FIELD OF THE INVENTION

THIS invention relates to a method and system for irradiating and activating objects, for example, though not necessarily exclusively, mineral containing objects, and animal/human bodies for purposes of detecting and/or imaging particles or substances of interest in these objects.

BACKGROUND OF THE INVENTION

In conventional diamond mining operations, vast amounts of resources such as water and energy are required to process mostly barren rock in order to recover diamonds. Processing of the rock typically includes a damaging sequence of rock crushing and diamond recovery, often with a relatively low yield, for example, approximately 1 carat per ton of rock processed. However, crushing of rock in a conventional fashion may lead to diamond breakage, thereby reducing the profitability of a diamond mine.

Sensor- or detector-based technologies attempt to negate these undesirable effects by enabling early detection of relatively unprocessed diamond bearing rocks which can then be isolated and processed in an environmentally friendly manner that preserves diamond integrity. However, such technology produces data which must be processed in complex ways to enhance the sensitivity and accuracy of the diamond detection. This processing may make use of relatively complex algorithmic processes to achieve desired sensitivity at the cost of computational resources. One prior art technology makes use of Positron Emission Tomography (PET) to be able to detect diamonds in rocks. This approach involves irradiating and activating a rock with a gamma ray beam from bremsstrahlung of, for example, 40 MeV electrons, or a different source of photons other than bremsstrahlung, for example, inverse Compton scattering, or other techniques. The rock returns to moderate levels of specific activity within minutes, by which time the PET isotopes represent the dominant residual activity. When the ¹¹ C PET isotope is the dominant activity, after about 30 minutes, the rock is then inspected by way of a detector arrangement to determine whether or not there is a diamond present therein.

Classification data generated when using this approach is usually associated with photons detected by the detector arrangement. These photons are emitted from the rock as a result of positron annihilation in the rock. When a PET isotope in the rock releases a positron particle through beta-decay, the positron annihilates with a nearby electron after following a short path that can involve multiple scattering events.

The step of Irradiation and activation of objects in a PET scheme, for example, of the type mentioned above is an important step as objects that are not irradiated and particularly activated in a uniform manner, for example, from one side, could have an exponential drop-off in activation uniformity of almost 50% across the object from the side nearest to the side furthest from the irradiation, for the typical larger rocks that are processed, or if one rock masked another, or if the exposures to the irradiating beam were not uniform in time, or if the irradiating beam itself were not sufficiently uniform in both space and time .

Accordingly, it is the object of the present invention to ensure that an object is uniformly irradiated so that the substance of interest contained therein, if any, is activated to the same degree. In general, non-uniform activation can amplify random features in the background such that they are classified falsely.

For medical applications, e.g., whole body PET detection systems require much lower doses of gamma rays than in mining applications to activate PET isotopes. In this example embodiment of the application of the technologies disclosed herein, activation of a human/animal body would be direct and in a similar fashion to activation of rocks described below albeit at much lower power levels.

In the context of this specification, the term“object” may be understood to mean a rock particle such as kimberlite, irrespective of the size thereof, or a loose diamond. Thus the terms“object”, “rock”,“particle”, “diamond” and“kimberlite” may be used interchangeably herein. The term“object” may also extend to other objects which are imaged or analysed in a detection method, e.g. a human or animal body or body part of a body. Moreover, the term“substance of interest” or“particle of interest” may be minerals within the objects, for example, diamonds within rocks, biological cells, etc.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a method of irradiating an object throughout all or a substantial volume thereof, the method comprising:

displacing the object along a displacement path in at least one displacement direction;

generating gamma rays including at least gamma ray photons of a predetermined energy level at which giant dipole resonance (GDR) occurs due to a nuclear reaction between the photons and carbon to produce ¹¹ C isotopes in the object, wherein the gamma rays are generated in a predetermined fashion to facilitate uniform irradiation of the object; and

irradiating the object with the generated gamma rays so as to irradiate and activate the object in substantially a uniform manner.

The gamma rays may travel in a propagation direction which is at least transverse to the displacement direction.

It will be understood that the gamma rays may be bremsstrahlung gamma rays. To this end, the term“activation” may be understood to mean that the object has been irradiated by the gamma ray photon to the extent that ¹¹ C isotopes are produced. The photons emitted from the object may be as a result of positron annihilation due to irradiation of the object with photons of a predetermined.

In some example embodiments for medical applications of the technology disclosed herein, coherent Brehmsstrahlung sources may be used for electron radiation free efficient gamma only activation of PET isotopes.

In some example embodiments of the invention, the predetermined energy may be outside the energy at which GDR occurs (either higher or lower). GDR is associated with the highest cross-section, but it will be appreciated that there is non zero cross-section in other energy areas, so in some applications one may be able get activation from photons without using GDR (either higher or lower energy).

It will be understood by those skilled in the art, that the isotopes introduced or produced may vary depending on the application of the disclosure herein. For example, in medical applications, activation of 15-Oxygen ( ¹⁵ 0) (which decays with a 2 minute half-life) would result in detection of photons by the arrangement described herein with the human/animal body returning to a “normal” condition after a few minutes. Other isotopes not described herein may equally be utilised herein.

The method may comprise generating gamma rays to have a broad cross- sectional area. The cross-sectional shape of the gamma rays may approximate an ellipse or a circle. The spatial intensity distribution of the gamma rays may be modified to be flat topped by way of suitable optical elements.

The method may comprise generating gamma rays to scan relative to the displacement path at a predetermined scan rate. The gamma rays may be scanned across the displacement path in a reciprocating fashion or in a single scan fashion.

The method may comprise scanning the generated gamma rays relative to the displacement path, across the predetermined displacement path, with a predefined repetitive pattern, so as to sufficiently irradiate the object. The method may comprise displacing the displacement path in a scan-like fashion relative to the generated gamma rays. For example, the displacement path may be displaced relative to the propagation direction of the generated gamma rays.

The method may comprise generating gamma rays by controlling at least one electron beam from an electron beam source to be incident on a high atomic number material in a predetermined fashion. The electron beam source may be selected from several electron accelerator technologies. For example, a linac, a microtron, or a betatron. It will be understood by those skilled in the art that there could also be new emerging technologies for the electron beam source such as a plasma wakefield accelerator, where there is a driver charged particle beam in a plasma or a laser generated plasma undulation, using the emerging technology of ultra-high power (TerraWatt) laser beams with very short (femptosecond) pulse widths.

The electron beam from the electron beam source may have a high energy. For example, since the resultant photon beam must be between 20-35 MeV, the electron beam should have an energy level which is higher than this. For the case that the photons are produced by Bremsstrahlung, the electron beam may have an energy of approximately 40 MeV. The latter is the preferred example embodiment.

In other example embodiments, such as the case that the photons are produced by inverse Compton Scattering, the electron beam may be approximately 1 GeV. For the case that the photons are produced by coherent bremmstrahlung, the electron beam energy may be some hundred MeV.

