A measurement arrangement and a method for measuring concentration of gold in a sample

Abstract

The invention relates to a measurement arrangement (100) for measuring concentration of gold in a sample (102). The measurement arrangement (100) comprises: a sample container (104a, 104b); an X-ray radiation source unit (106) configured to produce a radiation beam (112); a primary filter (108) arranged between the X-ray radiation source unit (106) and the sample container (104a, 104b) so that the primary filter (108) is in a close vicinity to the sample container (104a, 104b), wherein the primary filter (108) is configured to act as a filter and as a secondary target configured to excite a first fluorescence radiation (114) in response to an irradiation of the primary filter (108) with the radiation beam (112); and a radiation detector unit (110) configured to obtain a second fluorescence radiation (116) being characteristic to gold in response to an irradiation of the sample (102) with the first fluorescence radiation (114), wherein the second fluorescence radiation (116) is obtained from a direction (202) substantially perpendicular to the direction (204) of the maximum intensity of the radiation beam (112). The invention relates also to a method for measuring concentration of gold in a sample (102).

Description

[0001] A measurement arrangement and a method for measuring concentration of gold in a sample

[0002] TECHNICAL FIELD

[0003] The invention concerns in general the technical field of X-ray fluorescence analysis. Especially the invention concerns X-ray fluorescence analysis for measuring concentrations of gold in samples.

[0004] BACKGROUND

[0005] An X-ray fluorescence (XRF) analysis is a commonly used method for analyzing elements in a sample. Typically, XRF analysis -based measurements are based on reflection measurements, where an X-ray radiation source used for producing a radiation beam for irradiating the sample and a radiation detector used for obtaining radiation from the sample in response to the irradiation of the sample with the radiation beam are on the same side of the sample. However, the reflection measurements -based XRF analyzers do not necessarily provide sufficient measurement sensitivity.

[0006] Thus, there is a need to develop further solutions for measuring concentration of heavy elements in a sample.

[0007] SUMMARY

[0008] The following presents a simplified summary in order to provide basic understanding of some aspects of various invention embodiments. The summary is not an extensive overview of the invention. It is neither intended to identify key or critical elements of the invention nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

[0009] An objective of the invention is to present a measurement arrangement and a method for measuring concentration of gold in a sample. Another objective of the invention is that the measurement arrangement and the method for measuring concentration of gold in a sample enable improving measurement sensitivity. The objectives of the invention are reached by a measurement arrangement and a method as defined by the respective independent claims.

[0010] According to a first aspect, a measurement arrangement for measuring concentration of gold in a sample is provided, wherein the measurement arrangement comprises: a sample container for the sample; an X-ray radiation source unit configured to produce a radiation beam; a primary filter arranged between the X-ray radiation source unit and the sample container so that the primary filter is in a close vicinity to the sample container, wherein the primary filter is configured to act as a filter adapted to attenuate the radiation beam at the wavelengths of gold and as a secondary target configured to excite a first fluorescence radiation being characteristic to the material of the primary filter in response to an irradiation of the primary filter with the radiation beam from the X-ray radiation source unit; and a radiation detector unit configured to obtain a second fluorescence radiation being characteristic to gold in response to an irradiation of the sample with the first fluorescence radiation, wherein the second fluorescence radiation is obtained by the radiation detector unit from a direction substantially perpendicular to the direction of the maximum intensity of the radiation beam produced by the X-ray radiation source unit.

[0011] The X-ray radiation source unit may be positioned with respect to the sample container so that the sample is irradiated from a bottom surface side of the sample container, wherein the sample container may be a cup-shaped sample container.

[0012] In addition, the radiation detector unit may be positioned with respect to the sample container so that the second fluorescence radiation may be obtained through a side wall of the sample container.

[0013] Alternatively, the X-ray radiation source unit may be positioned with respect to the sample container so that the sample is irradiated through a side wall of the sample container, wherein the sample container may be a square tube-shaped sample container or a square cup-shaped sample container.

[0014] In addition, the radiation detector unit may be positioned with respect to the sample container so that the second fluorescence radiation is obtained through another side wall of the sample container being adjacent to the side wall of the sample container through which the sample is irradiated. The material of the primary filter may be uranium.

[0015] A distance between the primary filter and the sample container may be between 0 to 3 millimeters.

[0016] Alternatively or in addition, the primary filter may be arranged in a contact with the sample container.

[0017] Alternatively or in addition, the primary filter may be integrated into the sample container.

