Abstract:
A diffraction apparatus ( 10 ) for determining crystalline and polycrystalline materials of an item in objects, preferably in luggage, having a collimation/detector arrangement ( 11 ) and an X-ray source ( 12 ) and which is mounted to be adjustable in an X-ray testing machine ( 13 ). The collimation/detector arrangement ( 13 )is adjustable in height relative to the X-ray source ( 12 ), and the two are also laterally and synchronously adjustable via respective adjustment elements ( 5,6 ). The collimator ( 13 ) has a conically-expanding round slot ( 15 ), which simulates a predetermined angle (Θ M ) of a scatter-beam path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of U.S. application No. 09/645,486 filed Aug. 25, 2000, which is incorporated herein by reference.  
         [0002]    This application is related to concurrently filed U.S. applications (Attorney Docket Nos. 31659-152913A, 31659-152914A, 31659-152918A), and which are continuations of respective U.S. application Ser. Nos. 09/645,484, 09/09/645,485 and 09/645,487, each filed Aug. 25, 2000, the subject matter of each such application being incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0003]    The invention relates to an apparatus for determining the crystalline and polycrystalline materials of an item.  
         BACKGROUND OF THE INVENTION  
         [0004]    To assure safety in air travel, for example, it is necessary to check luggage (object) with travel items (items), particularly for explosive agents or materials, by employing the most modern technical equipment.  
           [0005]    A useful technique for checking for explosives is X-ray diffraction, in which X-rays that are scattered at the crystal structure of an item are measured and compared to the characteristic energy spectra of known explosives. Thus, the measured energies of the diffracted rays can indicate the presence of an explosive, and provide information about the explosive material in the object.  
           [0006]    An apparatus for executing this method is known from DE 195 10 168 A1. Here, at least one screen generates a fanned X-ray beam from an X-ray source, which then irradiates a test region of a material to be tested. On the side of the test region opposite the X-ray source, slot-shaped collimators are disposed symmetrically around the axis of the central X-ray beam, in a plane extending perpendicular to the fan plane of the X-ray beam. A plurality of detectors performs an evaluation over the entire X-rayed test region.  
           [0007]    EP 0 354 045 A2 also discloses an apparatus and a method in which a fanned X-ray beam is generated. As this fanned X-ray beam radiates through the object to be tested, it is diffracted at the lattice structure of the object. A plurality of detectors records the diffraction as an energy spectrum.  
           [0008]    A further apparatus is disclosed in U.S. Pat. No. 4,956,856. In this case, a narrow X-ray beam (pencil beam) is generated, and directed, by a rotating roller having a spiral-shaped slot, at an object to be X-rayed. The pencil beam passes through the slot transversely to the object to be tested.  
           [0009]    DE 41 01 544 A1 discloses the use of a primary beam having a small cross section in an X-ray device. Here, a plurality of detectors and a concentric collimator arrangement detect the scatter radiation generated from the primary beam.  
           [0010]    A drawback of the aforementioned apparatuses for checking luggage is that the entire piece of luggage must always be sampled or scanned by X-ray diffraction in order to ascertain all unacceptable luggage items.  
           [0011]    An arrangement for generating an expanded X-ray bundle is known from DE 41 30 039 A1. A screen arrangement used for this purpose comprises two limiting bodies, which are oriented relative to one another such that they limit a space corresponding to the shape of the ray bundle. This arrangement serves to increase the surface impacted by the X-ray.  
         BRIEF SUMMARY OF THE INVENTION  
         [0012]    In is an object of the invention to provide an apparatus of the general type discussed above, for quickly determining the crystalline and polycrystalline materials of an item.  
           [0013]    The above object generally is achieved according to the present invention by an apparatus that includes a diffraction apparatus with a collimator/detector arrangement, an X-ray source that is aimed at the collimation/detector arrangement, and a computer. The collimation/detector arrangement is adjustable, both laterally and height-wise relative to the X-ray source, by first adjustment elements. Additionally, the X-ray source is laterally adjustable, by second adjustment elements. Finally, the first and second adjustment elements are synchronously adjustable and are computer controlled by the computer.  