The high atomic number material may be tungsten, as tungsten is a compromise of large atomic number and good machinability and strength. Flowever, nothing precludes any high atomic number material suitably prepared, such as a thick foil even on a support substrate of the appropriate properties, for example, tantalum may be another possibility. Preferably the high atomic number may be greater than 60.

The method may comprise generating the gamma rays with a broad cross- sectional area by defocussing or fanning at least one electron beam prior to it being incident on the high atomic number material. It will be appreciated that in one example embodiment, the method may comprise defocussing or fanning gamma rays generated.

The method may comprise generating the gamma rays which scan across the displacement path by scanning or displacing the at least one electron beam relative to the displacement path at the predetermined scan rate. It follows that the at least one electron beam may be scanned across the displacement path in a reciprocating fashion or in a single scan fashion.

In one embodiment, the method may comprise displacing the at least one electron beam relative to the displacement path, across the predetermined displacement path, with a predefined repetitive pattern, so as to sufficiently irradiate the object.

The scan rate of the electron beam, and therefore the gamma rays, across the predetermined displacement path may be related to the speed at which the object travels in the predetermined displacement path.

The electron beam may be pulsed so that the gamma rays are generated in bursts. In this regard, the method may comprise selecting a scan rate based on a rate at which the bursts of gamma rays are generated, and the speed at which the object to be irradiated travels in the predetermined displacement path. Differently stated, the scan rate may be selected such that the gamma ray bursts are directed at each location along a scan path across the predetermined displacement path for a same amount of time.

In an embodiment, the displacement path may be provided by a displacement arrangement. The displacement arrangement may be a continuous conveyor arranged, for example, in a serpentine configuration having a plurality of vertically spaced and horizontally disposed conveyor belt portions for moving a stream of objects along the predetermined displacement path. The method may comprise directing generated gamma rays at one or more regions of each of the conveyor belt portions so as to irradiate and activate different regions of the object as the object travels along the predetermined displacement path.

It will be appreciated that in the displacement path, the different portions of the object are irradiated by the generated gamma rays. Each portion of the object is irradiated to the same extent and for the same amount of time, so as to obtain a substantially uniformly irradiated object.

In an embodiment, the displacement arrangement may comprise a rotatable platform such as a rotating toroid that is arranged to rotate about its axis thereby defining a substantially circular displacement/travel path for displacing the object placed thereon with generated gamma rays. The gamma rays may be directed to the platform in direction of propagation transverse to the axis of rotation of the platform.

In an embodiment, the displacement arrangement may comprise a suitable chute defining a travel/displacement path through which the objects can travel, for example under gravity. The method may therefore comprise directing gamma rays across the travel path defined by the chute for incidence with the object as it falls through the chute, wherein the chute is a choked chute such that objects descend more slowly than free-fall under gravity.

The method may comprise providing gamma rays from more than one direction to the objects falling through the chute. For example, from opposing directions.

In an embodiment, the method may comprise splitting the electron beam into at least first and second irradiating beams; diverting the at least one first and second beams so that they travel in different paths; and directing the at least one first and second electron beams to be incident on high atomic number materials to generate gamma rays which are propagated transverse to the displacement path in an opposing fashion which is seen to sandwich the displacement path.

The method may comprise irradiating a plurality of objects in an object stream. The objects may be diamonds or diamondiferous rocks, for example, kimberlite rocks. In one example embodiment, the displacement arrangement may comprise a fixed or displaceable platform defining the irradiation zone, wherein the displaceable platform either keeps the irradiation zone fixed relative to the generated gamma rays or is configured to spatially displace one or more objects located thereon relative to the generated gamma rays. The displaceable platform may be configured to spatially displace the one or more objects located thereon along a plane transverse to a propagation of the generated gamma rays.

According to a second aspect of the invention, there is provided a system for irradiating an object throughout all or a substantial volume thereof, the system comprising:

a displacement arrangement defining a displacement path along which the object is displaceable; and

at least one irradiating beam emitting device positioned operatively relative to the displacement path and configured to generate gamma rays including at least gamma ray photons of a predetermined energy level at which giant dipole resonance (GDR) occurs due to a nuclear reaction between the photons and carbon to produce ¹¹ C isotopes in the object, wherein the device is configured to generate the gamma rays in a predetermined fashion to facilitate irradiation of the object so as to irradiate and activate the object in substantially a uniform manner.

In an embodiment, the at least one irradiating beam emitting device may comprise an electron beam source configured to generate at least one electron beam; and a suitable material with a high atomic number, wherein the at least one irradiating device is configured to generate gamma rays by controlling the at least one electron beam from an electron beam source to be incident on a high atomic number material in a predetermined fashion.

The at least one irradiating beam emitting device may comprise a beam modification system configured to control or operate on the at least one electron beam to generate gamma rays in a predetermined fashion. The beam modification system may comprise suitable fanning magnetic arrangements (e.g., quadrupole or higher order magnets), or the like configured to defocus or fan the at least one electron beam. In this way, generated gamma rays may have broad cross-sectional area. In particular, the cross-sectional shape of the gamma rays may approximate an ellipse or a circle.

The beam modification system may also comprise suitable optical elements to modify the spatial intensity distribution of the generated gamma rays to be flat topped.

In an embodiment, the beam modification system may comprise suitable scanning magnetic arrangement (e.g., a varying dipole magnet or magnets), or the like configured to displace the at least one irradiating beam relative to the displacement path defined by the displacement arrangement. In this way, the gamma rays generated scan relative to the displacement path at a predetermined scan rate. The gamma rays may be scanned across the displacement path in a reciprocating fashion or in a single scan fashion.

In one embodiment, the scanning magnetic arrangement may be configured to displacing the at least one electron beam relative to the displacement path, across the predetermined displacement path, with a predefined repetitive pattern, so as to generate gamma rays which are displaced across the displacement path so as to sufficiently irradiate the object.

The scan rate of the electron beam, and therefore the gamma rays, across the predetermined displacement path may be related to the speed at which the object travels in the predetermined displacement path.

The at least one irradiating beam emitting device may pulse the electron beam so that the gamma rays are generated in bursts. In this regard, the scan rate may be selected based on a rate at which the bursts of gamma rays are generated, and the speed at which the object travels in the predetermined displacement path. Differently stated, the scan rate may be selected such that the gamma ray bursts are directed at each location along a scan path across the predetermined displacement path for a same amount of time. In an embodiment, the displacement arrangement may comprise a continuous conveyor, for example, in the form of a conveyor belt moving along the displacement path. The conveyor may be provided in a serpentine configuration having a plurality of vertically spaced and horizontally disposed conveyor belt portions for moving a stream of objects along the predetermined displacement path. The generated gamma rays may be directed at one or more regions of each of the conveyor belt portions so as to irradiate and activate different regions of the object as the object travels along the predetermined displacement path.

In one particular example embodiment, the displacement arrangement may comprise a first elongate, horizontally disposed belt portion; a vertically spaced, horizontally disposed second elongate belt portion; and a vertically spaced, horizontally disposed third belt portion, wherein the first, second, and third belts are of a predetermined belt length and are oriented in a predefined orientation with respect to each other and the ground, preferably arranged substantially parallel to the ground; and wherein the generated gamma rays are directed through the continuous conveyor at one or more various regions of the first belt portion, second belt portion, and third belt portion to define various activation regions.

It will be appreciated that in the displacement path, the different portions of the object are irradiated by the generated gamma rays. Each portion of the object is irradiated to the same extent and for the same amount of time, so as to obtain a substantially uniformly irradiated object.

In another example embodiment, the displacement arrangement may comprise a rotatable platform such as a rotating toroid that is arranged to rotate about its axis thereby defining a substantially circular displacement/travel path for displacing the object placed thereon with generated gamma rays. The gamma rays may be directed to the platform in direction of propagation transverse to the axis of rotation of the platform.

In an embodiment, the displacement arrangement may comprise a suitable chute defining a travel/displacement path through which the objects can travel, for example, under gravity. The generated gamma rays may be directed across the travel path defined by the chute for incidence with the object as it falls through the chute.

The at least one irradiating beam emitting device may be configured to generate and direct gamma rays from more than one direction to the objects falling through the chute. For example, from opposing directions.

In an embodiment, the at least one irradiating beam emitting device may comprise a suitable splitter arrangement configured to split the electron beam into at least first and second electron beams (e.g., by way of a suitable kicker magnet arrangement); divert the at least one first and second beams so that they travel in different paths (e.g., by way of a suitable conduit arrangement); and direct the at least one first and second electron beams (e.g., by way of a suitable conduit and/or bending arrangement); to be incident on high atomic number materials to generate gamma rays which are propagated transverse to the displacement path in an opposing fashion which is seen to sandwich the displacement path.

In an embodiment, the system may comprise a suitable computing device configured to control the beam modification system thereby to control the fanning and/or scanning of the electron beam.

According to a third aspect of the invention, there is provided a method of generating gamma rays for the irradiation of objects with gamma ray photons of a predetermined energy at which giant dipole resonance (GDR) occurs due to a nuclear reaction between the photons and carbon to produce ¹¹ C isotopes in the object, wherein the method comprises:

providing at least one electron beam;

fanning and scanning the electron beam in a predetermined fashion; and directing the fanned and scanned electron beam to material of a high atomic number to generate the gamma rays.

According to a fourth aspect of the invention, there is provided an irradiating beam emitting device for generating gamma rays for the irradiation of objects with gamma ray photons of a predetermined energy at which giant dipole resonance (GDR) occurs due to a nuclear reaction between the photons and carbon to produce ¹¹ C isotopes in the object, wherein the device comprises:

an electron beam source for providing at least one electron beam;

a beam modification system configured to fan and scan the electron beam in a predetermined fashion; and

a suitable conduit arrangement configured to direct the fanned and scanned electron beam to material of a high atomic number to generate the gamma rays.

In accordance with a further aspect of the invention, there is provided a diamond mine processing system which includes a system for irradiating an object substantially as described above.

According to another aspect of the invention, there is provided a method of irradiating an object located in an irradiation zone, wherein the method comprises:

generating gamma rays including at least gamma ray photons of a predetermined energy level at which isotopes are produced due to a nuclear reaction between photons and chemical elements in the object, wherein the gamma rays are generated in a predetermined fashion to uniformly irradiate the object; and

irradiating the object with the generated gamma rays so as to irradiate and activate the object in substantially a uniform manner.

It will be appreciated by those skilled in the art that the irradiation zone described herein may be the area of application of the generated gamma rays. This may be along the belt in the case of mining applications described herein or may be on a fixed platform in the case of medical applications of the invention disclosed herein.

According to another aspect of the invention there is provided a system for irradiating an object located in an irradiation zone, wherein the system comprises at least one irradiating beam emitting device configured to generate gamma rays including at least gamma ray photons of a predetermined energy level at which isotopes are produced due to a nuclear reaction between photons and chemical elements in the object, wherein the device is configured to generate the gamma rays in a predetermined fashion to facilitate irradiation of the object so as to irradiate and activate the object in substantially a uniform manner.

The system may comprise a displacement arrangement defining a displacement path along which the object is displaceable, wherein the irradiation zone is located in the displacement path, and wherein the irradiating beam emitting device is positioned operatively relative to the displacement path such that generated gamma rays travel in a propagation direction which is at least transverse to one or both of a displacement direction and the displacement path.

According to another aspect of the invention there is provided a method of generating gamma rays for the irradiation of objects in an irradiation zone with gamma ray photons of a predetermined energy level at which isotopes are produced due to a nuclear reaction between photons and chemical elements in the object, wherein the method comprises:

providing at least one electron beam;

fanning and scanning the electron beam in a predetermined fashion ; and directing the fanned and scanned electron beam to material of a high atomic number to generate the gamma rays.

According to another aspect of the invention there is provided an irradiating beam emitting device for generating gamma rays for the irradiation of objects with gamma ray photons of a predetermined energy level at which isotopes are produced due to a nuclear reaction between photons and chemical elements in the object, wherein the device comprises:

an electron beam source for providing at least one electron beam;

a beam modification system configured to fan and scan the electron beam in a predetermined fashion; and

a suitable conduit arrangement configured to direct the fanned and scanned electron beam to material of a high atomic number to generate the gamma rays. According to another aspect of the invention there is provided a medical positron emission tomography system which comprises a system as described above; or a device as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic diagram of an example of a diamond mine processing system in which embodiments of the invention may be implemented, wherein the irradiation and activation system in accordance with example embodiments of the invention is illustrated conceptually in a block diagrammatic fashion;

Figure 2 shows a Geant4 simulation of electrons (e) creating bremsstrahlung gamma rays (b), incident on an object in the form of mineral containing body, e.g. kimberlite (m);

Figure 3 shows simulated activation achieved within an object (e.g.

kimberlite) due to bremsstrahlung gamma rays of 40 MeV pencil beam electrons with a 1 mm diameter incident on a 3mm tungsten plate, as a function of perpendicular distance away from the beam centre in two dimensions on the left-hand side of Figure 3, and a slice through the centre on the right-hand side of Figure 3;

Figure 4 shows the number of 20-30 MeV gammas as a function of kimberlite depth, considering an irradiation by 1 ,000,000 40 MeV electrons ;

Figure 5 shows beam scanning patterns, with unidirectional beam spots shown on the top on the left-hand side of Figure 5, and beam centre positions shown on the bottom of the left-hand side of Figure 5, and a zig zag pattern shown on the right-hand side of Figure 5;

Figure 6 shows a beam scanning pattern of Figure 5 in accordance with an example embodiment of the invention; Figure 7 shows a diagram illustrating areas of least activation in view of the beam scanning pattern of Figure 6;

Figure 8 shows a system in accordance with the invention comprising a suitable splitter arrangement being arranged to split an electron beam, wherein system comprises a suitable beam modification system for fanning and scanning a beam incident on a displacement arrangement, i.e. a choked chute;

