of the beam by the freight transportation instrument.Preferably, if by each pixel course of the beam of freight transportation instrument overlapping at least half, then think pixel " correspondence ", although this is not necessarily.For example, pixel can be overlapping fewer than half.For those skilled in the art, obviously in some cases, if for example can tolerate lower sensitivity and selectivity, then respective pixel can (each other in several pixels) located adjacent one another, and needn't be overlapping.

For example as mentioned above, function can be the ratio of the radiation surveyed at higher-energy end points (as 9MeV) and the radiation surveyed at more low-yield end points (as 5MeV), or vice versa.This ratio is called as transmittance (TR).In an example,,, make the transmitted radiation of surveying at the higher-energy end points divided by the transmitted radiation of surveying at more low-yield end points to a plurality of respective pixel for calculating transmittance.Can be expressed as array or matrix with the number (corresponding to ratio) of the location association of each synthetic pixel to the TR that is called as " synthetic pixel (resultant pixel) " or only calls the respective pixel of " pixel ".Do not measure radiation transmission, and can measuring radiation decay, and use it in the ratio.Also can use other function.For example, can use the asymmetry parameter function, as the ratio between following: 1) energy of surveying at the first energy end points adds the energy of surveying at the second energy end points, and 2) energy surveyed at the first energy end points deducts the energy of surveying at the second energy end points.In other words, (radiation of under 9MeV, surveying+under 5MeV, survey radiation) ÷ (radiation of under 9MeV, surveying-under 5MeV, survey radiation), or vice versa.

In an embodiment of the present invention, compare with the TR of synthetic pixel with based on second function of test material with predetermined atomicity (material on this predetermined atomicity is considered to HANM).Whether satisfy criterion according to TR at least in part, discern potential HANM about second function.For example, second function can be a threshold value, and criterion can be TR be on the threshold value or under.Can determine threshold value by the synthetic pixel of test material being calculated being used for scanning the average T R of the transmitted radiation under two the same energy end points of two energy end points of tested object with system.Can analyze all synthetic pixels, perhaps can the enough synthesized images of analytic statistics epipodium characterization test spare usually.Preferably, average T R is regulated an integer or a non-integer TR standard deviation, to obtain the sensitivity and the selectivity of expectation.And, preferably calculate the average T R of different-thickness test block.Because transmission becomes with thickness, can calculate special threshold value thus, and use it for special transmission or the transmission range of surveying in each pixel.Can utilize the transmission under the higher-energy end points (being 9MeV) to select threshold value at this.On the contrary, can use transmission under the 5MeV.

Preferably, the atomicity of test material has the highest atomicity that is equal to or greater than known acceptable material.For example, radioactive material is special care as uranium (Z=92) and plutonium (Z=94), because they can experience self-holding fission reaction (self-sustaining fissionreaction). therefore, test material preferably has the atomicity less than the uranium atom number. as mentioned above, plumbous (Z=82), tungsten (Z=74) and bismuth (Z=83) also are special care, because they can be used for shielding radioactive material. therefore, more preferably, test material has the atomicity less than tungsten. more preferably, test material is iron (Z=26), iron is the highest atomicity material of generally finding in freight transportation instrument and a large amount of luggage. also can use atomicity to approach the copper (Z=29) of iron and nickel (Z=28) if. freight transportation instrument or other such object are equipped with agricultural product, for example can determine these agricultural product according to the detailed list of goods of freight transportation instrument, then can use based on plastic testing spare as

Or Threshold value.Also other material that can utilize iron, copper, nickel or have the atomicity of lacking than the material of being concerned about is analyzed the freight transportation instrument that agricultural product are housed.

The indication of the TR of pixel and the comparative result of threshold value, the atomicity of the material in the volume of the object that is crossed by radiation beam is higher than or is lower than the atomicity of test block material.Calculating under the situation of TR divided by the value of corresponding low energy pixel by the value that makes the high energy pixel, if TR is less than threshold value, then caused the volume that radiation beam crossed of those pixels to comprise that at least potentially atomicity is higher than the material of test block material atomicity, and be identified as and be at least potential HANM.The material that atomicity is lower than test block material atomicity is classified as non-HANM.Calculating under the situation of TR divided by the value of corresponding high energy pixel by the value that makes the low energy pixel, if TR is greater than threshold value, then caused the volume that radiation beam crossed of those pixels to comprise that at least potentially atomicity is higher than the material of test block material atomicity, and be identified as and be at least potential HANM.Note,, needn't discern the atomicity of material according to these embodiment of the present invention, although this choose wantonly, as this field known.For example, U.S. Patent No. 5,524,133 discussed above has been described a kind of dual energy technique, is used for recently discerning according to the X-radiation of surveying under every kind of energy the average atom number of material.

Fig. 2 is the image 10 that comprises the freight transportation instrument part of article 405, article 410 and selected pixel, and these selected pixels comprise illustrative pixel A, B, F, G and H.Pixel A is positioned at article 405.Pixel B is positioned at article 410.Also show inspection hatch W, below will go through it.The size of pixel can depend on the size of the detecting element that comprises detector and/or quantity, imaging integral time etc.The minimum pixel size can be corresponding to single detecting element or a plurality of detecting element.In an example, the size of each detecting element and each pixel is 0.5cm * 0.5cm.

If being used to scan the radiation beam of freight transportation instrument 10 is vertical fan, the then combination of a plurality of adjacent one dimension vertical scanning array that produces by scanning freight transportation instrument of Fig. 2 representative.If radiation beam is a conical beam, then Fig. 2 represents the one or more two-dimensional scans district that is produced by scanning freight transportation instrument 10.

The transmitted radiation value of surveying at these and other pixel place as the storer of array stores in scanning system in so that handle with processor such as computing machine.Fig. 3 is the example of the part of the emittance value array that the 9MeV radiation detection that sees through a freight transportation instrument part arrived in a plurality of pixels.Fig. 4 is the example of the corresponding array of the radiation of the 5MeV radiation detection that sees through freight transportation instrument counterpart being arrived at the respective pixel place.For example, under 9MeV, the standardization transmitted radiation of surveying at pixel X place is 5.9 * 10 ^-3, and under 5MeV, the standardization transmitted radiation of locating to survey at pixel X ' is 2.4 * 10 ^-3Because measuring, all transmitted radiation all have the identical order of magnitude (10 ^-3), so following omission 10 ^-3The same with Fig. 3 and Fig. 4, Fig. 5 is the example of the TR array of the freight transportation instrument same section that calculated.Show the TR of the synthetic pixel A that the value (5.9) by making X produces divided by the value (2.4) of X ', obtained 2.5 TR.Synthetic pixel typically has the size and dimension the same with initial pixel.All these values are all supposed.

Fig. 6 a is the process flow diagram of the example of calculating that can automatically realize with the X-ray scanning system and the method 800 of analyzing TR.In this example,, under 5MeV and 9MeV, survey the transmission of a plurality of respective pixel respectively in step 801 and 802.In step 803,, calculate the TR of each synthetic pixel, as shown in Figure 5 by making in the pixel transmission radiation of measuring under the 9MeV divided by the respective pixel transmitted radiation of under 5MeV, measuring.Then, select current synthetic pixel to be used for analyzing in step 805.In this example, select synthetic pixel A.In step 808, preferably select to be used for the threshold value that the TR with current pixel compares according to the transmission of surveying down at one of energy end points.May need to calculate threshold value applicatory according to the threshold value of storage is carried out interpolation, as discussed further below.In step 808, this selects the transmission of detection down based on 9MeV.On the contrary, this selection can be based on the 5MeV transmission of detection down.In this example, the threshold value of selection is 4.35.

Then, at TR that step 810 is determined current synthetic pixel A whether under the threshold value 4.35. because 2.5 less than 4.35, so satisfy this condition. therefore, synthetic pixel A may be that HANM. is in step 815, by the position of this pixel of mark in the array of Fig. 6 a, with this pixel " mark " be potential HANM. then, determine in step 820 whether synthetic pixel A is the last pixel that will analyze. because also have other pixel to analyze, so do not satisfy this condition, and method turns back to step 805 and analyzes to select new pixel, and this method continues. after computing machine is finished analysis to the TR of all pixels, because current pixel is last pixel, so the condition in the step 820 becomes very. can come the treatment step of implementation method 800 by the processor such as the computing machine of scanning system.

Can carry out prescan with known techniques, to determine whether object comprises the one or more dense areas that will further check, improves the handling capacity of scanning system thus.If be like this, can carry out one or multinomial test in the test described here.If not so, object can need not further be checked by system.Prescan can comprise, comes scanning object with the radiation beam with one of energy end points.Preferably use more low-yield end points radiation beam, because it is generally sensitiveer.The attenuation or the transmission of questionable material that can be possible with respect to indication come analysis result.For example, this can compare by the radiation that will survey or contrast and threshold value and realize.Also can produce image, and check image visually.

The radiation beam path that intersects with HANM will intersect with " background " material usually, as the Agricultural Materials or the industrial product of HANM front and/or back.Can be by according to the transmitted radiation of background material and the combination transmitted radiation that takies the suspicious HANM and the background material of identical radiation beam, calculate the TR of each pixel that embeds the suspicious HANM in the background material respectively, come the background of suspicious HANM is carried out standardization, improve the sensitivity and the selectivity of scanning system 100 thus.According to treatment technology known in this technical field, as cut apart, can discern the border of the dense area of the possible HANM of indication with respect to background.As mentioned above, can one of energy end points down inspected object is carried out prescan during, discern this dense area.Then, transmitted radiation that can be by making the pixel by the dense area under each energy end points is calculated the transmitted radiation by each pixel of dense area divided by the transmitted radiation by background.Then, as mentioned above, can calculate the TR of each pixel in the dense area by removing the transmitted radiation that is conditioned under each energy end points.