[0018] The radiation detector unit may comprise a germanium detector or a silicon drift detector, or the radiation detector unit may be based on a Soller slit crystal spectrometer -based detection comprising a germanium detector or a cadmium zinc telluride detector.

[0019] The material of an anode of the X-ray radiation source unit may have atomic number greater than or equal to 72.

[0020] According to a second aspect, a method for measuring concentration of gold in a sample with the measurement arrangement discussed above is provided.

[0021] Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying and non-limiting embodiments when read in connection with the accompanying drawings.

[0022] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of unrecited features. The features recited in dependent claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.

[0023] BRIEF DESCRIPTION OF FIGURES

[0024] The embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. Figures 1A illustrates schematically an example of a measurement arrangement for measuring concentration of gold in a sample.

[0025] Figure 1 B illustrates a top view of the measurement arrangement of Figure 1A.

[0026] Figure 1 C illustrates schematically another example of the measurement arrangement.

[0027] Figure 1 D illustrates schematically a perspective view of a square tube-shaped sample container of Figure 1C.

[0028] Figure 2A illustrates schematically an example of a sample container comprising an integrated primary filter.

[0029] Figure 2B illustrates schematically a closer view of the sample container and the primary filter of the example measurement arrangement of Figure 1 A.

[0030] Figure 2C illustrates schematically a closer view of the sample container and the primary filter of the example measurement arrangement of Figure 1 C.

[0031] Figure 3 illustrates schematically an example of X-ray energy distribution of a first fluorescence radiation excited by using a primary filter made of uranium.

[0032] Figure 4 illustrates schematically an example of a method for measuring concentration of gold in a sample.

[0033] DESCRIPTION OF THE EXEMPLIFYING EMBODIMENTS

[0034] Figures 1A and 1 B illustrate schematically an example of a measurement arrangement 100 for an X-ray fluorescence (XRF) analysis for measuring concentration of a heavy element in a sample 102. Figure 1A illustrates a side view of the measurement arrangement 100. Figure 1 B illustrates a top view of the measurement arrangement 100 of Figure 1A. Figure 1 C illustrates schematically another example of the measurement arrangement 100 for the X- ray fluorescence (XRF) analysis for measuring concentration of the heavy element in the sample 102. Figure 1 C illustrates a top view of the measurement arrangement 100. Preferably, the heavy element, which concentration is to be measured is gold. However, the heavy element may also be e.g. platinum. The measurement arrangement 100 comprises a sample container 104a, 104b for the sample 102, an X-ray radiation source unit 106, a primary filter 108, and a radiation detector unit 110.

[0035] The sample container 104a, 104b is configured to hold (e.g. accommodate) the sample 102. The sample 102 may for example be a slurry sample, a powder sample, or any other kind of sample. The sample container 104a, 104b may be a cup-shaped sample container 104a or a tube-shaped sample container 104b. In the example of Figures 1A and 1 B, the sample container 104a, 104b is the cup-shaped sample container 104a. In the example of Figure 1 C, the sample container 104a, 104b is the tube-shaped sample container 104b.

[0036] The cup-shaped sample container 104a comprises a bottom surface 105a and at least one side wall 105b. The number of side walls 105b depends on the shape of the cup-shaped sample container 104a. The cup-shaped sample container 104a may for example be cylindrical (i.e. a cylindrical cup-shaped sample container) or square-shaped (i.e. a square tube-shaped sample container). The cylindrical cup-shaped sample container 104a comprises a circular bottom surface 105a and one side wall 105b encircling the circular bottom surface 105a. The square cup-shaped sample container 104a comprises a square bottom surface 105a and four side walls 105b encircling the square bottom surface 105a. In the example of Figures 1A and 1 B the cup-shaped sample container 104a is the cylindrical cup-shaped sample container. The cupshaped sample container 104a may also have any other shape.

[0037] The tube-shaped sample container 104b comprises at least one side wall 105b, 105b’. The number of side walls 105b, 105b’ depends on the shape of the tubeshaped sample container 104b. The tube-shaped sample container 104b may for example be a square tube or a cylindrical tube. The square tube-shaped sample container 104b comprises four side walls 105b, 105b’ forming the square shaped tube 104b. The cylindrical tube-shaped sample container 104b comprises one side wall 105b forming the cylindrical tube 104b. Preferably, the tube-shaped sample container 104b is the square tube-shaped sample container. In the example of Figure 1 C the sample container 104b is a square tube-shaped sample container. Figure 1 D illustrates schematically a perspective view of the square tube-shaped sample container 104b of Figure 1 C. Also, a square cup-shaped sample container may be used in the measurement arrangement 100 according to the example of Figure 1 C as will be discussed. The square tube-shape of the sample container 104b allows a flow of the sample 102 along the sample tube 104b during the measurement of the concentration of gold in the sample 102. For example, if the sample 102 is a slurry sample, the slurry sample may flow along the square tube-shaped sample container 104b during the measurement of the concentration of the heavy element in the slurry sample 102 by using the measurement arrangement 100. This is especially beneficial in the field of mining technology. The flow of the sample 102 along the sample tube 104b is illustrated in the example of Figure 1 D with the arrows 120.

[0038] The material of the sample container 104a, 104b is such that an incident X-ray radiation (i.e. a first fluorescence radiation 114 as will be descripted) and an emergent radiation (i.e. a second fluorescence radiation 116 as will be described) penetrates through the sample container 104a, 104b. For example, the material of the sample container 104 may be polyethylene. The thickness of the bottom surface 105a of the cup-shaped sample container 104a may be dimensioned so that the incident X-ray radiation 114 penetrates through the bottom surface 105a of the sample container 104a. Similarly, the thickness of the at least one wall 105b of the cup-shaped sample container 104a may be dimensioned so that the emergent radiation 116 penetrates through the at least one wall 105b of the sample container 104a. According to a non-limiting example, the thickness of the bottom surface 105a of the cup-shaped sample container 104a may be between 1 to 2 millimeters. According to a non-limiting example, the thickness of the at least one side wall 105b of the cup-shaped sample container 104a may be between 0.5 and 1 millimeters. The diameter of the cup-shaped sample container 104a and the height of the at least one side wall 105b of the cup-shaped sample container 104a are not limited. According to a non-limiting example, the diameter of the cup-shaped sample container 104a may be between 15 and 30 millimeters. According to a non-limiting example, the height (i.e. the dimension in the direction of the z-axis) of the at least one side wall 105b of the cup-shaped sample container 104a may be between 10 and 20 millimeters. The cup-shaped sample container 104a may also comprise a cover at a top of the sample container 104. The thickness of the at least one wall 105b, 105b’ of the tube-shaped sample container 104b may be dimensioned so that the incident X-ray radiation 114 and the emergent radiation 116 penetrate through the at least one wall 105b, 105b’ of the sample container 104b. According to a non-limiting example, the thickness of the at least one side wall 105b, 105b’ of the tube-shaped sample container 104b may be between 0.5 and 1 millimeters. The diameter of the tube-shaped sample container 104b and the length (i.e. the dimension in the direction of the z-axis) of the tube-shaped sample container 104a are not limited. According to a non-limiting example, the diameter of the tube-shaped sample container 104a may be between 15 and 30 millimeters.

[0039] The X-ray radiation source unit 106 is configured to produce a radiation beam 112. The radiation beam 112 produced by the X-ray radiation source unit 106 comprises radiation being characteristics to an anode of the X-ray source unit 106 and continuous bremsstrahlung (i.e. braking radiation). In high atomic number XRF analysis the bremsstrahlung is required. The atomic number of gold is 79. Preferably, the material of the anode of the X-ray radiation source unit 106 may have atomic number greater than or equal to 72. This enables that the intensity of the produced bremsstrahlung is high. As a non-limiting example of the material for the anode of the X-ray radiation source unit 106 is hafnium (Hf), which atomic number is 72. The power of the X-ray radiation source unit 106 may for example be between 10 W to 3 kW. The voltage of the X-ray radiation source unit 106 may for example be between 140 kV to 250 kV. Preferably, the voltage of the X-ray radiation source unit 106 may for example be 160 kV. To achieve a cost-effective measurement solution, the power of the X-ray radiation source unit 106 may be adapted so that as high measurement sensitivity as possible is achieved with as low power of the X-ray radiation source unit 106 as possible.

[0040] The primary filter 108 is arranged between the X-ray radiation source unit 106 and the sample container 104a, 104b. In the example of Figure 1A, the primary filter 108 is arranged underneath (i.e. below) the sample container 104a and above the X-ray radiation source unit 106. In Figure 1 B, which is the top view of the measurement arrangement 100, the primary filter 108 and the X-ray radiation source 106 are not visible, because they are underneath the sample container 104a. In the example of Figure 1 C, the primary filter 108 is arranged on the side of the sample container 104b so that the primary filter 108 is between the X-ray radiation source unit 106. The primary filter 108 is configured to act both as a filter and as a permeable secondary target.

[0041] As discussed above, the radiation beam 112 produced by the X-ray radiation source unit 106 comprises the radiation being characteristics to the anode of the X-ray radiation source unit 106 and the continuous bremsstrahlung. The continuous bremsstrahlung would scatter from the sample 102 and cause a continuous background radiation, if the continuous bremsstrahlung is not filtered. Because the concentration of gold to be measured is substantially small, the background radiation limits the measurement sensitivity. Thus, the primary filter 108 is used as the filter to attenuate the radiation beam 112 at the wavelengths of gold (i.e. at the photon energies respective to gold). More specifically, the primary target is adapted to attenuate the continuous bremsstrahlung of the radiation beam 112 at the wavelengths respective to gold. Preferably, the primary filter 108 attenuates the radiation beam 112 so that the continuous bremsstrahlung at the wavelengths respective to gold is minimized. The attenuation of the continuous bremsstrahlung at the wavelengths respective to gold reduces the background radiation at the wavelengths respective to gold, which in turn improves the measurement sensitivity of the measurement arrangement 100.

[0042] As the primary filter 108 act also as the permeable secondary target, the primary filter 108 is configured to excite a first fluorescence radiation 114 being characteristic to the material of the primary filter 108 (i.e. a fluorescence radiation of the primary filter 108) in response to an irradiation of the primary filter 108 with the radiation beam 112 from the X-ray radiation source unit 106. In other words, a part of the radiation beam 112 from the X-ray radiation source unit 106 is absorbed into the primary filter 108 acting as the permeable secondary target and most of the absorbed radiation 112 is transformed into the first fluorescent radiation 114 being characteristics to the material of the primary filter 108. In yet another words, at least part of the radiation beam 112 from the X-ray radiation source unit 106 penetrates through the primary filter 108, wherein the penetrated part of the radiation beam 112 is the first fluorescence radiation 114. The first fluorescent radiation 114 is used to excite a second fluorescence radiation 116 to be measured as will be described. If separate primary filter and secondary target are used instead of the primary filter 108 acting also as the secondary target, the separate primary filter would absorb the radiation at the hard photon energies that excites in the secondary target the first fluorescence radiation 114 being characteristic to the material of the secondary target.

[0043] The primary filter 108 comprises a first surface 108a and a second surface 108b. The first and second surfaces 108a, 108b of the primary filter 108 are parallel with each other. The primary filter 108 is arranged between the X-ray radiation source unit 106 and the sample container 104a, 104b so that the first surface 106 and the second surface 108b of the primary filter 108 is facing towards the sample container 104a, 104b. The radiation beam 112 is produced by the X-ray radiation source unit 106 towards the first surface 108a of the primary filter 108. The first fluorescence radiation 114 radiates from the second surface 108b of the primary filter 108 evenly to all solid angels.

[0044] The primary filter 108 is arranged between the X-ray radiation source unit 106 and the sample container 104a, 104b so that the primary filter 108 is in a close vicinity of the sample container 104a, 104b. In other words, the primary filter 108 is arranged between the X-ray radiation source unit 106 and the sample container 104a, 104b so that the primary filter 108 is as close as possible to the sample container 104a, 104b. Arranging the primary filter 108 as close as possible to the sample container 104a, 104b (and thus also as close as possible to the sample 102) enables efficient filtering together with efficient excitation of the second fluorescence radiation 116, which, in turn, improves the measurement sensitivity of the measurement arrangement 100. This also enables that a low power X-ray radiation source unit 106 (e.g. 10 W) may be used, which in turn reduces the costs of the measurement arrangement 100. For example, a distance D between primary filter 108 and the sample container 104a, 104b may be less than few millimeters, e.g. between 0 and 3 millimeters. Preferably, the distance D between the primary filter 108 and the sample container 104a, 104b may be between 0 and 2 millimeters.

[0045] According to an example, the primary filter 108 may be arranged in contact with the sample container 104a, 104b. This minimizes the distance between the primary filter 108 and the sample container 104a, 104b, which, in turn, improves the measurement sensitivity of the measurement arrangement 100. According to another example, the primary filter 108 may be integrated into the sample container 104a, 104b. For example, the primary filter 108 may be integrated into the bottom surface 105a of the cup-shaped sample container 104a. The integration of the primary filter 108 into the sample container 104a, 104b enables that the distance between the primary filter 108 and the sample 102 inside the sample container 104a, 104b may be minimized, which, in turn, improves the measurement sensitivity of the measurement arrangement 100. Figure 2A illustrates schematically an example of the cup-shaped sample container 104a comprising the integrated primary filter 108. The distance between the primary filter 108 and the X-ray radiation source unit 106 is not as critical as the distance between the primary filter 108 and the sample container 104a, 104b. However, it is preferable to arrange the primary filter 108 as close to the X-ray radiation source unit 106 as possible. In other words, the distance between the primary filter 108 and the X-ray radiation source unit 106 is preferably as short as possible. This allows keeping the power X-ray radiation source unit 106 as low as possible, which in turn reduces the costs of the measurement arrangement 100. For example, the distance between the primary filter 108 and the X-ray radiation source unit 106 may be equal to or less than 10 millimeters. Preferably, the distance between the primary filter 108 and the X-ray radiation source unit 106 is less than 5 millimeters.

[0046] The thickness of the primary filter 108 may for example be selected so that the primary filter 108 attenuates the bremsstrahlung at least to one hundredth of the produced bremsstrahlung. According to a non-limiting example, the thickness of the primary filter 108 may be between 0.2 and 1.2 millimeters. Preferably, the thickness of the primary filter 108 may be between 0.6 and 1 millimeters. However, these are only non-limiting example values for the thickness of the primary filter 108.

[0047] The material of the primary filter 108 may for example be uranium. Uranium excites efficiently the second fluorescence radiation 116 being characteristics to gold. More specifically, K-alpha (Ka) and K-beta (Kp) emission of the uranium excites efficiently K-fluorescence radiation of gold, which corresponds to the second fluorescence radiation 116 being characteristics to gold. The emission spectrum of the K-fluorescence radiation of gold is characterized by Kai and Ka2 lines, respectively at approximately 67.0 keV and 68.8 keV. By measuring the intensity of the K-fluorescence radiation being characteristics to gold, the concentration of gold in the sample 102 may be determined. Figure 3 illustrates schematically an example of X-ray energy distribution of the first fluorescence radiation 114 excited by using the primary filter 108 made of uranium (i.e. the X- ray energy distribution of X-ray radiation beam 112 produced by the X-ray radiation source unit 106 and filtered by the primary filter 108 made of uranium). In other words, Figure 3 illustrates an example of how an example uranium primary filter 108 affects the energy spectrum of the radiation beam 112 produced by the X-ray radiation source unit 106, which is then used to excite in the sample 102 the second fluorescence radiation 116 being characteristics to gold. In the example of Figure 3 the spectrum of the unfiltered radiation beam 112 is also illustrated. The thickness of the primary filter 108 used in the example of Figure 3 is 0.6 millimeters. The K-alpha and K-beta emission of the uranium (i.e. Kaand Kp lines of the uranium, wherein Kaiis 98.4 keV, Ka2 is 94.7 keV, and Kp is 111 .3 keV) can be seen in the spectrum of the first fluorescence radiation 114 illustrated in the example of Figure 3. A part of the bremsstrahlung comprised in the radiation beam 112 produced by the X-ray radiation source unit 106 and being below the absorption limit of the uranium can also be seen in the spectrum of the first fluorescence radiation 114 illustrated in the example of Figure 3. The bremsstrahlung is useful for exciting in the sample 112 the second fluorescence radiation 116 being characteristics to gold. From the example of Figure 3 it can been seen that the background radiation is low at the photon energies respective to gold. It can also be seen from the example of Figure 3 that the first fluorescence radiation 114 (i.e. the radiation used to excite the second fluorescence radiation 116 being characteristics to gold) is attenuated at the hard photon energies.

[0048] The radiation detector unit 110 configured to obtain the second fluorescence radiation 116 being characteristic to gold in the sample 102 (i.e. the fluorescence radiation to be measured) in response to an irradiation of the sample 102 with the first fluorescence radiation 114 from the primary filter 108. The obtained second fluorescence radiation 116 comprises information representing the concentration of gold in the sample 102 (e.g. the intensity of of the K- fluorescence radiation being characteristics to gold). The radiation detector unit 110 may preferably have as high resolution as possible. This reduces the background radiation further, which in turn, improves the measurement sensitivity of the measurement arrangement 100. A detector with a narrow bandwidth may be used as the radiation detector unit 110 to achieve as high resolution as possible. The radiation detector unit 110 may for example comprise a germanium (Ge) detector or a silicon drift detector (SDD). Preferably, the radiation detector unit 110 comprises the Ge detector. The radiation detector unit 110 may alternatively or in addition be based on a Soller slit crystal spectrometer -based detection. In the Soller slit crystal spectrometer -based detection the radiation detector unit 110 comprises a Soller slit crystal spectrometer and a detector device. The Soller slit crystal spectrometer is used to enable a desired frequency spectrum to enter the detector device. The crystal of the Soller slit crystal spectrometer is made of pyrolytic graphite. The detector device of the radiation detector unit 110 in the Soller slit crystal spectrometer - based detection may for example be a Ge detector or a cadmium zinc telluride (CdZnTe) detector. The Soller slit crystal spectrometer -based detection has a very high resolution, but the intensity of the detector signal is lower with the Soller slit crystal spectrometer -based detection than with the mere Ge detector.

[0049] The X-ray radiation source unit 106 and the radiation detector unit 110 are positioned with respect to each other so that the second fluorescence radiation 116 is obtained by the radiation detector unit 110 from a direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106. In other words, the X-ray radiation source unit 106 and the radiation detector unit 110 are positioned with respect to each other so that the second fluorescence radiation 116 is obtained by the radiation detector unit 110 approximately at an angle of 90 degrees to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106. Yet in other words, the angle between the direction 202 from which the second fluorescence radiation 116 is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is approximately 90 degrees. For example, the angle being approximately 90 degrees may be 80 to 100 degrees. The maximum value of said angle may be limited so that the primary filter 108 is not visible to the detector of the radiation detector unit 110. The primary filter 108 being visible to the detector would destroy the measurements by the radiation detector unit 110. Preferably, the angle between the direction 202 from which the second fluorescence is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is 90 degrees. This enables that the scatter intensity of the excitation radiation (i.e. the first fluorescence radiation 114) is at the minimum. The excitation radiation scatters from the sample 102 mainly as a Compton scattering, which is at its minimum approximately at an angle of 90 degrees to its incident direction.

[0050] Figure 2B illustrates a closer view of the cup-shaped sample container 104a and the primary filter 108 of the example measurement arrangement 100 of Figure 1A. Figure 2B illustrates a closer view of the second fluorescence radiation 116, the first fluorescence radiation 114, and the radiation beam 112 as well. Figure 2C illustrates a closer view of the tube-shaped sample container 104b and the primary filter 108 of the example measurement arrangement 100 of Figure 1 C. Figure 2C illustrates a closer view of the second fluorescence radiation 116, the first fluorescence radiation 114, and the radiation beam 112 as well. In the examples of Figures 2B and 2C the direction from which the second fluorescence radiation 116 is obtained is illustrated with the arrow 202 and the direction of the maximum intensity of the radiation beam 112 is illustrated with the arrow 204. From the examples according to Figures 2B and 2C it can be seen that the second fluorescence radiation 116 is obtained by the radiation detector unit 110 from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106, i.e. that the angle between the direction 202 from which the second fluorescence 116 is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is approximately 90 degrees.

[0051] When the sample container 104a, 104b is the cup-shaped sample container 104a, the X-ray radiation source unit 106 may be positioned with respect to the sample container 104a so that the sample 102 is irradiated from the side of the bottom surface 105a of the sample container 104a. In other words, the X-ray radiation source unit 106 may be positioned with respect to the sample container 104a so that the produced radiation beam 112 is directed towards the bottom surface 105a of the cup-shaped sample container 104a as illustrated in the example of Figures 1A, 1 B, and 2B. As the bottom surface 105a of the cupshaped sample container 104a is flat, the irradiation of the sample 102 from the bottom surface 105a side of the cup-shaped sample container 104a increases the amount of the first fluorescence radiation 114 reaching the sample 102, for example in comparison to a curved surface. In other words, irradiating the sample container 104a, 104b from the bottom surface 105a side enables high efficiency of the excitation radiation.

[0052] As discussed above, the radiation detector unit 110 is positioned with respect to the sample container 104a so that the second fluorescence radiation 116 is obtained from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106. When the sample 102 is irradiated from the side of the bottom surface 105a of the cup-shaped sample container 104a, the radiation detector unit 110 may for example be positioned with respect to the sample container 104a so that the second fluorescence radiation 116 is obtained through a side wall 105b of the cup-shaped sample container 104a as illustrated in the example of Figures 1A and 2B. When the sample 102 is irradiated from the side of the bottom surface 105a of the cup-shaped sample container 104a and the second fluorescence radiation 116 is obtained through the side wall 105b of the cup-shaped sample container 104a, the second fluorescence radiation 116 is obtained by the radiation detector unit 110 from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106, i.e. so that the angle between the direction 202 from which the second fluorescence radiation 116 is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is approximately 90 degrees.

[0053] In the example of Figures 1A, 1 B and 2B the X-ray radiation source unit 106 is positioned underneath the cup-shaped sample container 104a, but the X-ray radiation source unit 106 together with the primary filter 108 may alternatively be positioned analogously above the cup-shaped sample container 104a as long as the radiation detector unit 110 obtains the second fluorescence radiation 116 from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106.

[0054] When the sample container 104a, 104b is the square tube-shaped sample container 104b or the square cup-shaped sample container 104a, the X-ray radiation source unit 106 may be positioned with respect to the sample container 104a, 104b so that the sample 102 is irradiated through a side wall 105b of the sample container 104a, 104b. In other words, the X-ray radiation source unit 106 may be positioned with respect to the sample container 104a, 104b so that the produced radiation beam 112 is directed towards the side wall 105b of the sample container 104a, 104b as illustrated in the example of Figures 1 C and 2C. As the side walls 105b, 105b’ of the square tube-shaped sample container 104b and the square cup-shaped sample container 104a are flat, the irradiation of the sample 102 through the side wall 105b of the sample container 104a, 104b increases the amount of the first fluorescence radiation 114 reaching the sample 102, for example in comparison to curved side walls. In other words, the square shape of the sample container 104a, 104b enables high efficiency of the excitation radiation.

[0055] As discussed above, the radiation detector unit 110 is positioned with respect to the sample container 104a, 104b so that the second fluorescence radiation 116 is obtained from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106. When the sample 102 is irradiated through the side wall 105b of the square tube-shaped sample container 104b or the square cupshaped sample container 104a, the radiation detector unit 110 may for example be positioned with respect to the sample container 104a, 104b so that the second fluorescence radiation 116 is obtained through another side wall 105b’ of the sample container 104a, 104b being adjacent to the side wall 105b of the sample container 104a, 104b through which the sample 102 is irradiated as illustrated in the example of Figures 1 C and 2C. When the sample 102 is irradiated through the side wall 105b of the square tube-shaped sample container 104b or the square cup-shaped sample container 104a and the second fluorescence radiation 116 is obtained through the side wall 105b’ being adjacent to the side wall 105b, through which the sample 102 is irradiated, the second fluorescence radiation 116 is obtained by the radiation detector unit 110 from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106, i.e. so that the angle between the direction 202 from which the second fluorescence radiation 116 is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is approximately 90 degrees. The measurement geometry according to the example of Figures 1 C and 2C enables the measurement of the concentration of gold in the sample 102 (e.g. a slurry sample) that is flowing along the square tube-shaped sample container 104b by using the measurement arrangement 100.

[0056] According to an example, when the sample 102 is irradiated from the side of the bottom surface 105a of the cup-shaped sample container 104a, the radiation detector unit 110 may comprise multiple detectors arranged symmetrically around the cup-shaped sample contained 104a so that each detector of the radiation detector unit 110 obtains the second fluorescence radiation 116 through a side wall 105b of the cup-shaped sample container 104a from the direction 202 substantially perpendicular to the direction 204 of the maximum intensity of the radiation beam 112 produced by the X-ray radiation source unit 106, i.e. so that the angle between the direction 202 from which the second fluorescence radiation 116 is obtained and the direction 204 of the maximum intensity of the radiation beam 112 is approximately 90 degrees. For example, the radiation detector unit 110 may comprise four detectors arranged symmetrically (i.e. 90 degrees apart) around the cup-shaped sample container 104a. The measurement arrangement 100 may further comprise a computing unit 118. The computing unit 118 may be configured to obtain data (e.g. the second fluorescence radiation 116) from the radiation detector unit 110, process the obtained data, and control the entities of the measurement arrangement 100. The processing of the obtained data may for example comprise determining the concentration of gold in the sample based on the second fluorescence radiation 116. The processing of the obtained data may further comprise any kind of signal processing needed to determine the concentration of gold in the sample 102 based on the second fluorescence radiation 116. For example, the concentration of gold in the sample 102 may be determined based on the intensity of the second fluorescence radiation 116, e.g. based on the intensity of the K- fluorescence radiation of being characteristics to gold.

[0057] Figure 4 illustrates schematically an example of a method for measuring concentration of gold in a sample 102. Figure 4 illustrates the method as a flow chart. The method of Figure 4 is performed by the measurement arrangement 100 discussed above.

[0058] At a step 410, the X-ray radiation source unit 106 produces the radiation beam 112 as discussed above.

[0059] At a step 420, the first fluorescence radiation 114 is excited by the primary filter 108 arranged between the X-ray radiation source 106 and the sample container 104a, 104b and acting as the permeable secondary target in response to the irradiation of the primary filter 108 with the radiation beam 112 from the X-ray radiation source unit 106 as discussed above. The excited first fluorescence radiation 114 is characteristic to the material of the primary filter 108.

[0060] At a step 430, the radiation detector unit 110 obtains the second fluorescence radiation 116 being characteristic to gold in response to the irradiation of the sample 102 with the first fluorescence radiation 114 as discussed above.

[0061] The measurement arrangement and the measurement method discussed above enable measuring the concentration of gold in the sample 102. The measurement sensitivity of the measurement arrangement 100 is improved for example in comparison to the reflection measurement -based XRF analyzers discussed in the background section. The specific examples provided in the description given above should not be construed as limiting the applicability and / or the interpretation of the appended claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.

Claims

CLAIMS1 . A measurement arrangement (100) for measuring concentration of gold in a sample (102), the measurement arrangement (100) comprises: a sample container (104a, 104b) for the sample (102); an X-ray radiation source unit (106) configured to produce a radiation beam (112); a primary filter (108) arranged between the X-ray radiation source unit (106) and the sample container (104a, 104b) so that the primary filter (108) is in a close vicinity to the sample container (104a, 104b), wherein the primary filter (108) is configured to act as a filter adapted to attenuate the radiation beam (112) at the wavelengths of gold and as a secondary target configured to excite a first fluorescence radiation (114) being characteristic to the material of the primary filter (108) in response to an irradiation of the primary filter (108) with the radiation beam (112) from the X-ray radiation source unit (106); and a radiation detector unit (110) configured to obtain a second fluorescence radiation (116) being characteristic to gold in response to an irradiation of the sample (102) with the first fluorescence radiation (114), wherein the second fluorescence radiation (116) is obtained by the radiation detector unit (110) from a direction (202) substantially perpendicular to the direction (204) of the maximum intensity of the radiation beam (112) produced by the X-ray radiation source unit (106).

2. The measurement arrangement (100) according to claim 1 , wherein the X- ray radiation source unit (106) is positioned with respect to the sample container (104a) so that the sample (102) is irradiated from a bottom surface (105a) side of the sample container (104a), wherein the sample container (104a) is a cupshaped sample container.

3. The measurement arrangement according (100) to claim 2, wherein the radiation detector unit (110) is positioned with respect to the sample container (104a) so that the second fluorescence radiation (116) is obtained through a side wall (105b) of the sample container (104a).

4. The measurement arrangement (100) according to claim 1 , wherein the X- ray radiation source unit (106) is positioned with respect to the sample container(104a) so that the sample (102) is irradiated through a side wall (105b) of the sample container (104b), wherein the sample container (104b) is a square tubeshaped sample container or a square cup-shaped sample container.

5. The measurement arrangement (100) according to claim 4, wherein the radiation detector unit (110) is positioned with respect to the sample container (104a, 104b) so that the second fluorescence radiation (116) is obtained through another side wall (105b’) of the sample container (104a, 104b) being adjacent to the side wall (105b) of the sample container (104a, 104b) through which the sample (102) is irradiated.

6. The measurement arrangement according (100) to any of the preceding claims, wherein the material of the primary filter (108) is uranium.

7. The measurement arrangement (100) according to any of the preceding claims, wherein a distance between the primary filter (108) and the sample container (104a, 104b) is between 0 to 3 millimeters.

8. The measurement arrangement (100) according to any of the preceding claims, wherein the primary filter (108) is arranged in a contact with the sample container (104a, 104b).

9. The measurement arrangement (100) according to any of the preceding claims, wherein the primary filter (108) is integrated into the sample container (104).

10. The measurement arrangement (100) according to any of the preceding claims, wherein the radiation detector unit (110) comprises a germanium detector or a silicon drift detector, or the radiation detector unit (110) is based on a Soller slit crystal spectrometer -based detection comprising a germanium detector or a cadmium zinc telluride detector.

11. The measurement arrangement (100) according to any of the preceding claims, wherein the material of an anode of the X-ray radiation source unit (106) has atomic number greater than or equal to 72.

12. A method for measuring concentration of gold in a sample (102) with the measurement arrangement (100) according to any of the preceding claims.

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