Figure 9 shows the degree of irradiation and activation of an object moving through the displacement arrangement of Figure 8, as a function of depth of the object, and where the irradiation occurs from both sides of the object, the left-hand side of Figure 9 shows activation of an object in the form of a mineral containing body having a depth of 30 cm, and the right-hand side shows activation of the mineral containing body having a depth of 18 cm;

Figure 10 shows another displacement arrangement (i.e. vertically spaced conveyor belts) and irradiation beams extending through the displacement arrangement, and objects moving along the path defined by the vertically spaced conveyors;

Figure 11 shows the vertical distance between the conveyor belts being reduced in order to optimise the activation of the objects by irradiation beams extending through the conveyor belts;

Figure 12 shows another displacement arrangement having a trapezoidal belt cross-section as shown on the left-hand side of Figure 12, and top view of interlocking arrangement of three belts as shown on the right-hand side of Figure 12; and Figure 13 shows another displacement arrangement having a rotating platform, and irradiation beams extending across the displacement arrangement.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS

The following description of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that many changes can be made to the embodiments described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible, and may even be desirable in certain circumstances, and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not a limitation thereof.

It will be appreciated that the phrase“for example,”“such as”, and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to “one example embodiment”, “another example embodiment”,“some example embodiments”, or variants thereof as described herein means that a particular feature, structure or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter. Thus, the use of the phrase“one example embodiment”,“another example embodiment”, “some example embodiment”, or variants thereof does not necessarily refer to the same embodiment(s).

Unless otherwise stated, some features of the subject matter described herein, which are, described in the context of separate embodiments for purposes of clarity, may also be provided in combination in a single embodiment. Similarly, various features of the subject matter disclosed herein which are described in the context of a single embodiment may also be provided separately or in any suitable sub combination. Though different reference numerals are used for the sake of clarity for different example embodiments of certain features described herein, it will be noted that the description provided herein pertaining to these features may apply mutatis mutandis across all example embodiment unless otherwise state/it is evident to those skilled in the art that such application is not applicable or possible.

Referring to Figure 1 of the drawings, an example of a diamond mine processing system is generally indicated by reference numeral 1 . Irradiation and activation of potential diamonds or diamondiferous objects such as kimberlite rocks for the purposes of detecting diamonds will be used as an example implementation of embodiments of the invention in this description. However, it should be appreciated that alternative embodiments extend to other applications, mutatis mutandis, e.g. PET imaging/detection applied to the body of a human or animal (such as total-body medical PET and PET video).

The system 1 typically includes a classification or detection system 2 which is usually a computerised system configured to perform imaging and to detect diamonds as individual, separate objects, as embedded in host objects or as objects included in a mass of other objects.

The diamond mine processing system 1 may be located at or adjacent a diamond mine and may comprise suitable conventional mining equipment such as a crusher 3 to coarsely crush mined rock to sizes of approximately 160 mm diameter, or less. The system 1 further comprises a suitable irradiation and activation system 10 to irradiate the crushed rock with photons of a predetermined energy level. The photons which irradiate the rock may be from gamma ray beams from bremsstrahlung of approximately 40 MeV electrons. Instead, or in addition, these photons may be from inverse Compton scattering, plasma wakefield device, or the like. The photons are at an energy at which giant dipole resonance (GDR) occurs due to a nuclear reaction between the photons and carbon in the rock.

The system 12 comprises a hopper arrangement 4 to hold the irradiated rock for a predetermined period of time. The irradiated rock returns to moderate levels of specific activity within minutes, by which time PET isotopes represent the dominant residual activity. In this regard, the hopper arrangement 4 is configured to hold the irradiated rock for a hold-time of between twenty and thirty minutes at which time the ¹¹ C PET isotope is the dominant activity. The hopper arrangement 4 may then automatically release the rock after the hold-time.

The system 1 comprises a suitable displacement arrangement 9, for example, comprising suitable conveyor belts which are non-attenuating to PET photons to transport rock in the system 1 in an automated fashion. The displacement arrangement 9 may be configured to transport rock in a rock stream at a constant predetermined speed through the system 1 , for example, 1 m per second as illustrated.

The system also comprises a detector arrangement 6 which is located downstream from the hopper arrangement 4 and adjacent the displacement arrangement 12, particularly the belt thereof, so as to detect PET photons emitted therefrom.

The detectors of the arrangement 6 may be in the form of scintillator crystals and photomultiplier tube (PMT) detectors with suitable electronics.

The system 1 also comprises a suitable sorter 7 which may be an electronically controlled mechanical sorter 7 configured to sort potentially diamondiferous or in other words diamond containing rocks or loose diamonds from potentially barren rocks or in other words rocks without diamonds therein.

The detection system 2 is communicatively coupled to the detector arrangement 6 and to the sorter 7 so as to receive classification data from the detector arrangement 6 and to generate suitable control signals to control the sorter 7 to sort diamondiferous rocks from barren rocks.

The sorter 7 may be configured to sort diamonds or diamondiferous rocks into one or more categories according to one or more specific properties of the diamond/diamondiferous rock detected, as opposed to simply sorting the same from barren rocks. The system 2 is configured/programmed to receive classification data and to determine whether or not the object is potentially a diamond or diamondiferous by processing the received classification data. The classification data is typically associated with photons detected by the arrangement 6 which are emitted from the object as a result of positron annihilation in the irradiated object received from the hopper 18. In particular, when a PET isotope in the kimberlite rock releases a positron particle through beta-decay, the positron annihilates with a nearby electron after following a short path that can involve multiple scattering events. The most common outcome of this annihilation is the production of nearly co-linear back-to-back 51 1 keV gamma ray photons. Each photon then travels through the surrounding material, sometimes changing energy and direction along the way. When the photons reach the detector arrangement 6, the arrangement 6 outputs classification data in the form of detector strike/hit event data, for example, which comprises data indicative of the location of the hit thereon, the energy of the photon, and a time stamp. This allows the position of a diamond to be determined or estimated.

A key aspect of the present invention which enables the detection of diamonds in Kimberlite rock steams in the manner highlighted above is the irradiation and activation of rocks in the rock streams in substantially a uniform fashion. To this end, the irradiation and activation system 10 will be further described with reference to Figures 2 to 1 1 . The singular term“rock” may be described interchangeably with the plural term“rocks” as it will be understood that irradiation and activation of a single kimberlite rock will be the same for a plurality of kimberlite rocks in a rock stream moving along the displacement path.

The system 10 typically comprises a displacement arrangement 15, as well as the other example embodiments thereof described below, which may or may not be part of the displacement arrangement 9 as will be described below. Much like the arrangement 9, the arrangement 15 defines a displacement path along which rocks are displaced through the system 1 . The system 10 also comprises an irradiating beam emitting device 17 that is arranged to emit irradiating beams in the form of gamma rays relative to the displacement path defined by the displacement arrangement 15 so as to irradiate the rocks in the displacement path. It will be appreciated that the term“irradiating beams” may refer to the generated gamma rays as contemplated herein.

In one example embodiment, the displacement arrangement 15, as well as the other example embodiments thereof described below, may be located in (and is part of) the system 10 and may effectively serve as a means to intercept the crushed rocks from the arrangement 9 and transport the same for irradiation by the device 17, and then to the hopper arrangement 4 which feeds the irradiated and activated rock to back to the arrangement 9 for transport in the system 1 as illustrated in Figure 1 . To this end, the arrangement 15 may be in operative rock flow communication with the arrangement 9.

However, as alluded to above, the arrangement 15 may form part of the arrangement 9 which effectively transports the crushed rock for irradiation by the device 17.

The device 17 may comprise a suitable electron beam source 17.1 , for example, a linac configured to generate and provide at least one beam of high energy electrons typically in a pulsed fashion. The device 17 further comprises a material with a high atomic number, such as tungsten 17.2.

Conventionally, referring additionally to Figure 2 of the drawings, a setup with the beam source 17.1 directing a beam of high energy electrons, e, to the tungsten 17.2, t, creates/generates high energy gamma rays, b via a process known as bremsstrahlung. In Figure 2, this process is simulated by way of a Geant4 simulation tool which models at least the physics of the generation of the gamma rays and the irradiation as well as activation of objects.

The bremsstrahlung gamma rays generated, b spread out in a cone centred around the original direction of the electron beam, e, as seen in Figure 2. However, with regard to the “Background of the Invention” section, a difficulty with this conventional configuration is that when gamma rays created in the described fashion strike an object, such as kimberlite, m, uniform activation of the kimberlite m is not achieved. As can be seen from the Geant4 simulation in Figure 3 activation of kimberlite with gamma rays g generated in a conventional fashion with the kimberlite m placed 1 meter away from the tungsten t results in activation of the kimberlite m more strongly in the centre than towards the sides, i.e., non-uniform activation.

Moreover, as conventionally generated gamma rays b travel through the kimberlite rock, they interact with the rock via electromagnetic and nuclear processes, leading ultimately to the extinction of the beam as a function of depth of the kimberlite rock. This means that positions deeper within the rock (i.e. kimberlite in the context of the present invention) receive a lower flux of gamma rays than the surface, and hence have a lower degree of irradiation and activation. This reduction of the gamma count with depth is shown in Figure 4. In Figure 4, the simulation conducted on the kimberlite has tracked and counted only those photons which are relevant to activation, i.e. the photons which can excite the Giant Dipole Resonance to produce the ¹¹ C PET isotope as mentioned previously. In this regard, it will be appreciated that the term“gamma rays” may be understood to be gamma ray beams containing a plurality of gamma ray photons. In the present invention, these gamma ray photons have a predetermined energy range (this range is from low energy radiation all the way the electron beam energy, but we are interested only on that segment, about 20 - 35 MeV, which excites the GDR) to excite GDR to which then leads to the production of the ¹¹ C isotopes in the target kimberlite rocks.

Conventional ways of addressing the lack of uniformity in irradiation and activation as mentioned above may be to: a) move the material further away from the bremsstrahlung target; and b) irradiate only thin layers of kimberlite. Flowever, these techniques have disadvantages. The former option means that a large portion of the beams will not strike the kimberlite, thereby greatly reducing the efficiency of activation. The latter option also reduces efficiency, as a large portion of the gamma ray irradiating beams will pass through a thin layer of kimberlite, and be lost on the other side. The latter option also limits the size of the rocks irradiated. Also, it is desirable to irradiate rocks of typical size of up to 10 cm diameter, or even somewhat larger. It follows from the foregoing that challenges of irradiating and activating kimberlite for the purposes of detecting diamonds or diamondiferous material include improving kimberlite activation while maintaining activation efficiency (i.e. using as much of the beam as possible).

To address these challenges and those mentioned above in the“Background of the Invention” section, the device 17 as described herein comprises a beam modification system 17.3. The beam modification system 17.3 is typically configured to perform one, or preferably both, of fanning/defocusing and scanning the electron beam from the source 17.1 prior to incidence on the tungsten 17.2 thereby to generate gamma rays comprising of gamma ray photons of a predetermined energy level which are also fanned and/or scanned as will be described in more detail below.

To achieve the desired beam modification, the system 17.3 may comprise suitable magnetic arrangements. In particular, the system 17.3 may comprise (albeit not illustrated) quadrupole, or higher order magnets, or any beam profile modification system known in the field of invention, which may be used to defocus the electron beam from the beam source 17.1 to achieve the fanning of the electron beam contemplated herein. The fanned/defocused electron beam from the beam source 17.1 leads to a broader gamma beam in cross sectional profile which is not as sharply peaked at the centre thereof.

It will be noted that the electron beam may be fanned independently in x and y directions, so the shape of the beam has a cross sectional profile which closer approximates to an ellipse than a circle, in either direction, if needed.

The beam modification system 17.3 may comprise suitable optical elements to modify the spatial intensity distribution of the electron beam so that it is flat topped.

Moreover, the beam modification system 17.3 comprises (albeit not illustrated) a varying dipole magnet or magnets that can steer/reciprocate the electron beam from the electron beam source 17.1 in a reciprocal fashion relative to the displacement path. In particular, the system 17.3 is configured to scan the electron beam across the rocks in the displacement path, as will be described below. In this way, the generated gamma rays are effectively scanned across the displacement path and the rocks therein. Notwithstanding, it will be appreciated that nothing precludes the device 17 scanning the electron beam parallel to the direction of travel of rocks in the displacement path.

It will be understood that reference to the“beam” described below may be with reference to the electron beam from the beam source 17.1 which is modified by the system 17.3. Notwithstanding, it will be appreciated that the resultant irradiating beams, i.e., the generated gamma rays/gamma ray beams may behave substantially similar to the modified electron beam in that they are effectively fanned and scanned in a manner described herein. For this reason, the term“beam” may refer to one or both of the electron beam and the irradiating beam from bremsstrahlung, unless it is specified/a person skilled in the art will appreciate that one of these beams are referred to.

The electron beams from the beam source 17.1 are typically pulsed, so that gamma rays emitted from the beam emitting device 17 are emitted from the device 17 in an intermittent fashion, or in other words, in bunches with gaps in between. The system 10 accordingly comprises a suitable computing device (not shown) configured to control the scanning pattern of the irradiating beam across the rocks and the speed travelled by the irradiating beam relative to the travel speed of the rocks in the displacement path, so as to achieve sufficient irradiation on sections or layers or rows within the rocks. The system 10 has a frequency response manifested in the scanning fields and ultimately in the beam sufficient that the beam trajectory spends the same time at each pixel or point it writes on the rocks, as a function of the position of the pixel. By way of clarification, one must consider the linear motion of the rock stream with its particular geometry, and also the moving gamma ray beam with its spatial footprint distribution as well as its pulsed nature. The integral exposure of the rock to the beam must be uniform within a close tolerance. This condition must take into account all considerations that could deteriorate achieving the appropriate integral uniform irradiation condition. For example, the frequency response of the actual beam is mentioned as there needs to be special design of the beam-optical elements such that the beam itself tracks the desired periodic motion with sufficient fidelity. It has been previously mentioned that the beam should be flat topped over a sufficient extent of its footprint. The pulsed nature of the beam means there will be but regular flashes of gamma ray intensity in a periodic pattern, while the rock stream also moves. All the dynamical time and space considerations, as well as beam envelope characteristics and irradiation configurations must conspire together for a uniform irradiation by the right photon energy range leading to a uniform activation regardless of the position in the rock volume considered, to a given tolerance.

The computing device may be one or more processors (e.g., a central processing unit (CPU), a graphics processing unit (GPU), or both) which may be provided with a computer readable storage medium, for example, memory on the computing device, or any external memory device, storing computer executable instructions which when executed by the computing device causes the same to control the components of the system 10 to provide the functionality as described herein.

The computing device may be arranged to cause the electron beam to scan the rocks at predefined repetitive patterns so as to ensure that the resultant irradiating beams spend substantially the same amount of time on each portion (layer or row or section) of the rocks that is being irradiated thereby as the said beam moves relative to the rocks. In this way, subsequent bunches of high energy photons strike the rocks with the pre-planned characteristics so as to give a uniform irradiation and activation to that portion (i.e. row or section or layer) of the rocks.

In Figure 5, the positions of the beam on the rocks are shown from a reference frame of a conveyor belt (not shown, however, imagining that the device 17 (not shown) on the conveyor belt (not shown) is moving downwards, rather than the conveyor belt (not shown) moving up the page).

The beam pulses are numbered on the left-hand side of Figure 5, where Dc represents the x distance between subsequent beam pulses or in other words the x distance travelled by the beam scanner in between beam bunches or groups. Dc is determined by pulse repetition rate and beam scanning speed which are controlled by the computing device (not shown). Ay represents the distance between consecutive rows of pulses or in other words the y distance travelled by the belt in the time that it takes to scan one line across the belt. Ay is affected by the belt speed, i.e. how far the belt (not shown) moves in the time it takes the beam to scan out one row of pulses on the portion (i.e. row) of the rocks.

Two possible beam scan patterns are shown in Figure 5. On the left-hand side of Figure 5 is a unidirectional scan pattern, where the beam traces out one row of pulses, then returns to the start point before tracing out the next row of pulses. This assumes the ability to move the beam back to the start point in a short time period relative to the pulse repetition rate. The alternative is a zig-zag pattern shown on the right-hand side of Figure 5. This does not require the beam to return to the start point, but does not give much of a uniform a distribution.

As mentioned above, the gamma rays are generated and directed to the rocks on the belt in subsequent bunches. Considering the beam pattern on the left hand side of Figure 5 as well as the distribution on the belt of useful gamma rays (roughly between 20 MeV and 30 MeV) that results from a single bunch, the distribution is highest at the centre of the distribution, then decreases as one moves on the belt radially out from the centre of the distribution, perpendicular to the beam direction. Defining r as the distance along the belt at which the flux of useful gammas reaches a certain minimum acceptable threshold, for example 75% of the maximum, if uniform activation is to be achieved, it is not desirable to have bunches to be separated by a distance that is greater than 2r.

In this regard, it will be understood by those skilled in the art that it is desirable to have a scanning speed selected to uniformly irradiate the rocks. To this end, with reference to Figure 6 of the drawings, one may define the following variables in the selection/calculation of the scanning speed

- N is the number of bunches in one line across the belt

- W The width of the conveyor belt

- vs The speed at which the beam scans across the belt

- vb The speed of the conveyor belt

- At The period of the beam, i.e. the length of time between consecutive bunches. In Figure 6, N = 4, or in other words there are 4 bunches of gamma rays illustrated. The two key variables that influence the distribution are the beam radius, r, and the period At, more commonly expressed as the repetition rate, which is the inverse of At. For example, if one were given the repetition rate of a particular accelerator, one would like to calculate how much the beam should be fanned out. Alternately, given a certain set of beam optics that determine r, one could calculate the required repetition to achieve uniform activation.

A relation between At and r may be derived. Velocity, distance and time are related as follows:

Ax=v _s At and Ay=Vb NAt (1 )

From Figure 6, we see that W = DcN. It follows that:

Assuming the beam is circular in cross-section, greatest uniformity is achieved when the gaps between bunches in the x and y directions are the same, i.e. Dc = Ay. The position of least activation is now found to be in between the centres of four beams. Because of the belt motion, if one joins four bunch centres in the belt’s frame of reference, it forms a parallelogram, show in Figure 7.

The point in the centre receives two activations at a distance of n, and two activations at a distance of r2. In realistic situations, N » 1 , and the angle of the parallelogram is small, in which r1 is approximately equal to r2. From Pythagoras: n ² + r2 ² = Ax ² (4)

2n ² = Dc ² (5) For uniform activation, the centre cannot be further away than the distance of minimum activation, i.e. r = \2 < r. Using Equation (5), Ax < sqrt(2r).

Therefore, for a certain beam size, which determines r, and the required accelerator repetition rate is to be determined, Equation (3) may be used:

. Ax ² 2 r ²

At - - < - vtW - v _b W (6)

Alternately, for a certain certain repetition rate, and therefore At, the required beam spread may be found accordingly:

The required scanning speed, v _s , may be found as follows, from Equation (3):

Ax ²

At =

v _b W (8)

Putting this into (1 ) :

Ax

v _s =

At

At V _b W

At

w

V At (12)

A similar calculation can be performed in the case of the’’zig-zag” pattern on the right hand side of Figure 5. In this case, the repetition rate must be increased, because at the edges, rows can be separated by a distance of 2Ay instead of Ay.

The degree to which the beam needs to be fanned is determined by how large the irradiating beam spot on the rocks needs to be in order to achieve a uniform distribution thereon. In particular, the degree to which the beam needs to be fanned is determined by how large the irradiating beam spot on the rocks needs to be in order to achieve uniform distribution of the irradiating beam on the portion (i.e. row or section or layer) of the rocks which is to be irradiated, based on a given value for the electron beam’s pulse repetition rate and conveyor belt speed. The irradiating beam spot may effectively be the cross-sectional profile of the gamma ray beam incident on the rocks.

Together, the scanning and fanning of the beam allows uniformity of irradiation and activation of the rocks regardless of the position of the rocks relative to the irradiating beam.

In one example of the present invention, as illustrated in Figure 8, the system 10 comprises a first conduit 12 defining a first travel path 13 in which at least one first irradiating beam 14, typically a 40MeV gamma ray, travels. The system 10 comprises a splitter arrangement comprising a kicker magnet arrangement 16, typically an ejection kicker magnet arrangement, which is arranged to split the at least one first irradiating beam 14 into a second beam 18 and a third beam 20 or direct alternate pulses of the first beam 12 as a second beam 18 and third beam 20.

The system 10 further comprises a second conduit 22 defining a second travel path 23 and a third conduit 24 defining a third travel path 25. The second and third conduits 22, 24 branch out from the kicker magnet arrangement 16 in a substantially Y- or V-shaped configuration.

The second beam 18 is arranged to travel in the second conduit 22, and the third beam 20 is arranged to travel in the third conduit 24.

The system 10 further comprises a first bending arrangement 26 dedicated for the second beam 18 and a second bending arrangement 28 dedicated for the third beam 20. Each bending arrangement 26, 28 comprises magnets (not shown) which are positioned along the path of travel of each of the second and third beams 18, 20 so as to bend and change the direction of travel of the beams 18, 20 so that the second and third beams 18, 20 can face each other from opposite directions, as shown on the right-hand side of Figure 8.

In this example embodiment, the system 10 comprises a displacement arrangement 30 comprising a choked chute 32 that defines a travel/displacement path 33 through which each rock 50 can travel at a predefined travel speed, for example, under gravity.

The chute 32 has an upper opened end 34 and a lower opened end 36, and the rocks 50 are arranged to be introduced into the chute 32 from the upper opened end 34. The second and third beams 18, 20 are arranged to extend across the travel path 33 defined by the choked chute 32, such that in use, one side of the mineral containing body 50 that is further from the first irradiating beam 18 is proximate the second irradiating beam 20, thereby ensuring that each mineral containing body 50 is irradiated at least from two sides of the mineral containing body 50. As shown on the right hand side of Figure 8, a plurality of second beams 18 and third beams 20 extend perpendicular to the travel path 33 defined by the chute 32, each second beam 18 is arranged to irradiate a rocks 50 travelling across its path from one side, and the opposite side of the rocks 50 which is further from the second beam 18 is irradiated by one of the plurality of third beams 20 extending across the travel path 33 from the opposite side.

The bending arrangement 26, 28 may be provided with suitable beam modification systems such as the system 17.3 described above for defocusing each of the plurality of second beams 18 and third beams 20, and scanning the beams 18, 20 with a repetitive predefined pattern across the rocks 50, as described above.

The scanning of each rock 50 in this fashion results in an activation distribution curve which is flat, indicative of substantially uniform irradiation of the rocks, as shown in Figure 9, compared to that shown in Figure 3.

Figure 9 therefore shows irradiation and activation of the rocks as a function of depth, for irradiation from both sides, for a rocks (i.e. kimberlite) having a thickness or depth of about 30 cm as shown on the left-hand side of Figure 9, and the rocks 50 having a depth of about 18 cm as shown on the right-hand side of Figure 9.

In an alternative arrangement, the system 10 may be arranged to have a plurality of beams facing the rocks from more than two directions so as to irradiate the rocks 50 from more than the two directions. For example, a cylindrical chute (not shown) with vertically descending rocks 50 could by irradiated by several beams directed inwardly into the cylindrical chute (not shown).

It is also part of the invention that the irradiating beams from alternate angles are displaced so that the remnant beam dumps in material prepared as a beam dump, rather than in any sensitive materials which could become damaged or activated. The beam line contains sensitive elements, like high precision magnets, that could be harmed by exposure to irradiation. Therefore, when irradiating from two different sides, two beams should not be pointed directly at each other. In essence the opposing beams are offset so that the remnant energy of the one after passage through the rock does not impinge on the delivery system of the other, but rather into a material known as a beam dump. In this way, sensitive material is not irradiated, and the remnant energy is dumped in a safe way. The beam dump would be chosen to be a material that does not get activated significantly and is cheap and easily replaceable. The beam dump would of course be designed to cope with the heat load of the remnant energy arrival rate via a suitable heat dissipation scheme.

In another example of the present invention, there is provided a technique for mitigating the effects of depth-related activation differences, this technique includes uniformly irradiating through several independent layers/rows/sections of the rocks.

Generally, each layer/row/section of the rocks are irradiated progressively by the irradiating beam to which it is exposed. This means that the total path length that the irradiating beam goes through the rocks is large, and the irradiating beam is therefore used efficiently. However, because each particle has a turn to be activated at the top layer/section/row, then the second successive layer/section/row, and so on, each rock receives a similar dose of irradiation from the irradiation beams.

Referring to Figure 10 of the drawings, another system in accordance with the invention designated generally by reference numeral 100. The system 100 comprises a displacement arrangement 102 in the form of a continuous conveyor arranged in a serpentine configuration in rock flow communication with the arrangement 9 as described above having. The arrangement 102 comprises a first elongate, horizontally disposed belt portion 104 for moving rocks 120 loaded thereon in direction A; a vertically spaced, horizontally disposed second elongate belt portion 106 for moving rocks 120 loaded thereon in direction B that is opposed to direction A; and a vertically spaced, horizontally disposed third elongate belt portion 108 for moving rocks 120 loaded thereon in direction C which is the same as direction A. The first, second, and third belt portions 104, 106, 108 are of a predetermined belt length and are oriented in a predefined orientation with respect to the ground, preferably arranged substantially parallel to the ground, and are each moved about rollers 109 of substantially the same size.

The system 100 comprises a first and a second spaced apart irradiating beam emitting devices 130, 132 respectively, for emitting a first beam 134 and a second beam 136, respectively. The first and second beams 134, 136 are defocused or fanned beams which are scanned repetitively (moved forwards and backwards) across the rocks, as described previously, and are arranged to extend through the continuous conveyor 102.

The first beam 134 extends vertically through the continuous conveyor 102 from the top of the continuous conveyor 102, and the first beam emitting device 130 is located proximate the first conveyor belt portion 104. The second beam 136 extends vertically through the continuous conveyor 102 from the bottom of the continuous conveyor 102, and the second beam emitting device 132 is located proximate the third conveyor belt portion 108.

As can be seen in Figure 10, the first and second beams 134, 136 are operatively opposite to each other, or in other words direct beams 134, 136 in opposite directions. The first beam 134 accordingly engages with a first region on the first belt portion 104 to define a first activation region 138 of the rocks 120, while the second beam 136 engages with a second region of the first belt portion 104 to define a second activation region 140 of each of the rocks 120 loaded thereon. As a result of the direction that the rocks 120 will move as they travel along the continuous conveyor 102, the second beam 136 engages a first region of the second belt portion 106 to define a third activation region 142 of each of the rocks 120, while the first beam 134 engages with a second region of the second belt portion 106 to define a fourth activation region 144 of the rocks 120. Lastly, as shown in Figure 10, the first beam 134 engages a first region of the third belt portion 108 to define a fifth activation region 146 of the rocks 120, while the second beam 136 engages a second region of the third belt portion 108 to define a sixth activation region 148 of the rocks 120. The first, second, third, fourth, fifth, and sixth activation regions correspond with a predefined portion (i.e. layer or row or section) of each of the rocks 120 that is to be irradiated by the irradiating beam passing through that region, so that the path length of the first and second irradiating beams 134, 136 can incrementally extend through the rocks as the rocks passes those activation regions.

Advantageously, each rock 120 is irradiated by the first beam 134 from the top as the rocks travel across the first activation region 138, fourth activation region 144 and fifth activation region 146, at the same time the same rocks 120 are irradiated from the bottom as it passes through the second activation region 140, third activation region 142, and sixth activation region 148. The continuous conveyor 102 and the first and second fanned beams 134, 136 are strategically arranged relative to each other - taking into account the speed of the belt, the broadness of the defocused beams, spot sizes of the beams, the width of the belt, the size of the rocks that are to be irradiated typically of a size of about 10cm to 30cm, the rate of scanning of the beams, the pulses of the beams (if any), etc. - so as to enable the irradiating beams 134, 136 to scan each rock 120 with a predefined repetitive pattern as it passes through the various activation regions, and are further arranged such that each layer/row/section through which each beam extends into the rocks, can be irradiated for substantially the same amount of time as the other layers/sections/rows which were previously irradiated.

It will be understood by those skilled in the art that optimisations can be made to the system 100 shown in Figure 10 in order to ensure that the irradiating beams irradiate a high number of layers or rows of the rocks 120 so as to maximise the extent of irradiation of each irradiated rocks 120. Generally, as a result of the angular spread of the irradiating beams (i.e. gamma rays) resulting from bremsstrahlung, the irradiating beams 132, 134 will, in most practical configurations, be divergent. The vertical spacing defined between the first, second, and third conveyor belt portions 104, 106, 108 should be minimized so that the adjacent, longitudinally spaced irradiating beams 132, 134 can be as close to each other as possible so as to substantially define a single continuous activation region 149, as shown in Figure 1 1 . One way of minimizing the vertical spacing between the conveyor belts 104, 106, 108 may be by using smaller sized rollers 150, on the end points of each of the belt portions 104, 106, 108 and bigger sized rollers 152, 154 at the start points of each of the belt portions 104, 106, 108, as shown in Figure 1 1 .

In an alternative arrangement, it is envisaged that one could have a return belt not pass through the activation region(s) shown in Figures 10 and 1 1 . This can be achieved, for example, by utilising carousel belts, like airport luggage retrieval belts, that rotate horizontally. This has the added benefit of halving the radiation dose to the belt, reducing the rate of radiation damage sustained by the belt.

Other schemes of belts that minimise vertical distance between the belts, and do not require the return belt to be irradiated can be designed. For example, if each of the three first, second, and third belt portions 104, 106, 108 define a substantially trapezoidal profile 160, as shown on the left-hand side of Figure 12, then the three belts 104, 106, 108 can be interlocked at an angle. In general, in such an arrangement 102 of a crossing network of the three belts 104, 106, 108, as shown on the right-hand side of Figure 12, which assume a trapezoidal cross-section shown on the left-hand side of Figure 12, a first transfer belt 162 moving in direction A that is the same as the direction of the first belt portion 104, would transfer rocks onto the first belt portion 104. A second transfer belt 164 collects the rocks at the end of the first belt portion 104 and transfers them to the second belt portion 106 that is arranged at an angle relative to the first belt portion 104 and moves in direction B.

A third transfer belt 166 collects the rocks at the end of the second belt portion 106 and transfers them to the start of the first belt portion 106 that is arranged at an angle relative to the first and second belt portions 104, 106 and moves in direction C. Albeit not shown on the right-hand side of Figure 12, the irradiating beams would extend from the top and bottom of the belts so that they can engage the various regions of the belts and thereby define activation regions for irradiating and activating the rocks as they move on the crossing belt arrangement 102. In yet another example of the present invention, another manner in which the rocks can be irradiated substantially uniformly is by rotating the rocks as it passes through at least one irradiation beam so that multiple sides of the rocks can be irradiated by that at least one irradiating beam, and so as to enable the irradiating beam to penetrate through the rocks up to multiple portions (i.e. layers or rows or sections) of the rocks, and allow the irradiating beam to spend sufficient time irradiating those portions (i.e. layers or rows or sections), as the rocks are rotated relative to the irradiating beam.

Figure 13 shows another embodiment of the system in accordance with the present invention, which is now designated generally by reference numeral 200. The system 200 comprises at least three irradiating beam emitters 202, 204, 206, each emitting a fanned irradiating beam 208, 210, 212, respectively. The system 200 further comprises a displacement arrangement in the form of a rotatable platform 220, such as a centrally opened disc or a toroid, as shown in Figure 13, which is arranged to rotate about a vertical rotational axis R-R thereby defining a circular path of travel for a rocks (not shown) deposited thereon. The rotatable platform 220 has an upper side above which the three irradiating beams 208, 210, 212 extend. In use, for example, rocks are introduced onto the rotatable platform at point X and are removed from or exit the platform at point Z, as shown in Figure 1 3.

The rocks are rotated by the platform for proximately 360 degrees, or up to a point whereby at least two sides of the rocks have been irradiated by at least one of the three irradiating beams. During the rotation of the rocks (not shown), each rock (not shown) is exposed to each beam twice, once at the one side of the rock that is closest to the source of the irradiating beam (i.e. emitting device 202, 204, 206), and once at the opposite side of the rock (not shown) that is further from the beam emitting device 202, 204, 206. Again, the irradiating beams 208, 210, 212 are fanned and scanned relative to the rotatable platform 220 with a predefined repetitive pattern. Each beam is further arranged to spend a sufficient amount of time at a portion (e.g. row or layer or section) of the rock, so as to uniformly irradiate that portion. It is envisaged that other complex rotation arrangement can be devised, for example, a model analogous to planetary motion, where individual rocks are rotated as they revolve around the centre of the platform.

It is envisaged that at least some of the techniques and architectures described herein may find application outside of diamond (or other precious particle) detection. For instance, at least some of the techniques and architectures described herein may be applied in PET imaging/detection applied to the body or a body part of a human or animal. In the application of the invention disclosed herein to medical PET, it will be appreciated that a human/animal body may be located on a displaceable platform which is then exposed to generated gamma rays in much the same way as described above. In this regard, the displaceable platform may be a displaceable bed defining a displacement zone where the human/animal body may be located. In this regard, instead of being conveyed in the fashion described above, the displaceable bed may spatially displace the human/animal body located thereon on a plane extending substantially transverse to the propagation direction of the generated gamma rays. In this way, parts or a whole body of the human/animal may be uniformly activated for purposes of medical PET.

It will be understood that in some example embodiments, for example, medical and/or mining applications of the invention described herein, some example embodiments do no entail displacement of the human/animal body, or part thereof, but the body, or part thereof is located on a fixed platform defining an irradiation zone. In this regard, the generated gamma rays are homogenous beams shaped to the irradiation zone and/or the body, or part thereof, which travel in a propagation direction transverse to a plane associated with the irradiation zone.

The Applicants believe that the invention described herein is useful and achieves a higher efficiency of irradiating of objects to ensure that a significant amount of the object is irradiated so as to activate the same in the manner described herein.