In order to make dense area and background have comparable TR primary system meter precision, preferably select the size of background like this, so that background area approximates the dense area area greatly or has the identical order of magnitude with the dense area area.In an example, can as 1 to the 5 centimetre of content on every side on each direction beyond the border, dense area, regard the fate as background material.The TR of background material can be mean value or other mathematical function of TR that constitutes the pixel of background.For example, also can use intermediate value.For example, can around the pixel of dense area, define two circle rings.For example, the circle ring of close dense area can be on each direction and the borderline phase of dense area every 2 to 3 pixels, so that the out of true of determining accurate border, dense area to be described.The next one ring that can surround with suspicious HANM area identical can be considered to surround background material.

Fig. 6 b can carry out so that the background of dense area is regulated the example of the method 850 of the probe radiation by the suspicious dense area of object by processor such as computing machine.In step 855, the dense area of recognition object.For example, can one of energy end points down object is carried out prescan during, the identification dense area.In step 860, determine the border of dense area.For example, can use the well-known image processing techniques of this technical field, as cut apart.

Background in step 862 identification dense area, and determine under each energy end points average transmission by background in step 864, as mentioned above.In step 866, under each energy end points, make the probe radiation that comprises along each pixel of the dense area of the background of course of the beam divided by the average probe radiation that sees through background.Not along under the situation of the influence of the background of course of the beam, the result is the transmitted radiation of the dense area under each energy end points.Then, this method may be advanced to the step 803 of Fig. 6 a, so that calculate the TR that the dense area synthesizes pixel according to the transmission of the respective pixel of being calculated, and these TR and threshold value is compared.

For some special applications, coming relatively to determine that according to independent TR and threshold value it may be not enough that low TR pixel is indicated the sensitivity of HANM and selectivity at least potentially. embodiments of the invention are managed the pixel count analyzed by increasing, improve selectivity and sensitivity that this is determined. the processor of scanning system, as computing machine, can be according to the following embodiment of the invention, further analysis result data.

The inspection hatch test

In one embodiment of the invention, check number with the pixel with the TR that is lower than threshold value (low TR pixel) that is comprised in one group of pixel (being called inspection hatch) of predetermined area.For example, inspection hatch can be the picture element matrix of 3 pixels * 3 pixels or 9 pixels * 9 pixels.Fig. 2 shows 9 * 9 pixel inspection hatch W.If the low TR pixel count in the inspection hatch has surpassed predetermined number, then think to have HANM.The minimum low TR pixel count that can select threshold value (the average T R of test block deducts/add the standard difference), window size like this and be considered to threat, so that non-HANM will satisfy the number that the probability that threatens criterion multiply by the independent check window (separate window is not shared common pixel) that has at least one pixel that is lower than threshold value in the object, less than the sensitivity and the selectivity of expectation.According to following statistical study, select the size of inspection hatch, and will from the average T R of test material, deduct standard difference with calculated threshold.This test is called as " inspection hatch test ".

The cross-sectional area of the minimum HANM that is concerned about that the size of inspection hatch can be surveyed corresponding to scanning system.Usually, smuggle HANM with the shape of ball.Inspection hatch can be and the inner largest square that cooperates of the xsect of this ball.In case selected window size is just selected threshold value, and if be found the following pixel count of minimum threshold value that just will be considered to threat.Preferably, select minimum sandards poor,, will reduce the probability of the response of true HANM because when the standard difference increases.Select threshold value and minimum pixel count like this, so that non-HANM will satisfy the probability of surveying criterion and multiply by the independent check window number of being analyzed, less than the false alarm rate of expectation.The example that can accept false alarm rate is less than one of percentage.Preferably less than per mille.More preferably less than ten thousand/.

In an example, will be used for scanning under two the same energy end points of two energy end points of freight transportation instrument scanning iron test spare with this same scan system.The independent measurement that is considered to the TR of iron at the TR of each pixel measurement.For each the standard difference below the average T R of test object (an integer or non-integer standard deviation), because statistical fluctuations, rather than, will exist single measurement will deduct every pixel probability " p " of that given standard difference less than average T R owing to there is HANM.After checking " N " individual pixel, also be because statistical fluctuations, will exist just in time has the probability " P " that " n " individual pixel will be below threshold value in these pixels.Provide this probability with binomial distribution:

P (n | N) = \frac{N!}{n! (N - n)!} p^{n} {(1 - p)}^{N - n} .

Therefore, can calculate the probability of each expected result.Therefore can discern those and have very little probability of happening on statistics, having high is the low TR pixel of the probability of real HANM.For given situation, false alarm rate " P is set _Fa", and as if calculating do not indicate the probability of all low TR pixels of high atomicity material existence.These probability additions, up to the difference of summation and 1 less than P _FaTill.This probability sum is corresponding to the number of the low TR pixel that will become wrong report.The existence that the above any low TR pixel count of this corresponding number is all indicated real HANM.

For example, suppose 9 * 9 pixel windows, and the average T R that threshold value equals iron deducts two standard deviations.Then, the every pixel probability of pixel below threshold value that causes owing to statistical fluctuations is p=0.02275.The probability P (n|N) of n pixel below threshold value that have in 9 * 9 windows that causes owing to statistical fluctuations is:

N	P(n\|81)	Probability and
N	P(n\|81)	Probability and	0	0.1550	0.1550

N	P(n\|81)	Probability and
N	P(n\|81)	Probability and	1	0.2923	0.4474
2	0.2722	0.7197	1	0.2923	0.4474
2	0.2722	0.7197	3	0.1669	0.8865
4	0.0757	0.9623	3	0.1669	0.8865
4	0.0757	0.9623	5	0.0272	0.9894
6	0.0080	0.9974	5	0.0272	0.9894
6	0.0080	0.9974	7	0.0020	0.9994
8	0.0004	0.9999	7	0.0020	0.9994

To find that owing to statistical fluctuations the probability P (n|81) of 8 pixels below threshold value is 0.0004.To find that owing to statistical fluctuations the probability sum of 8 pixels below threshold value is 0.9999.Therefore because statistical fluctuations rather than owing to there is HANM, find 8 or the probability of more pixels below threshold value be ten thousand/.This is based on the failing to report or false alarm rate P of every inspection hatch of 8 or more pixels _FaIn this example, the probability that 9 or how low TR pixel are the statistical fluctuations results less than ten thousand/ false alarm rate P _FaTherefore, for obtain every window less than ten thousand/ false alarm rate P _Fa, then need in inspection hatch, find 9 or more low TR pixel.

Fig. 7 is for various inspection hatch and standard deviation size, for obtaining ten thousand/false alarm rate P _FaThe bar chart of required minimum low TR pixel count.For example, if select the standard deviation of larger amt (3 or bigger), then the inspection hatch size may be inessential relatively, because at that false alarm rate P _FaOnly change (sub-fraction of pixel) very in a small amount for the required minimum pixel count of indication HANM down.If use the standard deviation of lesser amt, as 1, then at special false alarm rate P _FaBe the function that has stronger relation with the inspection hatch size for there is the required minimum pixel count of HANM in indication down.For example, for 9 * 9 matrix window sizes and 1 standard deviation, at ten thousand/false alarm rate P _FaSituation under need 27 pixels to indicate HANM.Under the situation of 8 * 8 matrix window sizes, need 24 pixels.

Can carry out two inspections, an inspection is to utilize to survey relatively large HANM than the thorough examination window, and another inspection is to utilize less inspection hatch to survey the HANM of a small amount of.As mentioned above, in this system, can survey relatively large HANM with 9 * 9 matrixes.For example, less inspection hatch can be 3 * 3 matrixes.Under 3 * 3 matrix situations, for example the standard difference that deducts from the average T R of test object can be 2 or 2.5.Under the situation of 2.5 standard deviations and 3 * 3 matrixes, at ten thousand/false alarm rate P _FaSituation under have 3 pixels below threshold value, will indicate HANM, as shown in Figure 7.The inspection hatch test can be the independent test that is used to determine whether to exist HANM, and perhaps the inspection hatch test can be used together with other inspection technology, comprises other embodiment of following the present invention.

Can check whole object by analyzing the traversing inspection hatch of crossing the TR of object.For example, can begin inspection hatch is placed on a position of corner as object and so on, then with one time one row pixel of inspection hatch move on to the diagonal angle.Subsequently, inspection hatch can be moved down one-row pixels, make one time one traversing TR of mistake in row pixel ground of inspection hatch then.Analyze the pixel in each window, and when the institute that has analyzed object might inspection hatch, analyze and finish.

In the examples of implementation of inspection hatch test, in the operating period of goods scanning system, make the freight transportation instrument be subjected to two kinds of X-radiation bundles, every kind of radiation beam has different energy end points, as 9MeV and 5MeV.Survey the radiation under each radiation end points after interacting with detector with the freight transportation instrument.Below discuss and to programme with the example of the goods scanning system of implementing this embodiment of the invention and other embodiment to it.

Fig. 8 is for example can be by carry out the example with the method 900 of implementing the inspection hatch test as the processor of computing machine.For example, in the method 800 of Fig. 6 a (and randomly together with method 850 of Fig. 6 b), calculate the TR of synthesized image element after, select pixel at step 910 computing machine, and structure is that the inspection hatch at center is as 9 * 9 matrixes with selected pixel.In step 912, the number of low TR (being labeled) pixel in the computer Recognition inspection hatch, and in step 915 itself and predetermined number are compared.As mentioned above, predetermined number is definite low TR pixel (even not being the pixel that HANM also the has low TR) number of the highest statistics that may become wrong report under selected condition.Below, for example further describe the calculating of threshold value with reference to Figure 13.

If low TR pixel count is more than or equal to predetermined number, then step 920 the freight transportation instrument in and the territorial classification of low TR pixel correspondence be HANM.If the low TR pixel count in the inspection hatch less than predetermined number, then determines in step 925 whether the current check window is the last inspection hatch that will analyze.

If not the last inspection hatch that will analyze, then make inspection hatch suitably be moved to the left a row pixel in step 910, move down one-row pixels, to construct new current check window.Then, computing machine repetition methods 900 the institute in steps, as mentioned above.Can be with less inspection hatch, the standard deviation of varying number and different predetermined number are come repetition methods 900.If the current check window is the last inspection hatch that will analyze, then provide output to the operator in step 930.

Fig. 9 be can be by carrying out as the processor of computing machine so that to the example of operator's display analysis result's of goods scanning system 100 method 950.For example in step 960, whether the processor inspection exists any inspection hatch that is labeled pixel count that has more than or equal to predetermined number, determined in the step 915 as method 900.If the pixel count (even if having) that is labeled in any inspection hatch all is not greater than or equal to predetermined number, then processor advances to step 970, and display message " does not have HANM ".If be labeled pixel count greater than predetermined number in any inspection hatch, then processor advances to step 980, so that for example display message " is found HANM ", has high atomicity material thus in the alert operator freight transportation instrument.In step 990, processor also can show the image of the window that inspection hatch or expression HANM exist.Also can show the entire image that comprises window or and the image of window show the entire image that comprises window together, rather than display window image.

If there is HANM in the output indication, then the operator can have several options.For example, can check the detailed list of goods of freight transportation instrument, to determine whether HANM is suitably stated and not threaten.For example, HANM may be HANM rather than radioactive material, as the industry or the medical silver that should identify on detailed list of goods.HANM also may be the medical radioactive material that state on detailed list of goods.The operator also can make scanister and processor that the freight transportation instrument is carried out additional scanning and/or mathematical analysis is carried out in measurement, is included in other test of this discussion, and/or the operator can carry out manual examination (check) to the freight transportation instrument.Can remove from the test zone owing to existing suspicious HANM to make and check the freight transportation instrument of failing, and handle according to known program.

If output is not indicated and is not had HANM, then can think the freight transportation instrument " by " check.Yet, if still suspecting, the operator has HANM (for example according to prescan), the operator still can carry out manual examination (check).And, if the method 850 of Fig. 6 b not with the method 800 of Fig. 6 a in TR calculate together and use, then can manner of execution 850, recomputate TR, analyze like that as mentioned above then.If still do not demonstrate HANM, then can carry out other known test of any or all of other test described here or this technical field.In case the operator has been satisfied with, the freight transportation instrument just can " by ".

In abutting connection with test

(for example synthesize pixel in case find to satisfy first of test philosophy, as described) with reference to figure 6a, the another kind of method that increases the synthesized image prime number analyzed is exactly to analyze the environment of pixel, with identification and that pixel adjacency, also satisfy the pixel of test philosophy.Environment of analyzing that first synthetic pixel has improved measurement statistical precision (having reduced standard deviation), because if adjacent pixels also be the part of HANM, then first pixel more likely is the part of HANM.Analyzing pixel around first pixel has also increased effectively and has helped the photon number determined.If the area of adjacent pixels is more than or equal to predetermined area, then the sensitivity of HANM identification and selectivity are greater than based on single pixel or have sensitivity and the selectivity determined less than one group of pixel of the area of predetermined area.

Predetermined area can be the cross-sectional area that can produce the minimum HANM of the nuclear reaction of controlling oneself.For example, area can be the foursquare area of 4.5cm * 4.5cm--20.25cm ²The cross-sectional area of the foursquare smallest sphere of these sizes is surrounded in the square representative of this size.Can determine area size (see the step 815 among Fig. 6 a discussed above, wherein low TR pixel is labeled) by pixel counts to being labeled.Also can use other littler or bigger area.The adjacent pixels district needs not to be square shape.

If find to cover adjacent pixels, then think to have HANM at least potentially more than or equal to the area of predetermined area.In an example, share the pixel at edge, as pixel G among Fig. 2 and pixel H, be considered to adjacency, and the pixel of only sharing the summit is not considered to adjacency as pixel F and G.Can use different " adjacency " definition, for example can comprise the pixel of sharing the summit.This embodiment of the present invention is called as " in abutting connection with test ".Based on area rather than shape relatively be considered to more reliable, but also can consider shape.

Figure 10 can carry out to implement in abutting connection with the example of the method 1000 of test by processor such as computing machine.Select the pixel be labeled in step 1010.In step 1020, determine whether to exist the additional pixel that is labeled with selected pixel adjacency.From the selected pixel that is labeled, the pixel on all directions in inspection and the accumulation array is till all arriving first " unmarked " pixel (its TR is higher than threshold value) on each direction.The method that is used for this analysis is well-known in this technical field.

If exist and the selected pixel that is labeled that is labeled the pixel adjacency, then area size that is labeled pixel and the predetermined area in step 1030 pair adjacency compares, the area of the minimum HANM that is designed to survey as system 100--and in this example 20.25cm ²For example, preferably, determine the area that pixel covers that is labeled by " accumulation " in the step 1030 by to being labeled pixel counts.For example, if each pixel is 0.5cm * 0.5cm, be that 81 adjacency at center are labeled the area that pixel covered and equal 20.25cm then with pixel A shown in Figure 5 ²(4.5cm * 4.5cm).Though the zone is a square in this example, this is optional.If satisfy the condition in the step 1030, be the zone marker that adjacency is labeled pixel HANM then in step 1040.Randomly, can produce this regional image, so that be shown to the operator.

If be labeled area that pixel covers less than predetermined area, then in step 1050 being unacknowledged HANM in abutting connection with the zone marker that is labeled pixel.After

step

1040 or 1050, determined whether that in step 1060 another is labeled pixel and will handles.If such, then select new pixel and the repetition methods 1000 of being labeled in step 1010.If there is not other pixel to handle, then do not satisfy the condition in the step 1060, and provide output to the operator at step 1070 computing machine.Note,, then needn't be again it be analyzed (though also can like this) with this process in case single pixel is the part of previous marked area.Therefore, step 1010 can be limited to the pixel that is labeled that selection is not a previous marked area part.Similarly, step 1060 can be limited to that to determine whether to exist another be not the pixel that is labeled of a previous marked area part.

Can use separately in abutting connection with test, perhaps can use, comprise other embodiment test described here with other inspection technology. the output that is provided can be provided the operator, as above described with respect to the inspection hatch test.

If only detect the photon of limited quantity at each synthetic pixel place, the environment of then analyzing suspicious synthetic pixel also is useful.For example, some no threat materials (non-HANM) as agricultural product, may be very fine and close.Because by the low transmission of dense material, so, cause high statistics inaccuracy thus even material is not HANM, may finds to hang down the TR pixel yet.Can improve the statistical precision of determining by the radiation of considering in the pixel environment, to detect in abutting connection with test based on the measuring radiation of pixel.

The matrix test

In another embodiment, to the plain grouping of synthesized image, and the function of the TR in the analysis pixel groups.For example, function can be mean value or the intermediate value of the TR in the pixel groups.Can a plurality of groupings (groupings) perhaps can be set comprise all pixels in the formation group on every side of suspect pixel.For example, grouping can be a matrix.Therefore, this test is called as " matrix test ".

Article 410 among Fig. 2 are examples of another article in the freight transportation instrument.Pixel B is the low TR pixel in the article 410, is suspect pixel therefore.3 * 3 picture element matrix B3 among Fig. 2 are examples of the grouping of " structure " around pixel B.Figure 11 is the example of the TR array of freight transportation instrument 10 parts, and it shows low TR pixel B and matrix B 3.For example, average the average T R of compute matrix B3 by TR to each pixel in the matrix.Then, average T R and threshold value are compared.If average T R is lower than threshold value, then can thinks and find HANM.At Pixel Dimensions is in the example of 0.5cm, and 3 * 3 picture element matrix B3 can be used for identification and have at least approximately potential HANM of 1.5cm * 1.5cm cross-sectional area.Can select to be used for the threshold value of comparison according to mean value or other such function of the transmission of pixel in the matrix.

The TR statistical precision of 3 * 3 matrixes than the TR statistical precision Senior Three of single low TR pixel doubly.Because wrong report may cause unnecessary, the high cost to the freight transportation instrument, time-consuming and destructive inspection, so determining to find that pixel B preferably obtains more high-precision additional affirmation before belonging to HANM.

For further improving definite precision (reducing standard deviation) to larger object, after checking 3 * 3 matrixes, be that the center generates bigger matrix as 9 * 9 picture element matrix B9 preferably with identical chosen low TR pixel B, Fig. 2 and Figure 11 have also shown matrix B 9.On the contrary or also can construct the matrix of other size, as 5 * 5 and 7 * 7 picture element matrixs.More the size of large matrix may depend on the size of the article that will discern and the size of pixel.9 * 9 picture element matrixs comprise 81 additional neighborhood pixels, and the data of these additional neighborhood pixels help to determine whether to exist HANM.Produce the more average T R of the pixel of large matrix, and similarly this average T R and threshold value are compared.If the average T R of first matrix and second matrix below threshold value, then determines that with bigger degree of confidence current low TR pixel represents HANM.In this example, 3 * 3 picture element matrix B3 provide first identification to potential HANM, and utilize 9 * 9 picture element matrix B9 to verify existing of potential HANM with bigger degree of confidence.

Continue to analyze, till all low TR pixels are all handled.Can cross a plurality of 3 * 3 overlapping matrixes of array structure and 9 * 9 overlapping matrixes.For example, Fig. 2 shows additional 3 * 3 matrix B 4 overlapping with matrix B 3.

In another example, be 1.5cm if detecting element is 1.5cm * 1.5cm and Pixel Dimensions, then 3 * 3 picture element matrixs will surround the HANM cube that the length of side is 4.5cm.If detecting element is 0.1cm and Pixel Dimensions is 0.1cm, then will needs 45 pixels * 45 picture element matrixs to surround the HANM body side body that the length of side is 4.5cm or surround and cover 20.25cm ²The HANM of area.

Figure 12 is can be by carry out the example with the method 1100 of implementing the matrix test as the processor of computing machine. in this example, Pixel Dimensions is that 0.5cm * 0.5cm. is in step 1105, after method 800 in execution graph 6a is hanged down the HANM pixel with identification and mark, and randomly after implementing the adjacency test, (illustrated in the method 1000 at Figure 10) in abutting connection with the example of test, select the current pixel that is labeled. for example, select the low TR pixel B in the object 410 among Fig. 2. in step 1115, " structure " is 3 * 3 matrix B 3 at center with the pixel B, surrounds 0.5cm * 0.5cm and more large-area HANM. with identification

Then, in step 1120,, come the average T R of compute matrix B3 by 9 TR in the matrix B 3 being sued for peace and making the TR sum divided by single pixel count.In this example, the average T R of matrix B 3 is 2.7.Then, determine in step 1125 whether the average T R of matrix B 3 is lower than threshold value.Threshold value in this example is 3.9.Because 2.7 less than 3.9, satisfy this condition.This meaning matrix B 3 represent HANM, and its precision is initial independent have low TR according to pixel B and suspect that pixel B may be 3 times of precision of HANM.

In this example, for the HANM that surrounds 4.5cm * 4.5cm and bigger cross-sectional area, preferably constructing in step 1130 with the pixel B equally is 9 * 9 matrix B 9 at center, finds sensitivity and selectivity so that the HANM higher than 3 * 3 picture element matrixs to be provided.Figure 12 shows the example of 9 * 9 matrix B 9.Average T R at step 1135 compute matrix B9.To the summation of the TR in the matrix B 9, and make this TR sum divided by 81 (single pixel counts).In this example, the average T R of the matrix B 9 of Figure 11 is 2.9.Because considered 9 times pixel, so the statistical probability of the TR precision of matrix B 9 is bigger 3 times than the statistical probability of the TR precision of matrix B 3.Average T R and threshold value in step 1138 pair matrix B 9 compare.Then, determine that in step 1138 whether average T R is less than threshold value.If such, then confirm that with higher sensitivity and selectivity the current pixel that is labeled is corresponding to HANM in step 1140.Because 2.9 less than 3.9, so satisfy condition.Then, step 1145 determine pixel B whether be to analyze be labeled pixel at last.Will analyze because also have other to be labeled pixel, so do not satisfy condition, this method 1100 turns back to step 1105, and next is labeled pixel repetition methods 1100.

If the average T R of matrix B 9 is not less than threshold value, then pixel B is not confirmed to be HANM in step 1140, and method 1100 advances to step 1145, as mentioned above.After all TR that are labeled pixel had analyzed, the condition in the step 1145 became very, and provides output to the operator.The operator can respond output, as above described with respect to the inspection hatch test.

It is believed that, matrix test can discern the thick iron baffle plate of 20cm back for example, the length of side is the HANM cube of 4.5cm, as the uranium cube.Can carry out the matrix test separately, perhaps can carry out the matrix test together with any or all of other test described here or other known test of this technical field.For example, if the preliminary dimension that the area of article 410 is tested less than adjacency discussed above, then this test will not be identified as HANM to article 410.Yet it still may be dangerous HANM, because can smuggle several special nuclear materials (SNM) object in one or more freight transportation instruments, and they is combined into a big object that must be enough to keep nuclear reaction.HANM less than preliminary dimension also can be used in " dirty " bullet.Can utilize less than matrix, test the article of discerning less than in abutting connection with the test predetermined area by matrix in abutting connection with the test predetermined area.When utilizing the matrix test-based examination less than the low TR pixel in the zone of test preliminary dimension, only needing to select is not that low TR pixel greater than the object part of preliminary dimension comes to analyze for the matrix test, but this is optional.

Noting, is the article section of HANM with article identification for less article-wherein have only minor matrix (as 3 * 3 picture element matrix B3) just to surround to be enough at least potentially, and the identification of HANM may not resemble use than reliable the large matrix.Yet this potential identification can prove further inspection, as carrying out in other known test of this description or this technical field, checking detailed list of goods and/or carry out manual examination (check).Be also noted that, can compare being different from the mean value of TR of grouping of matrix or other this function and threshold value, to determine whether grouping is HANM at least potentially.For example, as mentioned above, grouping can be the dense area of discerning in the prescan.Can define the border of dense area as mentioned above, can the TR of the pixel of dense area be averaged, and mean value and threshold value are compared.

Threshold calculations

As mentioned above, being preferably each scanning system calculating is used for dividing the threshold value of opening HANM and non-HANM. when calibrating the goods scanning system periodically, can carry out threshold calculations. threshold calculations partly depends on the expectation sensitivity and the selectivity of system. as mentioned above, can with two kinds of the same energy of two kinds of energy that will be used to scan the freight transportation instrument, scan the minimum atomicity little test material of atomicity than be concerned about material (as uranium), determine threshold value thus. preferably, the atomicity of test block is also more than or equal to the atomicity of common approved materials, to avoid wrong report. iron, nickel and copper are the examples of preferred test material.

Test block preferably has variable thickness, makes to pass through calculated threshold under the different transmissions of test block.For example, test block can be a wedge shape or step-like.Thickness can be corresponding to the expectation transmission range of acceptable material and HANM.The threshold value of calculating under different-thickness can be used together with the test philosophy of the synthetic pixel that is applied to have corresponding transmission.For example, the thickness of test block can be from about 1mm to about 400mm.Can use the transmission under arbitrary energy end points.If it is test block is a stepped appearance, then poor to the TR basis of calculation of crossing over each ladder.If it is test block is a wedge shape, then poor to the special thickness TR basis of calculation partly by wedge.For every kind of thickness, can use row or an a few column data.During checking object, utilize this standard deviation between the transmission of measuring, to carry out interpolation, to calculate based on the threshold value between the threshold value that test block was calculated.As selection, can use the calculated threshold of the most approaching measurement transmission, but this may be not as accurate like that.

Under every kind of thickness, calculate TR, and TR is sued for peace and on average.As this technical field known, measured value is that the probability as the measured amount statistics variations of TR is the function of the distance between the arithmetic mean that distributes of measured value and the measured value considered.Measure this distance with standard deviation.In table, represented this probability, and this probability is well-known in this technical field.For example, the measured value that departs from 3 standard deviations with the arithmetic mean of a plurality of measured values is that the probability of statistics variations is about 0.0013.This probability is a false alarm rate, is 13/10000ths in this example.Therefore, be the probability of the statistics variations of actual TR for reducing TR with 0.0013 incorrect probability, in this example, under every kind of thickness, select 3 standard deviations to come calculated threshold.Employed standard difference can be an integer, for example is 3 in this example, can be non-integer perhaps, as 2.5.Preferably, under every kind of thickness, use identical standard deviation.

For obtaining different sensitivity and selectivity, can deduct different standard differences from the average T R of the low atomicity material of test block, suppose that any given transmitted radiation measurement can be from HANM or non-HANM, the standard difference that selection will deduct from the TR of low atomicity material is to realize accepting reporting number by mistake and to fail to report expectation balance between the number.For example, deduct 8 standard deviations from the TR that hangs down the atomicity material and will cause 0 wrong report, but may cause the unacceptable number of failing to report.As mentioned above, if can tolerate more wrong report, then can consider standard deviation.

If make measurement under the higher-energy end points divided by the measurement under the more low-yield end points, then the average T R from test block deducts standard deviation.If make measurement under the more low-yield end points divided by the measurement under the higher-energy end points, then make the average T R of test block add the standard difference.The certain criteria difference will be determined the sensitivity and the selectivity of system.

Figure 13 has described can be by carrying out method 1200 examples with calculated threshold as the processor of computing machine.In step 1210, under multiple thickness, by the goods scanning system, the radiation that utilization has as the first high-energy end points of 9MeV comes the sweep test part.And in step 1210, each pixel is surveyed the radiation that sees through test block.On the contrary, can at first under 5MeV, scan.

Then,, utilize second radiation beam have less than the first energy end points to come the sweep test part as the second energy end points of 5MeV in step 1220, and to surveying the radiation that under multiple thickness, sees through test block with the corresponding a plurality of pixels of the pixel of step 1210.In step 1230,, calculate the TR of synthetic pixel thus for the transmitted radiation (or vice versa) that respective pixel, transmitted radiation that 9MeV is measured are down measured down divided by 5MeV.

In step 1240, the standard deviation of definite TR that is calculated. preferably, under every kind of thickness of test block, calculate the standard deviation of TR, to be used between the threshold value of being calculated, carrying out interpolation during the actual measurement. can come the basis of calculation poor according to following formula:

S = \sqrt{\frac{Σ_{i = 1}^{N} {(x_{i} - \overset{&OverBar;}{x})}^{2}}{N - 1}},

X wherein _iBe the measurement degrading radiation of pixel i, x is the arithmetic mean (mean value) of the measurement degrading radiation of all pixels, according to formula

Calculate x, and N is a pixel count.In this illustrative example, the standard deviation of the thermometrically of the transmitted radiation of being calculated is 0.2.Other statistical method can be used together with the different distributions of measuring degrading radiation.

In step 1250, calculate the average T R of the TR under every kind of thickness.In step 1260, calculate the threshold value under every kind of thickness.Preferably,, depend on the sensitivity and the selectivity of expectation, the average T R under every kind of thickness of test block is regulated integer or a non-integer standard deviation, calculated threshold thus in step 1250.In step 1270, the threshold value that storage is calculated.For example, can be stored in the threshold value under every kind of thickness of test block in the threshold data storehouse with corresponding transmission and standard deviation relatedly.

Utilization is based on the threshold value that may be approximately 4.5 iron average T R, distinguishes 4.5cm * 4.5cmHANM of embedding in 2 meters length of side agricultural product cubes (may have about 7 TR) (may have about 2.5 TR), may be difficult.Because the atomicity of typical agricultural product,, distinguishes HANM and agricultural product with required statistical precision so compare with HANM is distinguished with iron more away from the atomicity of HANM easilier than the atomicity of iron.In order to improve the sensitivity and the selectivity of HANM identification, can select threshold value according to the content of the freight transportation instrument of checking.Therefore,, then can utilize agricultural product or represent the material of agricultural product such as the TR of plastics or water replaces the TR of iron or other this material, determine threshold value if known freight transportation instrument is equipped with agricultural product.For example, can use

Or As mentioned above, preferably use the test block of variable thickness.Also can be stored in the threshold value of calculating in the threshold data storehouse, for the usefulness of above-mentioned inspection technology about grouping.

For example, can obtain the information of enough contents about the freight transportation instrument by the customs detailed list of goods.The cargo type that the typical detailed list of goods statement permission that the consignor or the owner submitted to of freight transportation instrument is loaded and transported in the freight transportation instrument is as agricultural product, industrial product etc.

Figure 14 is an example of selecting the method 1600 of threshold value according to the content type of stating in the detailed list of goods.Check detailed list of goods in step 1605, to determine whether freight transportation instrument 104 is equipped with industrial product.If industrial product is housed, then for example select aforesaid threshold value, as the threshold value of the content that will be used to analyze freight transportation instrument 104 based on iron and probe radiation in step 1610.On the contrary, threshold value can be based on copper or nickel.If detailed list of goods is not pointed out the freight transportation instrument industrial product is housed, then determine in step 1615 whether detailed list of goods points out that the freight transportation instrument is equipped with agricultural product.If agricultural product are housed, then select threshold value based on agricultural product, be used to analyze the content of freight transportation instrument.If agricultural product are not housed, then in the threshold value of step 1610 selection based on iron.Can check the detailed list of goods of the freight transportation instrument of checking by the operator, come implementation method 1600.Then, the operator can import the threshold value or the sets of threshold values that will be used for above-mentioned test.For example, if imported detailed list of goods electronically, then can implementation method 1600 as the processor of computing machine.

The nuclear test

Other X-ray scanning and/or analytical technology can be used together with above-mentioned technology about grouping, conclude that with further raising suspect pixel is the precision of HANM, and reducing false alarm rate. above test determines that whether any material in the freight transportation instrument can be classified as HANM.HANM can be that nuclear material is (fissible, easily fission or the appreciation material), need discern existing of nuclear material with high sensitivity and selectivity. as mentioned above, uranium-235, plutonium-239 and uranium the-the 233rd, the example of easy fissioner. fissile material comprises that easy fissioner and uranium-238. appreciation material comprise the uranium-238 that can be transformed into plutonium-239, and some easy fissioners than the easier experience fission of other material of thorium-232. that can be transformed into uranium-233 are called as special nuclear material (SNM). current, the definition SNM of U.S. Nuclear Regulatory Commission comprises plutonium, uranium-233 or be rich in isotope uranium-233 or the uranium of uranium-235. as this technical field known, because after causing the nuclear fission of nuclear material owing to the X-radiation exposure that is subjected to enough energy, the β decay has taken place, make nuclear material after exposure, launch the delayed neutron of 1～2 μ s. because non-nuclear material is not launched delayed neutron, so the existence of delayed neutron can be used for discerning the existence of nuclear material. for example, can survey delayed neutron with neutron detector, and the delayed neutron counting to surveying. following further discussion neutron detector.

Depend on material for bringing out the required least energy of nuclear material photofission, this least energy is called as photofission or fission threshold value.Table I has identified the chosen elements fission threshold value of being calculated according to the superfluous value of material (mass excess value) of chosen elements.Obtain the superfluous value of this material from NuclearWallet Cards, can be from NNDC Brookhaven Laboratory, January, 1985 obtain Nuclear Wallet Cards.The current version of Nuclear Wallet Cards can obtain at www.nndc.bnl.gov/wallet/wallet-2000.pdf.Note, in the very short time (10 that is subjected to the X-radiation exposure ^-15Second) in, nuclear material and non-nuclear material can produce photoneutron (photoneutron).Photoneutron is absorbed by the parts of material in the container and X-ray scanning system.Table I has also shown the threshold value for the photoneutron emission of selected nuclear material.At http: //+2.1an/gov/data/photonuclear.html is from T-2Nuclear InformationService, and Los Alamos obtains the photoneutron data.Also can be easily from these those skilled in the art other known multiple source obtain photofission and photoneutron data.

Table I

Interact Type	The U-233 threshold Value	The U-235 threshold Value	The U-238 threshold Value	The Th-232 threshold Value	The Pu-239 threshold Value
Interact Type	The U-233 threshold Value	The U-235 threshold Value	The U-238 threshold Value	The Th-232 threshold Value	The Pu-239 threshold Value	Photoneutron (γ, n), MeV	5.7	5.3	6.1	6.4	5.6
Photofission (γ, f), MeV	5.1	5.8	5.8	5.0	5.4	Photoneutron (γ, n), MeV	5.7	5.3	6.1	6.4	5.6

Because the fission threshold value of all nuclear materials all in the scope of the extremely about 5.8MeV of 5.0MeV, will be brought out photofission and delayed neutron so utilize the X-radiation of about at least 5.8MeV to scan nuclear material in all these materials.Energy brought up to will increase the delayed neutron number that will launch more than the threshold value, be convenient to like this survey.As in the above example, can use 9MeV.Preferably, when closing X-ray beam, and after the photoneutron emission stops, surveying delayed neutron.In addition, till now, there is not the x-ray photon that may disturb delayed neutron counting yet.

The example of the sequence of operation of surveying the delayed neutron that produces owing to photofission is described now. at first, in time t=0 second, electronic impulse string bump target with the 9MeV electronics, produce x-ray photon thus, as this technical field known. these x-ray photons are calibrated, and they being projected on the freight transportation instrument of examine. normal several microseconds that continue are ganged up in electronic impulse. and the representative value of pulse width is between 2.0 to the 4.5 μ s. produce 1.0～2.0 μ s after finishing at x-ray photon, connect neutron detection system, to survey delayed neutron from nuclear material (if existence) photofission. acquisition time can last till that next electronic impulse string will be transmitted into till the time point of target, 2.5～5.0 milliseconds (ms) behind time t=0 typically. this second train of impulses can be 9MeV or 5MeV. for example, can connect neutron detection system in each high energy pulse string (is 9MeV at this) back. in another example, (for example under two energy end points, scan after only in TR test pixel indication synthesized image pixel array, may having HANM aforesaid, calculate after TR and the analysis result), just connect neutron detector.

Can be to whole freight transportation instrument or only the photofission result is analysed in the suspicious differentiation of freight transportation instrument.Suspicious district can be that the synthetic pixel or with the TR that is lower than threshold value is combined into pixel, and may there be HANM in indication.In an example, the identification in suspicious district may have unacceptable sensitivity and selectivity, impels further test thus.In another example, if discerned HANM, then can analyze the photofission result, to determine whether to exist SNM or other nuclear material with acceptable sensitivity and selectivity.

The detection of any delayed neutron is all indicated in the freight transportation instrument and is had nuclear material.Also can discern the general position of this nuclear material, as this technical field known.In addition, identity that can the definite kernel material.Can the experiment counting by bringing out a plurality of delayed neutrons that the SNM photofission produced with different peak energies and the fall time of delayed neutron be organized in 5 or 6 scopes, each scope is all corresponding to special nuclear material.The delayed neutron counting of tested object and these scopes are compared, enable to discern special nuclear material (and atomicity).Delayed neutron counting and neutron detection technology are that this technical field is known in real time.For example, see Tsahi Gozani, the active non-destructive analysis of nuclear material (national technical information service 1981), the 173rd～205 page of (Tsahi Gozani, Active Non-Destructive Analysisof Nuclear Materials (National Technology Information Service 1981), pp.173～205).

Confirm further that if desired specific position in the freight transportation instrument exists as the nuclear material (for example before carrying out manual examination (check)) of SNM, can bring out another time photofission and react in the nuclear material photofission peak energy scope of 13MeV to 15MeV.This that carry out at high level more scans the delayed neutron number that photofission is produced for the third time and reaches at most, is convenient to neutron detection.Can or under other energy end points, produce the same radiation source of radiation by radiation source separately, the high-energy radiation bundle is provided.

Figure 15 a is the example of the method 1700 of neutron detection according to an embodiment of the invention.In step 1710, for example apparatus comes the part of scanning object just like the radiation of the low-yield end points of 5MeV.In step 1720, the radiation behind detection and the object interaction.In step 1730, apparatus comes the counterpart of scanning object just like the radiation of the high-energy end points of 9MeV, and step 1740 survey and object interaction after radiation.The object part that the object part can be crossed by the radiation beam under each radiation end points.For example, if radiation beam be shaped as fan beam, the object sheet that crossed by two radiation beams of each part of object then.Can scan round between 5MeV and 9MeV radiation beam, up to having collected till the enough number of pixels that cover enough areas implement one of test discussed above or other test.

In step 1744, analysis result.Analysis can comprise above-mentioned any test.Can carry out HANM identification to a pair of counterpart fast enough, whether connect neutron detection system with decision.As selection, according to above-mentioned test, existing of exist with expectation sensitivity and selectivity indication HANM or enough number of pixels can impel the activation of neutron detection system.

If do not suspect it is HANM, then to another part repetition methods 1700 of object.

If in step 1746, suspect it is HANM, then activate neutron detection system in step 1750.As mentioned above, preferably after the end of scan of 9MeV (in this example), neutron detection system is activated 1.0～2.0 μ s.

Then, determine whether to detect delayed neutron in step 1760. if such, then provide indication to have the output of delayed neutron in step 1770. if not so, be over if then another part repetition methods 1700. whole objects of object all are scanned, then also provide the indication delayed neutron to survey the output of failure.

According to another embodiment, if after other any test, suspect and have HANM or nuclear material, comprise above-mentioned test and this technical field known other test, then can examine test.For example, at first can carry out U.S. Patent No. 5,524, the 133 described dual energy ratio tests as being incorporated herein by reference, the real material content of coming preliminary recognition object is to determine whether object comprises special nuclear material at least potentially.U.S. Patent No. 5,524,133 have below been described in more detail.For example, can in the step 1774 of the method 1700 of Figure 15 a, carry out this dual energy test in more detail.Also can only under an energy end points, test.Initial testing may relate to result's the automatic analysis and/or the visual analysis of one or more image.If can not discern the object of being found, then also can after manual examination (check), examine test.

Figure 15 b is the example according to the method 1800 of this embodiment.In step 1810, at least a portion of object is carried out first test.Then, determine whether to suspect at least nuclear material in step 1820.If not, the remainder of test object if desired then, method just turns back to step 1810.Be over if whole object all scans, then can provide indication not suspect the output that nuclear material exists.

If suspect to have nuclear material, then in step 1830 with enough energy scan objects, to bring out delayed neutron, so that examine test.Can use the radiation beam of 5.8MeV energy end points at least.Then, check the detection of delayed neutron in step 1840.If detect delayed neutron, then identify the result that nuclear material exists in step 1860 output indication in step 1850.If do not detect delayed neutron in step 1850, then method turns back to step 1810 scanning object another part.Be over if whole object all scans, and do not detect delayed neutron, then also can provide suitable output.If in first test of step 1810, use sufficiently high energy, then needn't execution in step 1830.

Scanning system

Figure 16 is programmed so that implement the front elevation of example of the goods scanning system 2000 of the embodiment of the invention.Transmitter system 2020 supports and transmits freight transportation instrument 2040 by scanning system 100 between x-ray source 2060 and detector 2070.For example, transmitter system 2020 can be mechanically operated travelling belt, track or mechanically operated roller.X-ray source 2060 makes the radiation beam R of bremstrahlen X-radiation point to freight transportation instrument 2040.Barrier shield 2080 surrounds x-ray source 2060 and detector 2070.Transmitter system 2020 runs through the opening of barrier shield 2080, enters and withdraws to allow freight transportation instrument 2040.

Freight transportation instrument 2040 is transmitted device system 2020 and transmits by shielding tunnel 2100.Tunnel 2100 has first window 2110 and second window 2120, is delivered to freight transportation instrument 2040 and is delivered to detector array 2070 from freight transportation instrument 2040 from x-ray source 2060 to allow X-radiation bundle R.If radiation beam R and transmitter system 2020 intersects, and transmitter system 2020 is travelling belt or track, then causes the material of low attenuation can be used for travelling belt or track.If transmitter system 2020 comprises roller, then if necessary, can between a plurality of rollers, the gap be set.If necessary, also can in the structure that supports transmitter system 2020, window be set.Can between freight transportation instrument 2040 and detector 2070, the collimating apparatus (not shown) be set, arrive detector with the radiation that stops scattering.Can make transmitter system 2020 counter-rotatings, to check freight transportation instrument 2040 part and whole freight transportation instruments once more.As discussed further below, for example when freight transportation instrument 2040 just is being transmitted through scanning element 2000, can be by x-ray source 2060 being circulated between two energy end points fast or, utilizing multiple energy exposure freight transportation instrument 2040 by two adjacent x-ray sources are provided.

Collimating apparatus 2140 is stretched out from the end of x-ray source 2060. and collimating apparatus 2140 comprises the slit (not shown), this slit is formed the shape that the X-ray beam that x-ray source 2060 is launched is calibrated to expectation, as be calibrated to fan beam or conical beam. for example, slit can have vertical arc, this vertical arc changes, has the vertical fan of arc θ with definition from spending about 50 degree less than 1, and from about 5 spend about 45 degree change, with the definition conical beam. slit also can have other shape.

Detector 2070 is electrically connected to image processor 2160, and image processor 2160 is connected to display 2180.Image processor 2160 comprises analog to digital conversion and digital processing unit, as this technical field known.Processor such as computing machine 2200 are electrically connected to x-ray source 2060, detector array 2070, transmitter system 2020, image processor 2160 and display 2180, and control the one or more operation in them.Be reduced graph, not the connection between video-stream processor 122 and all parts.Processor 2200 can be programmed for and implement above-mentioned any or all of test.Processor 2200 can provide some or all processing capacities of image processor 2160.Though show a processor 2200, additional processor or computing machine also can be provided.Can differently arrange and be connected image processor 2160, computing machine 2200 and display 2180.For example, image processor 2160 can be the part of computing machine.Can come programmed computer with software and/or hardware, to implement above-mentioned any or all of test.In an example, for example can implement this program by special IC (ASIC).

Detector 2070 can be a detector array.The configuration of detector 2070 can be depended on the shape of the radiation beam R that is calibrated.For example, if radiation beam R is calibrated to fan beam, then can provide the one dimension detector array 2040 that comprises delegation's detecting element.If the radiation beam that is calibrated is a conical beam, as asymmetric pyramid cone-beam, then detector array can be the two-way detector array 2040 that comprises two row or the adjacent detecting element of multirow.Detector array 2040 can comprise a plurality of detector modules, and each detector module comprises delegation or the multirow detecting element that is supported in the shell, as this technical field known.Detector or detector array can be straight line or L shaped.The cut-open view of Figure 16 has shown the horizontal arm 2070a of L shaped detector array.Figure 19 discussed below has also shown L shaped detector.If use L shaped detector in Figure 16, then x-ray source 2060 can be positioned at following upright position, and radiation beam R will intersect with horizontal arm 2070a more, and the vertical component 2070b of detector 2070 can be shorter.

As this technical field known, detector 2070 can be a photon detector, as comprises the photodiode detector array of inorganic scintillation crystal (scintillator).For example, can use cadmium tungstate (CdWO ₄) scintillation crystal.Also can use amorphous silicon (aSi) detector, as can be from Varian medical system company limited (VarianMedical Systems, Inc., Palo Alto, the PaxScan that California) obtains of California Palo Alto ^TMDetector.

Neutron detector

2072,2074,2076 and 2078 is preferably located in a plurality of positions around the cargo container, to survey the neutron in all direction isotropy ground emissions.For example, can support neutron detector 2072 with x-ray source.Can support neutron detector 2074 with detector 2070.Can support neutron detector 2076 (seeing 2076a) with the top of detector 2070 or the upright arm of L shaped detector.Can support neutron detector 2078 with transmitter system 2020 or other certain part of scanning system below the freight transportation instrument 2040.

Neutron detector 2072～2078 can be to be full of ³The cylinder proportional counter of He.For example, they can have the effective length of about 15～25cm, for the usefulness of freight transportation instrument 2040.In an example, counter is covered by cadmium (Cd) and polyethylene layer.The cadmium layer is used for absorbing the thermal neutron as " slow neutron ".Fast neutron is at quilt ³Before the He detector detects, in polyethylene layer by thermalization.Therefore, in the 3He detector, only detect delayed neutron.For example, can be commercial from Canberra Industries, Meriden, CT obtains suitable neutron detector.

Figure 17 is the top view of a part of the example of goods scanning system 2000a, it has shown two adjacent radiation source 2060a and 2060b, each radiation source all produces the radiation with different-energy end points. and system's 2000 components identical of Figure 16 are numbered in the same manner. and transmitter system 2020 is between the first x-ray source 2060a and the first detector 2070a, and second between x-ray source 2060b and the second detector 2070b, supporting and transmit freight transportation instrument 2040 makes radiation beam R1 and R2 for example point to freight transportation instrument 2040. by scanning system 2000a.X radiographic source 2060a and 2060b, x-ray source 2060a can produce the first radiation beam R1 with the first X ray energy end points of 5MeV, and x-ray source 2060b can produce the second radiation beam R2 with the second energy end points of 9MeV, or vice versa .X radiographic source 2060a and 2060b are positioned at the equal angular with respect to freight transportation instrument 2040, and being positioned at same surface level. they can be close to, perhaps they can be separated from each other placement. also they can be placed to one on another. it is believed that, in system, can in about 30 to 60 seconds, check 40 feet container with two x-ray sources.

For checking the freight transportation instrument 2040 of width greater than about 5 feet (1.5 meters), x-ray source 2060a, 2060b preferably produce to have greater than the approximately radiation of the energy end points of 1MeV.As mentioned above, for example can use 5MeV and 9MeV.For example, be used for width and comprise 1MeV and 9MeV and 5MeV and 15MeV greater than other example of energy end points of the freight transportation instrument of about 5 feet (1.5 meters).In order to carry out neutron test, one of energy end points need be 5.8MeV at least.For example, x-ray source can be a linear accelerator, as can be from Varian medical system company limited (Varian MedicalSystems, the Inc. of California Palo Alto, Palo Alto, CA) (" Varian ") accelerating potential that obtain, that have suitable level

Linear accelerator

At Varian

In, 360 pulses of per second output.For example, Varian

Aperture angle with about 20～30 degree.For example, also can use other x-ray source, as electrostatic accelerator, microtron and betatron.Radiographic source also can comprise the radiographic source based on carbon-12 (C-12), cobalt-60 (Co-60), plutonium-beryllium (Pu-Be) and/or americium-beryllium (Am-Be).In checking the process of width, also can use the X-ray tube of emission keV scope energy less than the object of about 5 feet (1.5 meters).For this less object, can use the energy of a kind of 1MeV of being lower than and the energy of a kind of 1MeV of being higher than.For example, can use 600keV and 5MeV.Two kinds of energy also can be all below 1MeV.For example, can use 120keV and 200keV, as long as radiation can penetrate checked object.

For example, as the U.S. Patent No. 5,682 that is incorporated herein by reference, 411 and No.6, described in 438,201, also can use single X-ray beam with monoergic end points and monoergic sensing detector array together, to survey the high part and the lower part of power spectrum respectively.Described in these patents, the different piece of detector array such as interlacing, possibility can be more responsive to a kind of radiation of energy.

Also can use the single radiation source that between the energy end points, switches.The U.S. Patent application No.10/957 that submits on October 1st, 2004, among 212 " standing wave particle beam accelerator (the Standing Wave Particle Beam Accelerator) ", can find the description of suitable radiation source, this patented claim has been transferred to assignee of the present invention and has been introduced into by reference herein.In U.S. Patent No. 6,366,021B1, No.4 have also described other linear accelerator that can be used among the present invention in 400,650 and No.4,382,208, these United States Patent (USP)s also be transferred to assignee of the present invention and at this by with reference to being introduced into.The technology of utilizing mechanical switch such as relay and other type of switch such as solid-state switch to switch energy is well-known.For example, can realize about 100 milliseconds switching speed, so that at the long freight transportation instrument of 20 feet of a few minutes interscans (6.1 meters).

In another example, above-mentioned technology can be used for mobile system, so that the freight transportation instrument that real-time inspection truck and tractor-trailer are delivered. for example, can test at the highway rest station. system can comprise two scalable tractor-trailer, as the U.S. Patent application No.10/455 that submitted on June 6th, 2003,864 (' 864 patented claims), this patented claim has been transferred to assignee of the present invention, and be introduced into by reference at this. in the described example of ' 864 patented claim, a scalable tractor-trailer delivery x-ray source. another scalable tractor-trailer delivery x-ray photon detector and data analysis facilities. can be being compressed, telescopic trailer under the contraction state is driven to the inspection post, launch in the inspection post, the luggage of going forward side by side is equipped with just scanning. then, can be parked in the truck that will check between two trailers. then, the expansion telescopic section that makes radiation source and detector stride across each trailer as one man moves, with scanning freight transportation instrument.

The perspective diagram of the motion scan system 2300 described in ' 864 patented claim that Figure 18 is.Freight transportation instrument 2302 is by truck or tractor-trailer 2304 deliveries.Also show the radiation source 2306 of emission fan beam 2307 and comprise horizontal component 2308a and the part of the L shaped photon detector 2308 of vertical component 2308b.Be reduced graph, do not show the flexible trailer that is used to support radiation source 2306 and detector 2308.A neutron detector 2310 is supported by radiation source 2306, and another neutron detector 2312 is supported by the horizontal component 2308a of detector 2308, and another neutron detector 2314 (shown in Figure 19) is by the vertical component 2308b support of detector 2308.

Figure 19 is system's 2300 schematic rear views along the line 19-19 of Figure 18.Components identical is numbered in the same manner.Additional neutron detector 2314 is supported by upright arm 2308b.Can be placed on another neutron detector 2316, among the trench T of the ground G when parking truck or trailer under freight transportation instrument 2302 positions.Also can use vertical probe 2304, shown in the patented claim of ' 864.Under the sort of situation, for example can be supported on neutron detector 2314 near the top or top of vertical probe.Detector 2308～2316 can be connected to as shown above on the processor or computing machine with the test of describing, be programmed to implement above-mentioned any or all embodiment.For example, radiation source 2306 can be the single radiation source that alternately produces 9MeV and 5MeV X-radiation bundle.For example, also can pile up two radiation sources, perhaps they are close to placement mutually, one is used to produce the first energy emission bundle, and another is used to produce the second energy emission bundle.Can utilize above-mentioned any or all of test to survey HANM and nuclear material automatically.

Though the present invention is particularly suitable for scanning contraband goods freight transportation instrument, also can easily make the present invention be suitable for scanning other object, as luggage and handbag on airport and harbour.

In addition, though described x-ray source in above example, for example radiation source can provide the radiation of other type, as time-delay neutron beam or gamma ray.

In above example, the transmission that makes the higher energy (for example 9MeV) by the freight transportation instrument is divided by the transmission than low-energy radiation (for example 5MeV) by the freight transportation instrument, and with generation TR, and the test philosophy of potential HANM is that TR is less than threshold value.Yet, as mentioned above, can make than the transmission of low-energy radiation transmission divided by higher energy, in this case, in above all examples, all will regard the TR that is higher than threshold value as potential HANM.In addition, can be according to the attenuation under two energy end points, rather than radiation transmission, calculate TR.

Those of ordinary skills should be realized that, under situation about not breaking away from by following spirit and scope defined in claim of the present invention, can make other change to embodiment described here.

Claims

1. method of checking the content of object, this method comprises:

First with the first radiation beam scanning object of first energy;

Survey first radiation after first radiation beam and first interact;

Come the second portion of scanning object with second radiation beam of second energy that is different from first energy;

Survey second radiation after second radiation beam and second portion interact;

First and second portion to correspondence calculate first function of the radiation of being surveyed under first energy and second energy;

The first of a plurality of correspondences and first function of second portion are grouped at least one group;

First function and the criterion based on predetermined atomic number are at least in part compared;

Based on first that satisfies a plurality of correspondences in this at least one group of criterion and at least some first function in the second portion, calculate second function at least in part; And

Based on this second function of at least one group, determine whether object comprises the high atomic number material of atomic number greater than described predetermined atomic number at least potentially at least in part.

2. method according to claim 1, wherein:

The projection of at least a portion on detector of first radiation beam by each part defines each first pixel;

The projection of at least a portion on detector of second radiation beam by each part defines each second pixel;

Calculating first function comprises: first function that first and second pixels of correspondence is calculated the radiation of surveying under first and second energy;

The grouping of first function is comprised: first function of a plurality of respective pixel is grouped at least one group; And

Calculating second function comprises: first function according at least some pixels of a plurality of pixels in this at least one group, calculate second function.

3. method according to claim 1 comprises:

First function is grouped at least one inspection hatch with pre-sizing;

By first number of functions that satisfies criterion in the inspection hatch is counted, calculate second function; And

Number and the predetermined number counted are compared, to determine whether object comprises high atomic number material at least potentially.

4. method according to claim 3, wherein:

Predetermined number is at least in part based on predetermined rate of false alarm.

5. method according to claim 1 comprises:

First function in abutting connection with the first and second corresponding parts that satisfies criterion is divided into groups;

Calculate the area of grouping: and

This area and predetermined area are compared, to determine whether object comprises high atomic number material at least potentially.

6. method according to claim 1, wherein, at least one at least one matrix of grouping definition, and second function is mean value, and this method comprises:

Calculate first average value of a function of first and second parts of a plurality of correspondences at least one matrix; And

This mean value and criterion are compared, to determine whether object comprises high atomic number material at least potentially.

7. method according to claim 1 wherein, compares first function and criterion and comprises:

First function and threshold value are compared.

8. method according to claim 7 further comprises:

Come calculated threshold by following steps at least in part:

Scan with the 3rd radiation beam of first energy and to comprise that atomic number equals at least a portion of second object of the material of predetermined atomic number;

The 3rd radiation after at least a portion of surveying the 3rd radiation beam and second object interacts;

Scan at least a portion of second object with the 4th radiation beam of second energy;

The 4th radiation after at least a portion of surveying the 4th radiation beam and second object interacts; And

First function of the radiation that calculating is surveyed under third and fourth energy.

9. method according to claim 8, wherein, at least a portion that scans second object comprises:

Scanning comprises atomic number at least a portion less than second object of the material of uranium atom ordinal number.

10. method according to claim 9 comprises:

Scanning comprises atomic number at least a portion less than second object of the material of lead atom ordinal number.

11. method according to claim 10 comprises:

At least a portion of second object that scanning is selected from the group that comprises iron, copper and mickel.

12. method according to claim 10 comprises:

Scanning comprises at least a portion of second object of plastics.

13. method according to claim 8 comprises:

Scanning comprises a plurality of objects of multiple different materials, to calculate a plurality of threshold values; And

Select the threshold value of the usefulness of confession criterion at least in part according to the object content of expection.

14. method according to claim 1, wherein:

First energy is greater than second energy;

Calculating first function comprises and makes first radiation divided by second radiation: and

First and second parts that satisfy the correspondence of criterion have first function less than threshold value.

15. method according to claim 1, wherein:

First energy is less than second energy;

Calculating first function comprises and makes first radiation divided by second radiation; And

First and second parts that satisfy the correspondence of criterion have first function greater than threshold value.

16. method according to claim 2 comprises:

Survey first radiation and second radiation by the detecting element of detector;

Wherein, first radiation and second radiation of surveying by single detecting element defines first and second pixels respectively.

17. method according to claim 16, wherein:

The projection that produces first and second pixels is to obtain from seeing through overlapping at least half the projection of object part.