           [0014]    The concept underlying the invention is a diffraction apparatus, comprising a collimator/detector arrangement and an X-ray source that is aimed at this arrangement, and which can be brought into and aligned within a testing stage of an X-ray machine through adjustments in height and transverse position. X-ray diffraction is used to determine the material of an item at a predetermined location. To this end, the lateral positions of collimator/detector arrangement and the X-ray source can be adjusted synchronously, with the collimator/detector arrangement also preferably being adjustable in height relative to the X-ray source.  
           [0015]    If only two coordinates of a predetermined location (e.g., belt position and angle) are known, the adjustable diffraction unit continuously scans the missing third coordinate in a measuring sweep. Consequently, the materials positioned on this line (i.e., the line of the measuring sweep) can be measured and determined as a function of location. If three coordinates of the predetermined location are known, the diffraction apparatus is aimed at this point, and the type of material of the item is determined by, for example, X-ray diffraction analysis, without the need of a measuring sweep.  
           [0016]    The height-adjustable collimator/detector arrangement preferably comprises an adjustable round-slot collimator in the form of a conical jacket with a detector disposed behind it.  
           [0017]    In a further step of the analysis of the material of an item using the detector/collimator arrangement, additional information can be obtained for assessing the material if, in addition to the diffraction spectrum, the average atomic number of the material is known. For this purpose, the round-slot collimator has a central opening, which is closed to the detector and in which two different, separate detector devices are disposed one behind the other. In a known manner, these detector devices determine the average atomic number of the object located in the primary beam.  
           [0018]    The invention is described in detail below with reference to an embodiment illustrated in the drawing.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a schematic representation of an apparatus according to the invention.  
         [0020]    [0020]FIG. 2 is a more detailed illustration of the diffraction apparatus of FIG. 1.  
         [0021]    [0021]FIGS. 3 a  and  3   b  are schematic side and end views of a preferred embodiment of the collimation/detector arrangement of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    As shown in FIG. 1, an object  1  to be X-rayed is located in an X-ray tunnel  2  of an X-ray testing machine  3 . Disposed inside the X-ray tunnel  2  is an adjustable diffraction apparatus  10 . The diffraction apparatus  10  comprises a collimator/detector arrangement  11  and an X-ray source  12 . The collimator/detector arrangement  11  is aimed at an X-ray beam FX′, which is preferably a primary beam emitted as a ‘pencil beam’ from the X-ray source  12 , which is preferably disposed beneath a transport device  4  for the object to be tested in the X-ray tunnel  2 . The collimator/detector arrangement ( 11 ) is mounted to be adjustable both height-wise and laterally (in the Z and Y directions, respectively, as shown in the figure by arrows) by means of adjustment elements  5 , not shown in detail here, connected thereto. The X-ray source  12  is secured to adjustment elements  6 , and can also be adjusted laterally in the Y direction parallel to lateral adjustments of the collimator/detector arrangement ( 11 ). The collimation/detector arrangement  11  and the X-ray source  12  are guided synchronously, for which purpose the elements  5  and  6  (which can be, for example, linear guides with a spindle drive) are actuated centrally. This movement can be coordinated by a computer  30 , not shown in detail. The object  1  to be X-rayed is located, with its items  7 ,  8 , on the transport device  4 .  
         [0023]    If the primary beam FX′ of an X-ray source impacts a material, this primary beam FX′ is known to be partially deflected at the crystal-lattice structure of the material as scatter radiation FX″ (as known from Bragg&#39;s Law). Accordingly, the energy spectrum obtained with the energy-sensitive detector yields the crystal structure, and thus the identity of the material. In particular, explosives can be identified and distinguished in this manner.  
         [0024]    [0024]FIG. 2 shows, in detail, the diffraction apparatus  10  according to one embodiment of the present invention for making such X-ray diffraction measurements.  
