WO2024254632A1

WO2024254632A1 - Apparatus and method for analysis of ore

Info

Publication number: WO2024254632A1
Application number: PCT/AU2024/050022
Authority: WO
Inventors: Shaun Carlos DELPIANO; Yves Leon Jozef Van Haarlem; Jonathan Edward MASTERS
Original assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Current assignee: Commonwealth Scientific and Industrial Research Organization CSIRO
Priority date: 2023-06-14
Filing date: 2024-01-17
Publication date: 2024-12-19
Anticipated expiration: 2025-12-14
Also published as: AU2024304123A1; CN121752919A

Abstract

An apparatus for analysing ore comprises: a pulsed X-ray source configured to irradiate ore material with a pulsed X-ray beam; a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a shutter selectively adjustable between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and a gain control device configured to control a gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain.

Description

Apparatus and method for analysis of ore

Cross-reference to related application

[0001] The present application claims priority to Australian provisional patent application no. 2023901883, filed 14 June 2023, the entire content of which is incorporated herein by reference in its entirety.

Technical Field

[0002] The present disclosure relates to analysis of matter using an X-ray source, and particularly, although not necessarily exclusively, analysis of ore as part of an ore sorting process.

Background

[0003] High-grade mineral ore deposits are depleting around the world, with new mineral ore deposits being increasingly lower in quality. This presents a challenge to the mining industry as demand increases for raw materials found in ore. Selective mining and ore sorting seeks to solve this problem by carrying out mineral analysis of ore to identify ore with higher target element deposits and separating it from waste ore in real-time

[0004] Mineral analysis is typically directed towards determining a concentration of a target element in an ore sample. From this, ore material can be sorted based upon the determined concentration. However, mining plants process considerable quantities of material (e.g., thousands of tonnes per hour) and, therefore, an effective mining plant requires a rapid analytical technique that can operate at a high-throughput flow rate, with reliability and/or enhanced safety.

[0005] One method for the analysis of elements in mineral ores is based on sample activation by highly energetic X-rays, such as the gamma-activation analysis method (GAA). In GAA, a high-energy X-ray source is used to irradiate and activate an ore sample, which induces nuclear reactions in target elements in the sample. Subsequently, a detector measures the gamma radiation emitted by the radioactive decay of the activated sample to determine the concentrations of the target elements. By measuring the distinct energies of these emissions, different target elements can be identified. [0006] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

Summary

[0007] In a first aspect, the present disclosure provides an apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; and a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a shutter selectively adjustable between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; a gain control device configured to control a gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain.

[0008] The gain control device may be configured to control the gain of the PMT synchronously or cyclically with the adjusting of the shutter between the open and closed configurations.

[0009] The apparatus may comprise a processor that is configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT when the shutter is in the closed configuration and the gain of the PMT is the second gain.

[0010] The pulsed X-ray source may comprise a rhodotron. The frequency of the pulsed X-ray source may be greater than 300Hz or greater than 500Hz, for example. [0011] The difference between the first and second gains may be at least a factor of 1,000 or at least a factor of 10,000. In some embodiments, the first gain, which is lower than the second gain, may be a non-zero gain, or else zero gain.

[0012] The apparatus may comprise an actuator configured to adjust the shutter between the open and closed configurations, e.g. automatically and/or periodically. The actuator may comprise a mechanical actuator, such as a linear actuator or rotator, which may move the actuator, e.g. under the action of a motor. Alternatively, the shutter may be an electro- optical shutter that is electrically controlled.

[0013] The gain control device may control the voltage of an electrical signal supplied to the PMT and/or may control switching of dynodes of the PMT, in order to control the gain between the first and second gains. The gain control device may comprise a switching voltage divider circuit, for example, which may provide a switching voltage divider base of the PMT, for example.

[0014] The apparatus may comprise a controller configured to control at least one of: the adjusting of the shutter between the open configuration and the closed configuration; and the controlling of the gain of the PMT between the first gain and the second gain.

[0015] The shutter may comprises bismuth. In some embodiments, the apparatus may comprise a shield located between the X-ray source and the scintillator, wherein the shield reduces an intensity of the pulsed X-ray beam that impinges on the scintillator. The shield may comprise bismuth.

[0016] The scintillator of the beam monitoring device may comprise bromine.

[0017] The apparatus may comprise at least one detector to monitor emission radiation from the ore material in response to irradiation of the ore material by the pulsed X-ray beam. The detector may comprise a lanthanum bromide scintillator, for example.

[0018] The processor may be configured to determine a correction factor based on the measurement of voltage of the electrical output signal from the PMT and correct a signal from the detector based on the correction factor. The electrical output signal from the PMT may vary over time based on changes over time in one or more parameters of the pulsed X-ray beam that impinges on the scintillator of the beam monitoring device, including energy, intensity, frequency, duty cycle and/or angular distribution, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator, and the correction factor that is determined may therefore account for variations in one or more of these parameters. As parameters of the pulsed X-ray beam may change over time and may therefore be different when the X-ray beam irradiates different pieces or sections of ore material, different correction factors may be determined and used to correct signals from the detector corresponding to emission radiation from different pieces or sections of ore material.

[0019] The apparatus may comprise at least one conveyor belt, wherein the ore material irradiated by the pulsed X-ray beam is located on the at least one conveyor belt. The ore material may be moved along the at least one conveyor belt between an irradiation region where the ore material is irradiated by the pulsed X-ray beam and a detection region where emission radiation from the ore material in response to the irradiation of the ore material is monitored.

[0020] According to a second aspect of the present disclosure, a method for analysing ore is provided comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and controlling gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain. [0021] The method of the second aspect may utilise apparatus according to the first aspect and/or may carry out steps described with respect to one or more features of the apparatus according to the first aspect.

[0022] According to a third aspect, the present disclosure provides an apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; and a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and an optoelectronic device that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a shutter selectively adjustable between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the optoelectronic device when the shutter is in the closed configuration.

[0023] According to a fourth aspect, the present disclosure provides a method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and an optoelectronic device that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the optoelectronic device when the shutter is in the closed configuration. [0024] The optoelectronic device may be a silicon photomultiplier (SiPM), for example.

[0025] The apparatus and method of the third and fourth aspects may be similar to, and may comprise one of more features of, the apparatus and methods, respectively, of the first and second aspects, except that the PMT is replaced with an optoelectronic device such as a SiPM and there are not necessarily any specific features associated with the controlling of gain.

[0026] According to a fifth aspect, the present disclosure provides an apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; and a gain control device configured to control a gain of the PMT to be a first gain during each pulse of the pulsed X-ray beam and a second gain between pulses of the X-ray beam, the second gain being higher than the first gain.

[0027] The gain control device may be configured to control the gain of the PMT synchronously or cyclically with pulsing of the X-ray beam.

[0028] The apparatus may comprise a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT. The measurement may be during each pulse of the X-ray beam and between pulses of the X-ray beam.

[0029] The pulsed X-ray source may comprise a linear accelerator (LINAC). The frequency of the pulsed X-ray source may be about, or less than, 500Hz or 300Hz.

[0030] The difference between the first and second gains may be at least a factor of 1,000 or at least a factor of 10,000. In some embodiments, the first gain, which is lower than the second gain, may be a non-zero gain, or else zero gain. The gain control device may control the voltage of an electrical signal supplied to the PMT and/or control switching of dynodes of the PMT. The gain control device may comprise a switching voltage divider circuit, for example, which may provide a switching voltage divider base of the PMT, for example.

[0031] In some embodiments, the apparatus may comprise a shield located between the X-ray source and the scintillator, wherein the shield reduces an intensity of the pulsed X- ray beam that impinges on the scintillator. The shield may comprise bismuth.

[0032] The scintillator of the beam monitoring device may comprise bromine.

[0033] The apparatus may comprise at least one detector to monitor emission radiation from the ore material in response to irradiation of the ore material by the pulsed X-ray beam.

[0034] The processor may be configured to determine a correction factor based on the measurement of voltage of the electrical output signal from the PMT and correct a signal from the detector based on the correction factor. The detector may comprise a lanthanum bromide scintillator, for example. The electrical output signal from the PMT may vary over time based on changes over time in one or more parameters of the pulsed X-ray beam that impinges on the scintillator of the beam monitoring device, including energy, intensity, frequency, duty cycle and/or angular distribution, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator, and the correction factor that is determined may therefore account for variations in one or more of these parameters. As parameters of the pulsed X-ray beam may change over time and may therefore be different when the X- ray beam irradiates different pieces or sections of ore material, different correction factors may be determined and used to correct signals from the detector corresponding to emission radiation from different pieces or sections of ore material.

[0035] The apparatus may comprise at least one conveyor belt, wherein the ore material irradiated by the pulsed X-ray beam is located on the at least one conveyor belt. The ore material may be moved along the at least one conveyor belt between an irradiation region where the ore material is irradiated by the pulsed X-ray beam and a detection region where emission radiation from the ore material in response to the irradiation of the ore material is monitored. [0036] According to a sixth aspect of the present disclosure, a method for analysing ore is provided comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; and controlling a gain of the PMT to be a first gain during each pulse of the pulsed X-ray beam and a second gain between pulses of the X-ray beam, the second gain being higher than the first gain.

[0037] The method may comprise controlling the gain of the PMT synchronously or cyclically with pulsing of the X-ray beam.

[0038] The method may comprise monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT. The measurement may be during each pulse of the X-ray beam and between pulses of the X-ray beam.

[0039] The method of the sixth aspect may utilise apparatus according to the fifth aspect and/or may carry out steps described with respect to one or more features of the apparatus according to the fifth aspect.

[0040] According to a seventh aspect, the present disclosure provides apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; and a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT during each pulse of the X-ray beam. [0041] According to an eighth aspect, the present disclosure provides a method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; and monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT during each pulse of the X-ray beam.

[0042] The apparatus and method of the seventh and eighth aspects may be similar to, and may comprise one of more features of, the apparatus and methods, respectively, of the fifth and sixth aspects, except that monitoring of stability may be based on measurements only during each pulse of the X-ray beam, and associated with this, the apparatus and method may not necessarily have specific features associated with the controlling of gain of the PMT.

[0043] According to a ninth aspect, the present disclosure provides apparatus for analysing ore comprising: an X-ray source configured to irradiate ore material with a pulsed X-ray beam; and a detector configured to monitor emission radiation from the ore material in response to irradiation of the ore material by the X-ray source, wherein the detector comprises a lanthanum bromide scintillator.

[0044] According to a tenth aspect, the present disclosure provides apparatus for analysing ore comprising: an X-ray source configured to irradiate ore material with a pulsed X-ray beam; and a detector configured to monitor emission radiation from the ore material in response to irradiation of the ore material by the X-ray source, wherein the X-ray source is a rhodotron. [0045] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Brief Description of Drawings

[0046] By way of example only, embodiments of the present disclosure are now described with reference to the drawings in which:

[0047] Figs, la and lb show schematic views of apparatus for analysing ore according to an embodiment of the present disclosure;

[0048] Fig. 2 shows a flowchart of method steps for analysing ore according to an embodiment of the present disclosure;

[0049] Fig. 3 shows a schematic view of the operation of a scintillator and PMT;

[0050] Fig. 4 shows timelines of activity of components of an apparatus according to an embodiment of the present disclosure;

[0051] Figs. 5a and 5b show schematic views of an apparatus for analysing ore including a linearly actuated shutter according to an embodiment of the present disclosure;

[0052] Figs. 6a and 6b show schematic views of apparatus for analysing ore including a rotatably actuated shutter according to an embodiment of the present disclosure;

[0053] Figs. 7a and 7b show schematic views of apparatus for analysing ore including an electro-optically actuated shutter according to an embodiment of the present disclosure;

[0054] Fig. 8 shows a schematic view of apparatus for analysing ore according to an embodiment of the present disclosure;

[0055] Fig. 9 shows a flowchart of method steps for analysing ore according to an embodiment of the present disclosure;

[0056] Fig. 10 shows timelines of activity of components of an apparatus according to an embodiment of the present disclosure;

[0057] Fig. 11 shows a schematic view of apparatus for analysing ore according to an embodiment of the present disclosure; [0058] Figs. 12a and 12b show a PMT and associated gain control device according to an embodiment of the present disclosure in low and high gain modes, respectively;

[0059] Fig. 13 shows a block diagram of apparatus according to an embodiment of the present disclosure;

[0060] Figs. 14a and 14b show a schematic view of apparatus for analysing ore according to an embodiment of the present disclosure;

[0061] Fig. 15 shows a flowchart of method steps for analysing ore according to an embodiment of the present disclosure;

[0062] Fig. 16 shows a plot indicating isomer activity within a scintillator when exposed to successive individual X-ray pulses, where the pulse period is much shorter than isomer half-life in the scintillator;

[0063] Fig. 17 shows a plot of activation of Br-79m in a cerium bromide scintillator according to a first example of the present disclosure;

[0064] Fig. 18 shows a further plot of activation of Br-79m in a cerium bromide scintillator according to the first example of the present disclosure;

[0065] Fig. 19 shows a plot of activation of Br-79m in a cerium bromide scintillator according to a second example of the present disclosure; and

[0066] Fig. 20 shows a further plot of activation of Br-79m in a cerium bromide scintillator according to the second example of the present disclosure.

Description of Embodiments

[0067] Apparatus 100 for analysis of ore according to an embodiment of the present disclosure is illustrated in Figs, la and lb and includes an X-ray source 110 that is configured to emit a pulsed X-ray beam 111, for the purpose of irradiating ore material 120. The apparatus 100 also includes a beam monitoring device 130 including a scintillator 131 and a photomultiplier tube (PMT) 132. The scintillator 131 is configured to emit light when excited by the X-ray beam 111, and the PMT 132 is configured to absorb the light emitted by the scintillator 131 and convert the absorbed light into an electrical output signal 150. [0068] The apparatus 100 also includes a shutter 140 that is selectively adjustable between an open configuration as illustrated in Fig. la and a closed configuration as illustrated in Fig. lb. When the shutter 140 is in the open position, the X-ray beam 111 impinges on the scintillator 131 and, when the shutter 140 is in the closed configuration, the shutter 140 substantially shields the X-ray beam 111 from impinging on the scintillator 131.

[0069] The apparatus 100 also includes a gain control device 133 configured to control a gain of the PMT 132 and particularly, in this embodiment, to be a first gain when the shutter 140 is in the open configuration and a second gain when the shutter 140 is in the closed configuration, the second gain being higher than the first gain. For example, the second gain may be at least 10³ or at least 10⁴ times higher than the first gain. In some embodiments, the first gain may be a non-zero gain, or else zero gain.

[0070] The gain control device 133 may be part of the beam monitoring device 130 in some embodiments, or separate from the beam monitoring device 130 in alternative embodiments. For example the gain control device 133 may form part of a control system that optionally also controls adjustment of the shutter 140 between the open and closed configurations. In some embodiments, the gain control device 133 may comprise a switching voltage divider. In some embodiments, the gain control device 133 may provide a switching voltage divider base of the beam monitoring device 130. An embodiment of a PMT and associated gain control device that may be used with this and other embodiments of the present disclosure is discussed further below with reference to Figs. 12a, 12b and 13, although other configurations of PMT and gain control devices may also be used.

[0071] In some embodiments, the apparatus may include a processor configured to monitor (e.g. determine or measure) stability of the pulsed X-ray beam 111 based on the electrical output signal 150 from the PMT 132, e.g. a measured voltage of the electrical output signal 150, and particularly when the shutter 140 is in the closed configuration and the gain of the PMT 132 is the second gain. Monitoring of stability of the pulsed X-ray beam 111 may include monitoring variations resulting from changes in energy and/or intensity of the pulsed-X-ray beam 111 and/or other parameters such as frequency, duty cycle and/or angular distribution of the pulsed X-ray beam 111, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator 131 and therefore the amplitude of the electrical output signal from the PMT 132. The processor may be part of the beam monitoring device 130 in some embodiments or separate from the beam monitoring device 130 in alternative embodiments.

[0072] A method 200 according to an embodiment of the present disclosure, which may be carried out using the apparatus 100 of Figs, la and lb or otherwise, is illustrated by the flow chart of Fig. 2. The method includes:

[0073] At 210, irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source.

[0074] At 220, selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on a scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator. The scintillator and a photomultiplier tube (PMT) may form part of a beam monitoring device, wherein the scintillator emits light when excited by the X-ray beam and the photomultiplier tube (PMT) absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal.

[0075] At 230, controlling a gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain.

[0076] In some embodiments, the method may also include monitoring stability of the pulsed X-ray beam based on the electrical output signal from the PMT, e.g. a measured voltage of the electrical output signal, when the shutter is in the closed configuration and the gain of the PMT is the second gain. Monitoring of stability of the pulsed X-ray beam may include monitoring variations resulting from changes in energy and/or intensity of the pulsed-X-ray beam and/or other parameters such as frequency, duty cycle and/or angular distribution of the pulsed X-ray beam, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator and therefore the amplitude of the electrical output signal from the PMT. [0077] The apparatus and method may be suitable for use with ultrafast pulsed X-ray sources such as a rhodotron, that might otherwise cause damage to components of a beam monitoring device and/or cause a beam monitoring device be saturated by the high energy associated with such X-ray sources. For example, the apparatus and method may be suitable for use with pulsed X-ray sources having a pulse frequency of at least 300Hz or at least 500Hz. For example, an X-ray source such as a rhodotron may have a pulse frequency of over IMhz, over 10MHz, or over 100MHz.

[0078] To aid general understanding, the function of a scintillator and an associated PMT is now described with reference to the apparatus 300 of Fig. 3, although it will be recognized that features and advantages of the present disclosure are not necessarily bound by the following theory and that a variety of different types of scintillators and PMTs may be utilized in embodiments of the present disclosure.

[0079] A scintillator 310 includes material that emits light 302 (photons typically in the visible spectrum), through a photoluminescence process, when it is interacts with radiation that impinges on the material such as X-ray photons 301 or gamma rays. The PMT 320 includes a photocathode 321 at e.g. a front surface of a vacuum tube 322, the photocathode 321 having a layer of photosensitive material, such as caesium or alkali metals. When photons 302 emitted by the scintillator 310 strike the photocathode 321, electrons 303 are emitted by the photocathode due to the photoelectric effect.

[0080] Emitted electrons 303 from the photocathode 321 are accelerated within the vacuum tube 322 by an electric field provided by a high voltage power supply 330 and directed towards a series of dynodes 323. The dynodes 323 are electrodes typically maintained at successively more positive potentials (or less negative potentials in some variations of PMTs) by the high voltage power supply 330. As the electrons impact the dynodes 323, the dynodes 323 release additional electrons through a process called secondary emission and the cascading electron emission effect across successive dynodes 323 results in a significant amplification of the original electrical signal.

[0081] At the opposite end of the vacuum tube 322 to the photocathode 321, the PMT 320 includes an anode 324, which generates an electrical output signal based on the electrons collected at the last dynode 323 in the series. The electrical output signal, which may be passed through further electrical amplifiers and signal processing circuits, provides a measurable voltage signal that is proportional to parameters such as the intensity of the radiation incident on the scintillator 310.

[0082] According to the present disclosure, a scintillator and PMT form a beam monitoring device, which may be used to monitor the stability of the pulsed beam from the X-ray source based on the electrical output signal from the PMT. As described further below with reference to Fig. 11, this monitoring may be utilised, for example, to determine a correction factor for correcting measurements of the decay of isomers in the ore as a result of the irradiation of the ore by the X-ray source, which corrected measurements may be used as part of an ore analysis process, e.g. for the purpose of ore sorting or otherwise. Isomer activity is dependent on factors such as the intensity and energy of the X-ray beam that irradiated the ore and therefore correction based on the electrical output signal of the beam monitoring device may provide for more accurate analysis of ore and more effective ore sorting. The correction may take into account stability (e.g. changes in energy and/or intensity, but also changes in other parameters such as frequency, duty cycle and/or angular distribution) of the X-ray beam as it irradiates different ore material over time.

[0083] The adjustment of the shutter and control of gain of the PMT over time, according to one or more embodiments of the present disclosure, is illustrated in the timelines in Fig. 4 alongside timelines indicative of radiative activity of the scintillator and pulse status of the pulsed X-ray source. The pulsed X-ray source in this example is a high energy, ultrafast X-ray source and specifically a rhodotron, and the material of the scintillator in this example comprises bromine. The scintillator is specifically a cerium bromide (CeBr) scintillator although other bromine containing scintillators, or scintillators without bromine, may be used.

[0084] When exposed to the pulsed X-ray beam from the X-ray source, the scintillator emits a light at a high intensity which could damage the PMT and/or may result in a nonlinear electrical output signal from the PMT. In embodiments according to the present disclosure, the shutter is adjusted between the open and closed configuration. At the time that the shutter is open and the X-ray source impinges on the scintillator, the gain of the PMT is reduced to the first (low) gain, protecting the PMT against damage that might be caused as a result of high intensity light emission from the scintillator while subjected to successive X-ray pulses. However, when the shutter is closed, the scintillator is shielded from the pulsed X-ray beam and is therefore not irradiated or activated as intensely. At the time that the shutter is closed the gain of the PMT is increased to the second (high) gain, allowing continued but less intensive activity of the scintillator (e.g. isomer decay activity such as bromine decay activity based on gamma ray excitation within the scintillator material) to be more accurately measured by the PMT and associated circuitry. This approach can provide for semi-continuous monitoring of the stability of the X-ray beam/X- ray source.

[0085] The time period during which the shutter is maintained in each open and closed state may be significantly higher than the period of each X-ray pulse from the X-ray source. The shutter may be maintained in each open and closed state for a period of, for example, between 1 to 30 seconds, or 5 to 25 seconds, or 10 to 20 seconds, corresponding to a frequency of adjustment of the shutter of roughly 0.03 to 1Hz, whereas the X-ray source may have a frequency of roughly 500Hz to 200MHz. Thus, the frequency of the adjustment of the shutter may be significantly lower (e.g. at least a factor of 10³, or 10⁴, or IO^5, or 10⁶ or 10⁷ lower) than the frequency of the X-ray source.

[0086] The time period during which the shutter is maintained in each open state may be the same time period during which the shutter is maintained in each closed state.

Alternatively, the shutter may be maintained in each open state for longer than each closed state, or vice versa. The time periods may be selected or controlled dependent on the degree of exposure of the scintillator to the X-ray beam that is required and the length of time it is desired to monitor or measure consequential isomer decay activity.

[0087] Although the changes in the gain of the PMT is synchronous with the opening and closing of the shutter in the embodiment of Fig. 4, it will be recognised that the changes may be cyclic with, but not necessarily synchronous with, the opening and closing of the shutter in alternative embodiments. For example, the gain may be adjusted at a frequency or periodicity that is the same frequency or periodicity as the opening and closing of the shutter, but the different events may or may not occur exactly at the same time.

[0088] When the X-ray beam impinges on the scintillator immediately after the shutter is adjusted to an open configuration, the light emission from the scintillator may still be relatively low and may not have increased to a level that could damage the PMT. Thus, the gain of the PMT may maintained in a high, or higher, state during an initial portion of a period in which the shutter is open, before being adjusted to a low, or lower, state during the remaining, latter portion of the period in which the shutter is open. The initial portion of the period when the shutter is open may be, or may be within, the first 33% or less, 25% or less, 20% or less, 15% or less or 10% or less of that period.

[0089] Additionally or alternatively, when the X-ray beam is shielded from impinging on the scintillator immediately after the shutter is adjusted to a closed configuration, the light emission from the scintillator may still be relatively high and may not have reduced to a level that is appropriate for accurate measuring of activity by the PMT. Thus, the gain of the PMT may maintained in a low, or lower, state during an initial portion of a period in which the shutter is closed before being adjusted to a high, or higher, state during a latter portion of the period in which the shutter is open. The initial portion of the period when the shutter is closed may be the first 33% or less, 25% or less, 20% or less, 15% or less or 10% or less of that period.

[0090] In embodiments of the present disclosure, the shutter may be adjusted between the open and closed configurations through a movement of the shutter. For example, as illustrated in Figs. 5a and 5b, the shutter 141 may be connected to an actuator, such as a linear actuator 142, that moves the shutter between the closed and open positions. In the closed position as illustrated in Fig. 5a, the shutter 141 may be positioned directly between the X-ray source 110 and the scintillator 132, shielding direct irradiation of the scintillator by the X-ray source 110. In the open position as illustrated in Fig. 5b, the shutter may no longer be positioned directly between the X-ray source 110 and the scintillator 132, permitting direct irradiation of the scintillator by the X-ray source 110.

[0091] Optionally, as also illustrated in Figs. 5a and 5b, the apparatus 100 may include a shield 143 between the X-ray source 110 and the scintillator 132. The shield 143 may be considered a primary shield in conjunction with secondary shielding provided by the shutter 141. The shield 143 may provide for a reduction of the intensity of the pulsed X- ray beam that impinges on the scintillator, even when the shutter 141 is in an open configuration. [0092] As another example, as illustrated in Figs. 6a and 6b the shutter 144 may be connected to an actuator such as a rotator device 145, which moves the shutter 144, and more particularly rotates the shutter 144, between the open and closed configurations. The shutter 144 may comprise a planar element, for example, that may be rotated between a closed configuration as illustrated in Fig. 6a, where its plane is substantially perpendicular to, and shields, the X-ray beam, and an open configuration as illustrated in Fig. 6b, where its plane is substantially parallel to, and does not shield, the X-ray beam.

[0093] As another example, as illustrated in Figs. 7a and 7b the shutter may be an electro-optical shutter 146, which may not move when adjusted between the open and closed configurations. The electro-optical shutter 146 may be connected to an actuator such as an electro-optical controller 147, which sends one or more electrical signals to change polarization properties of the electro-optical shutter material (e.g. liquid crystal material). In the closed configuration as illustrated in Fig. 7a, polarization properties of the electro-optical shutter material may be controlled so that transmission of radiation from the X-ray source is shielded and, in the open configuration as illustrated in Fig. 7b, polarization properties of the electro-optical shutter material may be controlled so that transmission of radiation from the X-ray source is no longer shielded.

[0094] Although not illustrated, the apparatus of Figs. 6a and 6b, and of Figs 7a and 7b, may also employ a primary shield similar or identical to the primary shield 143 discussed above with respect to Figs. 5a and 5b.

[0095] In some embodiments, including when the shutter is a type of mechanical shutter as discussed above with respect to Figs. 5a to 6b, the shutter may comprise bismuth. Additionally or alternatively, the primary shield may comprise bismuth (e.g. a combination of bismuth and lead).

[0096] Although a variety of different shielding materials may be used in the shutter and primary shield, including lead or layered steel, bismuth has reduced activation properties compared to lead, reducing the possibility that the shutter may contribute to excitation of the scintillator, which could result in a reduced signal to noise ratio of the electrical output of the beam monitoring device. In particular, bismuth has only a single naturally occurring isotope and may have no major activation reactions associated within the energy range (e.g., 8-9 MeV) of the X-ray source that may be used to irradiate ore material for the purpose of identifying target element concentration (e.g. gold concentration) via gamma ray spectroscopy for example.

[0097] In embodiments discussed above, gain of the PMT is adjusted from a first (relatively low) gain when a shutter is open, to protect a PMT, to a second (relatively high) gain when the shutter is closed, to allow continued isomer activity at a scintillator to be more readily measured during this period. However, in alternative embodiments, a different optoelectronic device such as a silicon photomultiplier (SiPM) may be used in place of a PMT, which may not suffer the same risk of damage as a PMT when subjected to high intensity scintillation light while the shutter is open. In these alternative embodiments, there may be no gain control device provided, or at least no adjustment of gain of the optoelectronic device.

[0098] Following from this, in an embodiment of the present disclosure as illustrated in Figs. 14a and 14b, apparatus 900 for analysis of ore includes an X-ray source 910 that is configured to emit a pulsed X-ray beam 911, for the purpose of irradiating ore material 920. The apparatus 900 also includes a beam monitoring device 930 including a scintillator 931 and a SiPM 932. The scintillator 931 is configured to emit light when excited by the X-ray beam 911, and the SiPM 932 is configured to absorb the light emitted by the scintillator 931 and convert the absorbed light into an electrical output signal 950.

[0099] The apparatus 900 also includes a shutter 940 that is selectively adjustable between an open configuration as illustrated in Fig. 14a and a closed configuration as illustrated in Fig. 14b. When the shutter 940 is in the open position, the X-ray beam 911 impinges on the scintillator 931 and, when the shutter 940 is in the closed configuration, the shutter 940 substantially shields the X-ray beam 911 from impinging on the scintillator 931.

[0100] In some embodiments, the apparatus may include a processor configured to monitor (e.g. determine or measure) stability of the pulsed X-ray beam 911 based on the electrical output signal 950 from the SiPM 932, e.g. a measured voltage of the electrical output signal 950, and particularly when the shutter 940 is in the closed configuration. Monitoring of stability of the pulsed X-ray beam 911 may include monitoring variations resulting from changes in energy and/or intensity of the pulsed-X-ray beam 911 and/or other parameters such as frequency, duty cycle and/or angular distribution of the pulsed X- ray beam 911, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator 931 and therefore the amplitude of the electrical output signal 950 from the SiPM 932. The processor may be part of the beam monitoring device 930 in some embodiments or separate from the beam monitoring device 930 in alternative embodiments.

[0101] The apparatus 900 may have any of the same features and functions as the apparatus discussed above with respect to preceding embodiments, but without necessarily having the gain control features or function. The SiPM 932 may be replaced with alternative types of optoelectronic devices that may also have a reduced risk of damage, compared to a PMT, as a result of exposure to high intensity scintillation light.

[0102] A method 1000 according to an embodiment of the present disclosure, which may be carried out using the apparatus 900 of Figs. 14a and 14b or otherwise, is illustrated by the flow chart of Fig. 15. The method includes:

[0103] At 1010, irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source.

[0104] At 1020, selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on a scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator. The scintillator and a SiPM may form part of a beam monitoring device, wherein the scintillator emits light when excited by the X-ray beam and the SiPM absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal.

[0105] In this disclosure, terms such as “shield” or “shielded” and “closed” are generally used to describe the function of the shutter in preventing an X-ray beam from impinging directly on a scintillator. It should be recognised, however, that these terms do not necessarily mean that no irradiation at all from the X-ray source is incident on the scintillator when the beam is “shielded” or the shutter is “closed”. For example, some indirect X-ray radiation may still reach the scintillator, and/or a reduced portion of the X- ray beam may still impinge directly on the scintillator. Nevertheless, it should be recognised that, when the shutter is in the closed configuration and the X-ray beam is substantially shielded, the intensity of the X-ray radiation incident on the scintillator is substantially reduced in comparison to when the shutter is in the open configuration and the X-ray beam is not shielded. For example, in the closed/shielded state, the intensity may be reduced by at least 50%, at least 75%, at least 80%, at least 90%, or at least 95% in comparison to the open/non-shielded state.

[0106] Apparatus 400 for analysing ore 420 according to another embodiment of the present disclosure is illustrated in Fig. 8 and includes an X-ray source 410 that is configured to emit a pulsed X-ray beam 411, for the purpose of irradiating ore material 420. The apparatus 400 also includes a beam monitoring device 430 including a scintillator 431 and a photomultiplier tube (PMT) 432. The scintillator 431 is configured to emit light when excited by the X-ray beam 411, and the PMT 432 is configured to absorb the light emitted by the scintillator 431 and convert the absorbed light into an electrical output signal 450.

[0107] The apparatus 400 also includes a gain control device 433 configured to control a gain of the PMT 432 to be a first gain during each pulse of the pulsed X-ray beam 411 and to be a second gain between pulses (e.g. between each pulse) of the X-ray beam, the second gain being higher than the first gain. In some embodiments, the gain control device 433 may comprise a switching voltage divider. The gain control device 433 may provide a switching voltage divider base of the beam monitoring device 430. An embodiment of a PMT and associated gain control device that may be used with this and other embodiments of the present disclosure is discussed further below with reference to Figs. 12a, 12b and 13, although other configurations of PMT and gain control devices may also be used.

[0108] The apparatus 400 may also include a processor configured to monitor stability of the pulsed X-ray beam 411 based on the electrical output signal 450 from the PMT 432, e.g. based on a measured voltage of the electrical output signal 450. Monitoring of stability of the pulsed X-ray beam 411 may include monitoring variations resulting from changes in energy and/or intensity of the pulsed-X-ray beam 411 and/or other parameters such as frequency, duty cycle and/or angular distribution of the pulsed X-ray beam 411, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator 431 and therefore the amplitude of the electrical output signal 450 from the PMT 432.

[0109] The gain control device 433 may be part of the beam monitoring device 430 in some embodiments or separate from the beam monitoring device 430 in alternative embodiments. Similarly, the processor may be part of the beam monitoring device 430 in some embodiments or separate from the beam monitoring device 430 in alternative embodiments.

[0110] A method 500 according to an embodiment of the present disclosure, which may be carried out using the apparatus 400 of Fig. 8 or otherwise, is illustrated by the flow chart of Fig. 9. The method includes:

[0111] At 510, irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source.

[0112] At 520, controlling a gain of a PMT to be a first gain during each pulse of the pulsed X-ray beam and a second gain between pulses (e.g. between each pulse) of the X- ray beam, the second gain being higher than the first gain. The photomultiplier tube (PMT) and a scintillator may form part of a beam monitoring device, wherein the scintillator emits light when excited by the X-ray beam and the photomultiplier tube (PMT) absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal.

[0113] The method may include monitoring stability of the pulsed X-ray beam based on the electrical output signal from the PMT, e.g. a measured voltage of the electrical output signal. Monitoring of stability of the pulsed X-ray beam may include monitoring variations resulting from changes in energy and/or intensity of the pulsed-X-ray beam and/or other parameters such as frequency, duty cycle and/or angular distribution of the pulsed X-ray beam, for example. The variations in any one or more of these parameters, and potentially other parameters, may change the amount of energy absorbed by the scintillator and therefore the amplitude of the electrical output signal from the PMT.

[0114] The apparatus and method describe with reference to Figs. 8 and 9 may be suitable for use with a slower pulsed X-ray source than may be used with apparatus described above with respect to e.g. Figs, la and lb. For example, the apparatus and method may be suitable for use with pulsed X-ray sources having a pulse frequency of about, or less than, 500Hz or 300Hz. For example, the X-ray source may be a linear particle accelerator (LINAC) rather than a rhodotron.

[0115] The radiative energy of an X-ray source such as a LINAC can also cause damage to components of a beam monitoring device such as a PMT and/or cause a beam monitoring device to provide a non-linear electrical signal output. However, a LINAC generally has a much lower pulse rate than a rhodotron. On this basis, the present disclosure has identified that gain control, synchronized or cyclic with the periodic “on” and “off’ state of the pulse X-ray beam from a LINAC or other lower energy X-ray source, may be sufficient to avoid damage of the PMT and/or non-linear or saturation effects. Sufficiently fast switching of the gain of the PMT in time with the “on” and “off’ state of the pulse X-ray beam may be achievable for a lower frequency source such as a LINAC, but may not be achievable for a higher frequency source such as a rhodotron.

[0116] Again, the beam monitoring according to the apparatus and method of this embodiment may be utilised, for example, to determine a correction factor for correcting measurements of the decay of isomers in ore as a result of the irradiation by the X-ray source, which corrected measurements may be used as part of an ore analysis process, e.g. for the purpose of ore sorting or otherwise. As noted above, isomer activity is dependent on parameters such as the energy and/or intensity of the X-ray beam that irradiated the ore and therefore a correction based on the electrical output signal from the PMT of the beam monitoring device may provide for more accurate analysis of ore and more effective ore sorting. The correction may take into account stability (e.g. changes in energy and/or intensity, or other parameters such as frequency, duty cycle and/or angular distribution, for example) of the X-ray beam as it irradiates different ore material overtime. As parameters of the pulsed X-ray beam may change over time and may therefore be different when the X-ray beam irradiates different pieces or sections of ore material, different correction factors may be determined and used to correct signals from the detector corresponding to emission radiation from different pieces or sections of ore material.

[0117] The control of gain of the PMT over time, according to one or more embodiments of the present disclosure, is illustrated in the timelines in Fig. 10 alongside timelines indicative of radiative activity and associated fluorescent output of the scintillator and pulse status of the pulsed X-ray source. The pulsed X-ray source in this example is a LINAC, and the material of the scintillator in this example comprises bromine. The scintillator is specifically a cerium bromide (CeBr) scintillator although other bromine containing scintillators, or scintillators without bromine, may be used.

[0118] Although the control of the gain of the PMT is generally timed with the on and off state of the pulsed X-ray beam of Fig. 10, it will be recognised that the changes may be cyclic with, but not necessarily synchronous with, both the on and off state of the pulsed X-ray beam. For example, as seen in Fig. 10, the gain may be maintained at the lower gain for a time period that is longer than the on state of each X-ray beam pulse, and corresponding more closely to longer periods of high fluorescent activity from the scintillator following the emission of each X-ray pulse.

[0119] When exposed to the pulsed X-ray beam from the X-ray source, the scintillator is excited by the X-ray source and provides a large fluorescent light output which could damage the PMT and/or result in non-linear electrical output signals from the PMT. PMTs operating with a scintillator to measure the energy deposited within its volume are typically designed and optimised to convert and amplify light produced by the scintillator due to a single X-ray (or gamma ray) depositing around 50 keV to 2 MeV. While multiple photons might interact with the scintillator in a short time period, there typically is enough time to process each individual event before the next arrives. Under irradiation by a LINAC, however, the scintillator may have 10⁹ - 10¹⁵ X-ray photons depositing energy within its volume (depending on shielding, position, size of scintillator, etc.) with energy up to 9 MeV in a pulse several microseconds long. The resultant fluorescent signal does not have time to dissipate between each interaction, resulting in a powerful composite fluorescent pulse that may be 10⁶ - 10¹⁰times as intense, which, when amplified by the PMT, may cause substantial damage to the PMT and other processing electronics.

[0120] As evident from the timelines of Fig. 10, however, in embodiments according to the present disclosure the gain of the PMT is controlled to be a lower gain during each pulse (“on” state) of the pulsed X-ray beam, protecting the PMT during each fluorescent output peak and generally converting the output from the scintillator into a more measurable range. Moreover, the gain of the of the PMT is controlled to be a higher gain between each pulse (“off’ state) of the X-ray beam and therefore between each fluorescent output peak, providing for a higher electrical output signal from the PMT and therefore enabling more accurate monitoring of beam stability based on continued isomer activity (in this example bromine activity) between each pulse. The approach can enable the beam monitoring device to continuously or substantially continuously monitor the stability of the X-ray beam from the X-ray source. The monitoring is based on both fluorescent activity as the X-ray beam pulses impinge on the scintillator, and isomer activity within the scintillation material between X-ray pulses impinging on the scintillator, that may identify more specific energy profiles of the X-ray beam. Combining monitoring of these different activities can result in a more accurate or detailed information to be determined about the X-ray beam stability, e.g. in comparison to monitoring one of these activities alone.

[0121] In more detail, measuring isomer (e.g. bromine) activity, between pulses of an X- ray beam from an X-ray source such as a LINAC, on its own can have some limitations. For example, a LINAC running at 500 Hz has pulses arriving at the scintillator every 2 milliseconds. As bromine-79m, for example, has a half-life of 4.85 seconds, only a small proportion of activated nuclei will decay away in each 2 millisecond period, and the activity of the isomer will build up gradually over many pulses. This eventually causes a maximum bromine activity range to be reached (saturation) as the number of activated nuclei decaying each pulse is equal to the amount being added. The saturation point depends on the activation rate (a product of the dose rate and the reaction cross section) and the half-life (which is a constant). In the 2 millisecond long window between pulses where activated nuclei decay can be measured, only roughly 0.03% of these isomers will decay and produce a measurable result. The plot of Fig. 16 provides an example of this activity building across individual X-ray pulses (the axes are arbitrary for illustration).

Even fast scintillators can only process a limited number of radiation events in such a short window. Considering that bromine is only one of many potential isomers activated in this process, the device may have limited ability to detect and process enough events to accurately determine the activity of the bromine isomer produced by a single X-ray beam pulse. This can still allow, but puts a limit on the ability of the technique, to monitor beam stability across a full energy spectrum for the X-ray source, at least over a small number of X-ray beam pulses. [0122] Conversely, monitoring the fluorescent response of the scintillator while X-ray beam pulses impinge on the scintillator may provide useful information on the general performance of the X-ray ray source, but may provide more limited spectral information.

[0123] By combining monitoring of isomer activity with monitoring of the fluorescent activity as the pulses impinge on scintillator, however, greater accuracy or information about the X-ray beam stability may be achieved, e.g. in order to determine a suitable correction factor as per discussions above.

[0124] In alternative embodiments, despite the potential limitations indicated above, monitoring of X-ray beam stability may be based only on the electrical output signal from the PMT measured during each X-ray beam pulse (i.e. based on fluorescent activity as each X-ray beam pulse impinges on the scintillator) or only on the electrical output signal from the PMT between each X-ray beam pulse (i.e. based on isomer decay activity). Monitoring of X-ray beam stability in this manner may still provide sufficiently useful information for a correction factor to be determined.

[0125] Particularly when monitoring X-ray beam stability based only on the electrical output signal from the PMT measured during each X-ray beam pulse, the gain of the PMT may be maintained at a single (relatively low) gain value throughout the process, the gain being selected to prevent damage of the PMT as the X-ray beam pulses impinge on the scintillator. Since there is no monitoring based on isomer activity within the scintillation material between X-ray beam pulses, there may be no need to increase PMT gain between X-ray beam pulses.

[0126] Although different embodiments have been described above, with some employing both shutter and gain control, and others employing gain control only, or no gain control at all, apparatus according to embodiments of the present disclosure may be adaptable to enable different approaches to be taken. For example, apparatus may be provided with a shutter and associated shutter controller, along with a gain controller. However, the shutter controller may be selectively placed in either (i) an on mode in which the shutter is adjusted between the open and closed configurations to perform the method of e.g., Fig. 2 or Fig. 15, and (ii) and off mode in which the shutter is kept open, or at least is not adjusted between open and closed configurations, to carry out the method of e.g., Fig. 9. Moreover, the gain controller may be selectively placed in either (i) a first mode in which the gain is controlled in accordance with adjustment of the shutter, to perform the method of e.g. Fig. 2, and (ii) and a second mode in which the gain is controlled independently of adjustment of any shutter, to perform the method of e.g., Fig. 9, or (iii) a third mode in which gain control is not performed at all. This may allow the apparatus to be adapted for use with different types of X-ray source, such as a rhodotron or a LINAC, and to employ different methods according embodiments described herein.

[0127] The present disclosure recognises that use of a rhodotron as a pulsed X-ray source may present one more of more advantages in comparison to use of a LINAC. For example: (i) a rhodotron may be better shielded, reducing the degree to which further shielding may be required for detectors and/or the outside world; (ii) a rhodotron may be more power efficient and/or stable; (iii) a rhodotron may have a higher pulse rate that approaches near continuous irradiation, potentially increasing the homogeneity of irradiation of ore which may be increase accuracy of ore analysis; and/or (iv) a rhodotron may be more compact and modular.

[0128] Apparatus 600 for analysing ore according to an embodiment of the present disclosure, is illustrated in Fig. 11. The apparatus may comprises any of the apparatus 100, 400, 900 and/or be used to carry out any of the methods 200, 500, 1000 as discussed above or otherwise. The apparatus 600 may be ore sorting apparatus such as real time bulk ore sorting apparatus, and may be configured to detect valuable elements of interest in ore material such as gold, e.g. using gamma activation analysis/ gamma ray spectroscopy. In some embodiments, the ore material may be secondary crushed ore.

[0129] The apparatus 600 includes an X-ray source 610 that is configured to emit a pulsed X-ray beam 611 for the purpose of irradiating ore material 620 at an irradiation region 631, a conveyor system comprising one or more conveyor belts 630 to carry the ore material 620 along an ore transport path from the irradiation region 631 to a detection region 632, and one or more detectors 640 to detect a radiation output from the ore material 620 at the detection region 632. Adjacent the X-ray source 610 is a beam monitoring device 660 and associated shielding 670. The beam monitoring device 660 may comprise one or more of the beam monitoring features described above, e.g. with respect to the apparatus 100 of Figs, la and lb, or the apparatus 400 of Fig. 8, or the apparatus 900 of Figs. 14a and 14b, including a scintillator 131, 431, 931, PMT 132, 432 and/or SiPM 932, shutter 140, 141, 144, 146, and/or gain control device 133, 433. The shielding 670 may be similar or identical to the shield 143 discussed above with reference to Figs. 5a and 5b.

[0130] The ore transport path may include a bend 633, located between the irradiation region 631 and the detection region 632. The bend may 633 ensure that there is no line of sight path between the irradiation region 631 and the detection region 632. In this regard, the apparatus 600 may employ one or more of the bend and/or other shielding features described in applicant’s US patent publication no. US2021/0208087, the entire content of which is incorporated herein by reference.

[0131] As shown in Fig. 11, one or more radiation shields 650 are also provided that may surround the conveyor system including the one or more conveyor belts 630. The radiation shields 650 may be provided to supress radiation leakage from the apparatus 600 as ore travels along the conveyor system.

[0132] The one or more detectors 640 may each include a scintillator and optionally also a PMT or SiPM, and, in the case of a PMT may operate according to the discussions made above with reference to Fig. 3. In one embodiment, one or more of the detectors 630 comprises a lanthanum bromide (LaBr) scintillator. A LaBr scintillator may be mounted relatively closely to activated ore and may continuously detect radiation activity of the ore as it passes through the detection region.

[0133] Selection of a LaBr scintillator may be advantageous for one or more of the following reasons: (i) a LaBr scintillator may have relatively low activation and afterglow compared to other scintillators, (ii) a LaBr scintillator may be manufactured to have a relatively large volume compared to other scintillators, allowing the scintillator to detect radiation along a larger detection region/path of the conveyor system; (iii) a LaBr scintillator may have an improved resolution than other scintillators such as Sodium Iodide (Nal) scintillators (Nal scintillators may be considered industry standard conventional large area scintillators and may have a minimum required resolution to detect gold in ore); (iv) a LaBr scintillator may have a faster decay time compared to Nal scintillators, allowing for an increase in throughput and a reduction of loss of detection efficiency at higher count rates due to dead time; and (v) a LaBr scintillator may have a relatively high radiation hardness (resistance to radiation induced damage), which allows it to be positioned closer to the activation point.

[0134] The apparatus 600 may be adapted to irradiate ore 620 for the purpose of gamma activation analysis. The one or more detectors 640 may therefore be configured to detect gamma rays (gamma radiation) irradiated from the ore material 620.

[0135] In any of the embodiments disclosed herein, the apparatus 600 may be configured for bulk sorting of ore material based on analysis of an element of interest (target element) of the ore material. In some embodiments, the apparatus 600 may comprise a diverter station (not shown) configured to divert batches of ore material after passing through the detection region, the diversion being based on a measurement of the radiation output detected by the one or more detectors 640.

[0136] The apparatus 600 may comprise a processor 680 configured to monitor output signals from the one or more detectors which signals may be indicative of photon decay signals of the irradiated ore 620. The processor 680 may also be configured to monitor output signals from the beam monitoring device 660. Based on electrical output signals from the beam monitoring device 660 (e.g. measured voltage of the electrical output signals), the processor 680 may determine a correction factor to correct output signals from the one or more detectors 640. The processor 680 may be configured to determine a target element in the ore based on the corrected output signals and optionally control diverting and sorting of the ore based on the corrected output signals.

[0137] The correction process described above with respect to the apparatus 600 or otherwise may rely on a known ratio of two reaction cross sections, and particular for isomer (e.g. bromine) activity in the scintillator of the beam monitoring device vs target element (e.g. gold) activity in the ore material detected at the one or more detectors. The activity of the target element as detected by the one or more detectors is expected to vary due to differences in concentration of the target element and parameters such as the intensity and/or energy of the irradiation of the ore material, including the target element, by the pulsed X-ray beam (i.e. the stability or performance of the pulsed X-ray beam). On the other hand, since the quantity of isomer in the scintillator of the beam monitoring device is constant, any variation in the isomer activity in the scintillator of the beam monitoring device can be attributed to variation in the stability or performance of the pulsed X-ray beam and therefore the energy deposited by the pulsed X-ray beam in the scintillator. Ultimately, therefore, appropriate corrections can be made to eliminate variation due to X-ray beam stability when seeking to identify target element concentration. In this regard, the approach may employ various principles of gamma ray spectroscopy. Apparatus and or methods described in the present disclosure may optionally use gamma ray analysis techniques and principles described, for example, in PCT publication no. W02015/089580A1 and PCT publication no. WO2022/047537A1, the entire contents of which are incorporated herein by reference.

[0138] Where an electrical output signal is monitored from the beam monitoring device or one or more detectors, the voltage (or more specifically, charge) of these signals is proportional to the energy deposited in the scintillator. By measuring the time integral (area under a curve of the signals) and/or amplitude of these voltage signals, an estimate of the charge can be made, allowing an investigation of the energy spectrum of radiation that hits a scintillator to be determined.

[0139] An embodiment of a PMT and associated gain control architecture that may be used in embodiments of the present disclosure described above, including to switch between higher and lower PMT gain modes, is illustrated in Figs. 12a and 12b.

[0140] In particular, a PMT 700 is provided which, in this embodiment, includes a photocathode 701, a focusing dynode 702, a plurality of further dynodes 703-707, an anode 708, read-out electronics 709, a high voltage source 710, and resistor chain 711. The PMT 700 is configured to absorb scintillation light, convert that light into an electrical signal via the photoelectric effect, and amplify the electrical signal, generally in accordance with principles set out above with reference to Fig. 3. Amplification in a ‘high gain’ mode of the PMT is based on successively more positive potentials across the dynodes 703-707 resulting from their connections with the high voltage supply 710 and the associated resistor chain 711.

[0141] With reference to Fig. 12b, to place the PMT in a ‘low gain’ mode, a first dynode 703 is disconnected from the high voltage power supply and resistor chain 711 and connected to a separate power supply 712, providing for a less positive potential at the first dynode 703, and third and fourth dynodes 705, 706 have their voltages switched to again cause less positive potentials across the dynode sequence and therefore an overall reduction in gain.

[0142] While an 8-dynode PMT is illustrated in Figs. 12a and 12b (with additional focusing dynode), a variety of different PMT arrangements may be employed, including with a higher number of dynodes such as 12 or 16 dynodes, depending on the amount of gain required. Moreover, the arrangement illustrated in Figs. 12a and 12b is a grounded- cathode (positive high voltage) design, which may be replaced with a grounded anode (negative high voltage) design with minor modifications to associated electronics. However, the core dynode operation and switching method may remain much the same. For example, connection of one or more dynodes to an independent power supply and/or switching of voltage connections of two or more dynodes may again be employed.

[0143] Fig. 13 shows a block diagram of apparatus 800 according to an embodiment of the present disclosure, that can be used to monitor X-ray beam stability from an X-ray source and which can carry out gain switching generally as described above with reference to Figs. 12a and 12b. The apparatus 800 includes a PMT 801 and associated resistor chain 802 and switching dynode architecture 803 where some dynodes are switched or others non-switched when changing between high and low gains. The resistor chain 802 and switching dynode architecture 803 may be connected to (or indeed form part of) a voltage divider base 804 of the PMT 801. A high voltage power supply 805 is connected to the voltage divider base 804 and triggering of the switching between high and low gains is based on a gate signal generated by a pulse generator 807 in accordance with a logic signal of an X-ray source 808 (e.g. LINAC or rhodotron). The electrical output signal from the PMT 801 is fed via the voltage divider base 804 through a pre-amplifier 809 before being subjected to an analog to digital conversion at a digitiser 810 before the resulting digital signal is processed through a processor/software 811, e.g. to determine a correction factor as part of ore analysis as discussed further above. Although not shown in Fig. 13, the apparatus may further include a shutter and associated shutter controller in accordance with one or more embodiments described above. [0144] Apparatus and methods according to the present disclosure may employ memory storing executable code and a processor configured to access memory to execute the executable code, wherein when executing the executable code, the processor may be caused to perform any one or more of the processing/method steps described herein. Additionally or alternatively, a computer readable storage medium may provide storing instructions that, when executed by a processor, cause the processor to perform any one of the processing/method steps described herein.

Example 1

[0145] Activation of Br-79m in a cerium bromide (CeBr) scintillator was tested using a 100 kW 7 MV rhodotron emitting a pulsed X-ray beam and a PMT. In lieu of using an adjustable shutter between the rhodotron and the scintillator (and moving the shutter between an open and closed position), use of a shutter was emulated by switching the rhodotron off after a period where the rhodotron was on and pulsed X-ray irradiation from the rhodotron impinged on the scintillator for a short 10-30 second period. Gain of the PMT was switched between low gain during the period when the rhodotron was on, and high gain after the rhodotron was switched off. Data acquisition from the PMT/monitoring of activation of Br-79m was carried out while the rhodotron was switched off and the gain of the PMT was high. Fig. 17 provides a plot of the Br-79m activation and illustrates a Br- 79m photopeak representing a full energy deposition of the isomer at 207 keV.

[0146] Activation of Br-79m was measured for three different periods of pulsed X-ray irradiation, 5 seconds, 10 seconds and 30 seconds, resulting in three different Br-79m photopeaks as plotted in Fig. 18. Data was smoothed by convoluting with a gaussian function for clarity. Deviations in beam energy and intensity will produce similar (albeit smaller) changes in activity levels and the approach can therefore be used to monitor beam stability (which may be more or less stable depending on the degree to which parameters of the X-ray beam such as energy, intensity, etc. fluctuate) and to generate one or more correction factors for correcting measurements of activity, e.g. gold activation, in ore as a result of instability in the X-ray beam during irradiation of the ore overtime. Example 2

[0147] Activation of Br-79m in a cerium bromide (CeBr) scintillator was tested using a 10 MV linear accelerator (LINAC), emitting a pulsed X-ray beam at 12.5 Hz, and a PMT. Gain of the PMT was switched between low gain during each pulse and high gain between each pulse. Data acquisition from the PMT/monitoring of activation of Br-79m was carried out between thousands of the X-ray pulses. Fig. 19 provides a plot of the Br-79m activation and illustrates a Br-79m photopeak representing a full energy deposition of the isomer at 207 keV.

[0148] Activation of Br-79m was measured for three different periods (0-120 seconds, 240-360 seconds and 480-600 seconds) of pulsed X-ray irradiation within a 10 minute period of pulsed X-ray irradiation, resulting in three different Br-79m photopeak profiles as plotted in Fig. 20. Deviations in beam energy and intensity will produce similar (albeit smaller) changes in activity levels and the approach can therefore be used to monitor beam stability (which may be more or less stable depending on the degree to which parameters of the X-ray beam such as energy, intensity, etc. fluctuate) and to generate one or more correction factors for correcting measurements of activity, e.g. gold activation, in ore as a result of instability in the X-ray beam stability during irradiation of the ore over time.

[0149] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. For example, while embodiments of the present disclosure have been described as being particularly applicable to fields requiring the analysis of elements in mineral (ore) samples, the embodiments may be additionally applicable to radiography, cargo screening, fissionable material detection and/or sterilisation operations, where items other than ore material are irradiated by an X-ray beam and it may be desirable to monitor stability of that beam, provide shielding and/or detection features in accordance with embodiments described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. An apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a shutter selectively adjustable between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and a gain control device configured to control a gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain.

2. The apparatus of claim 1, wherein the gain control device is configured to control the gain of the PMT synchronously or cyclically with the adjusting of the shutter between the open and closed configurations.

3. The apparatus of claim 1 or 2 comprising a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT when the shutter is in the closed configuration and the gain of the PMT is the second gain.

4. The apparatus of claim 1, 2 or 3, wherein the pulsed X-ray source comprises a rhodotron.

5. The apparatus of any one of the preceding claims, wherein the frequency of the pulsed X-ray source is greater than 300Hz or greater than 500Hz.

6. The apparatus of any one of the preceding claims wherein the difference between the first and second gains is at least a factor of 1,000 or at least a factor of 10,000.

7. The apparatus of any one of claims 1 to 5, wherein the first gain is zero gain

8. The apparatus of any one of the preceding claims, comprising an actuator configured to adjust the shutter between the open and closed configurations.

9. The apparatus of claim 8, wherein the actuator automatically adjusts the shutter between the open and closed configurations periodically.

10. The apparatus of claim 8 or 9, wherein the actuator comprises a linear actuator.

11. The apparatus of any one of the preceding claims, wherein the gain control device controls the voltage of an electrical signal supplied to the PMT and/or controls switching of dynodes of the PMT.

12. The apparatus of any one of the preceding claims, wherein the gain control device comprises a switching voltage divider circuit.

13. The apparatus of any one of the preceding claims, comprising a controller, wherein the controller is configured to control at least one of: adjusting of the shutter between the open configuration and the closed configuration; and controlling the gain of the PMT between the first gain and the second gain.

14. The apparatus of any one of the preceding claims, wherein the shutter comprises bismuth.

15. The apparatus of any one of the preceding claims, comprising a shield between the X-ray source and the scintillator, wherein the shield reduces an intensity of the pulsed X-ray beam that impinges on the scintillator.

16. The apparatus of claim 15, wherein the shield comprises bismuth.

17. The apparatus of any one of the preceding claims, wherein the scintillator of the beam monitoring device comprises bromine.

18. The apparatus of any one of the preceding claims comprising a detector to monitor emission radiation from the ore material in response to irradiation of the ore material by the pulsed X-ray beam.

19. The apparatus of claim 18, when dependent on claim 3, wherein the processor is configured to determine a correction factor based on the measurement of voltage of the electrical output signal from the PMT and correct a signal from the detector based on the correction factor.

20. The apparatus of claim 19, wherein the detector comprises a lanthanum bromide scintillator.

21. The apparatus of any one of the preceding claims comprising at least one conveyor belt, wherein the ore material irradiated by the pulsed X-ray beam is located on the at least one conveyor belt.

22. An apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and an optoelectronic device that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; a shutter selectively adjustable between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the optoelectronic device when the shutter is in the closed configuration.

23. The apparatus of claim 22, wherein the optoelectronic device is a silicon photomultiplier (SiPM).

24. An apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; and a gain control device configured to control a gain of the PMT to be a first gain during each pulse of the pulsed X-ray beam and a second gain between pulses of the X-ray beam, the second gain being higher than the first gain.

25. The apparatus of claim 24, wherein the gain control device is configured to control the gain of the PMT synchronously or cyclically with pulsing of the X-ray beam.

26. The apparatus of claim 24 or 25, comprising a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT.

27. The apparatus of any one of claims 24 to 26, wherein the pulsed X-ray source comprises a linear accelerator (LINAC).

28. The apparatus of any one of claims 24 to 27, wherein the frequency of the pulsed X-ray source is about, or less than, 500Hz or 300Hz.

29. The apparatus of any one of claims 24 to 28 wherein the difference between the first and second gains is at least a factor of 1,000 or at least a factor of 10,000.

30. The apparatus of any one of claims 24 to 29, wherein the gain control device controls the voltage of an electrical signal supplied to the PMT and/or controls switching of dynodes of the PMT.

31. The apparatus of any one of claims 24 to 30, wherein the gain control device comprises a switching voltage divider circuit.

32. The apparatus of any one of claims 24 to 31, comprising a shield between the X- ray source and the scintillator, wherein the shield reduces the intensity of the pulsed X-ray beam that impinges on the scintillator.

33. The apparatus of claim 32, wherein the shield comprises bismuth.

34. The apparatus of any one of claims 24 to 33, wherein the scintillator of the beam monitoring device comprises bromine.

35. The apparatus of any one of claims 24 to 34 comprising a detector to monitor emission radiation from the ore material in response to irradiation of the ore material by the pulsed X-ray beam.

36. The apparatus of claim 35, when dependent on claim 26, wherein the processor is configured to determine a correction factor based on the measurement of voltage of the electrical output signal from the PMT and correct a signal from the detector based on the correction factor.

37. The apparatus of claim 36, wherein the detector comprises a lanthanum bromide scintillator.

38. The apparatus of any one of claims 24 to 37, comprising at least one conveyor belt, wherein the ore material irradiated by the pulsed X-ray beam is located on the at least one conveyor belt.

39. An apparatus for analysing ore comprising: a pulsed X-ray source configured to irradiate ore material with a pulsed X- ray beam; a beam monitoring device configured to monitor a stability of the pulsed X- ray beam, the beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; and a processor configured to monitor stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT during each pulse of the X-ray beam.

40. An apparatus for analysing ore comprising: an X-ray source configured to irradiate ore material with a pulsed X-ray beam; and a detector configured to monitor emission radiation from the ore material in response to irradiation of the ore material by the X-ray source, wherein the detector comprises a lanthanum bromide scintillator.

41. An apparatus for analysing ore comprising: an X-ray source configured to irradiate ore material with a pulsed X-ray beam; and a detector configured to monitor emission radiation from the ore material in response to irradiation of the ore material by the X-ray source, wherein the X-ray source is a rhodotron.

42. A method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and controlling gain of the PMT to be a first gain when the shutter is in the open configuration and a second gain when the shutter is in the closed configuration, the second gain being higher than the first gain.

43. The method of claim 42, comprising controlling the gain of the PMT synchronously or cyclically with the adjusting of the shutter between the open and closed configurations.

44. The method of claim 42 or 43 comprising monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT when the shutter is in the closed configuration and the gain of the PMT is the second gain.

45. A method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; controlling a gain of the PMT to be a first gain during each pulse of the pulsed X-ray beam and a second gain between pulses of the X-ray beam, the second gain being higher than the first gain.

46. The method of claim 45, comprising controlling the gain of the PMT synchronously or cyclically with pulsing of the X-ray beam.

47. The method of claim 45 or 46, comprising monitoring stability of the pulsed X- ray beam based on a measurement of voltage of the electrical output signal from the PMT.

48. A method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and an optoelectronic device that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; selectively adjusting a shutter between an open configuration and a closed configuration, wherein in the open position, the X-ray beam impinges on the scintillator and, in the closed configuration, the shutter substantially shields the X-ray beam from impinging on the scintillator; and monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the optoelectronic device when the shutter is in the closed configuration.

49. The method of claim 48, wherein the optoelectronic device is a silicon photomultiplier (SiPM).

50. A method for analysing ore comprising: irradiating ore material with a pulsed X-ray beam from a pulsed X-ray source; providing a beam monitoring device comprising a scintillator that emits light when excited by the X-ray beam and a photomultiplier tube (PMT) that absorbs light emitted by the scintillator and converts the absorbed light into an electrical output signal; monitoring stability of the pulsed X-ray beam based on a measurement of voltage of the electrical output signal from the PMT during each pulse of the X-ray beam.