18. method according to claim 7 further comprises:

Select threshold value according to the radiation of surveying down one of at least in first radiation and second radiation.

19. method according to claim 1 further comprises:

If object comprises high atomic number material at least potentially, just survey delayed neutron; And

According to whether detecting delayed neutron, determine whether described high atomic number material is nuclear material at least in part.

20. method according to claim 1, wherein:

The projection of at least a portion on detector of first radiation beam by each first defines each first pixel;

The projection of at least a portion on detector of second radiation beam by each second portion defines each second pixel;

Calculating first function comprises: to calculating the ratio of first function of radiation and second function of radiation, every pair of respective pixel all produces has the synthetic pixel of ratio separately to many each in first and second pixels of correspondence;

Described method also comprises: ratio separately is stored in the array that comprises the row and column corresponding with synthetic pixel;

Wherein first function and criterion are compared and comprise: ratio compares with threshold value as the function of being scheduled to atomic number separately; And

Wherein by select to comprise the multirow of lining up array and multiple row separately at least one inspection hatch of ratio calculate second function, and in window, the ratio number that satisfies criterion is counted; And

Described method also comprises: whether basis at least in part, the number of ratio separately that satisfies criterion in each of this at least one inspection hatch determine whether object at least potentially comprise atomic number material greater than predetermined atomic number greater than predetermined number.

21. method according to claim 20, wherein, predetermined number is at least in part based on predetermined rate of false alarm.

22. method according to claim 20, wherein, the size of inspection hatch is corresponding to the scantling of the nuclear reaction of can controlling oneself.

23. method according to claim 20, wherein:

The first and second corresponding pixels are to obtain from seeing through overlapping at least half the projection of object part.

24. method according to claim 1, wherein:

The projection of first radiation beam on detector by each first defines each first pixel;

The projection of second radiation beam on detector by each second portion defines each second pixel;

Calculating first function comprises: many first and second pixels to correspondence are calculated the function of first probe radiation and the ratio of functions of second probe radiation, and every pair of respective pixel all defines has the synthetic pixel of ratio separately;

First function and criterion compared comprise: will synthesize the ratio of pixel and compare with threshold value as the function of being scheduled to atomic number;

Described method also comprises: discern its separately ratio satisfy about the criterion of threshold value at least one group in abutting connection with synthetic pixel;

Wherein calculating second function comprises: this each group area and predetermined area of being covered of at least one group are compared; And

Described method comprises: compare according to second at least in part, determine whether object comprises the material of atomic number greater than predetermined atomic number at least potentially.

25. method according to claim 24, wherein, predetermined area is corresponding to the high atomic number material size of the nuclear reaction of can controlling oneself.

26. method according to claim 24 further comprises:

Calculate the mean ratio of a plurality of adjacent pixels;

Mean ratio and threshold value are compared; And

At least in part relatively, determine whether object comprises the material of atomic number greater than predetermined atomic number at least potentially according to this.

27. method according to claim 24, wherein:

Overlapping at least their half of area separately of the first and second corresponding pixels.

28. method according to claim 1, wherein:

Calculating first function comprises: many first and second pixels to correspondence are calculated the ratio of the function of the function of first probe radiation and second probe radiation, and every pair of respective pixel all produces has the synthetic separately pixel of ratio separately;

Described method also comprises: a plurality of synthetic pixels are divided into groups;

Wherein calculating second function comprises: the function that calculates the ratio of grouping; And

Described method also comprises: this second function and threshold value are compared; And

Described method comprises: at least in part according to this second comparison, determine whether object comprises the material of atomic number greater than predetermined atomic number at least potentially.

29. method according to claim 28, wherein, function is mean value or intermediate value.

30. method according to claim 28 further comprises:

Select synthetic pixel, this synthetic pixel has the ratio that satisfies about the criterion of ratio and threshold value; And

Come a plurality of pixels are divided into groups with respect to selected pixel.

31. method according to claim 30 comprises:

Being grouped into the synthetic pixel of a plurality of adjacency with selected synthetic pixel is the matrix at center.

32. method according to claim 31 further comprises:

Calculate second mean value of the ratio of second matrix, this second matrix is center and greater than first matrix with selected synthetic pixel;

Second mean value and threshold value are compared: and

Compare according to the second and the 3rd at least in part, determine whether object comprises high atomic number material at least potentially.

33. method according to claim 28, wherein:

The first and second corresponding pixels be from see through overlapping at least they separately the projection of the object part of half of the area obtain.

34. method according to claim 28, wherein, predetermined area is corresponding to the high atomic number material size of the nuclear reaction of can controlling oneself.

35. method according to claim 2 also comprises:

Second function and the predetermined criteria that is independent of object are compared; And

Based on described comparison, determine whether object comprises high atomic number material at least potentially at least in part.

36. method according to claim 1, wherein, predetermined atomic number is at least 26.

37. method according to claim 36, wherein, predetermined atomic number is at least 74.

38. according to the described method of claim 37, wherein, predetermined atomic number is at least 92.

39. method according to claim 1 also comprises:

40. method according to claim 1 wherein, comprises the material that has greater than the high atomic number of predetermined atomic number at least potentially if determine object, then this method also comprises:

Check the detection of delayed neutron; And

Based on delayed neutron whether after scanning, determine whether high atomic number material comprises nuclear material at least in part.

41., comprise that this method also comprises with the first and the second portion of X-ray scanning object according to the described method of claim 40:

Inspection is to the detection of the delayed neutron of generation by the content interaction of X ray and object; And

At least in part based on after with X-ray scanning to the detection of delayed neutron, determine whether high atomic number material comprises nuclear material.

42. method according to claim 1, wherein each of first and second energy is greater than 1MeV.

43. according to the described method of claim 42, wherein said object comprises container.

44. method according to claim 1 comprises whether the content of determining object comprises high atomic number material at least potentially and needn't determine the identity of described potential at least high atomic number material.

45. a system that checks the content of object, this system comprises:

At least one radiation source is used for respectively at least a portion that second radiation beam with first radiation beam of first emittance and second emittance comes scanning object, and wherein, first emittance is different from second emittance;

At least one detector, this at least one detector be placed with survey with object interaction after radiation under first emittance and second emittance;

Be connected at least one processor of detector, this at least one processor is programmed to:

Calculate second function based at least some of first function that satisfies a plurality of firsts in this at least one group of criterion and second portion at least in part; And

Based on this second function of at least one group, determine whether object comprises the high atomic number material of atomic number greater than predetermined atomic number at least potentially at least in part.

46. according to the described system of claim 45, wherein:

The projection of at least a portion on detector of first and second radiation beams by each part defines each first and second pixel respectively;

This at least one processor is programmed to:

First and second pixels of correspondence are calculated described first function of the radiation of under first and second energy, surveying; And

Described first function of a plurality of respective pixel is grouped at least one group.

47. according to the described system of claim 46, wherein, at least one processor is programmed to:

First function of respective pixel is grouped at least one inspection hatch with pre-sizing;

48. according to the described system of claim 47, wherein:

49. according to the described system of claim 46, wherein, at least one processor is programmed to:

First function in abutting connection with respective pixel that satisfies criterion is divided into groups;

Calculate the area of grouping; And

To divide into groups area and predetermined area compares, to determine whether object comprises high atomic number material at least potentially.

50. according to the described system of claim 46, wherein, at least one at least one matrix of grouping definition, and second function is mean value, and this at least one processor is programmed to:

Calculate first average value of a function of a plurality of respective pixel at least one matrix; And

The mean value and the criterion of this at least one matrix are compared, to determine whether object comprises high atomic number material at least potentially.

51. according to the described system of claim 46, wherein, criterion comprises threshold value.

52. according to the described system of claim 51, wherein, at least one processor is programmed to:

According in the radiation that equals with first and second emittance scanning atomic number to be surveyed behind the test material of predetermined atomic number, come calculated threshold at least in part.

53. according to the described system of claim 52, wherein, at least one processor further is programmed to:

54. according to the described system of claim 45, wherein, predetermined atomic number is at least 26.

55. according to the described system of claim 54, wherein, predetermined atomic number is at least 74.

56. according to the described system of claim 55, wherein, predetermined atomic number is at least 92.

57. according to the described system of claim 45, described processor also is programmed to:

58. according to the described system of claim 45, wherein:

At least one radiation source comprises at least one x-ray source; And

Described system also comprises the delayed neutron that second detector produces to survey because from least a portion interaction of the radiation of at least one x-ray source and object, and

At least potentially discerned if described processor also is set to high atomic number material, then checked the detection of delayed neutron.

59. according to the described system of claim 45, wherein each of first and second energy is greater than 1MeV.

60. according to the described system of claim 59, wherein said object comprises container.

61. according to the described system of claim 45, wherein said processor is set to determine the potential at least existence of high atomic number material and the identity that needn't determine described material.

62. a method of checking the content of object, this method comprises:

When the atomic number of all material suspicious at least potentially type of material of definition during greater than predetermined atomic number;

At least a portion with the second radiation beam scanning object of first radiation beam of first energy and second energy different with first energy;

Survey at least a portion interaction first radiation and second radiation afterwards of first radiation beam and second radiation beam and object respectively;

First function of the radiation that calculating is detected under first energy and second energy;

First function and criterion are compared;

Based on first function at least some, calculate at least one second function at least in part; And

Based at least one second function, determine whether object comprises the material in the class material at least potentially at least in part.

63. according to the described method of claim 62, wherein, predetermined atomic number is at least 26.

64. according to the described method of claim 63, wherein, predetermined atomic number is at least 74.

65., comprising according to the described method of claim 62:

Based on described comparison, determine whether object belongs in the described class material at least in part.