         [0025]    The collimator  13  comprises a round slot  15  in the form of a conical jacket such that, of the scatter radiation emanating from the tested point G M7  of the item  7  in the object, only the components that fall within a specific angle Θ M  are allowed through to the detector  14 . The energy-sensitive surface  14 . 1  of the detector  14  located behind the collimator  13  detects the scatter radiation FX″ passing through round slot  15  at the scatter angle Θ M . To attain a primary beam FX′ from the X-ray source  12 , a screen arrangement  16 , for example an apertured-diaphragm arrangement, is mounted in front of the X-ray source  12 .  
         [0026]    The diffraction apparatus should be aligned to the location of the material to be determined in order to make a X-ray diffraction measurement. If the position information in two spatial coordinates (e.g., transport-device position and angle) for the items  7  and  8 , for example, is known from a lower or prior test stage, the respective missing coordinate must be continuously scanned in a measuring sweep. For this purpose, the transportation device  4  and the collimation/detector arrangement  11  travel to an initial position specified for the respective item  7 . From there, the measuring sweep is initiated such that the arrangement  11  travels, as necessary, in its height direction and laterally, synchronously with the X-ray source  12 , in the direction of the missing coordinate. The signals recorded by the detector during a measuring sweep are stored in one or more energy spectra and compared in a known manner to known energy spectra in the computer  30 . This comparison thus yields the material type, particularly for explosive material.  
         [0027]    If the predetermined points G M7  and G M8  are known in three spatial coordinates, the collimator/detection arrangement  11  and the X-ray source  12  of the diffraction apparatus  10  are displaced one after the other and aligned to points G M7  and G M8 . The scatter radiation FX″ of the X-ray source  12 , which is deflected at the crystal lattice of the items  7  or  8 , is captured through the round slot  15  of the collimator  13 . No further adjustment of the collimator/detection arrangement  11  is necessary during the respective measurement.  
         [0028]    It is also possible to combine the coordinate information from the lower test stage and the additional, spatial information from the higher stage, possibly supplemented by numerous measuring sweeps, and thus determine the volume and the precise spatial position of, for example, the item  8  in the object  1 .  
         [0029]    [0029]FIG. 3 illustrates an advantageous embodiment of the annular-slot collimator  13 . A central, blind-bore-like opening  17  is preferably integrated into the collimator  13 . The opening  17  is closed in the direction toward the detector  14  disposed behind it. A first detection device  21  and, disposed behind it at a defined distance, a second detection device  22 , are located in the opening  17 . The first detection device  21  is embodied as a detector for relatively lower X-ray energies, and the second detection device  22  is embodied as a detector for higher X-ray energies. This collimator  13  can be used, for example, to additionally perform a conventional material detection through the determination of the average atomic number of the material of the item  7  or  8 . The combination of this atomic number and the determined energy spectrum can attain an improved identification of the material of the item  7  or  8 . This is of particular significance if the item  7  or  8  contains a highly-absorbent material. Often, lower energies of the central beam FX′ are absorbed in the material, so the corresponding lines of diffraction are missing in the measured energy spectrum. This absence can be reported to the computer with the additional determination of material, and considered in the comparison for the evaluation.  
         [0030]    In addition, the detection devices  21 ,  22 , which can also comprise, for example, quadrant detectors, can perform a precise spatial orientation (alignment) of the collimation/detection arrangement  11  relative to the X-ray source  12 . The alignment itself is effected without an object  1  being located between the collimator/detector arrangement  11  and the X-ray source  12 . To this end, the collimator  13  described in conjunction with FIG. 2 has the additional opening  17  with the detection devices, which was not shown in detail in FIG. 2 in order to provide a clear overview.  
         [0031]    Of course, modifications are possible within the scope of the concept of the invention. For example, other diffraction apparatuses  10  can be used, as are described in the state of the technology, in which case the diffraction apparatus  10 , as disclosed in the description, for example, is to be adjustable.  
         [0032]    The invention now being fully described, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein.